Publications by authors named "Andreas Schaeffer"

26 Publications

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Improving our understanding of the environmental persistence of chemicals.

Integr Environ Assess Manag 2021 Apr 29. Epub 2021 Apr 29.

Institute for Environmental Research, Aachen University, Aachen, Germany.

Significant progress has been made in the scientific understanding of factors that influence the outcome of biodegradation tests used to assess the persistence (P) of chemicals. This needs to be evaluated to assess whether recently acquired knowledge could enhance existing regulations and environmental risk assessments. Biodegradation tests have limitations, which are accentuated for "difficult-to-test" substances, and failure to recognize these can potentially lead to inappropriate conclusions regarding a chemical's environmental persistence. Many of these limitations have been previously recognized and discussed in a series of ECETOC reports and workshops. These were subsequently used to develop a series of research projects designed to address key issues and, where possible, propose methods to mitigate the limitations of current assessments. Here, we report on the output of a Cefic LRI-Concawe Workshop held in Helsinki on September 27, 2018. The objectives of this workshop were to disseminate key findings from recent projects and assess how new scientific knowledge can potentially support and improve assessments under existing regulatory frameworks. The workshop provided a unique opportunity to initiate a process to reexamine the fundamentals of degradation and what current assessment methods can achieve by (1) providing an overview of the key elements and messages coming from recent research initiatives and (2) stimulating discussion regarding how these interrelate and how new findings can be developed to improve persistence assessments. Opportunities to try and improve understanding of factors affecting biodegradation assessments and better understanding of the persistence of chemicals (particularly UVCBs [substances of unknown or variable composition, complex reaction products, or biological materials]) were identified, and the workshop acted as a catalyst for further multistakeholder activities and engagements to take the persistence assessment of chemicals into the 21st century. Integr Environ Assess Manag 2021;00:1-13. © 2021 European Petroleum Refiners Association - Concawe Division. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).
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http://dx.doi.org/10.1002/ieam.4438DOI Listing
April 2021

Fate and behavior of C-labelled ionic compounds in a soil simulation test.

Sci Total Environ 2021 May 30;768:144970. Epub 2021 Jan 30.

RWTH Aachen University, Institute for Environmental Research, Worringer Weg 1, 52074 Aachen, Germany; State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China; Chongqing University, College of Resources and Environmental Science, Chongqing, China.

The influence of an ionic functional group on the fate and behavior of chemicals in the environment has so far not been systematically investigated. This study, therefore, examines the following three substances with high structural similarity but differing charge: non-charged 4-n-dodecylphenol[phenylring-C(U)] (C-DP), negatively charged 4-n-dodecylbenzenesulfonicacid[phenylring-C(U)] sodium salt (C-DS) and positively charged 4-n-dodecylbenzyltrimethylammonium chloride[phenylring-C(U)] (C-DA). They were investigated in a soil simulation study according to the OECD 307 test guideline by measuring the distribution of the applied radioactivity (AR) among volatile, mineralized, extractable and non-extractable residues (NER) in one soil after 0, 1, 7, 14, 49, 84 and 124 days of incubation. Extractable portions of C were examined by means of radio-TLC and -HPLC analyses. Microbial activity of the soil incubated with and without C-DP, C-DS and C-DA was determined measuring the reduction of dimethylsulfoxide (DMSO) over time. After 124 days of incubation highest mineralization could be observed for C-DS (64.5% AR). Except CO, no volatile residues were formed over time. Besides the parent compounds, polar (C-DP, C-DS and C-DA) and nonpolar (C-DA) transformation products were detected. Highest amounts of C were extracted using methanol and were thus potentially bioavailable for soil microorganisms. Microbial activity was markedly higher in soil incubated with C-DP and C-DS compared to C-DA or soil without any treatment. Half-lives (DT) at 18 °C were as follows: DA (61.8 days) > DS (18.2 days) > DP (10.0 days). In case of the cationic compound and its transformation products we conclude that a higher sorption affinity to soil particles leads to reduced bioavailability for microorganisms and thus reduced mineralization resulting in a higher persistence compared to anionic and non-charged organic compounds in soil. The impact of our findings on the persistence assessment of chemicals when performing OECD guideline tests in soil, water-sediment and surface water is discussed.
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http://dx.doi.org/10.1016/j.scitotenv.2021.144970DOI Listing
May 2021

Do you smell the danger? Effects of three commonly used pesticides on the olfactory-mediated antipredator response of zebrafish (Danio rerio).

Chemosphere 2020 Feb 26;241:124963. Epub 2019 Sep 26.

Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany; Department of Evolutionary Ecology and Environmental Toxicology, Goethe University Frankfurt, Max-von-Laue-Str. 13, 60438, Frankfurt am Main, Germany. Electronic address:

Fish are warned about the presence of predators via an alarm cue released from the skin of injured conspecifics. The detection of this odor inherently initiates an antipredator response, which increases the chance of survival for the individual. In the present study, we assessed the effect of three commonly used pesticides on the antipredator response of zebrafish (Danio rerio). For this, we analyzed the behavioral response of zebrafish to a conspecific skin extract following 24 h of exposure to the respective contaminants. Results demonstrate that fish exposed to 20 μg/L of the organophosphate insecticide chlorpyrifos significantly reduced bottom-dwelling and freezing behavior, suggesting an impairment of the antipredator response. For the urea-herbicide linuron and the pyrethroid insecticide permethrin, no statistically significant effects could be detected. However, linuron-exposed fish appeared to respond in an altered manner to the skin extract; some individuals failed to perform the inherent behaviors such as erratic movements and instead merely increased their velocity. Furthermore, we determined whether zebrafish would avoid the pesticides in a choice maze. While fish avoided permethrin, they behaved indifferently to chlorpyrifos and linuron. The study demonstrates that pesticides may alter the olfactory-mediated antipredator response of zebrafish in distinct ways, revealing that particularly fish exposed to chlorpyrifos may be more prone to predation.
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http://dx.doi.org/10.1016/j.chemosphere.2019.124963DOI Listing
February 2020

Formation, classification and identification of non-extractable residues of C-labelled ionic compounds in soil.

