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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Effects of iron, calcium, and organic matter on phosphorus behavior in fluvo-aquic soil: farmland investigation and aging experiments
Ma, Yuling ; Ma, Jie ; Peng, Hao ; Weng, Liping ; Chen, Yali ; Li, Yongtao - \ 2019
Journal of Soils and Sediments (2019). - ISSN 1439-0108
Calcium carbonate - Fe mineral - Fluvo-aquic soil - Organic fertilizer - Phosphorus fractions - Phosphorus immobilization

Purpose: Excessive fertilization has led to a high risk of phosphorus (P) leaching and related problems in the North China Plain, where the most typical cropland soil is fluvo-aquic soil. The main factors controlling environmental P behavior and the acting time sequence of these factors in soil after long-term P fertilizer application have not been well recognized. A clear understanding is essential for effective P management. Materials and methods: Effects of Fe minerals, calcium carbonate, and organic matter (OM) on P immobilization in fluvo-aquic soil were studied systematically through farmland investigation and aging experiments. Results and discussion: Phosphorus associated with Ca was the primary fraction in fluvo-aquic soil. Even though there was no significant correlation between the total contents of P and Ca in soils, formation of P-Ca phases facilitated by Ca2+ in soil solution was a mechanism of P retention when soil received excess P fertilizer. Positive correlations between the contents of P and Fe and total organic carbon (TOC) indicate that Fe minerals and OM have significant effects on P immobilization. Through the aging experiments, P was found to primarily adsorb on goethite and gradually forms Ca-P compounds. Organic fertilizer caused P release and inhibition of P adsorption in the initial stages; however, OM derived from organic fertilizer might facilitate P immobilization in the long term through the formation of a P-Ca-OM complex. Conclusions: Although superfluous application of P fertilizers leads to the gradual formation of Ca-P in fluvo-aquic soils, there is still a risk of P loss because P is not immediately adsorbed by Fe minerals. Moreover, application of organic fertilizers increases the risk of P loss. These results provide an important scientific basis for initiating P management policies for fluvo-aquic soils.

Plastome based phylogenetics and younger crown node age in Pelargonium
Kerke, Sara J. van de; Shrestha, Bikash ; Ruhlman, Tracey A. ; Weng, Mao Lun ; Jansen, Robert K. ; Jones, Cynthia S. ; Schlichting, Carl D. ; Hosseini, Samin ; Mohammadin, Setareh ; Schranz, M.E. ; Bakker, Freek T. - \ 2019
Molecular Phylogenetics and Evolution 137 (2019). - ISSN 1055-7903 - p. 33 - 43.
Geraniaceae - Pelargonium - Phylogeny - Plastome - Time-calibrated

The predominantly South-African plant genus Pelargonium L'Hér. (Geraniaceae) displays remarkable morphological diversity, several basic chromosome numbers as well as high levels of organelle genomic rearrangements, and represents the 7th largest Cape Floristic Region clade. In this study, we reconstructed a phylogenetic tree based on 74 plastome exons and nuclear rDNA ITS regions for 120 species, which represents 43% taxon coverage for Pelargonium. We also performed a dating analysis to examine the timing of the major radiations in the genus. Phylogenetic analyses of nucleotide, amino acid, and ITS alignments confirmed the previously-documented subgeneric split into five main clades ((C1,C2),(B(A1,A2))) although clade only A1 received low bootstrap support. Using calibration evidence from a range of sources the Pelargonium crown age was estimated to be 9.7 My old, much younger than previous estimates for the genus but similar to recent studies of other Cape Floristic lineages that are part of both Fynbos and Succulent Karoo biomes.

Understanding major NOM properties controlling its interactions with phosphorus and arsenic at goethite-water interface
Deng, Yingxuan ; Weng, Liping ; Li, Yongtao ; Ma, Jie ; Chen, Yali - \ 2019
Water Research 157 (2019). - ISSN 0043-1354 - p. 372 - 380.
Adsorption - Arsenate - Arsenite - Natural organic matter - Phosphate - Surface complexation model

