Sorption of pymetrozine and dimethomorph to substrate materials
Boesten, J.J.T.I. ; Matser, A.M. - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research report 2841) - 47
plant protection - pesticides - soilless culture - rockwool - sorption - gewasbescherming - pesticiden - cultuur zonder grond - steenwol - sorptie
Does the combination of biochar and clinoptilolite enhance nutrient recovery from the liquid fraction of biogas digestate?
Kocatürk-Schumacher, Nazlı Pelin ; Zwart, Kor ; Bruun, Sander ; Brussaard, Lijbert ; Jensen, Lars Stoumann - \ 2017
Environmental Technology 38 (2017)10. - ISSN 0959-3330 - p. 1313 - 1323.
Biochar - clinoptilolite - liquid fraction of digestate - nutrient recovery - sorption
Concentrating nutrients on biochar and clinoptilolite and subsequently using the nutrient-enriched sorbents as a fertiliser could be an alternative way to manage nutrients in digestate. In this study, we investigated the use of biochar and clinoptilolite columns in removing ammonium, potassium, orthophosphate and dissolved organic carbon (DOC) from the liquid fraction of digestate. Our objectives were to investigate the effect of the initial loading ratio between liquid and biochar on nutrient removal, and to investigate the effect of combining biochar with clinoptilolite on nutrient and DOC removal efficiency. Increasing the initial loading ratios increased nutrient concentrations on biochar to 8.61 mg NH4-N g−1, 1.95 mg PO4-P g−1 and 13.01 mg DOC g−1, but resulted in decreasing removal efficiencies. The combination of biochar and clinoptilolite resulted in improved ammonium, potassium and DOC removal efficiencies compared to biochar alone, but did not significantly change PO4-P removal efficiencies. Removal efficiencies with combined sorbents were up to 67% for ammonium, 58% for DOC and 58% for potassium. Clinoptilolite showed higher removal efficiencies compared to biochar alone, and combining clinoptilolite with biochar improved only total P removal efficiency. Concentrating nutrients with clinoptilolite and biochar may be an option when both sorbents are available at low cost.
Evaluation of the Dutch leaching decision tree with the substances bentazone, MCPA and mecoprop
Linden, A.M.A. van der; Beltman, W.H.J. ; Boesten, J.J.T.I. ; Pol, J.W. - \ 2015
Bilthoven : RIVM (RIVM report 2015-0095) - 78
pesticides - groundwater - drinking water - water quality - water pollution - degradation - risk assessment - sorption - decision models - leaching - bentazone - mcpa - pesticiden - grondwater - drinkwater - waterkwaliteit - waterverontreiniging - degradatie - risicoschatting - sorptie - beslissingsmodellen - uitspoelen - bentazon - mcpa
Sinds 2004 wordt een beslismodel (beslisboom) gebruikt om te beoordelen in welke mate een gewasbeschermingsmiddel uitspoelt naar het grondwater. Uit een evaluatie van het RIVM, het College voor de toelating van gewasbeschermingsmiddelen en biociden (Ctgb) en onderzoekinstituut Alterra blijkt dat de beslisboom goed werkt en state of the art is. Wel laten de stofgegevens waarmee wordt gerekend te wensen over. Om de kwaliteit van het grondwater te waarborgen moeten deze gegevens zorgvuldiger worden afgeleid.
Establishing Guidelines to Retain Viability of Probiotics during Spray Drying
Perdana, J.A. ; Fox, M.B. ; Boom, R.M. ; Schutyser, M.A.I. - \ 2015
Drying Technology 33 (2015)13. - ISSN 0737-3937 - p. 1560 - 1569.
lactobacillus-plantarum wcfs1 - inactivation - integration - isotherms - products - sorption - storage - trends - foods - model
We present the application of a model-based approach to map processing conditions suitable to spray dry probiotics with minimal viability loss. The approach combines the drying history and bacterial inactivation kinetics to predict the retention of viability after drying. The approach was used to systematically assess the influence of operational co-current spray drying conditions on residual viability. Moreover, two promising alternative drying strategies for probiotics were evaluated involving encapsulation in a hollow particle and using an ‘ideal-mixed’ dryer system. Finally, a graph was constructed with the model to provide visual guidelines to optimize spray dying for probiotics in terms of viability and drying efficiency.
