Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    The Genetic Architecture of Post-Zygotic Reproductive Isolation Between Anopheles coluzzii and An. quadriannulatus
    Deitz, Kevin C. ; Takken, Willem ; Slotman, Michel A. - \ 2020
    Frontiers in Genetics Livestock Genomics 11 (2020). - ISSN 1664-8021
    Anopheles gambiae complex - Dobzhansky–Muller incompatibilities - hybrid - inviability - post-zygotic reproductive isolation - speciation - sterility

    The Anopheles gambiae complex is comprised of eight morphologically indistinguishable species and has emerged as a model system for the study of speciation genetics due to the rapid radiation of its member species over the past two million years. Male hybrids between most An. gambiae complex species pairs are sterile, and some genotype combinations in hybrid males cause inviability. We investigated the genetic basis of hybrid male inviability and sterility between An. coluzzii and An. quadriannulatus by measuring segregation distortion and performing a QTL analysis of sterility in a backcross population. Hybrid males were inviable if they inherited the An. coluzzii X chromosome and were homozygous at one or more loci in 18.9 Mb region of chromosome 3. The An. coluzzii X chromosome has a disproportionately large effect on hybrid sterility when introgressed into an An. quadriannulatus genetic background. Additionally, an epistatic interaction between the An. coluzzii X and a 1.12 Mb, pericentric region of the An. quadriannulatus 3L chromosome arm has a statistically significant contribution to the hybrid sterility phenotype. This same epistatic interaction occurs when the An. coluzzii X is introgressed into the genetic background of An. arabiensis, the sister species of An. quadriannulatus, suggesting that this may represent one of the first Dobzhansky–Muller incompatibilities to evolve early in the radiation of the Anopheles gambiae species complex. We describe the additive effects of each sterility QTL, epistatic interactions between them, and genes within QTL with protein functions related to mating behavior, reproduction, spermatogenesis, and microtubule morphogenesis, whose divergence may contribute to post-zygotic reproductive isolation between An. coluzzii and An. quadriannulatus.

    Ghost Introgression: Spooky Gene Flow in the Distant Past
    Ottenburghs, Jente - \ 2020
    Bioessays 42 (2020)6. - ISSN 0265-9247
    adaptation - demographic modelling - hybridization - macroevolution - phylogenetic networks - reproductive isolation - speciation

    Evolution is a continuous trial and error process in which most lineages go extinct without leaving fossil remains. Many of these lineages would be closely related and occasionally hybridized with lineages that gave rise to extant species. Hence, it is likely that one can find genetic signatures of these ancient introgression events in present-day genomes, so-called ghost introgression. The increasing availability of high-quality genome assemblies for non-model organisms and the development of more sophisticated methods for detecting introgression will undoubtedly reveal more cases of ghost introgression, indicating that the Tree of Life is even more reticulated than assumed. The presence of ghost introgression has important consequences for the study of numerous evolutionary processes, including adaptation, speciation, and macroevolutionary patterns. In addition, detailed studies of introgressed regions could provide insights into the morphology of the extinct lineage, providing an unexpected link between genomics and the fossil record. Hence, new methods that take into account ghost introgression will need to be developed.

    The Role of Transcriptional Regulation in Hybrid Vigor
    Botet, Ramon ; Keurentjes, Joost J.B. - \ 2020
    Frontiers in Plant Science 11 (2020). - ISSN 1664-462X
    Arabidopsis thaliana - breeding - gene expression - genetic regulation - heterosis - hybrid vigor - natural variation - speciation

    The genetic basis of hybrid vigor in plants remains largely unsolved but strong evidence suggests that variation in transcriptional regulation can explain many aspects of this phenomenon. Natural variation in transcriptional regulation is highly abundant in virtually all species and thus a potential source of heterotic variability. Allele Specific Expression (ASE), which is tightly linked to parent of origin effects and modulated by complex interactions in cis and in trans, is generally considered to play a key role in explaining the differences between hybrids and parental lines. Here we discuss the recent developments in elucidating the role of transcriptional variation in a number of aspects of hybrid vigor, thereby bridging old paradigms and hypotheses with contemporary research in various species.

    Data underlying the research of Geochemical multi-surface modeling of reactive zinc speciation in compost as influenced by extraction conditions
    Klinkert, Susan ; Comans, Rob ; Groenenberg, Bert Jan - \ 2020
    Wageningen University & Research
    compost - extraction conditions - fractionation - geochemical modelling - organic matter - zinc - speciation
    This dataset includes the data and calculations underlying the modeling work carried out for the scientific manuscript "Geochemical multi-surface modeling of reactive zinc speciation in compost as influenced by extraction conditions".
    Crossing species boundaries : the hybrid histories of the true geese
    Ottenburghs, Jente - \ 2016
    Wageningen University. Promotor(en): Herbert Prins; R.C. Ydenburg, co-promotor(en): Hendrik-Jan Megens. - Wageningen : Wageningen University - ISBN 9789462579781 - 268
    geese - anser - crossing - species - hybridization - speciation - phylogenomics - ganzen - anser - kruisen - soorten - hybridisatie - soortvorming - phylogenomica

    Hybridization, the interbreeding of different species, is a common phenomenon in birds: about 16% of bird species is known to have hybridized with at least one other species. Numerous avian hybrid zones have been studied from a morphological or genetic perspective, often documenting the interspecific exchange of genetic material by hybridization and backcrossing (i.e. introgression). The incidence of hybridization varies among bird orders with the Anseriformes (waterfowl: ducks, geese and swans) showing the highest propensity to hybridize. In this thesis, I provide a genomic perspective on the role of hybridization in the evolutionary history of one particular anseriform tribe, the Anserini or “True Geese”, which comprises 17 species divided over two genera: Anser and Branta . The diversification of this bird group took place in the late Pliocene and the early Pleistocene (between four and two million years ago), conceivably driven by a global cooling trend that led to the establishment of a circumpolar tundra belt and the emergence of temperate grasslands. Most species show a steady population increase during this period, followed by population subdivision during the Last Glacial Maximum about 110,000 to 12,000 years ago. The combination of large effective population sizes and occasional range shifts facilitated contact between the diverging goose species, resulting in high levels of interspecific gene flow. Introgressive hybridization might have enabled these goose populations to quickly adapt to changing environments by transferring of advantageous alleles across species boundaries, increasing standing genetic variation or expanding phenotypic variation of certain traits (e.g., beak morphology). Hybridization seems to be a common and integral component in the evolution and diversification of geese. The pervasiveness of rapid speciation and hybridization in geese complicates the attempt to capture their evolutionary history in a phylogenetic tree, advocating a phylogenetic network approach. Indeed, trying to capture the complex diversification of the True Geese in a branching tree can be regarded as a wild goose chase.

    Methodological approaches for fractionation and speciation to estimate trace element bioavailability in engineered anaerobic digestion ecosystems : An overview
    Hullebusch, Eric D. van; Guibaud, Gilles ; Simon, Stéphane ; Lenz, Markus ; Yekta, Sepehr Shakeri ; Fermoso, Fernando G. ; Jain, Rohan ; Duester, Lars ; Roussel, Jimmy ; Guillon, Emmanuel ; Skyllberg, Ulf ; Almeida, C.M.R. ; Pechaud, Yoan ; Garuti, Mirco ; Frunzo, Luigi ; Esposito, Giovanni ; Carliell-Marquet, Cynthia ; Ortner, Markus ; Collins, Gavin - \ 2016
    Critical Reviews in Environmental Science and Technology 46 (2016)16. - ISSN 1064-3389 - p. 1324 - 1366.
    Anaerobic digestion - analytical methods - bioavailability - fractionation - speciation - trace elements

    Optimal supply of trace elements (TE) is a prerequisite for microbial growth and activity in anaerobic digestion (AD) bioprocesses. However, the required concentrations and ratios of essential TE for AD biotechnologies strongly depend on prevailing operating conditions as well as feedstock composition. Furthermore, TE in AD bioreactors undergo complex physicochemical reactions and may be present as free ions, complex bound or as precipitates depending on pH, or on the presence of sulfur compounds or organic macromolecules. To overcome TE deficiency, various commercial mineral products are typically applied to AD processes. The addition of heavy metals poses the risk of overdosing operating systems, which may be toxic to microbial consortia and ultimately the environment. Adequate supplementation, therefore, requires appropriate knowledge not only about the composition, but also on the speciation and bioavailability of TE. However, very little is yet fully understood on this specific issue. Evaluations of TE typically only include the measurement of total TE concentrations but do not consider the chemical forms in which TE exist. Thus detailed information on bioavailability and potential toxicity cannot be provided. This review provides an overview of the state of the art in approaches to determine bioavailable TE in anaerobic bioprocesses, including sequential fractionation and speciation techniques. Critical aspects and considerations, including with respect to sampling and analytical procedures, as well as mathematical modeling, are examined. The approaches discussed in this review are based on our experiences and on previously published studies in the context of the “COST Action 1302: European Network on Ecological Roles of Trace Metals in Anaerobic Biotechnologies.”

