bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the response of three microalgae species exposed to elutriates of estuarine sediments based on growth and chemical speciation
Authors: Mucha Ana P. , Leal M. Fernanda C. , Bordalo Adriano A. , Vasconcelos M. Teresa S. D.
Published: March 2010

The elutriate sediment toxicity test (ESTT) provides a measure of the amount of a substance that is exchanged between the sediment and the aqueous phase during resuspension processes such as floods or dredging operations. This study used ESTT with two complementary aims: a comparison of the elutriates of two estuarine sediments (anaerobic muddy [A] and aerobic sandy [B]) in terms of toxicity and a comparison of the response of three different microalgae (Emiliania huxleyi (coccolithophore), Dunaliella minuta (green alga), and Phaeodactylum tricornutum (diatom)) to each elutriate in terms of growth, heavy metals uptake, and organic ligands release or uptake in order to find eventual differences of sensitivity. The interpretation of the results was based on chemical speciation in the culture media. Both elutriates, particularly A, were much richer than seawater (control medium) in some heavy metals and organic ligands able to bind strongly heavy metals. Elutriate A slightly inhibited P. tricornutum growth but stimulated growth of E. huxleyi and D. minuta. Elutriate B stimulated the growth of the three algal species. Therefore, the diatom behaved differently from both the coccolithophore and the green alga. Strong complexation of trace metals by organic ligands could be the cause of absence of the metallic toxicity of the elutriates. Growth inhibition of P. tricornutum in elutriate A could be caused by ammonia‐N and/or organic compounds. The concentration of the organic ligands decreased markedly (about 75%) in both elutriates after 10 d of incubation in contrast to the control culture, where their concentration increased about 50% because of exudation. This phenomenon was interpreted to result from ligand uptake by the algae, free or as metal complexes. This work demonstrated that beside the evaluation of toxicity of free heavy metals to alga species, the organic ligands must not be ignored. Depending on the amount of ligand present, the toxicity can be reduced (sequestration) or enhanced (better availability through uptake of metal‐ligand complexes). Since the applied ESTT is a standard procedure (U.S. Environmental Protection Agency) for the evaluation of dredged material proposed for ocean disposal, it is necessary to discuss results obtained during toxicity tests with such elutriates in detail.
Relationships between mercury body concentrations, standard metabolic rate, and body mass in eastern mosquitofish (Gambusia holbrooki) from three experimental populations
Authors: Hopkins William A. , Tatara Christopher P. , Brant Heather A. , Jagoe Charles H.
Published: March 2010

Eastern mosquitofish (Gambusia holbrooki) were sampled from three experimental populations (two Hg-exposed populations and one reference population) to determine whether transgenerational exposure (lifelong exposure of multiple generations) to Hg adversely affects standard metabolic rate (SMR). Mosquitofish subjected to lifelong Hg exposure accumulated significant concentrations of Hg in their tissues compared to fish from the reference population (mean: 3.89–4.13 vs 0.08 μHg/g wet mass, respectively). Less than 10% of the variability in Hg tissue concentrations could be explained by fish body mass, likely because of the short life span and/or dietary habits of this species. Despite the high body burdens of Hg in exposed fish, we found no significant difference in SMR among individuals from Hg-exposed or reference populations. Our findings contrast recent laboratory work describing elevated SMR in mosquitofish exposed to 100 μg/L dissolved inorganic Hg for 48 h. To account for contrasting results between studies, we hypothesize that acute exposure to dissolved inorganic Hg damages gill epithelium, resulting in increased metabolic rate, but that lifelong Hg exposure via trophic uptake of methyl mercury does not affect fish respiratory structures. Alternative hypotheses include the possibility that G. holbrooki is a species that can tolerate high body burdens of Hg or that more than four years of genetic isolation during Hg exposure (8–12 generations) resulted in selection for Hg-tolerant or -resistant individuals.
Essential and desirable characteristics of ecotoxicity quantitative structure–activity relationships
Authors: Schultz T. Wayne , Cronin Mark T. D.
Published: March 2010

Quantitative structure–activity relationships (QSAR) developed and applied in the prediction of ecotoxic potencies far out number those in other areas, such as health effects. There are yet to be any formal guidelines for the development of ecotoxicological QSARs. Despite this, the depth and breadth of our knowledge of QSARs as they apply to ecotoxicology, especially short-term aquatic toxicity, allow for the formulation of characteristics that appear to be essential and/or desirable for high-quality QSARs. The three components of a QSAR are the biological activity, the property/structural descriptors, and the statistical methodology. Problems may arise from all three components and may be compounded by interactions between them. In an effort to minimize any tribulations associated with development and application of ecotoxic QSARs, a number of essential or desirable characteristics have been identified. Ecotoxicological data used in formulating the QSAR must be reliable, of high quality, and reflect a well-defined and continuous endpoint; this dataset should be diverse both in terms of potency and chemical structure (i.e., property). Descriptors used in formulating the QSAR should be of high quality, reproducible, of a number and type consistent with the endpoint being modeled, and when possible allow for a mechanistic interpretation of the QSAR. The statistical process used in formulating a QSAR should be as rigorous as possible, appropriate for the endpoint being modeled, and allow for the development of as easily interpretable (i.e., transparent) QSARs as possible. The resultant QSAR should be validated, only used within the descriptor space and chemical domain of the model, and relied on in relation to the total weight of evidence; precision of the QSAR and expectations from its application need to be related to the error in the original ecotoxicological and descriptor measurements. Finally, development of QSARs should be through the interaction of a group of multidisciplinary experts.
Perfluorooctane sulfonic acid in bib (Trisopterus luscus) and plaice (Pleuronectes platessa) from the Western Scheldt and the Belgian North Sea: Distribution and biochemical effects
Authors: Hoff Philippe T. , Van de Vijver Kristin , Van Dongen Walter , Esmans Eddy L. , Blust Ronny , De Coen Wim M.
Published: March 2010