Description of the phosphorus sorption and desorption processes in coarse calcareous sandy soils
Schoumans, Oscar F. - \ 2014
Soil Science 179 (2014)5. - ISSN 0038-075X - p. 221 - 229.
calcareous soils - calcite - desorption - kinetics - phosphate - phosphate sorption capacity - Phosphorus - precipitation - sorption
In order to understand and predict the behavior of phosphorus (P) in calcareous sandy soils, sorption and desorption studies were carried out. Two main processes were distinguished: a fast, reversible phosphate reaction (within 1 day), which can be described by the Langmuir equation, and a precipitation reaction, which can be described by a time-dependent Freundlich equation. The maximum phosphate sorption capacity in the top 50 cm of the soil ranged from 3 to 6 t P2O5·ha-1. About 85% to 95% of the maximum amount of P bound was poorly soluble; the remaining portion of bound P determines the ortho-P concentration in soil solution under desorption conditions. The breakthrough curves of the two column experiments were described reasonably well by the proposed process description and the associated parameters, which were derived from batch experiments.
Surface properties and phosphate adsorption of binary systems containing goethite and kaolinite
Wei, S.Y. ; Tan, W.F. ; Liu, F. ; Zhao, W. ; Weng, L. - \ 2014
Geoderma 213 (2014). - ISSN 0016-7061 - p. 478 - 484.
iron-oxide - clay-minerals - aqueous-solution - soils - sorption - ferrihydrite - hematite - crystallinity - mechanisms - stability
In soils goethite and kaolinite are often cemented together as a binary association, which has a significant influence on the physical and chemical properties of soils. In this study, the surface properties and phosphate adsorption of goethite, kaolinite, goethite-kaolinite association (GKA) and goethite-kaolinite mixture (GKM) were investigated. Compared to the average simple sum values of goethite and kaolinite, the pore volume and specific surface area (SSA) of GKA increased, and those of GKM remained almost unchanged. Goethite, kaolinite, GKM and GKA have a pH of point of zero charge (PZC) at around 8.2, 4.1, 6.1, and 7.0, respectively; and their surface charge is 0561, -0.092, 0.041, and 0.097 mmol/g at pH 5.0, respectively. The phosphate adsorption data of goethite and kaolinite could be fitted by one-site Langmuir model (R-2 = 0.963 and 0.956, respectively). Two-site Langmuir model described the phosphate adsorption by GKM and GKA well (R-2 = 0.985 and 0.982, respectively); and the Freundlich correlation coefficients of GKM and GKA were 0.967 and 0.924, respectively. This indicated that GKM and GKA possessed the surface with two types of reactive sites, and the surface heterogeneity of GKM was higher than that of GKA. Compared to the average value of goethite and kaolinite, the adsorption capacities of GKM (q(max) = 198.17 and q(t) = 226.11 mmol/g) increased slightly and those of GKA (q(max) = 230.24 and q(t) = 235.96 mmol/g) significantly increased, indicating that GKA was a highly effective adsorbent for phosphate. (C) 2013 Elsevier B.V. All rights reserved.
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.
Analysis of electrostatic powder charging for fractionation of foods
Wang, J. ; Wit, M. de; Schutyser, M.A.I. ; Boom, R.M. - \ 2014
Innovative Food Science and Emerging Technologies 26 (2014). - ISSN 1466-8564 - p. 360 - 365.
polymer particles - glass-transition - metal plate - separations - electrification - solids - sorption - impacts - gluten - size
Electrostatic separation based on different tribo-electric charging behaviours of components has emerged as a novel, sustainable dry fractionation process. This study aims to characterise charging behaviour of single-component particles in nitrogen gas flowing through aluminium tubes. Experiments were carried out with polystyrene (PS) particles and wheat gluten as model particles. Results indicated that specific charge increased linearly with gas velocity up to 28 m/s for both materials. It was found that surface charge densities of different-sized PS particles overlapped for laminar gas flow, whereas for higher stronger gas flow rates, surface charge density of the smallest particles deviated from that of larger particles. Specific charge of PS particles increased linearly with increasing tube length from 125 to 225 mm. Additionally, charging of PS particles was unaffected by relative humidity (RH) of gas; however, specific charge of wheat gluten decreased for RH > 80%. Concluding, these results provide insight in critical parameters affecting charging behaviour, thus facilitating the development of electrostatic separation processes to fractionate food ingredients.
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.