    Asymmetric flow field-flow fractionation of manufactured silver nanoparticles spiked into soil solution
    Koopmans, G.F. ; Hiemstra, T. ; Regelink, I.C. ; Molleman, B. ; Comans, R.N.J. - \ 2015
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1392 (2015). - ISSN 0021-9673 - p. 100 - 109.
    natural organic-matter - engineered nanoparticles - calcium-chloride - ionic-strength - humic acids - molar-mass - aggregation - retention - ph - speciation
    Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV–vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10–90 nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV–vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used.
    The butterfly plant arms-race escalated by gene and genome duplications
    Edger, P.P. ; Heidel-Fischer, H.M. ; Bekaert, K.M. ; Rota, J. ; Glockner, G. ; Platts, A.E. ; Heckel, D.G. ; Der, J.P. ; Wafula, E.K. ; Tang, M. ; Hofberger, J.A. ; Smithson, A. ; Hall, J.C. ; Blanchette, M. ; Bureau, T.E. ; Wright, S.I. ; dePamphilis, C.W. ; Schranz, M.E. ; Conant, G.C. ; Barker, M.S. ; Wahlberg, N. ; Vogel, H. ; Pires, J.C. ; Wheat, C.W. - \ 2015
    Proceedings of the National Academy of Sciences of the United States of America 112 (2015)27. - ISSN 0027-8424 - p. 8362 - 8366.
    evolutionaire genetica - co-evolutie - diversificatie - brassica - pieridae - papilionidae - glucosinolaten - fylogenie - evolutionary genetics - coevolution - diversification - brassica - pieridae - papilionidae - glucosinolates - phylogeny - diversity - defense - cytochrome-p450 - polymorphism - arabidopsis - metabolism - expression - speciation
    Coevolutionary interactions are thought to have spurred the evolution of key innovations and driven the diversification of much of life on Earth. However, the genetic and evolutionary basis of the innovations that facilitate such interactions remains poorly understood. We examined the coevolutionary interactions between plants (Brassicales) and butterflies (Pieridae), and uncovered evidence for an escalating evolutionary arms-race. Although gradual changes in trait complexity appear to have been facilitated by allelic turnover, key innovations are associated with gene and genome duplications. Furthermore, we show that the origins of both chemical defenses and of molecular counter adaptations were associated with shifts in diversification rates during the arms-race. These findings provide an important connection between the origins of biodiversity, coevolution, and the role of gene and genome duplications as a substrate for novel traits.
    Mesocosm validation of the marine No Effect Concentration of dissolved copper derived from a species sensivity distribution
    Foekema, E.M. ; Kaag, N.H.B.M. ; Kramer, K.J.M. ; Long, K. - \ 2015
    Science of the Total Environment 521-522 (2015). - ISSN 0048-9697 - p. 173 - 182.
    principal response curves - organic-matter - toxicity - water - carbon - speciation - exposure - ph
    The Predicted No Effect Concentration (PNEC) for dissolved copper based on the species sensitivity distribution (SSD) of 24 marine single species tests was validated in marine mesocosms. To achieve this, the impact of actively maintained concentrations of dissolved copper on a marine benthic and planktonic community was studied in 18 outdoor 4.6 m3 mesocosms. Five treatment levels, ranging from 2.9 to 31 µg dissolved Cu/L, were created in triplicate and maintained for 82 days. Clear effects were observed on gastropod and bivalve molluscs, phytoplankton, zooplankton, sponges and sessile algae. The most sensitive biological endpoints; reproduction success of the bivalve Cerastoderma edule, copepod population development and periphyton growth were significantly affected at concentrations of 9.9 µg Cu/L and higher. The No Observed Effect Concentration (NOEC) derived from this study was 5.7 µg dissolved Cu/L. Taking into account the DOC concentration of the mesocosm water this NOEC is comparable to the PNEC derived from the SSD.
    Genomics and the challenging translation into conservation practice
    Shafer, A.B.A. ; Wolf, J.B.W. ; Alves, P.C. ; Bergstrom, L. ; Bruford, M.W. ; Brannstrom, I. ; Colling, G. ; Dalen, L. van; Meester, L. de; Ekblom, R. ; Vergeer, P. - \ 2015
    Trends in Ecology and Evolution 30 (2015)2. - ISSN 0169-5347 - p. 78 - 87.
    genetic diversity - background selection - population genomics - insular population - dna - divergence - speciation - evolution - sequence - markers
    The global loss of biodiversity continues at an alarming rate. Genomic approaches have been suggested as a promising tool for conservation practice as scaling up to genome-wide data can improve traditional conservation genetic inferences and provide qualitatively novel insights. However, the generation of genomic data and subsequent analyses and interpretations remain challenging and largely confined to academic research in ecology and evolution. This generates a gap between basic research and applicable solutions for conservation managers faced with multifaceted problems. Before the real-world conservation potential of genomic research can be realized, we suggest that current infrastructures need to be modified, methods must mature, analytical pipelines need to be developed, and successful case studies must be disseminated to practitioners.
    Structural variations in pig genomes
    Paudel, Y. - \ 2015
    Wageningen University. Promotor(en): Martien Groenen, co-promotor(en): Ole Madsen; Hendrik-Jan Megens. - Wageningen : Wageningen University - ISBN 9789462572171 - 204
    varkens - dierveredeling - genomen - genomica - single nucleotide polymorphism - dna-sequencing - fenotypische variatie - chromosoomafwijkingen - evolutie - soortvorming - pigs - animal breeding - genomes - genomics - single nucleotide polymorphism - dna sequencing - phenotypic variation - chromosome aberrations - evolution - speciation

    Abstract

    Paudel, Y. (2015). Structural variations in pig genomes. PhD thesis, Wageningen University, the Netherlands

    Structural variations are chromosomal rearrangements such as insertions-deletions (INDELs), duplications, inversions, translocations, and copy number variations (CNVs). It has been shown that structural variations are as important as single nucleotide polymorphisms (SNPs) in regards to phenotypic variations. The general aim of this thesis was to use next generation sequencing data to improve our understanding of the evolution of structural variations such as CNVs, and INDELs in pigs. We found that: 1) the frequency of copy number variable regions did not change during pig domestications but rather reflected the demographic history of pigs. 2) CNV of olfactory receptor genes seems to play a role in the on-going speciation of the genus Sus. 3) Variation in copy number of olfactory receptor genes in pigs (Sus scrofa) seems to be shaped by a combination of selection and genetic drift, where the clustering of ORs in the genome is the major source of variation in copy number. 4) Analysis on short INDELs in the pig genome shows that the level of purifying selection of INDELs positively correlates with the functional importance of a genomic region, i.e. strongest purifying selection was observed in gene coding regions. This thesis provides a highly valuable resource for copy number variable regions, INDELs, and SNPs, for future pig genetics and breeding research. Furthermore, this thesis discusses the limitations and improvements of the available tools to conduct structural variation analysis and insights into the future trends in the detection of structural variations.

    Speciation and domestication in Suiformes: a genomic perspective
    Frantz, L.A.F. - \ 2015
    Wageningen University. Promotor(en): Martien Groenen, co-promotor(en): Ole Madsen; Hendrik-Jan Megens. - Wageningen : Wageningen University - ISBN 9789462572546 - 227
    domesticatie - suiformes - soortvorming - dierveredeling - genomica - evolutie - genenstroom - dna-sequencing - moleculaire fylogenetica - domestication - suiformes - speciation - animal breeding - genomics - evolution - gene flow - dna sequencing - molecular phylogenetics

    Abstract

    Frantz, L.A.F. (2015). Speciation and Domestication in Suiformes: a genomic perspective. PhD thesis, Wageningen University, the Netherlands

    The diversity of life on earth owes its existence to the process of speciation. The concept of speciation is primordial for evolutionary biologists because it provides a framework to understand how contemporary biodiversity came to be. Moreover, not only natural phenomena can result in the differentiation of life forms. Indeed, biodiversity can also be the result of direct and indirect human influence such as domestication. In this thesis, I investigate these evolutionary processes (speciation and domestication) in the Suiformes superfamily (pigs and related species). I use complete genome sequences to illuminate many specific aspects of the speciation and domestication in Suiformes as well as to draw general conclusions on these crucial processes. In chapter 2 I show how genomes provide an essential source of information to retrieve deep taxonomic relationships among Suiformes. This allows me to describe multiple novel aspects of their early evolutionary history such as the fact that Suiformes colonised North America at least twice. In this chapter, I further highlight and discuss novel methodological limitations that are inherent to phylogenomics. In chapters 3, 4 and 5 I use genome sequences to resolve the evolutionary history of the genus Sus (domestic pigs and wild boars species). More precisely, I show that, contrary to the expectation of simple models of speciation, the evolutionary history of these species involved alternating periods of gene-flow and genetic differentiation that are tightly linked to past climatic fluctuations that took place over the last 4 million years. In addition, these chapters also provide novel insights into the process of speciation by demonstrating that genetic differentiation between species can be achieved, even when gene-flow is strong. Lastly, in chapter 6 I tested multiple models of domestication for S. scrofa. In this chapter I show that models involving reproductive isolation between wild and domestic forms are incompatible with genomic data. Moreover, this chapter demonstrates that, while domestic pigs are morphologically homogenous, they are not genetically homogenous. Together, these findings have important implications for our understanding of the process of domestication because it shows that this process was not solely the result of captivity. Together, the results of this work not only provide a comprehensive evolutionary history for the Suiformes, but also novel insights into the complex processes (speciation and domestication) that are responsible for the diversity of life on earth.