A biomonitoring campaign was conducted in the Belgian North Sea and in the Western Scheldt (The Netherlands) with the primary goal to assess perfluorooctane sulfonic acid (PFOS) contamination and distribution in different biota. This study covers the results obtained for bib (Trisopterus luscus) and plaice (Pleuronectes platessa) and includes the assessment of some stress-related biochemical endpoints. Analysis of liver and muscle PFOS concentrations of both species provided evidence for the existence of a PFOS pollution gradient along the Western Scheldt with higher levels at the upstream locations and a lower degree of PFOS pollution at the marine locations. Cellular necrosis was studied by measuring aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in the serum. Serum ALT but not serum AST was shown to correlate positively with the PFOS liver concentration in bib (r = 0.44, p < 0.05), indicating that PFOS might contribute to the induction of hepatic damage in bib in the area of study. Analysis of total carbohydrate, lipid, and protein content of bib liver tissue revealed a positive correlation between the protein content and the PFOS liver concentration (r = 0.55, p < 0.01). Whether this is due to induction of compensatory mechanisms, detoxification, or repair processes remains unclear.
Biomass growth, micronucleus induction, and antioxidant stress enzyme responses in Vicia faba exposed to cadmium in solution
Authors: Rosa Edson V. Cordova , Valgas Cleidson , Souza-Sierra Maria M. , Corrěa Albertina X. R. , Radetski Claudemir Marcos
Published: March 2010

Biomass growth, micronucleus induction, and antioxidative stress enzymes (superoxide dismutase, peroxidase, glutathione reductase, and catalase) were investigated simultaneously in the Vicia faba plant exposed to cadmium in solution. The biomass lowest-observed-effect concentration (LOEC) value was 2,000 μM Cd2+. In the shoots, enzymic activities increased without concentration–response relationships. In the roots, after an initial increase, activities of all enzymes showed negative concentration-response relationships. A significant increase in micronucleus induction was observed at 20 μM Cd2+. Regarding sensitivity, our results showed that biomass endpoint was less sensitive than micronucleus induction, which was less sensitive than antioxidative enzyme activities. The increase of antioxidant stress enzyme activities in response to cadmium exposure may be taken as evidence for an enhanced detoxification capacity of V. faba plants toward reactive oxygen species (and derivatives) that might be generated in the stressed plants. Concomitant micronucleus induction may be also interpreted as a consequence of oxidative stress, upholding the view that cadmium-induced DNA damage is, to some extent, via generation of reactive (intermediate) oxygen species.
Analysis of monitoring data of pesticide residues in surface waters using partial order ranking theory
Authors: Sørensen Peter B. , Brüggemann Rainer , Carlsen Lars , Mogensen Betty B. , Kreuger Jenny , Pudenz Stefan
Published: March 2010

In this investigation, a new and simple way to analyze, interpret, and generalize monitoring data of occurrence of pesticide active ingredients in surface waters was developed. The occurrence is quantified using the variables frequency of detection and the concentration level. These two parameters are associated with basically different ecotoxicological effects; for example, a high frequency of detection may be related to bioaccumulation problems, while the level of concentration also controls the acute toxicological effects. The active ingredients were ranked on the basis of the monitoring data in relation to both the frequency of finding and concentration level using the concept of partial ordered sets. The resulting rankings was correlated with other rankings based on descriptors such as sprayed area, applied dose, adsorption to soil organic carbon, vapor pressure, and soil dissipation half-life. A similarity index was applied in order to compare the ranking of the monitoring data with the ranking of the descriptors. It is shown how partial order theory can be used to evaluate the relevance of every single descriptor. The dosage is found to be the most important descriptor, followed by the sprayed area and the adsorption to organic carbon ending up a very close similarity between, respectively, the rankings using monitoring data and rankings using these three descriptors.
Genetic structure and mtDNA diversity ofFundulus heteroclituspopulations from polycyclic aromatic hydrocarbon-contaminated sites
Authors: Mulvey Margaret , Newman Michael C. , Vogelbein Wolfgang K. , Unger Michael A. , Ownby David R.
Published: March 2010