Chemosphere 2019 Oct 9;232:164-170. Epub 2019 May 9.

RWTH Aachen University, Institute for Environmental Research, Worringer Weg 1, 52074, Aachen, Germany; State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210093, PR China; Chongqing University, College of Resources and Environmental Science, Chongqing, PR China. Electronic address:

The influence of an ionic functional group on the fate of chemicals in the environment, especially the formation of non-extractable residues (NER), has not been systematically investigated. Using 4-n-dodecylphenol[phenylring-C(U)], 4-n-dodecylbenzenesulfonicacid[phenylring-C(U)] sodiumsalt (C-DS) and 4-n-dodecylbenzyltrimethylammoniumchloride[phenylring-C(U)] (C-DA) all with a high structural similarity, the formation, classification and identification of NER of negatively (C-DS), positively (C-DA) and uncharged (C-DP) chemicals were investigated in a sterilized and non-sterilized soil. After 84 days of incubation in non-sterile soil, 40.6%, 21.7% and 33.5% of the applied radioactivity (AR) of C-DP, C-DS and C-DA, respectively, were converted to NER. In contrast, in sterile soil NER formation was markedly lower. The NER were further investigated with respect to sequestered, covalently bound and biogenic residues (i.e. NER types I, II, and III). Silylation of C-DP, C-DS and C-DA derived NER released 3.0-23.2% AR, indicating that these were sequestered, whereas the residual NER (12.9-33.1% AR) was covalently bound to the soil. Analysis of extracts derived by silylation showed that C-DP, but neither C-DS nor C-DA, were released by silylation, suggesting that DP might be part of the sequestered NER. Acid hydrolysis of the NER containing soil and subsequent analysis of soil extracts for C-aminoacids indicated that 2.5-23.8% AR were biogenic residues. Most DP and DS derived NER were biogenically or covalently bound, whereas DA predominantly forms sequestered NER in soil. From these results we propose that chemicals forming high amounts of NER should be investigated regarding types I-III NER because sequestered parent compounds should be considered in persistence assessments.
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http://dx.doi.org/10.1016/j.chemosphere.2019.05.038DOI Listing
October 2019

Genotoxicity of three biofuel candidates compared to reference fuels.

Environ Toxicol Pharmacol 2018 Dec 17;64:131-138. Epub 2018 Oct 17.

RWTH Aachen University, Institute for Environmental Research, Worringerweg 1, 52074 Aachen, Germany; Chongqing University, College of Resources and Environmental Science, Chongqing, 400715, China; Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing, 210093, China; Tongji University, College of Environmental Science and Engineering and State Key Laboratory of Pollution Control and Resource Reuse, Shanghai, 200092, China. Electronic address:

Global demand for alternative energy sources increases due to concerns regarding energy security and greenhouse gas emissions. However, little is known regarding the impacts of biofuels to the environment and human health even though the identification of such impacts is important to avoid biofuels leading to undesired effects. In this study mutagenicity and genotoxicity of the three biofuel candidates ethyl levulinate (EL), 2-methyltetrahydrofuran (2-MTHF) and 2-methylfuran (2-MF) were investigated in comparison to two petroleum-derived fuels and a biodiesel. None of the samples induced mutagenicity in the Ames fluctuation test. However, the Micronucleus assay revealed significant effects in Chinese hamster (Cricetulus griseus) V79 cells caused by the potential biofuels. 2-MF revealed the highest toxic potential with significant induction of micronuclei below 20.0 mg/L. EL and 2-MTHF induced micronuclei only at very high concentrations (>1000.0 mg/L). In regard to the genotoxic potential of 2-MF, its usage as biofuel should be critically discussed.
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http://dx.doi.org/10.1016/j.etap.2018.10.003DOI Listing
December 2018

The impact of chemical pollution on the resilience of soils under multiple stresses: A conceptual framework for future research.

Sci Total Environ 2016 Oct 30;568:1076-1085. Epub 2016 Jun 30.

RWTH Aachen University, Institute for Environmental Research (Biology 5), 52074 Aachen, Germany.

Soils are faced with man-made chemical stress factors, such as the input of organic or metal-containing pesticides, in combination with non-chemical stressors like soil compaction and natural disturbance like drought. Although multiple stress factors are typically co-occurring in soil ecosystems, research in soil sciences on this aspect is limited and focuses mostly on single structural or functional endpoints. A mechanistic understanding of the reaction of soils to multiple stressors is currently lacking. Based on a review of resilience theory, we introduce a new concept for research on the ability of polluted soil (xenobiotics or other chemical pollutants as one stressor) to resist further natural or anthropogenic stress and to retain its functions and structure. There is strong indication that pollution as a primary stressor will change the system reaction of soil, i.e., its resilience, stability and resistance. It can be expected that pollution affects the physiological adaption of organisms and the functional redundancy of the soil to further stress. We hypothesize that the recovery of organisms and chemical-physical properties after impact of a follow-up stressor is faster in polluted soil than in non-polluted soil, i.e., polluted soil has a higher dynamical stability (dynamical stability=1/recovery time), whereas resilience of the contaminated soil is lower compared to that of not or less contaminated soil. Thus, a polluted soil might be more prone to change into another system regime after occurrence of further stress. We highlight this issue by compiling the literature exemplarily for the effects of Cu contamination and compaction on soil functions and structure. We propose to intensify research on effects of combined stresses involving a multidisciplinary team of experts and provide suggestions for corresponding experiments. Our concept offers thus a framework for system level analysis of soils paving the way to enhance ecological theory.
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http://dx.doi.org/10.1016/j.scitotenv.2016.06.161DOI Listing
October 2016

Acute embryo toxicity and teratogenicity of three potential biofuels also used as flavor or solvent.