    Data from: Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island Southeast Asian Sus species during the Plio-Pleistocene climatic fluctuations
    Frantz, L.A.F. ; Madsen, O. ; Megens, H.J.W.C. ; Groenen, M. ; Lohse, H. - \ 2014
    Wageningen UR
    speciation - hybridization - population genetics - empirical - phylogeography - genomics / proteomics - conservation genetics
    In many temperate regions, ice ages promoted range contractions into refugia resulting in divergence (and potentially speciation), while warmer periods led to range expansions and hybridization. However, the impact these climatic oscillations had in many parts of the tropics remains elusive. Here, we investigate this issue using genome sequences of three pig (Sus) species, two of which are found on islands of the Sunda-shelf shallow seas in Island Southeast Asia (ISEA). A previous study revealed signatures of inter-specific admixture between these Sus species (Frantz et al. (2013) Genome sequencing reveals fine scale diversification and reticulation history during speciation in Sus. Genome biology, 14, R107). However, the timing, directionality and extent of this admixture remain unknown. Here we use a likelihood based model comparison to more finely resolve this admixture history and test whether it was mediated by humans or occurred naturally. Our analyses suggest that inter-specific admixture between Sunda-shelf species was most likely asymmetric and occurred long before the arrival of humans in the region. More precisely, we show that these species diverged during the late Pliocene but around 23% of their genomes have been affected by admixture during the later Pleistocene climatic transition. In addition, we show that our method provides a significant improvement over D-statistics which are uninformative about the direction of admixture.
    Neandertal Admixture in Eurasia Confirmed by Maximum-Likelihood Analysis of Three Genomes
    Lohse, K. ; Frantz, L.A.F. - \ 2014
    Genetics 196 (2014)4. - ISSN 0016-6731 - p. 1241 - 1251.
    ancestral population sizes - dna-sequences - divergence - speciation - history - number - recombination - coalescent - migration - inference
    Although there has been much interest in estimating histories of divergence and admixture from genomic data, it has proved difficult to distinguish recent admixture from long-term structure in the ancestral population. Thus, recent genome-wide analyses based on summary statistics have sparked controversy about the possibility of interbreeding between Neandertals and modern humans in Eurasia. Here we derive the probability of full mutational configurations in nonrecombining sequence blocks under both admixture and ancestral structure scenarios. Dividing the genome into short blocks gives an efficient way to compute maximum-likelihood estimates of parameters. We apply this likelihood scheme to triplets of human and Neandertal genomes and compare the relative support for a model of admixture from Neandertals into Eurasian populations after their expansion out of Africa against a history of persistent structure in their common ancestral population in Africa. Our analysis allows us to conclusively reject a model of ancestral structure in Africa and instead reveals strong support for Neandertal admixture in Eurasia at a higher rate (3.4-7.3%) than suggested previously. Using analysis and simulations we show that our inference is more powerful than previous summary statistics and robust to realistic levels of recombination.
    Adsorption of levofloxacin onto goethite: Effects of pH, calcium and phosphate
    Qin, X.P. ; Liu, F. ; Wang, G.C. ; Weng, L. ; Li, L. - \ 2014
    Colloids and Surfaces. B: Biointerfaces 116 (2014). - ISSN 0927-7765 - p. 591 - 596.
    fluoroquinolone antibacterial agents - water interface - ciprofloxacin removal - antibiotic ofloxacin - humic substances - iron-oxides - sorption - complexation - tetracycline - speciation
    Adsorption of levofloxacin (LEV), one of the extensively used antibiotics, onto goethite was investigated using batch experiments. The adsorption of LEV on goethite was pH-dependent. A maximum adsorption was reached at pH 6. Above or below pH 6, the adsorption decreased. In the presence of calcium (Ca2+), a decrease in adsorption was observed, due to probably formation of Ca2+-LEV complexes in solutions. Phosphate also showed a significant inhibition on LEV adsorption over a pH range of 3-10. Phosphate competed with LEV for binding sites on the surface of goethite, and the electrostatic competition between LEV and phosphate on goethite surface might be another reason for the decrease in adsorption. These results indicated that Ca2+ and phosphate have a great influence on the distribution of LEV in soils and waters, which will eventually affect its antibacterial activity in the environment. (C) 2013 Elsevier B.V. All rights reserved.
    A decade of uncertainty: Resolving the phyologenetic position of Diclinanona (Annonaceae), inlcuding taxonomic notes and a key to the species
    Erkens, R.H.J. ; Chatrou, L.W. ; Chaowasku, T. ; Westra, L.I.T. ; Maas, J.W. ; Maas, P.J.M. - \ 2014
    Taxon 63 (2014)6. - ISSN 0040-0262 - p. 1244 - 1252.
    palms sheds light - historical biogeography - global biogeography - evolution - diversification - speciation - genus - taxa - biodiversity - convergence
    The molecular phylogenetic placement of Diclinanona (Annonaceae) has been debated in the literature for a decade. On the basis of morphological studies the genus was thought to be related to genera now all placed in subfam. Annonoideae. This early hypothesis was supported by the first phylogenetic analyses of Annonaceae. However, more recently a placement in subfam. Malmeoideae was hypothesised based on an analysis of more plastid data, thus contradicting older but also new morphological findings and previous phylogenetic work. The current study uses newly sequenced plastid data for two species of Diclinanona to show that the earlier hypothesised placement was correct and discusses the (little) anatomical and morphological data on Diclinanona that is available in a phylogenetic framework. Furthermore, an online revision of the three species of Diclinanona is presented in order to update the taxonomic knowledge of this genus.
    Genetic divergence and evidence for sympatric host-races in the highly polyphagous brown tail moth, Euproctis chrysorrhoea (Lepidoptera: Erebidae)
    Marques, J.F. ; Wang, H.L. ; Svensson, G.P. ; Frago Clols, E. ; Anderbrant, O. - \ 2014
    Evolutionary Ecology 28 (2014)5. - ISSN 0269-7653 - p. 829 - 848.
    plant-feeding insects - tree arbutus-unedo - evolutionary history - mitochondrial - populations - speciation - refugia - time - diversification - differentiation
    The brown tail moth (BTM) Euproctis chrysorrhoea (Linnaeus 1758) (Lepidoptera: Erebidae) is a forest and ornamental pest in Europe and the United States. Its extreme polyphagy, and documented phenological shift associated with host use suggest the presence of distinct host-races. To test this hypothesis, we sampled BTM infesting different host species in several locations along its distribution, and used DNA sequence data (a total of 1,672 bp from cytochrome c oxidase subunit I, elongation factor 1-alpha, and wingless) to produce haplotype networks and reconstruct the phylogenetic relationships between individuals. Population genetic diversity indices pointed out a higher genetic diversity in Europe, particularly in the samples from southern Spain and southern England. Lower F ST values were found between geographically closer populations when compared to more distant ones, but analyses of molecular variance and Mantel tests failed to reveal geographically associated genetic differentiation. However, haplotype networks and phylogenetic reconstructions revealed a previously unknown genetic differentiation within the BTM, with one lineage circumscribed to southern Europe. Although BTM haplotypes did not cluster according to their host plant, host-associated haplotypes were observed within certain geographic regions. Hence, our data support the existence of host-races of BTM within southern Spain and southern England, where populations from different hosts occur in sympatry.
    Characterization of colloidal Fe from soils using field-flow fractionation and Fe K-edge X-ray absorption spectroscopy
    Regelink, I.C. ; Voegelin, A. ; Weng, L. ; Koopmans, G.F. ; Comans, R.N.J. - \ 2014
    Environmental Science and Technology 48 (2014)8. - ISSN 0013-936X - p. 4307 - 4316.
    iron-oxide nanoparticles - natural organic-matter - acid forest soils - exafs spectroscopy - mineral nanoparticles - trace-metals - speciation - surface - ferrihydrite - associations
    Colloids may facilitate the transport of trace elements and nutrients like phosphate in soil. In this study, we characterized soil colloids (
    Differences in olfactory species recognition in the females of two Australian songbird species
    Krause, E.T. ; Brummel, C. ; Kohlwey, S. ; Baier, M.C. ; Müller, C. ; Bonadonna, F. ; Caspers, B.A. - \ 2014
    Behavioral Ecology and Sociobiology 68 (2014)11. - ISSN 0340-5443 - p. 1819 - 1827.
    finches taeniopygia-guttata - zebra finches - odor recognition - kin recognition - wild - birds - nest - cues - discrimination - speciation
    Although birds have recently been shown to possess olfactory abilities and to use chemical cues in communication, limited effort has been made to demonstrate the use of odorants in social contexts. Even less is known regarding the use of odorants in species recognition. The ability to recognize conspecifics should be more pronounced in social species. This study investigated the importance of olfactory cues in species recognition in females of two estrildid finch species with different levels of sociality. Combining odor preference tests with chemical analyses, we surveyed whether female zebra finches and diamond firetails are able to distinguish between the species based on volatile traits and whether individuals exhibit species-specific differences in body odorants. Zebra finches are more social than diamond firetails; nevertheless, both species have an overlapping distribution area. Applying an experimental Y-maze paradigm, we showed that zebra finches can use differences in their species odor fingerprints and displayed a significant preference for the odor of conspecifics over that of heterospecifics, whereas diamond firetails did not reveal a preference. Using gas chromatography and mass spectrometry, we demonstrated that body odorants of the two species were significantly different in relative composition. This finding demonstrates the potential importance of olfactory cues in species recognition, at least in social bird species. Even these two closely related species displayed remarkable differences in their responsiveness to similar chemical cues, which might be caused by species-specific differences in ecology, physiology, or evolution. Keywords Songbird . Zebra finch . Taeniopygia guttata . Diamond firetail . Stagonopleura guttata . Sociality . Olfaction . Smell . Scent . Olfactory fingerprint