Genetic structure and diversity of mummichog (Fundulus heteroclitus) populations were investigated using mitochondrial DNA (mtDNA) sequences. Forty-six haplotypes were identified among 208 mummichog from the Elizabeth and York Rivers in Virginia, USA. No evidence of decreased gene or nucleotide diversity for mummichog from polycyclic aromatic hydrocarbon (PAH)-contaminated sites was observed. However, based on mtDNA data from 17 sites, a significant correlation (Mantel analysis, p = 0.035) was noted between genetic distance (FST) and PAH concentration but not between genetic distance and geographic distance. Mummichog from the most heavily PAH-contaminated site, Atlantic Wood (AW), were genetically distinct from those of other Elizabeth River sites. At AW, high frequencies of several divergent haplotypes were observed that were more closely allied to the northern mummichog than to the more abundant southern form in the Chesapeake Bay. These data suggested that a locally stable population existed at the AW site. This conclusion is consistent with the observation that mummichog from the AW site display enhanced tolerance to PAH contamination relative to mummichog from noncontaminated sites. Conclusions about gene diversity and the correlation between genetic distance with site differences in PAH concentrations were also consistent with those from tandem genetic analyses based on allozymes.
Population-level responses to long-term cadmium exposure in two strains of the freshwater gastropod Biomphalaria glabrata: Results from a life-table response experiment
Authors: Salice Christopher J. , Miller Thomas J.
Published: March 2010

A life-table response experiment was conducted to ascertain the demographic effects of low-level cadmium exposure on two strains, BS90 and NMRI, of the freshwater gastropod Biomphalaria glabrata. Snails were exposed to cadmium continuously from the embryonic stage through adulthood. Results indicated that cadmium significantly affected a number of individual-based parameters, including %hatch, juvenile survival, and adult survival in both strains. Also, fecundity and time to maturity were significantly affected in the NMRI strain. A stage-based, deterministic, population model indicated that population growth rate (Λ) was significantly affected by cadmium. Elasticity analysis indicated that juvenile survival, in general, had the greatest contribution to Λ. Decomposition analysis indicated that the effects of cadmium on the juvenile stage in BS90 and the embryonic stage in NMRI contributed most to cadmium-induced changes in Λ. The BS90 strain was more sensitive to cadmium toxicity than NMRI. Moreover, the two strains differed in pattern of response with different aspects of their respective life histories contributing to cadmiuminduced changes in Λ. Comparisons were also made between the main model, based on a Z transformation of the life-cycle graph, and more commonly used matrix models.
Enhancement of aerobic microbial degradation of polychlorinated biphenyl in soil microcosms
Authors: Manzano Manuel A. , Perales José A. , Sales Diego , Quiroga José M.
Published: March 2010

This article reports the results of various biodegradation experiments on polychlorinated biphenyl (PCB)-contaminated sandy soil employing a mixed culture of acclimatized bacteria. Following the optimization of different variables without chemical pretreatment, the elimination rate achieved of Aroclor® 1242 in slurry-phase reactors was 61% after four months of treatment, with the presence of biphenyl as cosubstrate being the most important factor affecting PCB biodegradation. The biodegradation occurred as a first-order process, and it proved most effective in respect to dichlorinated biphenyls (100% removal), followed by trichlorinated (92%) and tetrachlorinated biphenyls (24%). The results also showed that the degradability of PCBs in soil may be enhanced by an advanced oxidation pretreatment (Fenton reaction), producing almost 100% elimination of PCBs at the end of the integrated chemical-biological process and 72% mineralization of the intermediates generated during the chemical pretreatment.
Mineralization of aged atrazine, terbuthylazine, 2,4-D, and mecoprop in soil and aquifer sediment
Authors: Johannesen Helle , Aamand Jens
Published: March 2010

The effect of aging of the herbicides atrazine, terbuthylazine, 2,4-D, and mecoprop on their bioavailability to degrading microorganisms was studied in soil and aquifer sediment. 14C-ring-labeled herbicide (2.5 mg/kg) was added to sterilized soil or aquifer sediment and stored at 10°C for up to 103 d before inoculation with either the atrazine and terbuthylazine-degrading Pseudomonas sp. strain ADP (atrazine-degrading Pseudomonas) or an enriched culture able to mineralize 2,4-D and mecoprop. The initial mineralization rate and recovery of 14CO2 after 62 to 113 d of incubation were used as measures of the availability of the compounds to the microorganisms. Aging in soil reduced the initial mineralization of atrazine. Thus, only 17% of the added 14C-atrazine had been mineralized after 21 h of incubation when aged for 88 d as compared with 33% when the atrazine had been aged for 1 d. 14CO2 recovery was only 58% after 88 d of aging as compared with 81% when aged for 1 d. A similar effect of aging was seen with terbuthylazine. With 2,4-D, the effect of aging in soil on mineralization by the enriched culture was much smaller. Aging had no effect on mineralization of mecoprop in soil or on mineralization of any of the herbicides in aquifer sediment.
Degradation of carbazole, dibenzothiophene, and dibenzofuran at low temperature byPseudomonassp. strain C3211
Authors: Jensen Anne-Mette , Finster Kai Waldemar , Karlson Ulrich
Published: March 2010