Limited Reversibility of Bioconcentration of Hydrophobic Organic Chemicals in Phytoplankton
Koelmans, A.A. - \ 2014
Environmental Science and Technology 48 (2014)13. - ISSN 0013-936X - p. 7341 - 7348.
granular activated carbon - selenastrum-capricornutum - polychlorinated biphenyl - kinetics - sediment - water - chlorobenzenes - desorption - sorption - fluxes
Aging, reversibility and desorption rates for the binding of hydrophobic chemicals (HOC) to phytoplankton cells have not been directly measured. Here the effect of bioconcentration time on subsequent desorption of hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) was studied for the alga Monoraphidium minutum. Cell suspensions were exposed to HCB and PCBs spanning a range of logKow values of 5.7 to 8.2, for 0.13 to 14 d. Subsequently, reversibility and desorption rates were assessed by extracting the chemicals from the cells using infinite sink extractions with Tenax beads or Empore disks employed in the cell suspension. Uptake was biphasic with constant relative contributions of fast surface sorption. Desorption was biphasic too and fitted well to a first order two compartment model. Increasing exposure times resulted in increasing slowly desorbing chemical fractions and decreased desorption rates from these fractions. For the most hydrophobic PCBs, slowly desorbing fractions were >80-90%, whereas desorption half-lives from these fractions ranged up to 120 days. The slow desorption rates directly prove that bioconcentration to algae can be rate limited and imply that already after a few hours of exposure HOCs may become practically unavailable for repartitioning.
Analysis of organic contaminant desorption kinetic data for sediments and soils: Implications for the Tenax extraction time for the determination of bioavailable concentrations
Noort, P.C.M. van; Poot, A. ; Koelmans, A.A. - \ 2014
Science of the Total Environment 490 (2014). - ISSN 0048-9697 - p. 235 - 238.
polybrominated diphenyl ethers - in-field sediments - black carbon - availability - insecticides - pyrethroids - sorption - predict - tool
Solid-phase extractions with adsorbents like Tenax have been widely used to assess bioaccessible or bioavailable concentrations and non-extractable residues (NER) of organic contaminants in soils or sediments. This paper presents an analysis of literature rate constants and fractions for rapid, slow and very slow contaminant desorption from soils and sediments. Contaminant fractions desorbed from sediment to Tenax in 6 or 24. h were evaluated as to their adequacy as a proxy for rapidly desorbing fractions, which have been shown to correlate with bioavailable concentrations. Desorption rate constants appear to decrease with increasing contaminant n-octanol-water partition coefficient. The ratio of the fraction of contaminant desorbed from sediment to Tenax in 6. h and the rapidly desorbing fraction appeared to slightly decrease on increasing contaminant hydrophobicity. This was not the case for the extraction for 24. h. Rapidly desorbing fractions or bioavailable fractions can be estimated, within a factor of 1.4, by multiplying the fraction desorbed in 24. h by a factor of 0.7.
Partitioning of perfluorooctanesulfonate and perfluorohexanesulfonate in the aquatic environment after an accidental release of aqueous film forming foam at Schiphol Amsterdam Airport
Kwadijk, C.J.A.F. ; Kotterman, M.J.J. ; Koelmans, A.A. - \ 2014
Environmental Toxicology and Chemistry 33 (2014)8. - ISSN 0730-7268 - p. 1761 - 1765.
perfluorinated surfactants - perfluoroalkyl acids - firefighting foam - organic-compounds - water - sulfonate - sediment - sorption - biota - fate
In the summer of 2008, an accidental release of Aqueous Film Forming Foam (AFFF) took place at Schiphol Amsterdam Airport (The Netherlands). After the release, water, fish and sediment samples were collected and analyzed for perfluoroalkyl sulfonates (PFSA). In situ perfluorooctane sulfonate (PFOS) KD values, BAF and BSAF values showed a remarkable agreement among reference and impacted sites, 10 weeks after the incident as well as after 3 years.