    Oral bioaccessibility and human exposure to anthropogenic and geogenic mercury in urban, industrial and mining areas
    Rodrigues, S.M. ; Coelho, C. ; Cruz, N. ; Monteiro, R.J.R. ; Henriques, B. ; Duarte, A.C. ; Romkens, P.F.A.M. ; Pereira, E. - \ 2014
    Science of the Total Environment 496 (2014). - ISSN 0048-9697 - p. 649 - 661.
    atomic-absorption-spectrometry - potentially toxic elements - chloralkali plant - inorganic mercury - part i - contaminated soils - asturias spain - speciation - sediments - portugal
    The objective of this study was to characterize the link between bioaccessibility and fractionation of mercury (Hg) in soils and to provide insight into human exposure to Hg due to inhalation of airborne soil particles and hand-to-mouth ingestion of Hg-bearing soil. Mercury in soils from mining, urban and industrial areas was fractionated in organometallic forms; mobile; semi-mobile; and non-mobile forms as well as HCl-extractable Hg. The in vitro bioaccessibility of Hg was obtained by extracting soils with (1) a simulated human gastric fluid (pH 1.5), and (2) a simulated human lung fluid (pH 7.4). Total soil Hg concentrations ranged from 0.72 to 1.8 mg kg- 1 (urban areas), 0.28 to 94 mg kg- 1 (industrial area) and 0.92 to 37 mg kg- 1 (mining areas). Both organometallic Hg as well as 0.1 M HCl extractable Hg were lower (<0.5% of total Hg) than Hg extracted by gastric fluid (up to 1.8% of total Hg) and lung fluid (up to 12% of total Hg). In addition, Hg extracted by lung fluid was significantly higher in urban and industrial soils (average 5.0–6.6% of total Hg) compared to mining soils. Such differences were related to levels of mobile Hg species in urban and industrial soils compared to mining soils. These results strengthen the need to measure site-specific Hg fractionation when determining Hg bioaccessibility. Results also show that ingestion and/or inhalation of Hg from soil particles can contribute up to 8% of adult total Hg intake when compared to total Hg intake via consumption of contaminated fish and animal products from contaminated areas.
    Chemical communication in tilapia: A comparison of Oreochromis mossambicus with O. niloticus
    Hubbard, P.C. ; Mota, V.C. ; Keller-Costa, T. ; Paulo da Silva, J. ; Canário, A.V.M. - \ 2014
    General and Comparative Endocrinology 207 (2014). - ISSN 0016-6480 - p. 13 - 20.
    maturation-inducing hormone - african cichlid fish - mozambique tilapia - olfactory sensitivity - speciation - pheromone - signals - urine - radiations - evolution
    In allopatric speciation species differentiation generally results from different selective pressures in different environments, and identifying the traits responsible helps to understand the isolation mechanism(s) involved. Male Mozambique tilapia (Oreochromis mossambicus) use urine to signal dominance; furthermore, 5b-pregnane-3a,17,20b-triol-3a-glucuronide (and its a-epimer, 5b-pregnane-3a,17,20atriol-3a-glucuronide), in their urine is a potent pheromone, the concentration of which is correlated with social status. The Nile tilapia (Oreochromis niloticus) is a close relative; species divergence probably resulted from geographical separation around 6 million years ago. This raises the question of whether the two species use similar urinary chemical cues during reproduction. The olfactory potency of urine, and crude extracts, from either species was assessed by the electro-olfactogram and the presence of the steroid glucuronides in urine from the Nile tilapia by liquid-chromatography/mass-spectrometry. Both species showed similar olfactory sensitivity to urine and respective extracts from either species, and similar sensitivity to the steroid glucuronides. 5b-Pregnan-3a,17a,20b-triol-3a-glucuronide was present at high concentrations (approaching 0.5 mM) in urine from Nile tilapia, with 5b-pregnan-3a,17a,20a-triol-3a-glucuronide present at lower concentrations, similar to the Mozambique tilapia. Both species also had similar olfactory sensitivity to estradiol-3-glucuronide, a putative urinary cue from females. Together, these results support the idea that reproductive chemical cues have not been subjected to differing selective pressure. Whether these chemical cues have the same physiological and behavioural roles in O. niloticus as O. mossambicus remains to be investigated.
    Terrestrial selenium distribution in China is potentially linked to monsoonal climate
    Blazina, T. ; Sun, Y. ; Voegelin, A. ; Lenz, M. ; Berg, M. ; Winkel, L.H.E. - \ 2014
    Nature Communications 5 (2014). - ISSN 2041-1723
    red clay formation - loess plateau - atmospheric selenium - trace-metals - adsorption - speciation - pliocene - records - water - soil
    The prevalence of terrestrial environments low in the essential trace element selenium (Se) results in large-scale Se deficiency worldwide. However, the underlying processes leading to Se-depleted environments have remained elusive. Here we show that over the last 6.8 million years (Ma) climatic factors have played a key role in the Se distribution in loess–paleosol sequences in the Chinese Loess Plateau (CLP), which lies in a severely Se-depleted region with a history of Se deficiency-related diseases. We use a combination of geochemical and paleoclimate data to demonstrate that during interglacial periods between 2.30 and 0.16¿Ma, variations in the Se concentration in the CLP are potentially related to variability in Se input via East Asian monsoon-derived precipitation. Our results identify precipitation as an important controlling factor of Se distribution in monsoonal China. We suggest that atmospheric Se inputs via precipitation could also play an important role in other regions worldwide.
    Influence of pH on the redox chemistry of metal (hydr)oxides and organic matter in paddy soils
    Pan, Y. ; Koopmans, G.F. ; Bonten, L.T.C. ; Song, J. ; Luo, Y. ; Temminghoff, E.J.M. ; Comans, R.N.J. - \ 2014
    Journal of Soils and Sediments 14 (2014)10. - ISSN 1439-0108 - p. 1713 - 1726.
    flooded soil - ion-binding - cadmium - iron - speciation - manganese - reduction - sorption - dynamics - mobilization
    The primary purpose of this study was to determine how flooding and draining cycles affect the redox chemistry of metal (hydr)oxides and organic matter in paddy soils and how the pH influences these processes. Our secondary purpose was to determine to what extent a geochemical thermodynamic equilibrium model can be used to predict the solubility of Mn and Fe during flooding and draining cycles in paddy soils. We performed a carefully designed column experiment with two paddy soils with similar soil properties but contrasting pH.We monitored the redox potential (Eh) continuously and took soil solution samples regularly at four depths along the soil profile during two successive flooding and drainage cycles. To determine dominant mineral phases of Mn and Fe under equilibrium conditions, stability diagrams of Mn and Fe were constructed as a function of Eh and pH. Geochemical equilibrium model calculations were performed to identify Mn and Fe solubility-controlling minerals and to compare predicted total dissolved concentrations with their measured values. Flooding led to strong Eh gradients in the columns of both soils. In the acidic soil, pH increased with decreasing Eh and vice versa, whereas pH in the alkaline soil was buffered by CaCO3. In the acidic soil, Mn and Fe solubility increased during flooding due to reductive dissolution of their (hydr)oxides and decreased during drainage because of re-oxidation. In the alkaline soil, Mn and Fe solubility did not increase during flooding due to Mn(II) and Fe(II) precipitation as MnCO3, FeCO3, and FeS. The predicted levels of soluble Mn and Fe in the acidic soil were much higher than their measured values, but predictions and measurements were rather similar in the alkaline soil. This difference is likely due to kinetically limited reductive dissolution of Mn and Fe (hydr)oxides in the acidic soil. During flooding, the solubility of dissolved organic matter increased in both soils, probably because of reductive dissolution of Fe (hydr)oxides and the observed increase in pH. Conclusions Under alternating flooding and draining conditions, the pH greatly affected Mn and Fe solubility via influencing either reductive dissolution or carbonate formation. Comparison between measurements and geochemical equilibrium model predictions revealed that reductive dissolution of Mn and Fe (hydr)oxides was kinetically limited in the acidic soil. Therefore, when applying such models to systems with changing redox conditions, such rate-limiting reactions should be parameterized and implemented to enable more accurate predictions of Mn and Fe solubility.
    Characterization of Phosphorus in Animal Manures Collected from Three (Dairy, Swine, and Broiler) Farms in China
    Li, G. ; Li, H. ; Leffelaar, P.A. ; Shen, J. ; Zhang, F. - \ 2014
    PLoS ONE 9 (2014)7. - ISSN 1932-6203
    magnetic-resonance-spectroscopy - enzymatic-hydrolysis - organic phosphorus - northwest germany - poultry litter - forms - soil - diets - speciation - fractions
    In order to identify the phosphorus species and concentration in animal manure, we comparatively characterized phosphorus in dairy manure, swine manure, and broiler litter, using a sequential procedure, a simplified two-step procedure (NaHCO3/NaOH+EDTA), and a solution Phosphorus-31 Nuclear Magnetic Resonance (31P-NMR) spectroscopy procedure. In the sequential procedure, deionized water extracted 39, 22, and 32%; NaHCO3 extracted 48, 26, and 37%; NaOH extracted 8, 9, and 13.8%; and HCl extracted 3, 42.8, and 17% of the total phosphorus in dairy manure, swine manure and broiler litter, respectively. Total phosphorus extracted by the NaHCO3/NaOH+EDTA procedure was 7.5, 32.4, and 15.8 g P kg-1 for dairy manure, swine manure, and broiler litter, respectively. The solution 31P-NMR procedure detected that 9, 34, and 29% of total phosphorus was phytic acid in dairy manure, swine manure, and broiler litter, respectively. These results show that phosphorus forms, availability, and quantities differ between animal manures, which provides valuable information for P characterization of animal manures in China.