Sci Total Environ 2016 Oct 28;566-567:786-795. Epub 2016 May 28.

RWTH Aachen University, Institute for Environmental Research, Worringerweg 1, 52074 Aachen, Germany; Chongqing University, College of Resources and Environmental Science, Chongqing 400715, China; Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing 210093, China; Tongji University, College of Environmental Science and Engineering and State Key Laboratory of Pollution Control and Resource Reuse, Shanghai 200092, China. Electronic address:

The demand for biofuels increases due to concerns regarding greenhouse gas emissions and depletion of fossil oil reserves. Many substances identified as potential biofuels are solvents or already used as flavors or fragrances. Although humans and the environment may be readily exposed little is known regarding their (eco)toxicological effects. In this study, the three potential biofuels ethyl levulinate (EL), 2-methyltetrahydrofuran (2-MTHF) and 2-methylfuran (2-MF) were investigated for their acute embryo toxicity and teratogenicity using the fish embryo toxicity (FET) test to identify unknown hazard potentials and to allow focusing further research on substances with low toxic potentials. In addition, two fossil fuels (diesel and gasoline) and an established biofuel (rapeseed oil methyl ester) were investigated as references. The FET test is widely accepted and used in (eco)toxicology. It was performed using the zebrafish Danio rerio, a model organism useful for the prediction of human teratogenicity. Testing revealed a higher acute toxicity for EL (LC50: 83mg/L) compared to 2-MTHF (LC50: 2980mg/L), 2-MF (LC50: 405mg/L) and water accommodated fractions of the reference fuels including gasoline (LC50: 244mg DOC/L). In addition, EL caused a statistically significant effect on head development resulting in elevated head lengths in zebrafish embryos. Results for EL reduce its likelihood of use as a biofuel since other substances with a lower toxic potential are available. The FET test applied at an early stage of development might be a useful tool to avoid further time and money requiring steps regarding research on unfavorable biofuels.
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http://dx.doi.org/10.1016/j.scitotenv.2016.05.055DOI Listing
October 2016

Quantitative Identification of Biogenic Nonextractable Pesticide Residues in Soil by (14)C-Analysis.

Environ Sci Technol 2016 06 10;50(12):6415-22. Epub 2016 Jun 10.

RWTH Aachen University , Institute for Environmental Research (Biology 5), Worringer Weg 1, 52074 Aachen, Germany.

Quantification of nonextractable residues (NER) of pesticides in soil is feasible by use of radioactively labeled compounds, but structural information on these long-term stabilized residues is usually lacking. Microorganisms incorporate parts of the radiolabeled ((14)C-) carbon from contaminants into microbial biomass, which after cell death enters soil organic matter, thus forming biogenic nonextractable residues (bioNER). The formation of bioNER is not yet determinable in environmental fate studies due to a lack of methodology. This paper focuses on the development of a feasible analytical method to quantify proteinaceous carbon, since proteins make up the largest mass portion of bacterial cells. The test substance (14)C-bromoxynil after 56 days forms more than 70% of NER in soil. For further characterization of NER the amino acids were extracted, purified, and separated by two-dimensional thin-layer chromatography (TLC). Visualization of the (14)C-amino acids was performed by bioimaging, unambiguous identification by GC-MS and LC-MS/MS. Our analysis revealed that after 56 days of incubation about 14.5% of the (14)C-label of bromoxynil was incorporated in amino acids. Extrapolating this content based on the amount of proteins in the biomass (55%), in total about 26% of the NER is accounted for by bioNER and thus is not environmentally relevant.
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http://dx.doi.org/10.1021/acs.est.6b00689DOI Listing
June 2016

Uptake, elimination, and biotransformation of 17α-ethinylestradiol by the freshwater alga Desmodesmus subspicatus.

Environ Sci Technol 2014 Oct 13;48(20):12354-61. Epub 2014 Oct 13.

Institute for Environmental Research (Biology V), RWTH Aachen University , Worringerweg 1, Aachen 52074, Germany.

Bioconcentration and transformation of the potent and persistent xeno-estrogen 17α-ethinylestradiol (EE2) by organisms at the basis of the food web have received only little research attention. In this study, uptake, elimination, and biotransformation of radiolabeled EE2 ((14)C-EE2) by the freshwater green alga Desmodesmus subspicatus were investigated. The alga highly incorporated radioactivity following (14)C-EE2 exposure. Up to 68% of the test compound was removed from the medium by D. subspicatus within a rather short time period (72 h C(algae)/C(water): 2200 L/kg wet weight). When the algae were transported to clear medium, a two-stage release pattern was observed with an initially quick elimination phase following slower clearance afterward. Interestingly, D. subspicatus brominated EE2 when bromide was available in the medium, a transformation process demonstrated to occur abiotically but not by algae. The consequence of the presence of more hydrophobic mono- and dibrominated EE2 in the environment remains to be further investigated, as these products were shown to have a lower estrogenic potency but are expected to have a higher bioaccumulation potential and to be more toxic than the mother compound.
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http://dx.doi.org/10.1021/es503574zDOI Listing
October 2014

Behavior of nanoscale titanium dioxide in laboratory wastewater treatment plants according to OECD 303 A.