Pseudomonas sp. strain C3211 was isolated from a temperate climate soil contaminated with creosote. This strain was able to degrade carbazole, dibenzothiophene and dibenzofuran at 10°C with acetone as a co-substrate. When dibenzothiophene was degraded by strain C3211, an orange compound, which absorbed at 472 nm, accumulated in the medium. Degradation of dibenzofuran was followed by accumulation of a yellowish compound, absorbing at 462 nm. The temperature optimum of strain C3211 for degradation of dibenzothiophene and dibenzofuran was at 20 to 21°C, while the maximum temperature for degradation was at 27°C. Both compounds were degraded at 4°C. Degradation at 10°C was faster than degradation at 25°C. This indicates that strain C3211 is adapted to life at low temperatures.
The application of high-performance liquid chromatography humic acid columns in determination of Koc of polycyclic aromatic compounds
Authors: Jonassen Kristoffer E. N. , Nielsen Torben , Hansen Poul Erik
Published: March 2010

An improvement of a method for determination of the distribution coefficient for polycyclic aromatic compounds (PAC) between organic carbon and water (Koc) by high-performance liquid chromatography (HPLC) is presented in this paper. By use of silica-based HPLC columns with chemically immobilized humic acid (Aldrich, Zigma-Aldrich, Taufkirchen, Germany), the retention of PAC to humic acid can be measured, and the results can, when they are compared to those from a blank column, be used to a direct determination of Koc. These values agree quite well with literature Koc values for two- to four-ringed PAC. Our work has shown that it is possible to use this method to investigate how environmental parameters like electrolyte concentration, pH, and temperature affect the sorption of PAC to humic acid. Thermodynamic parameters can be estimated from variable temperature experiments. The advantage of the method is its cost and manpower effectiveness.
Calculation of the interaction between dissolved organic carbon and organic micropollutants by three dimensional force field methods
Authors: Govers Harrie A. J. , van Roon André , Parsons John R.
Published: March 2010

A 3D optimized potential for liquid simulation (OPLS) force field method with 6–31 G* atomic charges and a geometrical optimization approach was studied for the calculation of enthalpies of transfer at 300 K of partitioning processes. A 3D fulvic acid model of dissolved organic carbon was built. Limonene, α-pinene, fluoranthene, p,p′-DDT, and 2,4-D were inserted into a general site of preference, and interaction energies were calculated. Energies of hydration were calculated and subtracted from fulvic acid-contaminant interactions. The resulting values for the enthalpies of transfer from water to dissolved organic carbon were -2.2, +0.9, -6.4, -4.0, and -4.3 kcal/mol for limonene, α-pinene, fluoranthene, p,p′-DDT, and 2,4-D, respectively. This led to a change of the partition constant by a factor of 0.17 to 1.27 at a temperature increase from 5 to 55°C. The values of fluoranthene and p,p′-DDT compared favorably with their experimental values of -4.4 and -5.0 kcal/mol. Prior to this, a general scaling factor for electrostatic interactions in both the pure liquid (sliq = 2.89) and the hydrated solute (shyd = 3.70) was derived from the experimental values of enthalpies of vaporization and aqueous solution. Resulting predicted enthalpies of vaporization deviated by -3.1 (water), 0.4 (limonene), 0.2 (α-pinene), 3.9 (fluoranthene), -3.0 (p,p′-DDT), and 0.9 (2,4-D) kcal/mol from experimental data, whereas enthalpies of aqueous solution deviated by -1.3 (limonene), -5.7 (α-pinene), 4.2 (fluoranthene), and 0.3 (p,p′-DDT) kcal/mol. Results are discussed in terms of molecular structures and their interactions.
A potential link between the turnover of soil organic matter and the release of aged organic contaminants
Authors: Reemtsma Thorsten , Savric Irena , Jekel Martin
Published: March 2010

Soil column experiments were conducted to investigate the release of aged organic contaminants (adsorbable organo-halogens, [AOX]) and the potential effects of microbial turnover of soil organic matter onto the contaminant release from two different soils of former wastewater infiltration sites. Under reference conditions, the total carbon flux ranged from 6 to 9 mg/kg/d from the two soils. More than 92% of it was due to mineralization (CO2) and below 8% to the dissolved organic carbon (DOC) in the column effluent. Despite very different organohalogen levels in the two soils, the fluxes of AOX were similar (1 μg/kg/d). Microbial activity was altered by changing temperature and the solution pH and by drying. In all experiments where increased microbial respiration (CO2 production) was observed, the release of organic contaminants in the column effluent also increased. Fluxes of nickel, zinc, and phosphate showed a completely different pattern, suggesting that their retention in soil is determined by chemical parameters. A linear correlation analysis provided clear evidence that AOX and DOC fluxes are closely linked to each other. However, the superimposition of abiotic and biotic processes in the soils did not allow a causal relation to be established between the mineralization of soil organic matter and the release of organic contaminants sequestered in the soil. Our findings suggest that microbial activity may have a significant impact on the extent to which contaminated soils may act as a source of persistent organic pollutants.
Availability of polycyclic aromatic hydrocarbons to earthworms (Eisenia andrei, Oligochaeta) in field-polluted soils and soil-sediment mixtures
Authors: Jager Tjalling , Baerselman Rob , Dijkman Ellen , de Groot Arthur C. , Hogendoorn Elbert A. , de Jong Ad , Kruitbosch Jantien A. W. , Peijnenburg Willie J. G. M.
Published: March 2010