    Multi-face modeling to predict free zinc ion concentrations in low-zinc soils
    Duffner, A. ; Weng, L. ; Hoffland, E. ; Zee, S.E.A.T.M. van der - \ 2014
    Environmental Science and Technology 48 (2014)10. - ISSN 0013-936X - p. 5700 - 5708.
    donnan membrane technique - organic-matter - heavy-metals - contaminated soils - isotopic exchange - humic substances - trace-metals - sandy soil - adsorption - speciation
    Multi-surface models are widely used to assess the potential ecotoxicological risk in metal-contaminated soils. Their accuracy in predicting metal speciation in soils with low metal levels was not yet tested. Now highly sensitive analytical techniques are available to experimentally validate such models at low concentration levels. The objective of this study was to test the accuracy of a multi-surface model to predict the Zn2+ concentration and to improve our understanding of Zn bioavailability in low-Zn soils. High-Zn soils were included as controls. Model parameters were determined independently on the basis of earlier peer-reviewed publications. Model output was validated against free Zn2+ concentrations determined with the soil column Donnan membrane technique in a range of soils varying in potentially available Zn, organic matter, clay silicate, and iron (hydr)oxide contents and pH. Deviations between predicted Zn2+ concentrations and experimentally determined values over the whole Zn concentration range were less or equal to the experimental standard error, except for one low-Zn soil. The Zn2+ concentration was mainly controlled by adsorption, where organic matter was predicted to be the dominant soil sorbent. The predicted Zn2+ concentration depends more sensitively upon changes of the reactive Zn pool (application of 0.6, 1.2, 2.4, and 3.6 mg of Zn kg–1 of soil) and organic matter content (±0.2 and 0.4%) than pH changes (±0.5 and 1 pH unit).
    Natural wetland emissions of methylated trace elements
    Vriens, B. ; Lenz, M. ; Charlet, L. ; Berg, M. ; Winkel, L.H.E. - \ 2014
    Nature Communications 5 (2014). - ISSN 2041-1723
    yellowstone-national-park - selenium volatilization - atmospheric selenium - biomethylation - soil - speciation - bacterium - products - sulfide - sulfur
    Natural wetlands are well known for their significant methane emissions. However, trace element emissions via biomethylation and subsequent volatilization from pristine wetlands are virtually unstudied, even though wetlands constitute large reservoirs for trace elements. Here we show that the average volatile fluxes of selenium (
    Data from: Genetic consequences of breaking migratory traditions in barnacle geese Branta leucopsis
    Jonker, R.M. ; Kraus, Robert ; Zhang, Q. ; Hooft, Pim van; Larsson, K. ; Jeugd, H.P. van der; Kurvers, Ralf ; Wieren, Sip van; Loonen, M.J.J.E. ; Crooijmans, Richard ; Ydenberg, Ron ; Groenen, Martien ; Prins, Herbert - \ 2013
    Wageningen University & Research
    population genetics - SNP - admixture - Branta leucopsis - migration modelling - speciation - cultural evolution
    Cultural transmission of migratory traditions enables species to deal with their environment based on experiences from earlier generations. Also, it allows a more adequate and rapid response to rapidly changing environments. When individuals break with their migratory traditions, new population structures can emerge that may affect gene flow. Recently, the migratory traditions of the Barnacle Goose Branta leucopsis changed, and new populations differing in migratory distance emerged. Here, we investigate the population genetic structure of the Barnacle Goose to evaluate the consequences of altered migratory traditions. We used a set of 358 single nucleotide polymorphism (SNP) markers to genotype 418 individuals from breeding populations in Greenland, Spitsbergen, Russia, Sweden and the Netherlands, the latter two being newly emerged populations. We used discriminant analysis of principal components, FST, linkage disequilibrium and a comparison of geneflow models using migrate-n to show that there is significant population structure, but that relatively many pairs of SNPs are in linkage disequilibrium, suggesting recent admixture between these populations. Despite the assumed traditions of migration within populations, we also show that genetic exchange occurs between all populations. The newly established nonmigratory population in the Netherlands is characterized by high emigration into other populations, which suggests more exploratory behaviour, possibly as a result of shortened parental care. These results suggest that migratory traditions in populations are subject to change in geese and that such changes have population genetic consequences. We argue that the emergence of nonmigration probably resulted from developmental plasticity.
    Mechanisms contributing to the thermal analysis of waste incineration bottom ash and quantification of idfferent carbon species
    Rocca, S. ; Zomeren, A. van; Costa, G. ; Dijkstra, J.J. ; Comans, R.N.J. ; Lombardi, F. - \ 2013
    Waste Management 33 (2013)2. - ISSN 0956-053X - p. 373 - 381.
    loss-on-ignition - fly-ash - unburned carbon - behavior - speciation - residues - coal
    The focus of this study was to identify the main compounds affecting the weight changes of bottom ash (BA) in conventional loss on ignition (LOI) tests and to obtain a better understanding of the individual processes in heterogeneous (waste) materials such as BA. Evaluations were performed on BA samples from a refuse derived fuel incineration (RDF-I) plant and a hospital waste incineration (HW-I) plant using thermogravimetric analysis and subsequent mass spectrometry (TG–MS) analysis of the gaseous thermal decomposition products. Results of TG–MS analysis on RDF-I BA indicated that the LOI measured at 550 °C was due to moisture evaporation and dehydration of Ca(OH)2 and hydrocalumite. Results for the HW-I BA showed that LOI at 550 °C was predominantly related to the elemental carbon (EC) content of the sample. Decomposition of CaCO3 around 700 °C was identified in both materials. In addition, we have identified reaction mechanisms that underestimate the EC and overestimate the CaCO3 contents of the HW-I BA during TG–MS analyses. These types of artefacts are expected to occur also when conventional LOI methods are adopted, in particular for materials that contain CaO/Ca(OH)2 in combination with EC and/or organic carbon, such as e.g. municipal solid waste incineration (MSWI) bottom and fly ashes. We suggest that the same mechanisms that we have found (i.e. in situ carbonation) can also occur during combustion of the waste in the incinerator (between 450 and 650 °C) demonstrating that the presence of carbonate in bottom ash is not necessarily indicative for weathering. These results may also give direction to further optimization of waste incineration technologies with regard to stimulating in situ carbonation during incineration and subsequent potential improvement of the leaching behavior of bottom ash.
    Arsenate and phosphate adsorption in relation to oxides composition in soils: LCD modelling
    Cui, Y. ; Weng, L. - \ 2013
    Environmental Science and Technology 47 (2013)13. - ISSN 0013-936X - p. 7269 - 7276.
    charge-distribution - humic substances - competitive adsorption - ion adsorption - heavy-metals - speciation - parameters - minerals - sorption - binding
    The pH dependent solid-solution distribution of arsenate and phosphate in five Dutch agricultural soil samples was measured in the pH range 4–8, and the results were interpreted using the LCD (ligand and charge distribution) adsorption modeling. The pH dependency is similar for both oxyanions, with a minimum soluble concentration observed around pH 6–8. This pH dependency can be successfully described with the LCD model and it is attributed mainly to the synergistic effects from Ca adsorption. The solubility of phosphate is much lower than that of arsenate. This big difference cannot be sufficiently explained by the reduction of small amount of As(V) into As(III), neither by slow desorption/adsorption. The difference between phosphate and arsenate in their solid-solution distribution becomes larger with the increase of aluminum (hydr)oxides (Al-oxides) contribution to the total amount of metal (Al and Fe) (hydr)oxides. The influence of Al-oxides is much larger than its relative amount extracted from the soils. When Al-oxides account for >40% of the soil oxides, the whole adsorbents behave apparently similarly to that of pure Al-oxides. These results indicated that surface coating and substitution may have modified significantly oxyanion adsorption to Fe-oxides in soils, and how to account for this complexity is a challenge for geochemical modeling.
    The effect of phosphorus binding clay (Phoslock) in mitigating cyanobacterial nuisance: A laboratory study on the effects on water quality variables and plankton
    Oosterhout, J.F.X. ; Lurling, M. - \ 2013
    Hydrobiologia 710 (2013)1. - ISSN 0018-8158 - p. 265 - 277.
    rare-earth-elements - organic-matter - lake restoration - eutrophication - microcystis - netherlands - sediments - blooms - complexation - speciation
    This laboratory study examined the lanthanum modified clay Phoslock® for its effectiveness to bind soluble reactive phosphorus (SRP), release of nutrients from this modified clay, its influence on water quality variables (pH, oxygen saturation %, conductivity and turbidity), effects on phytoplankton growth (green alga Scenedesmus obliquus, cyanobacteria Microcystis aeruginosa and Anabaena sp.), and, lastly, its effect on the population growth of the rotifer Brachionus calyciflorus. A clear dose–response for SRP binding by the modified clay was observed. A small amount of ammonium is released from Phoslock®. We found no effect of Phoslock® on pH or oxygen saturation. Conductivity increased with the increasing concentration of Phoslock®. An application of Phoslock® caused a transient increase of turbidity up to 211 NTU. However, due to rapid settlement, turbidity fell below 13 NTU (~1 m Secchi depth), after 6 h. Phoslock® addition caused a reduction in growth of all phytoplankton species tested that we attribute to the combined effects of light limitation, flocculation with the bentonite and binding of SRP to Phoslock®. We estimated the EC50 of Phoslock® on the population growth of rotifer B. calyciflorus to be 0.15 g Phoslock® l-1. Overall, the results of our study indicate Phoslock® seems to be suitable for field applications.