Among natural organic matter (NOM), oxyanions and metal (hydr)oxides, a complicated interaction exists in natural aquatic and terrestrial systems and in waste waters. Effects of seven types of NOM (four humic acids (HA), three fulvic acids (FA)) that vary in properties on the adsorption of oxyanions, including phosphate, arsenate and arsenite, at goethite-water interface were quantitatively studied. Results show that the adsorption of oxyanions to goethite is decreased by the presence of NOM, especially for phosphate and arsenate at low pH. In general, the effects of the three FA are similar, which are more effective than HA in reducing oxyanion adsorption at low pH (<6). Differences were observed between the four HA in their competition with oxyanions. The adsorption of phosphate, arsenate and arsenite in the presence of NOM are well described with both the NOM-CD (CD: Charge Distribution) and LCD (Ligand and Charge Distribution) model. The NOM-CD model is relatively simple to use, whereas the LCD model can better reveal different factors in the interaction, including the spatial distribution of adsorbed NOM on oxide surface. According to these two models: site density of carboxylic groups, protonation constant of carboxylic groups, and particle size of NOM are major properties of NOM determining its effect on oxyanion adsorption to oxides. At relatively low loadings, morphological change of adsorbed NOM takes place, and the degree of morphological change of adsorbed NOM depends on the particle size, site density of carboxylic groups and aromaticity of NOM. The influence of particle size on the interaction becomes more important at higher NOM loadings. The results suggested that the fixation or removal efficiency of phosphate, arsenate and arsenite with iron oxides (e.g. goethite) can be significantly decreased by the presence of NOM, especially when NOM rich in acidic and aromatic groups.

Using chromatographic and spectroscopic parameters to characterize preference and kinetics in the adsorption of humic and fulvic acid to goethite
Wang, Long ; Li, Yongtao ; Weng, Liping ; Sun, Yang ; Ma, Jie ; Chen, Yali - \ 2019
Science of the Total Environment 666 (2019). - ISSN 0048-9697 - p. 766 - 777.
Fulvic acid - Humic acid - Kinetics - Oxide minerals - Preferential adsorption - Replacement

Humic substances (HS) are very heterogeneous, and preferential adsorption of certain components takes place during their interaction with minerals. Our results indicated that for fulvic acid (FA) the relatively large (3.6–18.2 kDa) particles were preferred in the adsorption to goethite, whereas for humic acid (HA) the intermediate sized (3.6–12.0 kDa) fractions were preferred. Correlations between molar mass (M w ) and specific UV absorption values (SUVA) with ratios of UV light absorbance (E 2 /E 3 , E 4 /E 6 ) were observed. The adsorption did not change the relation between E 2 /E 3 and M w , E 4 /E 6 and SUVA. The E 2 /E 3 and E 4 /E 6 can probably be used as indicators of molar mass and aromaticity of HS in studying the preferential adsorption. The adsorption of HA and FA to goethite was fast and reached a steady state in about 6 h. The intermediate sized HA particles (3.6–12.0 kDa) were adsorbed quickly, and part of them was subsequently replaced by somewhat larger particles (>50 kDa). For FA, preferential adsorption of relative large particles (3.6–18.2 kDa) took place quickly, and there was a limited substitution by particles with higher aromaticity. Without specifying the property especially the molar mass range of HS under study, confusion can arise from researches using different HS materials.

A common genetic mechanism underlies morphological diversity in fruits and other plant organs
Wu, Shan ; Zhang, Biyao ; Keyhaninejad, Neda ; Rodríguez, Gustavo R. ; Kim, Hyun Jung ; Chakrabarti, Manohar ; Illa-Berenguer, Eudald ; Taitano, Nathan K. ; Gonzalo, M.J. ; Díaz, Aurora ; Pan, Yupeng ; Leisner, Courtney P. ; Halterman, Dennis ; Buell, C.R. ; Weng, Yiqun ; Jansky, Shelley H. ; Eck, Herman van; Willemsen, Johan ; Monforte, Antonio J. ; Meulia, Tea ; Knaap, Esther van der - \ 2018
Nature Communications 9 (2018)1. - ISSN 2041-1723

Shapes of edible plant organs vary dramatically among and within crop plants. To explain and ultimately employ this variation towards crop improvement, we determined the genetic, molecular and cellular bases of fruit shape diversity in tomato. Through positional cloning, protein interaction studies, and genome editing, we report that OVATE Family Proteins and TONNEAU1 Recruiting Motif proteins regulate cell division patterns in ovary development to alter final fruit shape. The physical interactions between the members of these two families are necessary for dynamic relocalization of the protein complexes to different cellular compartments when expressed in tobacco leaf cells. Together with data from other domesticated crops and model plant species, the protein interaction studies provide possible mechanistic insights into the regulation of morphological variation in plants and a framework that may apply to organ growth in all plant species.