The bioavailability of polycyclic aromatic hydrocarbons (PAHs) for earthworms (Eisenia andrei) was experimentally determined in seven field-polluted soils and 15 soil-sediment mixtures. The pore-water concentration of most PAHs was higher than predicted. However, most of the compound was associated with dissolved organic carbon (DOC) and not directly available for uptake by earthworms. The apparent sorption could be reasonably predicted on the basis of interactions with DOC; however, the biota-soil accumulation factors (BSAFs) for earthworms were up to two orders of magnitude lower than predicted by equilibrium partitioning. The large variability between sites was not fully explained by differences in sorption. Experimental results indicate that the pool of freely dissolved PAHs in the pore water became partially depleted because of uptake by the earthworms and that bioaccumulation is thus also influenced by the kinetics of PAH desorption and mass transport. A pilot study with Lumbricus rubellus showed that steady-state body residues were well correlated to E. andrei. Current results show that depositing dredge spoil on land may lead to increased bioavailability of the lower-molecular-weight PAHs. However, risk assessment can conservatively rely on equilibrium partitioning, but accurate prediction requires quantification of the kinetics of bioavailability.
Structural and functional approach to studying pesticide side-effects on specific soil functions
Authors: Liebich Jost , Schäffer Andreas , Burauel Peter
Published: March 2010

The microbial communities in the soil are responsible for material cycling and thus also for maintaining the fertilityof agricultural soils. In order to assess pesticide side effects on the soil processes, detailed knowledge is required about the structure and function of the soil microflora. Therefore, the degradation and humification of 14C-labeled maize straw was studied in processoriented microcosms. Apart from a native orthic luvisol, a heat-treated soil was used that has been freed from organic carbon by incineration at 600°C. Microbial communities involved in the turnover of the crop residues were investigated using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA sequences. Both 13C-nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography were used to analyze humic acids produced in the microcosms. To evaluate the sensitivity of the microcosms, the influence of the fungicide dithianon was used in a case study at a concentration of 50 mg/kg. Microbial activity was reduced because of the application of the pesticide, especially in the native soils, while mineralization of 14C-labeled maize straw was only slightly affected. The buildup of fungal biomass was inhibited for at least three weeks. Despite these effects on the microbial communities, no significant differences in the humification products after 26 weeks of incubation were observed.
Effects of organic amendments on the toxicity and bioavailability of cadmium and copper in spiked formulated sediments
Authors: Besser John M. , Brumbaugh William G. , May Thomas W. , Ingersoll Christopher G.
Published: March 2010

We evaluated the partitioning and toxicity of cadmium (Cd) and copper (Cu) spiked into formulated sediments containing two types of organic matter (OM), i.e., cellulose and humus. Amendments of cellulose up to 12.5% total organic carbon (TOC) did not affect partitioning of Cd or Cu between sediment and pore water and did not significantly affect the toxicity of spiked sediments in acute toxicity tests with the amphipod Hyalella azteca. In contrast, amendments of natural humus shifted the partitioning of both Cd and Cu toward greater concentrations in sediment and lesser concentrations in pore water and significantly reduced toxic effects of both metals. Thresholds for toxicity, based on measured metal concentrations in whole sediment, were greater for both Cd and Cu in sediments amended with a low level of humus (2.9% TOC) than in sediments without added OM. Amendments with a high level of humus (8.9% TOC) eliminated toxicity at the highest spike concentrations of both metals (sediment concentrations of 12.4 μg Cd/g and 493 μg Cu/g). Concentrations of Cd in pore water associated with acute toxicity were similar between sediments with and without humus amendments, suggesting that toxicity of Cd was reduced primarily by sorption to sediment OM. However, toxic effects of Cu in humus treatments were associated with greater pore-water concentrations than in controls, suggesting that toxicity of Cu was reduced both by sorption and by complexation with soluble ligands. Both sorption and complexation by OM tend to make proposed sediment quality guidelines (SQGs) based on total metal concentrations more protective for high-OM sediments. Our results suggest that the predictive ability of SQGs could be improved by models of metal interactions with natural OM in sediment and pore water.
Prediction of soil sorption coefficient of organic pesticides from the atom-type electrotopological state indices
Authors: Huuskonen Jarmo
Published: March 2010

A group contribution approach based on atom-type electrotopological state indices for predicting the soil sorption coefficient (log KOC) of a diverse set of 201 organic pesticides is presented. Using a training set of 143 compounds, for which the log KOC values were in the range from 0.42 to 5.31, multiple linear regression (MLR) and artificial neural networks were used to build the models. The models were validated using two test sets of 20 and 38 chemicals not included in the training set. The statistics for a linear model with 12 structural parameters were, in test set 1, r2 = 0.79, s = 0.45 and, in test set 2, r2 = 0.74, s = 0.65. These results clearly show that soil sorption coefficients can be accurately and rapidly estimated from easily calculated structural parameters.
Induction of CYP1A by the N-imidazole derivative, 1-benzylimidazole
Authors: Navas José María , Chana Antonio , Herradón Bernardo , Segner Helmut
Published: March 2010