Chemosphere 2014 Jun 5;104:197-204. Epub 2013 Dec 5.

Institute of Energy and Environmental Technology e.V., Air Quality & Sustainable Nanotechnology Unit, Duisburg, Germany.

The fate assessment of nanomaterials in municipal sewage treatment plants (STP) is a crucial step for their environmental risk assessment and may be assessed by monitoring full scale STP, dosage to medium scale pilot STP or by laboratory testing. For regulatory purposes preferably standardised test protocols such as the OECD guidelines for testing of chemicals should be used. However, these test protocols have not yet been specifically designed for nanoparticles. Therefore, the fate and behavior of a TiO2 nanomaterial (P25, average hydrodynamic diameter <250 nm) was investigated in laboratory sewage treatment plants according to the OECD Guideline for the Testing of Chemicals 303 A. It is concluded that this guideline is applicable for the testing of nanomaterials if modifications regarding the dosage, nitrifying conditions, and a characterisation of the nanoparticles in the effluent are applied. A compilation of the cumulative mass balance by comparison of the total dosage added with the amount in the outflow and in the activated sludge is recommended. In this study, the majority of the TiO2 nanomaterial (>95%) was retained in the sewage sludge and only 3-4% was found in the effluent. No effect of the TiO2 nanomaterials on the biodegradation or nitrification was observed.
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http://dx.doi.org/10.1016/j.chemosphere.2013.11.015DOI Listing
June 2014

Birnessite-induced binding of phenolic monomers to soil humic substances and nature of the bound residues.

Environ Sci Technol 2012 Aug 10;46(16):8843-50. Epub 2012 Aug 10.

Biology 5, Environmental Biology and Chemodynamics, RWTH Aachen University, D-52056 Aachen, Germany.

The nature of the abiotic birnessite (δ-MnO(2))-catalyzed transformation products of phenolic compounds in the presence of soil organic matter is crucial for understanding the fate and stability of ubiquitous phenolic carbon in the environment. (14)C-radioactive and (13)C-stable-isotope tracers were used to study the mineralization and transformation by δ-MnO(2) of two typical humus and lignin phenolic monomers--catechol and p-coumaric acid--in the presence and absence of agricultural and forest soil humic acids (HAs) at pH 5-8. Mineralization decreased with increasing solution pH, and catechol was markedly more mineralized than p-coumaric acid. In the presence of HAs, the mineralization was strongly reduced, and considerable amounts of phenolic residues were bound to the HAs, independent of the solution pH. The HA-bound residues were homogeneously distributed within the humic molecules, and most still contained the unchanged aromatic ring as revealed by (13)C NMR analysis, indicating that the residues were probably bound via ester or ether bonds. The study provides important information on δ-MnO(2) stimulation of phenolic carbon binding to humic substances and the molecular distribution and chemical structure of the bound residues, which is essential for understanding the environmental fates of both naturally occurring and anthropogenic phenolic compounds.
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http://dx.doi.org/10.1021/es3018732DOI Listing
August 2012

Effect of soil organic matter chemistry on sorption of trinitrotoluene and 2,4-dinitrotoluene.

J Hazard Mater 2010 Jan 25;173(1-3):343-8. Epub 2009 Aug 25.

Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi-110012, India.

The sorption of organic contaminants in soil is mainly attributed to the soil organic matter (SOM) content. However, recent studies have highlighted the fact that it is not the total carbon content of the organic matter, but its chemical structure which have a profound effect on the sorption of organic contaminants. In the present study sorption of two nitroaromatic contaminants viz. trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT) was studied in different SOM fractions viz. a commercial humic acid, commercial lignin and humic acid and humin extracted from a compost. (13)C-DP/MAS NMR studies indicated that the structural composition of the organic carbon in different SOM fractions was different. The order of sorption of the nitroaromatics in the different sorbents was: humic acid-commercial>humic acid-compost>humin approximately lignin. Among the aliphatic and aromatic carbon fractions (representing bulk of SOM matrix), adsorption parameter K(f)(1/n) for nitroaromatics sorption correlated well with the aliphatic carbon (r=0.791 for TNT and 0.829 for 2,4-DNT) than the aromatic carbon (r=0.634 for TNT and r=0.616 for 2,4-DNT). However, among carbon containing functional groups, carbonyl carbon showed strong positive correlation with sorption of TNT (r=0.991) and 2,4-DNT (r=0.967) while O-alkyl carbon showed negative correlation (r=0.832 for TNT and r=0.828 for 2,4-DNT). The study indicates that aliphatic domains in the SOM significantly affect the non-specific sorption of both the nitroaromatic contaminants.
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http://dx.doi.org/10.1016/j.jhazmat.2009.08.090DOI Listing
January 2010

An indispensable asset at risk: merits and needs of chemicals-related environmental sciences.

Environ Sci Pollut Res Int 2009 Jun 26;16(4):410-3. Epub 2009 May 26.

Institute for Environmental Research (Biology V), RWTH Aachen University, 52074, Aachen, Germany.

Background: Modern societies depend on environmental sustainability and on new generations of individuals well-trained by environmental research and teaching institutions. In the past, significant contributions to the identification, assessment, and management of chemical stressors with legal consequences have been made.

Main Features: Within this article, we intend to elucidate the merits and the emerging challenges of chemicals-related environmental sciences. The manuscript is supported by more than 70 professors and university academics of leading institutions in Germany, Switzerland, Austria, and other countries in Europe, but addresses topics of global concern.