Impact of organic carbon and nutrients mobilized during chemical oxidation on subsequent bioremediation of a diesel-contaminated soil
Sutton, N.B. ; Grotenhuis, J.T.C. ; Rijnaarts, H.H.M. - \ 2014
Chemosphere 97 (2014). - ISSN 0045-6535 - p. 64 - 70.
in-situ ozonation - community composition - matter - biodegradation - oil - bioavailability - oxidants - sorption
Remediation with in situ chemical oxidation (ISCO) impacts soil organic matter (SOM) and the microbial community, with deleterious effects on the latter being a major hurdle to coupling ISCO with in situ bioremediation (ISB). We investigate treatment of a diesel-contaminated soil with Fenton’s reagent and modified Fenton’s reagent coupled with a subsequent bioremediation phase of 187 d, both with and without nutrient amendment. Chemical oxidation mobilized SOM into the liquid phase, producing dissolved organic carbon (DOC) concentrations 8–16 times higher than the untreated field sample. Higher aqueous concentrations of nitrogen and phosphorous species were also observed following oxidation; increased 14–172 times. During the bioremediation phase, dissolved carbon and nutrient species were utilized for microbial growth-yielding DOC concentrations similar to field sample levels within 56 d of incubation. In the absence of nutrient amendment, the highest microbial respiration rates were correlated with higher availability of nitrogen and phosphorus species mobilized by oxidation. Significant diesel degradation was only observed following nutrient amendment, implying that nutrients mobilized by chemical oxidation can increase microbial activity but are insufficient for bioremediation. While all bioremediation occurred in the first 28 d of incubation in the biotic control microcosm with nutrient amendment, biodegradation continued throughout 187 d of incubation following chemical oxidation, suggesting that chemical treatment also affects the desorption of organic contaminants from SOM. Overall, results indicate that biodegradation of DOC, as an alternative substrate to diesel, and biological utilization of mobilized nutrients have implications for the success of coupled ISCO and ISB treatments.
A Paradigm Shift in Drying of Food Materials via Free-Volume Concepts
Sman, R.G.M. van der; Jin, X. ; Meinders, M.B.J. - \ 2013
Drying Technology 31 (2013)15. - ISSN 0737-3937 - p. 1817 - 1825.
water-vapor absorption - moisture transport - simultaneous heat - mass-transfer - porous-media - meat - polymers - behavior - sorption - models
We give an overview of the prediction of thermodynamics of food materials, and the kinetics of water transport in them using universal theories based on free volume concepts. These material properties are highly relevant to the prediction of food drying. These presented theories are shown to hold for a large class of polysaccharides and proteins. These different food materials apparently follow the soft matter paradigm that materials' behavior at length scales larger than the molecular scale are dominantly determined by physical characteristics rather than their chemical details. We pose that for food and other bio-materials hydrogen-bonding is largely determining their physical behavior, as in drying. [Supplementary materials are available for this article. Go to the publisher's online edition of Drying Technology for the following free supplemental resource(s): Data sets.]
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.
Carbon Nanofiber-Supported K2CO3 as an Efficient Low-Temperature Regenerable CO2 Sorbent for Post-Combustion Capture
Meis, N.N.A.H. ; Frey, A.M. ; Bitter, J.H. ; Jong, K.P. de - \ 2013
Industrial & Engineering Chemistry Research 52 (2013)36. - ISSN 0888-5885 - p. 12812 - 12818.
metal-organic frameworks - fixed-bed operations - solid base catalysts - flue-gas - dioxide - adsorption - recovery - adsorbents - sorption - k2co3-on-carbon
This study focuses on regenerable sorbents for post-combustion CO2 capture at low temperature (373 K). K2CO3 loaded on three different supports, carbon nanofibers (CNF), alumina (¿-Al2O3), and activated carbon (AC), was investigated. K2CO3–CNF revealed excellent properties as CO2 sorbent, displaying capacities of 1.2–1.6 mmol g–1 and fast desorption kinetics at low temperatures (423 K). This temperature was too low to completely regenerate K2CO3–Al2O3 and K2CO3–AC, and consequently, these sorbents lost 8% and 50%, respectively, of their capacity after the first absorption–desorption cycle. K2CO3–CNF could be regenerated to restore 80% of its capacity with a low energy input, estimated at 2–3 GJ/ton CO2, which is competitive to currently used amines.
Sustainable gold mining wastewater treatment by sorption using low-cost materials
Acheampong, M.A. - \ 2013
Wageningen University. Promotor(en): Piet Lens. - [S.l.] : S.n. - ISBN 9789461737403 - 163
afvalwaterbehandeling - mijnbouw - goud - sorptie - technologie - methodologie - waste water treatment - mining - gold - sorption - technology - methodology
Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon
Kupryianchyk, D. ; Noori, A. ; Rakowska, M.I. ; Grotenhuis, J.T.C. ; Koelmans, A.A. - \ 2013
Environmental Science and Technology 47 (2013)10. - ISSN 0013-936X - p. 5092 - 5100.