CD-MUSIC-EDL modeling of Pb2+ adsorption on birnessites : Role of vacant and edge sites
Zhao, Wei ; Tan, Wenfeng ; Wang, Mingxia ; Xiong, Juan ; Liu, Fan ; Weng, Liping ; Koopal, Luuk K. - \ 2018
Environmental Science and Technology 52 (2018)18. - ISSN 0013-936X - p. 10522 - 10531.
adsorption - Birnessite - CD-MUSIC Modeling - Electrical double layer model - External surface - Interlayer space - Manganese oxide - Mn average oxidation state - Pb - Rietveld refinement

The surface complexation modeling of metal adsorption to birnessites is in its infancy compared to the charge-distribution multi-site ion complexation (CD-MUSIC) models for iron/aluminum (hydr)oxides. Therefore, using X-ray diffraction with Rietveld refinement to obtain the reactive sites and their densities, a CD-MUSIC model combined with a Stern-Gouy-Chapman electrical double layer (EDL) model for the external surface and a Donnan model for the interlayer surface is developed for birnessites with different Mn average oxidation state (MnAOS). Proton affinity constants and the charge distributions of Pb surface complexes were calculated a priory. By fitting Pb adsorption data to the model the obtained equilibrium constants (logKPb) of Pb complexes were 6.9-10.9 for the double-corner-sharing and double-edge-sharing Pb2+ complexes on the edge sites and 2.2-6.5 for the triple-corner-sharing Pb2+ complex on the vacancies. The larger logKPb value was obtained for higher MnAOS. Speciation calculations showed that with increasing MnAOS from 3.67 to 3.92 the interlayer surface contribution to the total Pb2+ adsorption increased from 43.2% to 48.6%, and the vacancy contribution increased from 43.9% to 54.7%. The vacancy contribution from interlayer surface was predominant. The present CD-MUSIC-EDL model contributes to understand better the difference in metal adsorption mechanism between birnessite and iron/aluminum (hydr)oxides.