Results And Discussion: Many environmental problems of pollutants remain to be addresses, since new chemical compounds or classes of new compounds are continuously developed and brought to the market and sooner or later "emerge" in the environment. Further issues are the inclusion of transformation products and chemical mixtures in environmental risk assessment, the long-term presence of xenobiotics bound to soils and sediments, as well as an understanding of the ecological relevance of ecotoxicological end points.

Conclusion And Perspectives: We point out the need for a strong academic research and education system in chemicals-related environmental sciences to ministries, politicians, and research funding institutions and we propose to create specific units in the national funding bodies that address basic and interdisciplinary research in this field.
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http://dx.doi.org/10.1007/s11356-009-0157-xDOI Listing
June 2009

Spatial distribution and characterization of long-term aged 14C-labeled atrazine residues in soil.

J Agric Food Chem 2008 Oct 23;56(20):9548-54. Epub 2008 Sep 23.

Institute of Chemistry and Dynamics of the Geosphere, ICG-4Agrosphere, Central Division of Analytical Chemistry (ZCH), Forschungszentrum Julich GmbH, 52425 Julich, Germany.

The long-term behavior of the herbicide atrazine and its metabolites in the environment is of continued interest in terms of risk assessment and soil quality monitoring. Aqueous desorption, detection, and quantification of atrazine and its metabolites from an agriculturally used soil were performed 22 years after the last atrazine application. A lysimeter soil containing long-term aged atrazine for >20 years was subdivided into 10 and 5 cm layers (at the lysimeter bottom: soil 0-50 and 50-55 cm; fine gravel 55-60 cm depth, implemented for drainage purposes) to identify the qualitative and quantitative differences of aged (14)C-labeled atrazine residues depending on the soil profile and chemico-physical conditions of the individual soil layers. Deionized water was used for nonexhaustive cold water shaking extraction of the soil. With increasing soil depth, the amount of previously applied (14)C activity decreased significantly from 8.8% to 0.7% at 55-60 cm depth whereas the percentage of desorbed (14)C residues in each soil layer increased from 2% to 6% of the total (14)C activity in the sample. The only metabolite detectable by means of LC-MS/MS was 2-hydroxyatrazine while most of the residual (14)C activity was bound to the soil and was not desorbed. The amount of desorbed 2-hydroxyatrazine decreased with increasing soil depth from 21% to 10% of the total desorbed (14)C residue fraction. The amount of (14)C residues in the soil layers correlated well with the carbon content in the soil and in the aqueous soil extracts ( p value = 0.99 and 0.97, respectively), which may provide evidence of the binding behavior of the aged atrazine residues on soil carbon. The lowest coarse layer (55-60 cm) showed increased residual (14)C activity leading to the assumption that most (14)C residues were leached from the soil column over time.
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http://dx.doi.org/10.1021/jf8017832DOI Listing
October 2008

Bioaccessibility of environmentally aged 14C-atrazine residues in an agriculturally used soil and its particle-size aggregates.

Environ Sci Technol 2008 Aug;42(16):5904-10

Forschungszentrum Jülich GmbH, Institute of Chemistry and Dynamics of the Geosphere, ICG-4--Agrosphere, 52425 Jülich, Germany.

After 22 years of aging under natural conditions in an outdoor lysimeter the bioaccessibility of 14C-labeled atrazine soil residues to bacteria was tested. Entire soil samples as well as sand-sized, silt-sized, and clay-sized aggregates (>20, 20-2, and <2microm aggregate size, respectively) were investigated under slurried conditions. The mineralization of residual radioactivity in the outdoor lysimeter soil reached up to 4.5% of the total 14C-activity after 16 days, inoculated with Pseudomonas sp. strain ADP. The control samples without inoculated bacteria showed a mineralization maximum of only about 1% after 44 days of incubation. Mineralization increased in the clay-sized aggregates up to 6.2% of the total residual 14C-activity within 23 days. With decreasing soil aggregate sizes, residual 14C-activity increased per unit of weight, but only minor differences of the mineralization in the soil and soil size aggregates using mineral-media for incubation was observed. Using additional Na-citrate in the incubation, the extent of mineralization increased to 6.7% in soil after 23 days following incubation with Pseudomonas sp. strain ADP. These results show that long-term aged 14C-atrazine residues are still partly accessible to the atrazine degrading microorganism Pseudomonas sp. strain ADP.
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http://dx.doi.org/10.1021/es800196zDOI Listing
August 2008

Sorption-desorption of trinitrotoluene in soils: effect of saturating metal cations.

Bull Environ Contam Toxicol 2008 May 22;80(5):443-6. Epub 2008 May 22.

Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi 110012, India.

Clay minerals in soils control the sorption and mobility of nitroaromatics in munitions contaminated soils. Therefore, effect of exchangeable cations (NH4+ , K+, Ca2+, and Al3+) on sorption-desorption of trinitrotoluene (TNT) was studied in two reference soils viz sandy loam and silty clay. Compared to control soils, K+ ion saturation significantly increased TNT sorption in both the soils, while other cations decreased TNT sorption. Effect of K+ saturation on sorption of TNT was more pronounced in organic matter poor sandy loam soil (seven times) then silty clay (two times). Desorption followed the reverse trend and greater amounts of sorbed TNT were retained in the K+ saturated soils.
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http://dx.doi.org/10.1007/s00128-008-9455-0DOI Listing
May 2008

Hydrolysed wool: a novel chelating agent for metal chelant-assisted phytoextraction from soil.

Chemosphere 2008 Jun 16;72(4):525-31. Epub 2008 May 16.