polycyclic aromatic-hydrocarbons - polychlorinated-biphenyls - marine-sediments - sorption - water - coefficients - transport - bioavailability - consequences - remediation
Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we report polychlorobiphenyl (PCB) pore water concentrations, fluxes, mass transfer coefficients, and survival data of two benthic species, for four treatments: no AC addition (control), powdered AC addition, granular AC addition and addition and subsequent removal of GAC (sediment stripping). AC addition decreased mass fluxes but increased apparent mass transfer coefficients because of dissolved organic carbon (DOC) facilitated transport across the benthic boundary layer (BBL). In turn, DOC concentrations depended on bioturbator activity which was high for the PAC tolerant species Asellus aquaticus and low for AC sensitive species Lumbriculus variegatus. A dual BBL resistance model combining AC effects on gradients, DOC facilitated transport and biodiffusion was evaluated against the data and showed how the type of resistance differs with treatment and chemical hydrophobicity. Data and simulations illustrate the complex interplay between AC and contaminant toxicity to benthic organisms and how differences in species tolerance affect mass fluxes from sediment to the water column
In situ Treatment with Activated Carbon Reduces Bioaccumulation in Aquatic Food Chains
Kupryianchyk, D. ; Rakowska, M.I. ; Roessink, I. ; Reichman, E.P. ; Grotenhuis, J.T.C. ; Koelmans, A.A. - \ 2013
Environmental Science and Technology 47 (2013)9. - ISSN 0013-936X - p. 4563 - 4571.
polycyclic aromatic-hydrocarbons - polychlorinated-biphenyls pcbs - contaminated sediments - organic-chemicals - sorbent amendment - marine-sediments - bioconcentration - sorption - polychlorobiphenyls - water
In situ activated carbon (AC) amendment is a new direction in contaminated sediment management, yet its effectiveness and safety have never been tested on the level of entire food chains including fish. Here we tested the effects of three different AC treatments on hydrophobic organic chemical (HOC) concentrations in pore water, benthic invertebrates, zooplankton, and fish (Leuciscus idus melanotus). AC treatments were mixing with powdered AC (PAC), mixing with granular AC (GAC), and addition–removal of GAC (sediment stripping). The AC treatments resulted in a significant decrease in HOC concentrations in pore water, benthic invertebrates, zooplankton, macrophytes, and fish. In 6 months, PAC treatment caused a reduction of accumulation of polychlorobiphenyls (PCB) in fish by a factor of 20, bringing pollutant levels below toxic thresholds. All AC treatments supported growth of fish, but growth was inhibited in the PAC treatment, which was likely explained by reduced nutrient concentrations, resulting in lower zooplankton (i.e., food) densities for the fish. PAC treatment may be advised for sites where immediate ecosystem protection is required. GAC treatment may be equally effective in the longer term and may be adequate for vulnerable ecosystems where longer-term protection suffices.
Estimating degradation rates in outdoor stagnant water by inverse modelling with TOXSWA: a case study with prosulfocarb
Adriaanse, P.I. ; Boesten, J.J.T.I. ; Crum, S.J.H. - \ 2013
Pest Management Science 69 (2013)6. - ISSN 1526-498X - p. 755 - 767.
sediment/water systems - experimental ditches - pesticides - herbicide - behavior - biodegradation - persistence - simulation - sorption - field
Background The regulatory risk assessment of pesticides requires the assessment of exposure of aquatic ecosystems in small surface waters adjacent to agricultural fields. This exposure is predicted using simulation models, for which an important input parameter is the degradation rate in water. In regulatory dossiers, the decline rate in water from outdoor mesocosms is often available, but this rate encompasses more processes than degradation. Therefore, a procedure was designed for estimating the degradation rate in water that was suitable for mesocosm studies with limited datasets, e.g. datasets lacking site-specific sorption coefficients and relevant sediment properties. The procedure, based upon inverse modelling with TOXSWA, has been tested on a dataset for prosulfocarb in stagnant ditches. Results A degradation half-life in the ditch water of 2.9 days (20 °C) was found. This short half-life was to a significant extent accounted for by biodegradation rather than hydrolysis or photolysis. This half-life was considerably shorter than the half-life in the water layer of two laboratory water–sediment system experiments. Conclusion The estimation procedure resulted in a unique half-life for the degradation rate in water. Such outdoor mesocosm studies seem to be better suited to assessing the degradation rate in water in ditches than the conventional water–sediment studies.