Effects of natural organic matter with different properties on levofloxacin adsorption to goethite : Experiments and modeling
Qin, Xiaopeng ; Du, Ping ; Chen, Juan ; Liu, Fei ; Wang, Guangcai ; Weng, Liping - \ 2018
Chemical Engineering Journal 345 (2018). - ISSN 1385-8947 - p. 425 - 431.
Fluoroquinolone - Fulvic acid - Goethite - Humic acid - Hydrophobic interactions - Specific ultraviolet absorbance
Adsorption of levofloxacin (LEV) to goethite in the pH range of 3–10, and in the absence or presence of natural organic matter (NOM) represented by nine types of humic acid (HA) and fulvic acid (FA), was studied using batch experiments. The adsorption of LEV to goethite was weak and showed a maximum around pH 5.8. Adding NOM to goethite strongly increased LEV adsorption to goethite, but hardly affected its pH dependency. The adsorption envelopes were well fitted to a linear additive model, in which LEV adsorption to goethite was simulated with the Charge Distribution Multi-Site Complexation (CD-MUSIC) model, and LEV adsorption to NOM was simulated with the Langmuir model. The fitted affinity constants (log K) for LEV adsorption to NOM were significantly and positively correlated with the SUVA (specific ultraviolet absorbance at 280 nm) values of NOM, and negatively correlated with E2/E3 (absorbance ratio at 250 nm and 365 nm) values, carboxyl contents, and the polarity of NOM. The results indicated that aromatic moieties of NOM play a key role in the interactions between LEV and NOM, and hydrophobic interactions and π-π interactions were the major mechanisms for LEV adsorption to NOM, whereas H-bond or surface complexation might not play an important role. Results show that both the concentrations and properties of NOM have a significant effect on the distribution or treatment of antibiotics in soils and waters, which will eventually affect the influence of antibiotics on microorganisms in the environmental systems.
Modes of selenium occurrence and LCD modeling of selenite desorption/adsorption in soils around the selenium-rich core, Ziyang County, China
Zhang, Yu ; Wu, Siyuan ; Zheng, Hong ; Weng, Liping ; Hu, Yajie ; Ma, Hongwen - \ 2018
Environmental Science and Pollution Research 25 (2018)15. - ISSN 0944-1344 - p. 14521 - 14531.
Desorption/adsorption - High-Se soils - LCD modeling - Modes of selenium occurrence - Selenium-rich core - Ziyang County
Studying the modes of selenium occurrence in high-Se soils and its behaviors can improve understanding and evaluating its cycling, flux, and balance in geo-ecosystems and its influence on health. In this paper, using a modified sequential chemical extraction technique, seven operationally defined selenium fractions and Se valence distribution were determined about five soils in which paddy was planted (W1, W2, W3, W4, W5) and five soils in which maize was planted (H1, H2, H3, H4, H5) around the selenium-rich core, Ziyang County, Shaanxi Province, China. The results show that selenium fractions in the soils mainly include sulfide/selenide and base-soluble Se, and ligand-exchangeable Se is also high for five soils in which paddy was planted. For water-soluble Se, Se (IV) is main Se valence and almost no Se (VI) was determined about five soils in which paddy was planted, while almost 1:1 of Se (IV) and Se (VI) coexist about five soils in which maize was planted. For exchangeable Se, similar results were found. For the first time, two typical high-Se soils (W1 soil and H1 soil) were chosen to measure the pH-dependent solid-solution distribution of selenite in the pH range 3–9, and the results were explained using LCD (ligand and charge distribution) adsorption modeling. The desorbed selenite concentrations from the two soils are in general underestimated by the model due to a comparable binding affinity of phosphate and selenite on goethite and much lower amount of total selenite than total reactively adsorbed phosphate. The pH dependency of adsorption of selenite added to the soil can be successfully described with the LCD model for W1 soil. Whereas considering the influence of Al-oxides, by lowering selenite adsorption affinity constant K of Se adsorption on goethite by 16 times, the LCD model can describe the adsorption much better. The results can help to understand selenium cycling, flux, and balance in typical high-Se soils.
Influence of calcium and phosphate on pH dependency of arsenite and arsenate adsorption to goethite
Deng, Yingxuan ; Li, Yongtao ; Li, Xiaojing ; Sun, Yang ; Ma, Jie ; Lei, Mei ; Weng, Liping - \ 2018
Chemosphere 199 (2018). - ISSN 0045-6535 - p. 617 - 624.
Adsorption - Arsenic - CD-MUSIC - Modeling - Multi-component
In the environment, simultaneous presence of arsenic (As) of different oxidation states is common, which hampers our understanding of As behavior. In the current study, the pH dependency of arsenite (As(III)) and arsenate (As(V)) adsorption to goethite under the influence of calcium (Ca2+) (as a major cation) and phosphate (PO4 3−) (as a major anion) was studied, and the reliability of the CD-MUSIC model prediction was tested. The results show that the presence of the major ions led in general to a weaker and more complicated pH dependency of As adsorption. Calcium promoted As(V) adsorption especially at high pH, which can reverse the direction of the pH dependency. The presence of Ca2+ can even decrease As(III) adsorption when As(V) and/or PO4 3− are present. Phosphate competed strongly with both As(III) and As(V) in their adsorption, especially at intermediate and low pH. In the multi-component system, As(III) adsorbs weaker than As(V) over the environmental relevant pH range, therefore it is often the dominant As species in solution and soluble As(III) concentration generally decreases with increasing pH. In the same pH range, As(V) adsorption shows a complicated pH dependency. Soluble As(V) reaches a minimum around pH 6 at high concentration of major bivalent cations (e.g. Ca2+), whereas soluble As(V) will decrease with pH at low bivalent cation concentrations. The experimental results can be reliably predicted and explained with the CD-MUSIC model. The outcome of this study can provide understanding needed in the risk assessment and remediation of As contaminated soils and water.