Institut für Biologie V - Umweltchemie, RWTH Aachen, Worringerweg 1, 52056 Aachen, Germany.

Phytoextraction has revealed great potential, however it is limited by the fact that plants need time and nutrient supply and have a limited metal uptake capacity. Although the use of synthetic chelators, such as EDTA, enhances heavy metal extraction, it also produces the negative side effects of high phytotoxicity, as well as leaching of essential metals. The aim of this research was to investigate the application of wool, in mobilising metals and in improving the phytoextraction of metals-contaminated soil. We performed column experiments with 14 d and 7 d partially hydrolysed wool as chelating agent on a silty-loamy sand agricultural soil. In the column experiment the 14 d wool hydrolysate mobilised 68% of Cu in soil, whereas in the case of Cd it mobilised 5.5%. The model plant selected for the phytoextraction experiments was tobacco (Nicotiana tabacum). The plant uptake of Cd and Cu, assisted by the application of 6.6 g kg(-1) wool hydrolysate was increased by 30% in comparison to the control plants. The application of 13.3 g kg(-1) wool hydrolysate enhanced the Cu uptake by up to 850%. Moreover, high leaching probability frequently observed when applying chelating agents, such as EDTA or ethylene diamine disuccinate (EDDS), were not detected. The use of hydrolysed wool therefore merits further investigation.
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http://dx.doi.org/10.1016/j.chemosphere.2008.03.063DOI Listing
June 2008

Mobility and degradation of trinitrotoluene/metabolites in soil columns: effect of soil organic carbon content.

J Environ Sci Health A Tox Hazard Subst Environ Eng 2008 Jun;43(7):682-93

Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi, India.

There has been increasing interest in enhancing natural attenuation of munitions-contaminated soils. Present study reports the effect of increasing soil organic matter content on fate and mobility of trinitrotoluene (TNT) and metabolites in soil columns. This study was performed using 30-cm-long columns containing a top 5 cm of contaminated soil as a source layer and an uncontaminated soil (25 cm) adjusted to 0.5, 1.0, 1.5 and 3.0% organic carbon (OC) content using compost. Contaminated soil layer was fortified with uniformly ring-labeled (14)C-trinitrotoluene (TNT) or 2,4-dinitrotoluene (DNT); in total there were 8 treatments. Columns were leached with synthetic rain water under unsaturated flow conditions in downside up direction. There was significant increase in the retention of both (14)C-TNT and (14)C-DNT in soils with increasing soil OC content and in 3.0% soil OC content column < 1% TNT/DNT was recovered in the leachate. Further, degradation of TNT and metabolites from contaminated soil was significantly increased and resulted in greater soil-bound residues. Formation of monoamino-dinitrotoluene (ADNTs), diamino-mononitrotoluene (DANTs) and monoamino-mononitrotoluene (ANTs) metabolites was greatly enhanced with increase in OC content of soils. Study suggests that increasing OC content of contaminated soil to 3.0% significantly enhanced the reduction of nitroaromatics to more polar amine metabolites and the formation of soil-bound residues.
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http://dx.doi.org/10.1080/10934520801959823DOI Listing
June 2008

Degradation of trinitrotoluene in contaminated soils as affected by its initial concentrations and its binding to soil organic matter fractions.

J Environ Sci Health A Tox Hazard Subst Environ Eng 2008 Mar;43(4):348-56

Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi, India.

Trinitrotoluene (TNT), a nitroaromatics, is a major pollutant in explosive contaminated soils. Present study reports the effect of initial concentration of TNT on its degradation kinetics in soils. Soils from two contaminated sites viz. Clausthal and Elsnig, Germany, were mixed with an uncontaminated reference soil to get different initial concentrations (mg/kg) viz Clausthal-1 (54.29), Clausthal-2 (30.86), Clausthal-3 (7.05) Elsnig-1 (879.67), Elsnig-2 (86.43); Elsnig-3 (8.16) and Elsnig-4 (0.99) and were spiked with ring UL-(14)C-TNT (100KBq/50g soil). Except Elsnig-1 and Elsnig-2 soils, TNT degraded at same rate in all the soils. Higher persistence of TNT in Elsnig-1 and Elsnig-2 soils appears to be due to higher initial concentrations of nitroaromatics which may be toxic to soil microorganisms. 2-Amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT) were recovered as major metabolites of TNT. Distribution of bound (14)C-activity in different soil organic matter (SOM) fractions (humic acid, fulvic acid and humin) was assayed by alkali extraction of solvent extracted Clausthal-1 and Elsnig-1 soils. Results indicate that humic acid accounted for maximum bound activity followed by fulvic acid and humin fractions. Expressing (14)C-activity bound/unit weight of organic carbon content of SOM fractions showed that 3 times more (14)C-activity was bound to Elsnig humic acid than Clausthal humic acid. Similarly, activity associated with Elsnig fulvic acid was 7 times higher than that of Clausthal fulvic acid suggesting that chemical nature of SOM fractions plays a significant role in binding of contaminants.
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http://dx.doi.org/10.1080/10934520701795434DOI Listing
March 2008

Chelate assisted phytoextraction of heavy metals from soil. Effect, mechanism, toxicity, and fate of chelating agents.

Chemosphere 2007 Jun 8;68(6):989-1003. Epub 2007 Mar 8.

Institut für Biologie V, RWTH Aachen, Worringerweg 1, 52056 Aachen, Germany.