    Biovailability of copper and zinc in pig and cattle slurries
    Jakubus, M. ; Dach, J. ; Starmans, D.A.J. - \ 2013
    Fressenius Environmental Bulletin 22 (2013)4. - ISSN 1018-4619 - p. 995 - 1002.
    sequential extraction procedures - heavy-metals - soils - fractionation - speciation - sediments - manganese - sludge - nickel - lead
    Slurry is an important source of macronutrients, micro-nutrients and organic matter. Despite the considerable fertilizer value of slurry, it may be abundant in amounts of copper and zinc originating from dietary. The study presents quantitative changes in copper and zinc in individual slurries (pig and cattle slurries). The bioavailability of copper and zinc was estimated on the basis of amounts of the metals in isolated fractions using the sequential extraction method. Sequential techniques identify fractions which describe different connections of metals with the compost solid phase beginning with those that are easiest soluble up to those that dissolve with the greatest difficulties.Pig slurry was characterized by 2-fold higher amounts of copper and zinc in comparison to the levels detected in cattle slurries. Quantitative changes of the elements in the sequentially isolated fractions of analyzed slurries differed. First of all, this was dependent on the chemical character of a given metal, followed by the animal species, or the type of management. Irrespective of the type of slurry, 40-56% of the total amounts of copper were found in hardly available combinations, while available copper forms accounted for only 6.6–10.9%. Zinc was found predominantly in com-binations with iron and manganese oxides which, irrespective of the tested slurry, ranged from 130.64 mg·kg-1 to 293.60 mg·kg-1. Bioavailable metal contents, potentially introduced to soil with slurry doses, calculated as 170 kg total N/ha/year, ranged from 63.6 to 124.5 g for copper, and from 349.5 to 696.4 g for zinc. The estimated amounts of metal inputs to agricultural land demonstrate that soils are potentially at risk of heavy metal accumulation from the application of pig and cattle slurries.
    Crossability patterns in Asia Pacific Oryza series Sativae
    Banaticla-Hilario, M.C.N. ; Sackville Hamilton, R. ; Berg, R.G. van den; McNally, K.L. - \ 2013
    Genetic Resources and Crop Evolution 60 (2013)6. - ISSN 0925-9864 - p. 1899 - 1914.
    reproductive isolation - rice oryza - wild-rice - genome - hybridization - evolution - speciation - diversity - rufipogon - differentiation
    Reproductive barriers are thought to intensify with increasing genetic distance between species. To assess the extent of post-pollination reproductive isolation within and among the Asia Pacific species of Oryza series Sativae, crossing experiments using 15 accessions of O. meridionalis Ng, O. nivara Sharma et Shastry, and O. rufipogon Griff. were conducted. Intra- and interspecific crosses of the selfing species O. meridionalis and O. nivara had very low seed set and produced inviable F1 seeds indicative of strong pre- and post-zygotic barriers. Contrastingly, the outcrossing O. rufipogon exhibited high intraspecific crossability and modest compatibility with O. nivara and O. meridionalis in terms of seed set suggesting substantial pre-zygotic reproductive isolation of the species. O. rufipogon was asymmetrically compatible with O. meridionalis and symmetrically with O. nivara. The two inbreeding species manifested comparable degrees of isolation from O. rufipogon despite differences in strength of several post-zygotic barriers. Mating compatibility within and between the Asia Pacific species of Oryza series Sativae is not strongly spatially influenced, but some resistance to gene flow under sympatric conditions was observed. Intraspecific O. rufipogon F1s were more vegetatively robust and more late-flowering than their parents. Intra- and interspecific hybrids of Australasian O. rufipogon differed phenotypically from crosses with non-Australasian populations. Interspecific hybrids displayed both intermediate and parental character traits. O. nivara and O. rufipogon generated early-flowering F1s that are more similar to the former. O. meridionalis and O. rufipogon produced F1s that varied in phenology and morphology depending on the maternal and paternal species.
    Corresponding Mitochondrial DNA and Niche Divergence for Crested Newt Candidate Species
    Wielstra, B.M. ; Beukema, W. ; Arntzen, J.W. ; Skidmore, A.K. ; Toxopeus, A.G. ; Raes, N. - \ 2012
    PLoS ONE 7 (2012)9. - ISSN 1932-6203
    absence data - models - phylogeography - delimitation - speciation - ecology - areas
    Genetic divergence of mitochondrial DNA does not necessarily correspond to reproductive isolation. However, if mitochondrial DNA lineages occupy separate segments of environmental space, this supports the notion of their evolutionary independence. We explore niche differentiation among three candidate species of crested newt (characterized by distinct mitochondrial DNA lineages) and interpret the results in the light of differences observed for recognized crested newt species. We quantify niche differences among all crested newt (candidate) species and test hypotheses regarding niche evolution, employing two ordination techniques (PCA-env and ENFA). Niche equivalency is rejected: all (candidate) species are found to occupy significantly different segments of environmental space. Furthermore, niche overlap values for the three candidate species are not significantly higher than those for the recognized species. As the three candidate crested newt species are, not only in terms of mitochondrial DNA genetic divergence, but also ecologically speaking, as diverged as the recognized crested newt species, our findings are in line with the hypothesis that they represent cryptic species. We address potential pitfalls of our methodology.
    Determination of free Zn2+ concentration in synthetic and natural samples with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) and DMT (Donnan Membrane Techniques)
    Chito, D. ; Weng, L.P. ; Galceran, J. ; Companys, E. ; Puy, J. ; Riemsdijk, W.H. van; Leeuwen, H.P. van - \ 2012
    Science of the Total Environment 421-422 (2012). - ISSN 0048-9697 - p. 238 - 244.
    dissolved organic-matter - metal-ion concentrations - humic-acid - electroanalytical technique - lolium-perenne - soil solution - trace-metals - speciation - binding - waters
    The determination of free Zn2+ ion concentration is a key in the study of environmental systems like river water and soils, due to its impact on bioavailability and toxicity. AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) and DMT (Donnan Membrane Technique) are emerging techniques suited for the determination of free heavy metal concentrations, especially in the case of Zn2+, given that there is no commercial Ion Selective Electrode. In this work, both techniques have been applied to synthetic samples (containing Zn and NTA) and natural samples (Rhine river water and soils), showing good agreement. pH fluctuations in DMT and N2/CO2 purging system used in AGNES did not affect considerably the measurements done in Rhine river water and soil samples. Results of DMT in situ of Rhine river water are comparable to those of AGNES in the lab. The comparison of this work provides a cross-validation for both techniques.
    Olivine Weathering in Soil, and Its Effects on Growth and Nutrient Uptake in Ryegrass (lolium perenne L.): A Pot Experiment
    Berge, H.F.M. ten; Meer, H.G. van der; Steenhuizen, J.W. ; Goedhart, P.W. ; Knops, P. ; Verhagen, J. - \ 2012
    PLoS ONE 7 (2012)8. - ISSN 1932-6203
    carbon-dioxide - plant - bioavailability - sequestration - phytotoxicity - serpentine - nickel - co2 - speciation - models
    Mineral carbonation of basic silicate minerals regulates atmospheric CO2 on geological time scales by locking up carbon. Mining and spreading onto the earth's surface of fast-weathering silicates, such as olivine, has been proposed to speed up this natura
    Age structure in neutral theory resolves inconsistencies related to reproductive size threshold
    Rosindell, J. ; Jansen, P.A. ; Etienne, R.S. - \ 2012
    Journal of Plant Ecology 5 (2012)1. - ISSN 1752-9921 - p. 64 - 71.
    species-area relationships - biodiversity - speciation - model - biogeography - limitation - dispersal - diversity - abundance - forests
    Neutral theory consists of a suite of models that assume ecological equivalence among individual organisms. They have been most commonly applied to tropical forest tree communities either as null models or as approximations. Neutral models typically only include reproductive adults; therefore, fitting to empirical tree community data requires defining a reproductive-size threshold, which for trees is usually set arbitrarily to a diameter at breast height (DBH) of 100 mm. The inevitable exclusion of some reproductive adults and inclusion of some saplings cause a non-random sampling bias in neutral model fits. Here, we investigate this problem and resolve it by introducing simple age structure into a neutral model.
    Environmental Selenium Research: From Microscopic Processes to Global Understanding
    Winkel, L.H.E. ; Johnson, C.A. ; Lenz, M. ; Grundl, T. ; Leupin, O.X. ; Amini, M. ; Charlet, L. - \ 2012
    Environmental Science and Technology 46 (2012)2. - ISSN 0013-936X - p. 571 - 579.
    plasma-mass spectrometry - icp-ms - arsenic contamination - agricultural soils - sewage-sludge - speciation - se - chromatography - groundwater - metabolism
    Selenium is a natural trace element that is of fundamental importance to human health. The extreme geographical variation in selenium concentrations in soils and food crops has resulted in significant health problems related to deficient or excess levels of selenium in the environment. To deal with these kinds of problems in the future it is essential to get a better understanding of the processes that control the global distribution of selenium. The recent development of analytical techniques and methods enables accurate selenium measurements of environmental concentrations, which will lead to a better understanding of biogeochemical processes. This improved understanding may enable us to predict the distribution of selenium in areas where this is currently unknown. These predictions are essential to prevent future Se health hazards in a world that is increasingly affected by human activities.
    Hg transfer from contaminated soils to plants and animals