Effect of Soil Fulvic and Humic Acids on Pb Binding to the Goethite/Solution Interface: Ligand Charge Distribution Modeling and Speciation Distribution of Pb
Xiong, Juan ; Weng, Liping ; Koopal, Luuk K. ; Wang, Mingxia ; Shi, Zhihua ; Zheng, Lirong ; Tan, Wenfeng - \ 2018
Environmental Science and Technology 52 (2018)3. - ISSN 0013-936X - p. 1348 - 1356.
The effect of adsorbed soil fulvic (JGFA) and humic acid (JGHA) on Pb binding to goethite was studied with the ligand charge distribution (LCD) model and X-ray absorption fine structure (XAFS) spectroscopy analysis. In the LCD model, the adsorbed small JGFA particles were evenly located in the Stern layer, but the large JGHA particles were distributed over the Stern layer and the diffuse layer, which mainly depended on the JGHA diameter and concentrations. Specific interactions of humic substances (HS) with goethite were modeled by inner-sphere complexes between the -FeOH 2 0.5+ of goethite and the -COO - of HS and by Pb bridges between surface sites and COO - groups of HS. At low Pb levels, nearly 100% of Pb was bound as Pb bridges for both JGFA and JGHA. At high Pb levels and low HS loading, Pb-goethite almost dominated over the entire studied pH range, but at high HS loading, the primary species was goethite-HS-Pb at acidic pH and goethite-Pb at alkaline pH. Compared with JGFA, there was a constant contribution of Pb bridges of about 10% for JGHA. The linear combination fit of EXAFS, using Pb-HS and Pb-goethite as references, indicated that with increased HS loading more Pb was bound to adsorbed HS and less to goethite, which supported the LCD calculations.
Cation accumulation leads to the electrode aging in soil microbial fuel cells
Li, Xiaojing ; Li, Yue ; Zhao, Xiaodong ; Weng, Liping ; Li, Yongtao - \ 2018
Journal of Soils and Sediments 18 (2018)3. - ISSN 1439-0108 - p. 1003 - 1008.
Cations accumulation - Electrode aging - Remediation and biosensors application - Soil microbial fuel cell
Purpose: The electrode aging in soil microbial fuel cells (MFCs) disturbed the removal of pollutants and sensitivity of electrophysiological signal. Therefore, surveying the causes of aging electrodes could assist to take the prevention measures for remediation and biosensor application of soil MFCs. Materials and methods: The surface morphology, element accumulation on the surface of electrodes, and element migration in soils between electrodes were investigated by scanning electronic microscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy in a constructed soil MFC. Results and discussion: The rust was observed on the anode, and the soil gypsification was noted on the cathode after a long-term (300-day) contribution of soil MFCs. The major elements (At%) Na and Ca in soils on two electrodes increased by 338–562 and 100–119%, respectively. Beside, Al and Fe of increment (24 and 21%) in the anode and Mg and Fe of augmenter (84 and 155%) in the cathode were detected. Conclusions: The stacking of Ca and Fe besides Na in soils adjacent to electrodes probably led to the electrode corrosion and soil gypsification on the surface of electrodes. Thus, the electrode aging of soil MFCs should be paid more attention in further applications.
Speciation of Zn, Fe, Ca and Mg in wine with the Donnan Membrane Technique
Lao, Mireia ; Companys, Encarnació ; Weng, Liping ; Puy, Jaume ; Galceran, Josep - \ 2018
Food Chemistry 239 (2018). - ISSN 0308-8146 - p. 1143 - 1150.
Absence of Gradients and Nernstian Equilibrium Stripping - Donnan Membrane Technique - Free metal - Iron - Wine - Zinc
Free concentrations of Zn2+, Fe3+, Ca2+ and Mg2+ in a red wine (Raimat, Catalonia, Spain) have been determined, with the Donnan Membrane Technique (DMT) for the first time. The required equilibration time benefits from the acceptor solution including major cations. K+ and Na+, mainly unbound to any ligand in the sample, have been identified as suitable reference ions. A free Zn concentration of 1.76 μmol L−1 determined with DMT was in excellent agreement with the free Zn concentration independently provided by the electroanalytical technique Absence of Gradients and Nernstian Equilibrium Stripping (AGNES), 1.7 μmol L−1, amounting to 14.4% of the total Zn. The free concentrations found in this wine were 1.79 μmol L−1 Fe3+, 1.11 mmol L–1 Ca2+ and 3.4 mmol L−1 Mg2+ (8.82%, 40% and 57% of their total concentrations). Prior to the application of the techniques to the red wine, they had been cross-validated in Zn-tartrate solutions.
Microbial Fuel Cells for Organic-Contaminated Soil Remedial Applications : A Review
Li, Xiaojing ; Wang, Xin ; Weng, Liping ; Zhou, Qixing ; Li, Yongtao - \ 2017
Energy Technology 5 (2017)8. - ISSN 2194-4288 - p. 1156 - 1164.
biocatalysis - electrochemistry - environmental chemistry - microbial fuel cells - soil remediation