The low-cost, plant-based phytoextraction technique has often been described as a promising technique to remediate heavy metal contaminated agricultural land. The application of chelating agents has shown positive effects in increasing the solubility of heavy metals in soil and therefore in enhancing phytoextraction. This paper gives an overview of the chelating agents applied in recent studies. Various synthetic aminopolycarboxylic acids, such as ethylene diamine tetraacetic acid, and natural ones such as, ethylene diamine disuccinate and nitrilotriacetic acid, are described. Additionally, results of the application of natural low molecular weight organic acids, such as citric and tartaric acid are given. The effectiveness of these different chelating agents varies according to the plant and the heavy metals used. Furthermore, a focus is laid on the chelating agents fate after application and on its toxicity to plants and soil microorganisms, as well as it degradation. The rate of degradation is of great importance for the future of chelate assisted phytoextraction as it has a direct impact on the leaching probability. An effective prevention of leaching will be crucial for the acceptance and the economic breakthrough of enhanced phytoextraction, but a satisfactory solution to this key issue has so far not been found. Possibly further experiments in the field of enhanced phytoextraction will be able to solve this major problem, but over decades various greenhouse experiments and recently field experiments have resulted in different observations. Therefore, it is questionable if further research in this direction will lead to a promising solution. Phytoextraction has possibly reached a turning point in which it should distance itself from chelate assisted phytoextraction and focus on alternative options.
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http://dx.doi.org/10.1016/j.chemosphere.2007.01.062DOI Listing
June 2007

The influence of EDDS and EDTA on the uptake of heavy metals of Cd and Cu from soil with tobacco Nicotiana tabacum.

Chemosphere 2007 Jun 5;68(2):345-53. Epub 2007 Feb 5.

Institut für Biologie V, RWTH Aachen, Worringerweg 1, 52056 Aachen, Germany.

Phytoextraction, the use of plants to extract contaminants from soils and groundwater, is a promising approach for cleaning up soils contaminated with heavy metals. In order to enhance phytoextraction the use of chelating agents has been proposed. This study aims to assess whether ethylene diamine disuccinate (EDDS), a biodegradable chelator, can be used for enhanced phytoextraction purposed, as an alternative to ethylene diamine tetraacetate (EDTA). EDDS revealed a higher toxicity to tobacco (Nicotiana tabacum) in comparison to EDTA, but no toxicity to microorganisms. The uptake of Cu was increased by the addition of EDTA and EDDS, while no increase was observed in the uptake of Cd. Both chelating agents showed a very low root to shoot translocation capability and the translocation factor was lower than the one of the control. Heavy metals where significantly more phytoavailable than in the control, even after harvesting, resulting in a high heavy metal leaching possibility, probably owing to a low biodegradation rate of EDDS. New seedlings which were transplanted into the EDDS treated pots 7d after the phytoextraction experiment, showed signs of necrosis and chlorosis, which resulted in a significantly lower biomass in comparison to the control. The seedlings on the EDTA treated pots showed no toxicity signs. Contrary to previous opinions the results of this study revealed the chelating agents EDTA and EDDS as unsuitable for enhanced phytoextraction using tobacco.
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http://dx.doi.org/10.1016/j.chemosphere.2006.12.058DOI Listing
June 2007

Cyanide phytoremediation by water hyacinths (Eichhornia crassipes).

Chemosphere 2007 Jan 25;66(5):816-23. Epub 2006 Jul 25.

Institut für Biologie V, Umweltchemie, RWTH Aachen, Worringerweg 1, 52056 Aachen, Germany.

Although cyanide is highly toxic, it is economically attractive for extracting gold from ore bodies containing only a few grams per 1000 kg. Most of the cyanide used in industrial mining is handled without observable devastating consequences, but in informal, small-scale mining, the use is poorly regulated and the waste treatment is insufficient. Cyanide in the effluents from the latter mines could possibly be removed by the water hyacinth Eichhornia crassipes because of its high biomass production, wide distribution, and tolerance to cyanide (CN) and metals. We determined the sodium cyanide phytotoxicity and removal capacity of E. crassipes. Toxicity to 5-50 mg CN L(-1) was quantified by measuring the mean relative transpiration over 96 h. At 5 mgCNL(-1), only a slight reduction in transpiration but no morphological changes were observed. The EC(50) value was calculated by probit analysis to be 13 mgCNL(-1). Spectrophotometric analysis indicated that cyanide at 5.8 and 10 mgL(-1) was completely eliminated after 23-32 h. Metabolism of K(14)CN was measured in batch systems with leaf and root cuttings. Leaf cuttings removed about 40% of the radioactivity from solution after 28 h and 10% was converted to (14)CO(2); root cuttings converted 25% into (14)CO(2) after 48 h but only absorbed 12% in their tissues. The calculated K(m) of the leaf cuttings was 12 mgCNL(-1), and the V(max) was 35 mg CN(kg fresh weight)(-1)h(-1). Our results indicate that E. crassipes could be useful in treating cyanide effluents from small-scale gold mines.
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http://dx.doi.org/10.1016/j.chemosphere.2006.06.041DOI Listing
January 2007

Evaluation of the effect of small organic acids on phytoextraction of Cu and Pb from soil with tobacco Nicotiana tabacum.

Chemosphere 2006 May 6;63(6):996-1004. Epub 2005 Dec 6.

Institut für Biologie V, RWTH Aachen, Worringerweg 1, 52056 Aachen, Germany.