    Rodrigues, S.M. ; Henriques, B. ; Reis, A.T. ; Duarte, A.C. ; Pereira, E. ; Romkens, P.F.A.M. - \ 2012
    Environmental Chemistry Letters 10 (2012)1. - ISSN 1610-3653 - p. 61 - 67.
    potentially toxic elements - chloralkali plant - available pools - total mercury - part ii - speciation - transport - portugal - slovenia - samples
    Understanding the transfer of mercury (Hg) from soil to crops is crucial due to Hg toxicity and Hg occurrence in terrestrial systems. Previous research has shown that available Hg in soils contributes to plant Hg levels. Plant Hg concentrations are related to soil conditions and plant characteristics. Mechanistic models describing such soil–plant interactions are however difficult to quantify. Here we performed a field study in agricultural, mining and industrial areas in Portugal to evaluate potential food chain risks. The uptake of Hg by Italian ryegrass, ryegrass, orchard grass, collard greens and rye was measured to calculate daily intakes (DI) of Hg for cows and sheep grazing. A total of 136 soil samples and 129 plant samples were analysed. Results show that total Hg concentrations ranged from 0.01 to 98 mg kg-1 in soils; 0.01–5.4 mg kg-1 in shoots and 0.01–42 mg kg-1 in roots. Calculated DI ranged from 0.18 to 132 mg d-1 for cows, and from 0.028 to 23 mg d-1 for sheep. In 27 grassland sites, daily intakes exceeded the acceptable daily intake of both cows and sheep in view of food safety considering Hg in animal kidneys evidencing potential risks to human health. The transfer of Hg from soil to crops was described using empirical Freundlich-type functions. For ryegrass, orchard grass and collard greens, the soil-to-root or soil-to-shoot transfer of Hg appeared to be controlled by the total soil Hg concentration and levels of Alox and Feox. Empirical functions allowed us to obtain realistic estimates of Hg levels in crops and can be used as an alternative to mechanistic models when evaluating food chain risks of Hg contamination in agricultural soils.
    Pyrrolizidine alkaloid variation in shoots and roots of segregating hybrids between Jacobaea vulgaris and Jacobaea aquatica
    Cheng, D. ; Kirk, H. ; Mulder, P.P.J. ; Vrieling, K. ; Klinkhamer, P.G.L. - \ 2011
    New Phytologist 192 (2011)4. - ISSN 0028-646X - p. 1010 - 1023.
    senecionine n-oxide - british-isles - natural hybridization - plant hybridization - chemical diversity - tyria-jacobaeae - asteraceae - speciation - evolution - translocation
    Hybridization can lead to novel qualitative or quantitative variation of secondary metabolite (SM) expression that can have ecological and evolutionary consequences.•We measured pyrrolizidine alkaloid (PA) expression in the shoots and roots of a family including one Jacobaea vulgaris genotype and one Jacobaea aquatica genotype (parental genotypes), two F1 hybrid genotypes, and 102 F2 hybrid genotypes using liquid chromatography–tandem mass spectrometry (LC-MS/MS).•We detected 37 PAs in the roots and shoots of J. vulgaris, J. aquatica and the hybrids. PA concentrations and compositions differed between genotypes, and between roots and shoots. Three otosenine-like PAs that only occurred in the shoots of parental genotypes were present in the roots of F2 hybrids; PA compositions were sometimes novel in F2 hybrids compared with parental genotypes, and in some cases transgressive PA expression occurred. We also found that PAs from within structural groups covaried both in the roots and in the shoots, and that PA expression was correlated between shoots and roots.•Considerable and novel variation present among F2 hybrids indicates that hybridization has a potential role in the evolution of PA diversity in the genus Jacobaea, and this hybrid system is useful for studying the genetic control of PA expression
    Unraveling the rapid radiation of crested newts, Triturus cristatus superspecies, using complete mitogenomic sequences
    Wielstra, B.M. ; Arntzen, J.W. - \ 2011
    BMC Evolutionary Biology 11 (2011). - ISSN 1471-2148 - 8 p.
    complete mitochondrial genomes - historical biogeography - phylogenetic analysis - mixed models - dna - salamandridae - phylogeography - nuclear - mtdna - speciation
    Background - The rapid radiation of crested newts (Triturus cristatus superspecies) comprises four morphotypes: 1) the T. karelinii group, 2) T. carnifex - T. macedonicus, 3) T. cristatus and 4) T. dobrogicus. These vary in body build and the number of rib-bearing pre-sacral vertebrae (NRBV). The phylogenetic relationships of the morphotypes have not yet been settled, despite several previous attempts, employing a variety of molecular markers. We here resolve the crested newt phylogeny by using complete mitochondrial genome sequences. Results - Bayesian inference based on the mitogenomic data yields a fully bifurcating, significantly supported tree, though Maximum Likelihood inference yields low support values. The internal branches connecting the morphotypes are short relative to the terminal branches. Seen from the root of Triturus (NRBV = 13), a basal dichotomy separates the T. karelinii group (NRBV = 13) from the remaining crested newts. The next split divides the latter assortment into T. carnifex - T. macedonicus (NRBV = 14) versus T. cristatus (NRBV = 15) and T. dobrogicus (NRBV = 16 or 17). Conclusions - We argue that the Bayesian full mitochondrial DNA phylogeny is superior to previous attempts aiming to recover the crested newt species tree. Furthermore, our new phylogeny involves a maximally parsimonious interpretation of NRBV evolution. Calibrating the phylogeny allows us to evaluate potential drivers for crested newt cladogenesis. The split between the T. karelinii group and the three other morphotypes, at ca. 10.4 Ma, is associated with the separation of the Balkan and Anatolian landmasses (12-9 Ma). No currently known vicariant events can be ascribed to the other two splits, first at ca. 9.3 Ma, separating T. carnifex - T. macedonicus, and second at ca. 8.8 Ma, splitting T. cristatus and T. dobrogicus. The crested newt morphotypes differ in the duration of their annual aquatic period. We speculate on the role that this ecological differentiation could have played during speciation
    The contribution of organic and mineral colloidal nanoparticles to element transport in a podzol soil.
    Regelink, I.C. ; Weng, L.P. ; Riemsdijk, W.H. van - \ 2011
    Applied Geochemistry 26 (2011)Suppl.. - ISSN 0883-2927 - p. S241 - S244.
    field-flow fractionation - montmorillonite - competition - separation - adsorption - speciation - water - fe
    The aim of this work is to analyze the size-distribution and composition of nanoparticles in a water-extract of a podzol B horizon. AsFlowFFF coupled to ICP–MS and a UV/VIS detector was used for particle fractionation and simultaneous measurement of the composition of the nanoparticles. Detected nanoparticles were organic and mineral particles; the mineral particles were dominated by clay and Fe-(hydr)oxides. Both organic- and inorganic particles contributed to the mobility of Fe, Al, trace metals and P. For Zn, Pb and P respectively 73%, 92% and 72% of the colloidal concentrations were associated with clay minerals. The large contribution of clay particles to the mobility of trace metals and P can be partly explained by the high amount of dispersed clay due to drying, sieving and rewetting of the soil. Inorganic nanoparticles can contribute significantly to the mobility of metals and P in soils.
    Transfer functions for solid solution partitioning of cadmium for Australian soils
    Vries, W. de; Mc Laughlin, M.J. ; Groenenberg, J.E. - \ 2011
    Environmental Pollution 159 (2011)12. - ISSN 0269-7491 - p. 3583 - 3594.
    metal-ion activities - contaminated soils - humic substances - organic-matter - heavy-metals - surface waters - fresh-waters - pore-water - copper - speciation
    To assess transport and ecotoxicological risks of metals, such as cadmium (Cd) in soils, models are needed for partitioning and speciation. We derived regression-based “partition-relations” based on adsorption and desorption experiments for main Australian soil types. First, batch adsorption experiments were carried out over a realistic range of dissolved Cd concentrations in agricultural soils in Australia. Results showed linear sorption relationships, implying the adequacy of using Kd values to describe partitioning. Desorption measurements were then carried out to assess in-situ Kd values and relate these to soil properties The best transfer functions for solid–solution partitioning were found for Kd values relating total dissolved Cd concentration to total soil Cd concentrations, accounting for the variation in pH, SOM contents and DOC concentrations. Model predictions compared well with measurements of an independent data set, but there was a tendency to underestimate dissolved Cd concentrations of highly polluted soils.
    Using advanced surface complexation models for modelling soil chemistry under forests: Solling forest, Germany
    Bonten, L.T.C. ; Groenenberg, J.E. ; Vries, W. de - \ 2011
    Environmental Pollution 159 (2011)10. - ISSN 0269-7491 - p. 2831 - 2839.
    acid deposition - heavy-metals - hydraulic conductivity - contaminated soils - atmosphere models - ion-binding - speciation - ecosystems - water - acidification
    Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well.
    Bioavailability pathways underlying zinc-induced avoidance behavior and reproduction toxicity in Lumbricus rubellus earthworms.
    Ma, W.C. ; Bonten, L.T.C. - \ 2011
    Ecotoxicology and Environmental Safety 74 (2011)6. - ISSN 0147-6513 - p. 1721 - 1726.
    metal accumulation - organic-matter - eisenia-andrei - contaminated field - heavy-metals - soils - copper - ph - speciation - calcium
    We investigated possible bioavailability pathways underlying zinc-induced avoidance behavior and sublethal reproduction impairment in Lumbricus rubellus. Clay-loam (pH 7.3) and sandy soil (three pH values of 4.3–6.0) were amended with zinc sulfate at six soil concentrations of total Zn ranging from 0.1 to 36 mmol/kg dw. Estimated and measured concentrations of free and exchangeable Zn ranged 10-4 to 7.1 mmol/l. Avoidance behavior responses were fast and could be directly predicted from the activity of free zinc ions without a modifying pH effect. The repellent effect is thus likely mediated by a direct action of Zn2+ ions on epidermal chemosensitive receptors. Body zinc uptake, however, was determined by proton competition with free Zn2+ sorption. Excess accumulation of body Zn was a good predictor of reproduction decline, which is indicative of internal zinc poisoning. The results indicated that zinc affects earthworms via both direct and indirect mechanisms of external and internal exposure.