Efficient noninvasive techniques are desired for repairing organic-contaminated soils. Bioelectrochemical technology, especially microbial fuel cells (MFCs), has been widely used to promote a polluted environmental remediation approach, and applications include wastewater, sludge, sediment, and soil remediation. Soil MFC remediation has been of significant concern in recent years, and thus, several aspects, including reactor configuration, electrode materials, soil conductivity, mass transfer, and microbial activity, are reviewed. Recent studies and key issues of soil MFCs and perspectives of organic-contamination remedial application are summarized, with the aim of assisting environmental scholars and engineers to gain a comprehensive understanding of MFC remediation. Insights are also offered on how to extend applications to help soil MFC remediation technology to advance and be applied in the future on a large scale.

Soil Functions in Earth's Critical Zone : Key Results and Conclusions
Banwart, S.A. ; Bernasconi, S.M. ; Blum, W.E.H. ; Souza, D.M. de; Chabaux, F. ; Duffy, C. ; Kercheva, M. ; Krám, P. ; Lair, G.J. ; Lundin, L. ; Menon, M. ; Nikolaidis, N. ; Novak, M. ; Panagos, P. ; Ragnarsdottir, K.V. ; Robinson, D.A. ; Rousseva, S. ; Ruiter, P. de; Gaans, P. van; Weng, L. ; White, T. ; Zhang, B. - \ 2017
Advances in Agronomy 142 (2017). - ISSN 0065-2113 - p. 1 - 27.
Critical zone - Ecosystem services - Soil - Soil functions - Water
This chapter summarizes the methods, results, and conclusions of a 5-year research project (SoilTrEC: Soil Transformations in European Catchments) on experimentation, process modeling, and computational simulation of soil functions and soil threats across a network of European, Chinese, and United States Critical Zone Observatories (CZOs). The study focused on the soil functions of biomass production, carbon storage, water storage and transmission, water filtration, transformation of nutrients, and maintaining habitat and genetic diversity.The principal results demonstrate that soil functions can be quantified as biophysical flows and transformations of material and energy. The functions can be simulated with mathematical models of soil processes within the soil profile and at the critical zone interfaces with vegetation and atmosphere, surface waters and the below-ground vadose zone and groundwater. A new dynamic model for soil structure development, together with data sets from the CZOs, demonstrate both seasonal fluctuations in soil structure dynamics related to vegetation dynamics and soil carbon inputs, and long-term trends (decadal) in soil carbon storage and soil structure development.Cross-site comparison for 20 soil profiles at seven field sites with variation in soil type, lithology, land cover, land use, and climate demonstrate that sites can be classified, using model parameter values for soil aggregation processes together with climatic conditions and soil physical properties, along a trajectory of soil structure development from incipient soil formation through productive land use to overly intensive land use with soil degradation.A new modeling code, the Integrated Critical Zone model, was applied with parameter sets developed from the CZO site data to simulate the biophysical flows and transformations that quantify multiple soil functions. Process simulations coupled the new model for soil structure dynamics with existing modeling approaches for soil carbon dynamics, nutrient transformations, vegetation dynamics, hydrological flow and transport, and geochemical equilibria and mineral weathering reactions. Successful calibration, testing, and application of the model with data sets from horticulture plot manipulation experiments demonstrate the potential to apply modeling and simulation to the scoping and design of new practices and policy options to enhance soil functions and reduce soil threats worldwide.
Selenium speciation and bioavailability in Dutch agricultural soils: the role of soil organic matter
Supriatin, Supriatin - \ 2016
Wageningen University. Promotor(en): Rob Comans, co-promotor(en): Liping Weng. - Wageningen : Wageningen University - ISBN 9789462579309 - 265
agricultural soils - selenium - bioavailability - soil organic matter - grasslands - soil chemistry - fertilizers - fertilizer application - netherlands - landbouwgronden - selenium - biologische beschikbaarheid - organisch bodemmateriaal - graslanden - bodemchemie - kunstmeststoffen - bemesting - nederland

Selenium (Se) is an essential micronutrient for animals and humans. In the food chain, the intake of Se by animals and humans depends largely on Se content in plants, whereas the major source of Se in plants lies in the soil. Therefore, understanding Se bioavailability in soils for plant uptake and its controlling factors and mechanisms is important. The objective of this thesis is to study the amount, speciation, bioavailability, plant uptake and fertilization of Se in agricultural soils in the Netherlands and underlying controlling factors and mechanisms, to provide guidance for soil testing and fertilization recommendation for efficient Se management in agriculture.

The majority of agricultural soils (grassland and arable land) in the Netherlands contains low total Se (i.e. in the range of Se deficient), which is predominantly present as organic Se. Only a small fraction of total Se is present as inorganic Se (mainly as selenite) and residual Se. In this thesis, the evidences of association between Se and soil organic matter in these low Se soils have been shown. The associations include: (1) the total Se content is positively correlated to soil organic matter content; (2) the solubility and extractability of Se in soils follow the solubility and extractability of soil organic C; (3) the majority of Se present in soils is in organic form, both in the soil solution and solid phase; (4) the distributions of Se and organic C in the different fractions of solid organic matter (i.e. humic acids, hydrophobic organic neutral, hydrophilic acids) and dissolved organic matter (i.e. hydrophilic acids and fulvic acids) are comparable; and (5) the Se richness in solid and dissolved organic matter are related to properties of soil organic matter from different land uses. The relatively high soil organic matter content in these low Se soils is likely responsible for these associations.

In general, Se content in crops (e.g. grass and wheat) grown on grassland soils and arable land soils, respectively in the Netherlands is low due to low amount of bioavailable Se in the soils. Different soil parameters determine Se plant uptake in these low Se soils with predominantly organic Se, depending on the properties of Se-containing soil organic matter. The intensity parameter of Se-rich dissolved organic matter (DOM) in soil solution (i.e. Se to DOC ratio in 0.01 M CaCl2 extraction) determines Se plant uptake in soils containing Se-rich organic matter (e.g. potato arable land soils), whereas the buffer capacity of labile organic Se to supply Se-rich DOM in soil solution limits Se plant uptake in soils containing Se-poor organic matter (e.g. grassland soils). Further research is needed to confirm the generality of the conclusion above, because the two experiments were carried out under different conditions (pot experiment and field experiment), using different plant species (wheat and grass) and covering different soil types from different land uses (potato fields and grassland). Site-specific properties in the field in addition to soil parameters included in the current study may largely (> 50%) determine Se content in grass under field conditions, which is in contrast with the results of the pot experiment in which the soil parameter explains 88% of Se content in wheat shoots. In general, the content of Se-rich DOM in soils increases with the increase of soil pH (with the decrease of soil C:N ratio), and the amount of labile organic matter in soils that can resupply Se-rich DOM is determined by the amount of clay (and Fe-(hydr)oxide). NPK fertilization, as one of the external factors, can reduce Se plant uptake, especially in organic-rich soils.