Phytoremediation, the use of plants to extract contaminants from soils and groundwater, is a promising approach for cleaning up soils contaminated with heavy metals. However its use is limited by the time required for plant growth, the nutrient supply and, moreover, by the limited metal uptake capacity. Synthetic chelators have shown positive effects in enhancing heavy metal extraction, but they have also revealed several negative side-effects. The objective of this study was to investigate the use of three natural low molecular weight organic acids (NLMWOA) (citric, oxalic, and tartaric acid) as an alternative to synthetic chelators. Slurry-, column-, toxicity- and phytoextraction experiments were performed. For the phytoextraction experiment the three NLMWOA were applied to a copper- and a lead-contaminated soil respectively. A significant increase in copper uptake was visible only in the citric acid treatment (67 mg kg-1) in comparison to the EDTA treatment (42 mg kg-1). The NLMWOA application showed no enhanced effect concerning the lead phytoextraction. A possible explanation for this lack of significance could be the rate of the degradation of NLMWOA. This rate might well be too high for these heavy metals with low mobility and bioavailability such as lead. The amounts of NLMWOA applied to the soil were very high (62.5 mmol kg-1 of soil) and the effect was too little. In this respect EDTA, which was applied in very small amounts (0.125 mmol kg-1) was more efficient. Thus making NLMWOA unsuitable to enhance phytoextraction of heavy metals from soil.
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http://dx.doi.org/10.1016/j.chemosphere.2005.08.042DOI Listing
May 2006

The influence of humic acids on the phytoextraction of cadmium from soil.

Chemosphere 2004 Oct;57(3):207-13

Institut für Biologie V-Umweltchemie, RWTH Aachen, Worringerweg 1, Aachen D-52056, Germany.

Cadmium poses a major environmental and human health threat because of its constant release through anthropogenic activities. A need, therefore, exists for cost-effective remediation procedures. Phytoremediation, the use of plants to extract contaminants from soils and groundwater, has revealed great potential. However, it is limited by the fact that plants need time, nutrient supply and, moreover, have a limited metal uptake capacity. Synthetic chelators have shown positive effects in enhancing heavy metal extraction through phytoremediation, but they have also revealed a vast number of negative side-effects. The objective of this research was to investigate the use of humic acids as an alternative to synthetic chelators. Humic acids were applied to a cadmium-contaminated soil at various dosages, and the uptake of cadmium into Nicotiana tabacum SR-1 was determined in relation to the amounts of total and bioavailable cadmium in the soil. It was found that the theoretical bioavailability of cadmium, as determined by diethylenetriaminepentaacetic acid (DTPA) extraction, did not change, but its plant uptake was enhanced significantly, in some cases up to 65%. Humic acids added at a rate of 2 g kg(-1) soil increased the cadmium concentration in the shoots from 30.9 to 39.9 mg kg(-1). A possible reason for this enhancement is the decrease in pH, resulting in higher cadmium availability. Another possibility taken into account is that plants may take up cadmium complexes with humic acid fragments, which result from microbiological degradation or, self-dissociation.
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http://dx.doi.org/10.1016/j.chemosphere.2004.06.017DOI Listing
October 2004

Mineralization, metabolism and formation of non-extractable residues of 14C-labelled organic contaminants during pilot-scale composting of municipal biowaste.

Environ Pollut 2003 ;126(1):83-91

Fraunhofer-Institute for Molecular Biology and Applied Ecology, Auf dem Aberg 1, D-57392 Schmallenberg, Germany.

Use of municipal biowaste for composting instead of its disposal has become a major source of concern as regards contamination by hazardous substances. To elucidate the hazard potential of compost application, municipal biowaste was amended with 14C-labelled model substances (pyrene, simazine) and incubated in a pilot-scale composting simulation system. A mass balance incorporating the mineralization, metabolism and sorption of the two model substances was established over a period of 370 days. The results are quite different for the two chemicals, reflecting their intrinsic properties: more than 60% of the applied 14C-simazine resulted in non-extractable residues (NER). Silylation experiments indicated that the formation of NER from simazine and its metabolites was due to both physical entrapment in the matrix and chemical binding. The mineralization and formation of NER represented the major pathways of disappearance for pyrene during one year of composting, accounting for 60 and 26% of initially applied 14C-activity, respectively. Mineralization occurred delayed after the thermophilic phase. As regards remobilization, release of pyrene from NER during composting could be excluded, whereas simazine, data were inconclusive in this respect.
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http://dx.doi.org/10.1016/s0269-7491(03)00143-xDOI Listing
October 2003

Investigations on the binding mechanism of the herbicide simazine to dissolved organic matter in leachates of compost.

Chemosphere 2002 Nov;49(6):597-604

Department of Biology V-Environmental Chemistry, University of Technology Aachen, Germany.

14C-labelled simazine was composted together with biowaste on a pilot (m3) scale. The herbicide was quickly bound to the compost matrix. By aqueous extraction of 29 and 200 days old compost (equivalent to thermophilic and mesophilic phase of composting) only 4.2% and 3.1% respectively of the radioactivity in the compost samples could be extracted with water. Analysis of the extracts using high-performance size exclusion chromatography (HPSEC) revealed that the dissolved organic matter (DOM) had molecular weights ranging between 2 and 28 kDa. The amount of DOM-associated radioactivity increased from 53% (day 29) to 65% (day 200) of total extractable radioactivity. The type of binding of the 14C-labelled residues and the DOM was elucidated by silylation of humic matter and subsequent HPSEC. The data demonstrated that besides polar metabolites also intact simazine was bound to the DOM. A distinct shift from rather weak interactions to strong covalent linkages of simazine and its metabolites with increasing age of the compost was observed. The results showed that only low amounts of free simazine and its degradates can be extracted with water. We concluded that the shift towards stable covalent linkages is equivalent to a detoxification of the contaminant in aged compost. Consequently, the use of the analysed compost in its mature stage should not pose an environmental risk to the groundwater or the subsoil.
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http://dx.doi.org/10.1016/s0045-6535(02)00333-8DOI Listing
November 2002