Xenobiotics can induce cytochrome P4501A (CYP1A) by ligand binding to the aryl hydrocarbon receptor (AhR). Typical AhR ligands are polycyclic aromatic compounds with planar molecular conformation. The present work investigated the ability of the N-imidazole derivative, 1-benzylimidazole (BIM), to induce CYP1A in rainbow trout hepatocytes. Benzylimidazole increased hepatocellular CYP1A catalytic activity (determined as 7-ethoxyresorufin-O-deethylase [EROD] activity) and CYP1A mRNA in a concentration-dependent way. Computational studies on the molecular structure of BIM indicated that the energetically most stable BIM conformer has the imidazole ring and the phenyl ring in different planes, i.e., does not take a planar conformation. This property of BIM does not agree with the structural requirements of a typical AhR ligand. In line with this observation, we found that the AhR antagonist, α-naphthoflavone (αNF), was not able to inhibit BIM induction of EROD activity and CYP1A mRNA, although it inhibited the induction of CYP1A by the prototypic AhR ligand, β-naphthoflavone (βNF). The results suggest that transcriptional activation of CYP1A by the N-imidazole derivative, BIM, is not mediated through direct ligand binding to the AhR.
The relative sensitivity of four benthic invertebrates to metals in spiked-sediment exposures and application to contaminated field sediment
Authors: Milani Danielle , Reynoldson Trefor B. , Borgmann Uwe , Kolasa Jurek
Published: March 2010

The relative sensitivity of four benthic invertebrates (Hyalella azteca, Chironomus riparius, Hexagenia spp., and Tubifex tubifex) was determined for Cd, Cu, and Ni in water-only and in spiked-sediment exposures. Survival (median lethal concentrations [LC50s] and the concentrations estimated to be lethal to 25% of test organisms [LC25s]), and endpoints for growth and reproduction (mean inhibitory concentrations [IC25s]) were compared. The sensitivities differed depending on the species and metal, although some trends emerged. In water-only exposures, H. azteca is the most sensitive species to cadmium and nickel, with mean LC50s of 0.013 and 3.6 mg/L, respectively; C. riparius is the most sensitive species to copper, with a mean LC50 of 0.043 mg/L. In the spiked-sediment exposures, the order in decreasing sensitivity to copper is Hyalella = Hexagenia < Chironomus < Tubifex for survival and growth/reproduction. For cadmium, the order in decreasing sensitivity is Hyalella = Chironomus < Hexagenia < Tubifex, and for nickel is Hyalella ≪ Hexagenia < Chironomus < Tubifex. Chironomus riparius and Hexagenia spp. survival can be used to distinguish between toxicity caused by different metals. Species test responses in field-collected sediment (Collingwood Harbour, ON, Canada) were examined in an attempt to determine the causative agent of toxicity throughout, using the established species sensitivities. Sediment toxicity was categorized first by comparing species responses to those established for a reference database. Test responses in the field-collected sediment do not support causality by Cu, a suspected toxicant based on comparison of sediment chemistry with sediment quality guidelines.
Reproductive effects of estrogenic and antiestrogenic chemicals on sheepshead minnows (Cyprinodon variegatus)
Authors: Karels Arthur Alan , Manning Steve , Brouwer Thea Hoexum , Brouwer Marius
Published: March 2010

Environmental estrogens can activate genes of the reproductive system, such as vitellogenin (VTG), a precursor to egg yolk protein, by activating the estrogen receptor (ER), whereas antiestrogens can inhibit ER activation. Adult lab-reared male sheepshead minnows (Cyprinodon variegatus) were exposed to estrogenic 4-tert-octylphenol (OP) and females to antiestrogenic cadmium (Cd), and the effects on four potential indicators of impaired reproductive function were examined: VTG in F0 male blood as sign of feminization, F0 generation fecundity/fertility, embryonic development/egg hatching/survival rate of F1 generation fry, and F0 gonadal histology. Mean VTG in the control, 11.5, 33.6, and 61.1 μg/L OP male fish were 0, 10.7, 38.7, and 65.6 mg/ml postexposure and 0, 2.5, 19.4, and 30.0 mg/ml postreproduction. A significant inverse relationship between increasing VTG in male blood and reproductive success of mating groups involving these males was shown, with higher OP decreasing percent viable eggs (fertility) by approximately 60%. Histology showed increased testis anomalies and decreased spermatozoa with increasing OP exposure. No effects on F1 embryonic development, egg hatching, or fry survival rate were observed. A significant decline in percent viable egg production involving Cd-exposed females occurred only when mated with OP-exposed males, with no eggs produced by fish exposed to the highest OP and Cd concentration. A three-week field exposure near a wastewater treatment plant outfall showed no elevated VTG in male plasma, but significantly higher total egg production per female per collection day (∼45%) was observed at the site furthest from the outfall.
Uptake and depuration of nonionic organic contaminants from sediment by the oligochaete,Lumbriculus variegatus
Authors: Ingersoll Christopher G. , Brunson Eric L. , Wang Ning , Dwyer F. James , Ankley Gerald T. , Mount David R. , Huckins James , Petty Jim , Landrum Peter F.
Published: March 2010