Selenium (as selenate) fertilization on grassland with N plus cattle slurry or NPK application shows a positive effect to increase Se content in grass grown on different soil types with a large range of total Se, pH, clay content and organic matter content. Selenium content in grass grown on different soil types upon Se fertilization becomes more similar than before the fertilization. The results indicate that the effectiveness of Se fertilization is only weakly modified by soil properties, probably due to the high solubility of selenate in the soils. Nevertheless, the Se fertilization tends to be slightly more effective on sandy soils than on clay and organic rich soils.

This thesis has shown that the content and quality of soil organic matter play an important role in determining the amount, speciation and bioavailability of Se in low Se soils with predominantly organic Se. The results in this thesis can be used as guidance to develop soil testing and fertilization recommendation for efficient Se management, especially in low Se soils with predominantly organic Se, such as in Dutch agricultural soils.

Effectiveness of FeEDDHA, FeEDDHMA, and FeHBED in Preventing Iron-Deficiency Chlorosis in Soybean
Bin, Levi M. ; Weng, Liping ; Bugter, Marcel H.J. - \ 2016
Journal of Agricultural and Food Chemistry 64 (2016)44. - ISSN 0021-8561 - p. 8273 - 8281.
EDDHA - EDDHMA - Glycine max (L.) Merr. - HBED - iron chelates - iron deficiency chlorosis

The performance of FeHBED in preventing Fe deficiency chlorosis in soybean (Glycine max (L.) Merr.) in comparison to FeEDDHA and FeEDDHMA was studied, as well as the importance of the ortho-ortho and ortho-para/rest isomers in defining the performance. To this end, chlorophyll production (SPAD), plant dry matter yield, and the mass fractions of important mineral elements in the plant were quantified in a greenhouse pot experiment. All three Fe chelates increased SPAD index and dry matter yield compared to the control. The effect of FeHBED on chlorophyll production was visible over a longer time span than that of FeEDDHA and FeEDDHMA. Additionally, FeHBED did not suppress Mn uptake as much as the other Fe chelates. Compared to the other Fe chelates, total Fe content in the young leaves was lower in the FeHBED treatment; however, total Fe content was not directly related to chlorophyll production and biomass yield. For each chelate, the ortho-ortho isomer was found to be more effective than the other isomers evaluated.

Selenium-rich dissolved organic matter determines selenium uptake in wheat grown on Low-selenium arable land soils
Supriatin, Supriatin ; Weng, Liping ; Comans, Rob N.J. - \ 2016
Plant and Soil 408 (2016)1. - ISSN 0032-079X - p. 73 - 94.
Calcium chloride extraction - Dissolved organic C - Plant uptake - Selenium - Soil C:N ratio - Soil pH

Aims: The study aimed to find soil parameters that are best related to Se plant uptake for low Se soils with predominantly organic Se, and to explore the mechanisms that control Se bioavailability in the soils under study. Methods: A pot experiment using nineteen soil samples taken from different fields of arable land (potato fields) in the Netherlands was conducted on summer wheat (Triticum aestivum L.). Selenium in wheat shoots and soil parameters, including basic soil properties, C:N ratio, inorganic selenite content, and Se and organic C in different soil extractions (0.01 M CaCl2, 0.43 M HNO3, hot water, ammonium oxalate, aqua regia) were analysed. Regression analysis was performed to identify soil parameters that determine Se content in wheat shoots. Results: The regression model shows that Se:DOC ratio in 0.01 M CaCl2 soil extraction explained about 88 % of the variability of Se uptake in wheat shoots. Selenium uptake increased with Se:DOC ratio in CaCl2 extraction, which can be interpreted as a measure of the content of soluble Se-rich organic molecules. Selenium:DOC ratio in CaCl2 extraction and Se uptake increased towards higher soil pH and lower soil C:N ratio. The soil C:N ratio is also negatively correlated to Se:organic C ratio in other extractions (0.43 M HNO3, hot water, ammonium oxalate, aqua regia), indicating that at low soil C:N ratio soil organic matter is richer in Se. Contrarily, the soil pH is positively and strongly correlated to Se:organic C ratio in CaCl2 and hot water extractions, but only weakly correlated to Se:organic C ratio in other extractions. Conclusions: Selenium-rich dissolved organic matter is the source of bioavailable Se in low Se soils with predominantly organic Se. The soil pH and quality of soil organic matter (i.e. soil C:N ratio) are the main soil properties determining Se bioavailability in these soil types.