    Sulfate reduction during the acidification of sucrose at pH 5 under thermophilic (55 degrees C) conditions. I: Effect of trace metals
    Lopes, S.I.C. ; Capela, M.I. ; Lens, P.N.L. - \ 2010
    Bioresource Technology 101 (2010)12. - ISSN 0960-8524 - p. 4269 - 4277.
    anaerobic granular sludge - desulfovibrio-desulfuricans - waste-water - inhibition - speciation - toxicity - degradation - 8-degrees-c - reactors - methanol
    This work studied the effect of supplying trace metals (7.5 mu M Fe and 0.5 mu M Co, Ni, Mn, Zn, Cu, B, Se, Mo and W) on sulfate reduction and acidification in thermophilic (55 degrees C) UASB reactors fed with sucrose (4 gCOD (I-reactor d)(-1)) operated at a reactor mixed liquor pH controlled at 5. Trace metals were supplied to one UASB reactor and were omitted from the influent of a second UASB reactor. The influence of different trace metal concentrations was further assessed in batch tests performed with the sludge from the UASB reactor receiving no trace metals. The absence of trace metals in the influent did not affect the performance of the acidifying UASB reactor throughout the 305 day long reactor run, but supplying low concentrations of trace metals inhibited sulfate reduction.
    Evaluation of an approach for the characterization of reactive and available pools of 20 potentially toxic elements in soils: Part II – Solid-solution partition relationships and ion activity in soil solutions
    Rodrigues, S.M. ; Henriques, B. ; Ferreira da Silva, E. ; Pereira, M.E. ; Duarte, A.C. ; Groenenberg, J.E. ; Romkens, P.F.A.M. - \ 2010
    Chemosphere 81 (2010)11. - ISSN 0045-6535 - p. 1560 - 1570.
    organic-matter - contaminated soils - heavy-metals - trace-elements - speciation - extraction - copper - adsorption - mercury - field
    To assess environmental risks related to contaminants in soil it is essential to predict the available pool of inorganic contaminants at regional scales, accounting for differences between soils from variable geologic and climatic origins. An approach composed of a well-accepted soil extraction procedure (0.01 M CaCl2) and empirical Freundlich-type models in combination with mechanistically based models which to date have been used only in temperate regions was applied to 136 soils from a South European area and evaluated for its possible general use in risk assessment. Empirical models based on reactive element pools and soil properties (pH, organic carbon, clay, total Al, Fe and Mn) provided good estimations of available concentrations for a broad range of contaminants including As, Ba, Cd, Co, Cu, Hg, Mo, Ni, Pb, Sb, Se and Zn (r2: 0.46–0.89). The variation of the pools of total Al in soils expressed the sorptive capacity of aluminosilicates and Al oxides at the surfaces and edges of clay minerals better than the actual variability of clay contents. The approach has led to recommendations for further research with particular emphasis on the impact of clay on the solubility of As and Sb, on the mechanisms controlling Cr and U availability and on differences in binding properties of soil organic matter from different climatic regions. This study showed that such approach may be included with a good degree of certainty for first step risk assessment procedures to identify potential risk areas for leaching and uptake of inorganic contaminants in different environmental settings.
    Evaluation of an approach for the characterization of reactive and available pools of twenty potentially toxic elements in soils: Part I – The role of key soil properties in the variation of contaminants’ reactivity
    Rodrigues, S.M. ; Henriques, B. ; Ferreira da Silva, E. ; Pereira, M.E. ; Duarte, A.C. ; Romkens, P.F.A.M. - \ 2010
    Chemosphere 81 (2010)11. - ISSN 0045-6535 - p. 1549 - 1559.
    iberian pyrite belt - heavy-metals - acid soils - organic-matter - trace-elements - mercury - extraction - sediments - desorption - speciation
    Harmful effects of potentially toxic elements (PTE’s) in soils relate to their geochemically reactive fraction. To assess the degree of the reactivity, specific extractions or models are needed. Here we applied a 0.43 M HNO3 chemical extraction to assess reactive pools of a broad range of PTE’s in 136 contaminated and non-contaminated soils. Furthermore we derived Freundlich-type models based on commonly available soil properties (pH, organic carbon and clay) as well as extended models that used other properties such as amorphous Al and Fe oxides and evaluated their possible use in risk assessment. The approach allowed to predict the reactivity of As, Hg, Co, U, Ba, Se, Sb, Mo, Li, Be (r2: 0.55–0.90) elements not previously included in such studies, as well as that of Cd, Zn, Cu, Pb, Ni and Cr (r2: 0.73–0.90). The inclusion of pH, organic carbon and clay improved the performance of all models except for Be and Mo, although the role of clay is not completely clear and requires further investigation. The ability of amorphous metal oxides to affect the reactivity of As, Hg, Cu, Ni, Cr, Sb, Mo and Li was expressed by the models in agreement with known geochemical processes leading to the retention of PTE’s by the solid matrix. Hence, such approach can be a useful tool to account for regional differences in soil properties during the identification of risk areas and constitute a significantly more powerful tool than the analysis of total pools of PTE’s in soils.
    Assessment of in situ immobilization of Lead (Pb) and Arsenic (As) in contaminated soils with phosphate and iron: solubility and bioaccessibility
    Cui, Y.S. ; Du, X. ; Weng, L.P. ; Riemsdijk, W.H. van - \ 2010
    Water Air and Soil Pollution 213 (2010)1-4. - ISSN 0049-6979 - p. 95 - 104.
    competitive interaction - amendments - bioavailability - phosphorus - stabilization - speciation - cement - china - adsorption - extraction
    The effect of in situ immobilization of lead (Pb) and arsenic (As) in soil with respectively phosphate and iron is well recognized. However, studies on combined Pb and As-contaminated soil are fewer, and assessment of the effectiveness of the immobilization on mobility and bioaccessibility is also necessary. In this study, a Pb and As-contaminated soil was collected from an abandoned lead/zinc mine in Shaoxing, Zhejiang province of China, which has been treated with three phosphates, i.e., calcium magnesium phosphate (CMP), phosphate rock, and single super-phosphate (SSP) for 6 months in a field study. The ferrous sulfate (FeSO4) at 20 g kg-1 was then amended to the soil samples and incubated for 8 weeks in a greenhouse. The solubility and bioaccessibility tests were used to assess the effectiveness of the in situ immobilization. The result showed that phosphates addition decreased the concentrations of CaCl2-extractable Pb; however, the concentrations of water-soluble As increased upon CMP and SSP addition. With the iron addition, the water-soluble As concentrations decreased significantly, but CaCl2-extractable Pb concentrations increased. The bioaccessibility of As and Pb measured in artificial gastric and small intestinal solutions decreased with phosphate and iron application except for the bioaccessibility of As in the gastric phase with SSP addition. Combined application of phosphates and iron can be an effective approach to lower bioaccessibility of As and Pb, but has opposing effects on mobility of As and Pb in contaminated soils
    Enrichment of the African catfish Clarias gariepinus (Burchell) with functional selenium originating from garlic: effect of enrichment period and depuration on total selenium level and sensory properties
    Schram, E. ; Schelvis-Smit, A.A.M. ; Heul, J.W. van der; Luten, J.B. - \ 2010
    Aquaculture Research 41 (2010)6. - ISSN 1355-557X - p. 793 - 803.
    fatty-acid-composition - oil finishing diet - cancer prevention - fish-oil - speciation
    We wanted to optimize the procedure for the selenium enrichment of farmed African catfish, using garlic as dietary selenium source. In the first experiment we established the relation between the length of the selenium enrichment period and the resulting total selenium level in the fillet of the fish. It was found that at a dietary level of 11.7 mg kg-1 Se, a total selenium level in the fillet of 0.7 mg kg-1 was reached in a relatively short enrichment period of 10 days before harvest. In the second experiment we studied the effect of depuration on the selenium level in the fillet and the sensory properties of selenium-enriched African catfish. It was found that total selenium levels in the fillet were not affected during a 7-day depuration period, while garlic odours and flavours in the raw and cooked fillets were significantly reduced after 2 days of depuration. We concluded that selenium enrichment of farmed African catfish can be obtained by selenium-enriched finishing diets, while garlic odours and flavours resulting from dietary garlic can be effectively reduced in the fillet during a short depuration period without negatively affecting fillet levels of total selenium.
    Modelling ion composition in simulated milk ultrafiltrate (SMUF). I: Influence of calcium phosphate precipitation.
    Gao, R. ; Halsema, F.E.D. van; Temminghoff, E.J.M. ; Leeuwen, H.P. van; Valenberg, H.J.F. van; Eisner, M.D. ; Giesbers, M. ; Boekel, M.A.J.S. van - \ 2010
    Food Chemistry 122 (2010)3. - ISSN 0308-8146 - p. 700 - 709.
    donnan membrane technique - salt solution - ph - 50-degrees-c - equilibria - speciation - additives
    Freshly prepared simulated milk ultrafiltrate (SMUF) is a solution that is supersaturated with respect to various calcium phosphate phases that precipitate in time. As a consequence, the ion composition of equilibrated SMUF was found to be significantly different from that of freshly prepared SMUF. This study proposes a thermodynamic ion-speciation model that is able to describe ion equilibria in SMUF. Moreover, it is also able to describe calcium phosphate precipitation in fresh SMUF on its way to equilibrium by using an apparent solubility product for CaHPO4·2H2O as a function of time. The model was validated by experiments in which CaCl2 and Na2HPO4 were added to freshly prepared SMUF. The changes in calcium activity and pH were followed and the precipitates were characterised by X-ray diffraction. The model was able to predict the observed changes
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