Uptake of sediment-associated contaminants by the oligochaete Lumbriculus variegatus was evaluated after 1, 3, 7, 14, 28, and 56 d of exposure to a field-collected sediment contaminated with DDT and its metabolites, dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE), or to a field-collected sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). Depuration of contaminants by oligochaetes in a control sediment or in water was also evaluated over a 7-d period after 28 d of exposure to the field-collected sediments. Accumulation of PAHs with a log octanol-water partitioning coefficient (log Kow) <5.6 typically reached a peak at day 3, followed by a lower plateau between days 7 and 56 of the sediment exposure. Similarly, 4,4′-DDT exhibited a peak in accumulation at day 14 followed by a decline at days 28 and 56. In contrast, accumulation of PAHs with a log Kow >5.6 or DDD and DDE typically exhibited a steady increase from day 1 to about day 14 or 28, followed by a plateau. Therefore, exposures conducted for a minimum of 14 to 28 d better reflected steady-state concentrations for DDT and its metabolites and for PAHs. Depuration rates for DDT and its metabolites and high-Kow PAHs were much higher in organisms held in clean sediment relative to both water-only depuration and model predictions. This suggests that depuration in clean sediment may artificially accelerate depuration of hydrophobic compounds. Comparisons between laboratory-exposed L. variegatus and oligochaetes collected in the field from these sediments indicate that results of laboratory tests can be extrapolated to the field with a reasonable degree of certainty.
Effects of the herbicide imazapyr on benthic macroinvertebrates in a logged pond cypress dome
Authors: Fowlkes Mark D. , Michael Jerry L. , Crisman Thomas L. , Prenger Joseph P.
Published: March 2010

Increased herbicide use in silviculture over the last several decades has led to concern over potential water contamination, which may affect biotic health. In the southeastern United States, pine flatwoods are important for timber production and are often interspersed with cypress wetlands. Cypress domes are isolated, shallow basins that collect surficial waters from adjacent forested areas and therefore might be expected to contain pesticide from storm runoff. This study utilizes in situ microcosm experiments to assess the effects of a concentration gradient of the herbicide imazapyr (0.184, 1.84, and 18.4 mg/L, equivalent to 1, 10, and 100 times the expected environmental concentration from a normal application rate) on the macroinvertebrate community of a logged pond cypress dome using changes in macroinvertebrate composition, chironomid biomass, and chironomid head-capsule deformities. The control core was not significantly different from the surrounding cypress dome for any parameter, suggesting that enclosure effects were likely of minimal importance in the final experimental results. The lack of statistical difference (p < 0.05) in macroinvertebrate community composition, chironomid deformity rate, and chironomid biomass between treatments suggests that imazapyr did not affect the macroinvertebrate community at the concentrations tested. Chironomid deformity rate ranged from 0.97% for imazapyr control to 4.96% for the 100× treatment, with chironomid biomass being 1.79 and 1.87 mg/L, respectively.
Estimation of potential and limits of bivalve closure response to detect contaminants: Application to cadmium
Authors: Tran Damien , Ciret Pierre , Ciutat Aurélie , Durrieu Gilles , Massabuau Jean-Charles
Published: March 2010

Bivalve closure responses to detect contaminants have often beens studied in ecotoxicology as an aquatic pollution biosensor. We present a new laboratory procedure to estimate its potential and limits for various contaminants and animal susceptible to stress. The study was performed in the Asiatic clam Corbicula fluminea and applied to cadmium. To take into account the rate of spontaneous closures, we integrated stress problems associated with fixation by a valve in common apparatus and the spontaneous rhythm associated with circadian activity to focus on conditions with the lowest probability of spontaneous closing. Moreover, we developed an original system by impedance valvometry, using light-weight impedance electrodes, to study free-ranging animals in low-stress conditions and a new analytical approach to describe valve closure behavior as a function of response time and concentration of contaminant. In C. fluminea, we show that cadmium concentrations above 50 μg/L can be detected within less than 1 h, concentrations down to 16 μg/L require 5 h of integration time, and values lower than 16 μg/L cannot be distinguished from background noise. Our procedure improved by a factor of six the cadmium sensitivity threshold reported in the literature. Problems of field applications are discussed.
A simulation study of methods for constructing confidence intervals for bioaccumulation factors
Authors: Wheeler Matthew W. , Bailer A. John
Published: March 2010

Toxicokinetics describe the time course of xenobiotics in an exposed organism. The steady state concentration of the xenobiotic is a characteristic of frequent concern, often summarized in terms of bioaccumulation factors (BAFs). Two experimental protocols are commonly used when estimating BAFs: a continuous exposure experiment and a start-stop exposure experiment. Nonlinear regression is then used for estimating components of the BAF. A variety of methods are available for constructing confidence intervals (CI) for the BAF, including the delta method and Fieller's method. The properties of these CI methods are explored through a simulation study. In particular, the coverage properties of the two CI methods along with their interval widths are examined for a variety of time-course patterns, error distributions, experimental protocols, and sampling designs. Fieller's method is observed to exceed nominal coverage probabilities for all conditions considered (the coverage probability being the probability that a confidence interval contains a parameter it estimates over repeated experiments). The delta method exhibited observed coverage probabilities lower than nominally specified for a number of conditions. For sampling designs in which more of the sampling times are prior to steady state or the stop exposure time, the delta method is observed to provide nominal coverage probabilities with interval widths much narrower than observed with the Fieller's method. Thus, the delta method is preferable when the above sampling time condition is met; however, in all other cases, Fieller's method should be used.
Time and space issues in ecotoxicology: Population models, landscape pattern analysis, and long-range environmental chemistry
Authors: Ares Jorge
Published: March 2010