Adsorption of Levofloxacin to Goethite : Batch and Column Studies
Qin, Xiaopeng ; Liu, Fei ; Zhao, Long ; Hou, Hong ; Wang, Guangcai ; Li, Fasheng ; Weng, Liping - \ 2016
Environmental Engineering Science 33 (2016)4. - ISSN 1092-8758 - p. 235 - 241.
antibiotic - CXTFIT - Desorption - Hemimellitic acid - Phthalic acid - STANMOD

Batch experiments were conducted to investigate the adsorption of a widely used fluoroquinolone antibiotic levofloxacin (LEV) to goethite and effects of nitrate, sulfate, small organic acids, and humic acid (HA). The concentrations of LEV and small organic acids in single systems or mixtures were determined by a high-performance liquid chromatography. Presence of nitrate or sulfate almost had no influence on the adsorption of LEV to goethite. HA promoted the adsorption significantly, and similar results were also observed in column experiments. LEV adsorption to goethite increased slightly in the presence of small organic acids. The π-π interactions between LEV molecules and the aromatic ring of organic acids (or HA) might be the main mechanism. In column experiments, LEV adsorption to the goethite-coated sand was well fitted with the two-site nonequilibrium model using the CXTFIT 2.1 program within the software STANMOD. The desorption process was well predicted with the model using the same parameters. In the presence of HA, more LEV was adsorbed to goethite-coated sand, and the desorption process showed some delay. Some LEV adsorbed to goethite-coated sand could not be desorbed with NaCl but was desorbed with phosphate. Presence of HA (or natural organic matters, phosphate) had a great influence on the mobility and distribution of LEV in soils and waters, which might also affect its degradability and antibacterial activity. Results obtained in this study were seldom reported in previous studies, which help us to better understand the behavior of antibiotics in the natural environment.

Tourism destination image development: a lesson from Macau
Kong, Weng Hang ; Cros, Hilary du; Ong, Chin Ee - \ 2015
International Journal of Tourism Cities 1 (2015)4. - ISSN 2056-5607 - p. 299 - 316.
Community involvement - Destination image - DMO - Macau - Stakeholder views - Tourism planning

Purpose – Drawing upon an analysis of resident and visitor survey data and Macau Government Tourist Office (MGTO) press releases in 2012, the purpose of this paper is to understand the tourism destination image for this tourist historic city produced by these three key stakeholder groups in Macau. Design/methodology/approach – This is achieved using a new stakeholder analysis tool, developed from previous studies, which compares the perspective of the MGTO, the city’s destination marketing organization, with that of its residents and visitors. This study examines the perceptions that residents and visitors have about the general images projected and generated in Macau. Findings – This research highlights the multiplicity of images and producers of images in Macau. Originality/value – The lesson from this case study is that public sector agencies need to acknowledge more clearly the tourism planning role of the host community in particular. The possibility of detecting disconnections and misalignments of shared destination imagery by residents and visitors has implications for the public sector in Macau and other destinations in relation to managing and developing a destination and contributes to a greater understanding of stakeholders and sustainable tourism development overall.

Selenium speciation and extractability in Dutch agricultural soils
Supriatin, Supriatin ; Weng, Liping ; Comans, Rob N.J. - \ 2015
Science of the Total Environment 532 (2015). - ISSN 0048-9697 - p. 368 - 382.
Agricultural soils - Organic carbon - Selenium - Soil extraction - Speciation

The study aimed to understand selenium (Se) speciation and extractability in Dutch agricultural soils. Top soil samples were taken from 42 grassland fields and 41 arable land fields in the Netherlands. Total Se contents measured in aqua regia were between 0.12 and 1.97mgkg-1(on average 0.58mgkg-1). Organic Se after NaOCl oxidation-extraction accounted for on average 82% of total Se, whereas inorganic selenite (selenate was not measurable) measured in ammonium oxalate extraction using HPLC-ICP-MS accounted for on average 5% of total Se. The predominance of organic Se in the soils is supported by the positive correlations between total Se (aqua regia) and total soil organic matter content, and Se and organic C content in all the other extractions performed in this study. The amount of Se extracted followed the order of aqua regia>1M NaOCl (pH8)>0.1M NaOH>ammonium oxalate (pH3)>hot water>0.43M HNO3>0.01M CaCl2. None of these extractions selectively extracts only inorganic Se, and relative to other extractions 0.43M HNO3 extraction contains the lowest fraction of organic Se, followed by ammonium oxalate extraction. In the 0.1M NaOH extraction, the hydrophobic neutral (HON) fraction of soil organic matter is richer in Se than in the hydrophilic (Hy) and humic acid (HA) fractions. The organic matter extracted in 0.01M CaCl2 and hot water is in general richer in Se compared to the organic matter extracted in 0.1M NaOH, and other extractions (HNO3, ammonium oxalate, NaOCl, and aqua regia). Although the extractability of Se follows to a large extent the extractability of soil organic carbon, there is several time variations in the Se to organic C ratios, reflecting the changes in composition of organic matter extracted.

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