Advances in ecotoxicology addressing problems of time and spatial scales are presented and interpreted in the frame of concepts on population/community dynamics and landscape pattern analysis. Example deterministic/probabilistic modeling experiments are used to illustrate key concepts. Space and time scales analyzed are single and multigenerations of local populations, metapopulations, community, and ecosystem/landscape. Most population models used in recent ecotoxicology studies are deterministic and do not include a formal treatment of spatial processes, like migration or local random extinction. Some metapopulation models have been applied with success. Upscaling of ecotoxicological results at the community level is less developed, probably because of the inherent complexity of indirect and direct coactions among organisms. Community and ecosystem toxicity end points that could find a broad use in regulatory applications have not yet been identified. Some practical issues like the estimation of the potential for the natural attenuation of toxicity and the transport of contaminants along food chains must be addressed at these scales/levels of biological complexity. The estimation of ecotoxicological effects has been increasingly evolving to integrate modeling and monitoring contaminant transport and fate, landscape pattern analysis, and spatially explicit population dynamics (including direct and indirect communal interactions).
Closing the loop: A spatial analysis to link observed environmental damage to predicted heavy metal emissions
Authors: Colgan Anja , Hankard Peter K. , Spurgeon David J. , Svendsen Claus , Wadsworth Richard A. , Weeks Jason M.
Published: March 2010

In many cases, the link between industrial emissions and damage to the environment can only be inferred. The Environment Agency of the United Kingdom imposes emissions limits on industrial sites so that predicted concentrations and deposition rates remain below standard thresholds. Estimates of appropriate critical levels and loads are usually based on laboratory results and rarely estimate synergistic effects between pollutants or consider biological adaptation or selection in the target receptor organisms. The Avonmouth smelter has been emitting zinc and other heavy metals since 1929. It has been the subject of a number of detailed and synoptic studies, especially the impact on soil invertebrates. Damage was assessed using both physiological and ecological measurements. Two methods of spatial analysis were investigated, namely interpolation using standard geographical information system (GIS) operators and atmospheric dispersal modeling using an off-the-shelf model. Both methods can be used to compute contours (isolines) of predicted biological effect. Correlation results show that dispersal modeling is at least as good as kriging but requires much less data. This article demonstrates the usefulness of GIS and dispersal models as tools in decision making to determine the most suitable sampling sites in the assessment and monitoring of the impact of contamination around major point sources.
Dos and don'ts of spatially explicit ecological risk assessments
Authors: Woodbury Peter B.
Published: March 2010

Location affects exposure and response to stressors at scales ranging from small sites to large regions. Tools such as geographic information systems (GIS) make it feasible to conduct spatially explicit ecological risk assessments (ERAs). However, no tools provide a panacea, and complex models based on sparse data can be inappropriate and misleading. Operations such as an interpolation within a GIS are models, and so they contain assumptions and uncertainties. Errors can propagate easily as numerous operations are performed, and the resulting uncertainties should be made explicit. Analysts should assure that space actually matters by using explanatory data prior to investigating spatial correlation. Exposure and risk estimates from experimental plots or monitoring stations may require scaling factors if they are to be used for larger watersheds or regional analyses. Maps are useful because they present complex spatial information in a manner that is easily interpreted. However, they must be prepared and interpreted with caution because they can suggest that there is a great deal more information than actually exists. In addition to presenting maps of predicted risks, maps of the spatial patterns in the uncertainties in these risk estimates should be included in risk assessments.
Database mining with adaptive fuzzy partition: Application to the prediction of pesticide toxicity on rats
Authors: Pintore Marco , Piclin Nadège , Benfenati Emilio , Gini Giuseppina , Chrétien Jacques R.
Published: March 2010

A data set of 235 pesticide compounds, divided into three classes according to their toxicity toward rats, was analyzed by a fuzzy logic procedure called adaptive fuzzy partition (AFP). This method allows the establishment of molecular descriptor/chemical activity relationships by dynamically dividing the descriptor space into a set of fuzzily partitioned subspaces. A set of 153 molecular descriptors was analyzed, including topological, physicochemical, quantum mechanical, constitutional, and electronic parameters, and the most relevant descriptors were selected with the help of a procedure combining genetic algorithm concepts and a stepwise method. The ability of this AFP model to classify the three toxicity classes was validated after dividing the data set compounds into training and test sets, including 165 and 70 molecules, respectively. The experimental class was correctly predicted for 76% of the test-set compounds. Furthermore, the most toxic class, particularly important for real applications of the toxicity models, was correctly predicted in 86% of cases. Finally, a comparison between the results obtained by AFP and those obtained by other classic classification techniques showed that AFP improved the predictive power of the proposed models.