bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural requirements for anaerobic biodegradation of organic chemicals: A fragment model analysis
Authors: Rorije Emiel , Peijnenburg Willie J.G.M , Klopman Gilles
Published: March 2010

A computer-automated structure evaluation program (MCASE) has been used to analyze rates of aquatic anaerobic biodegradation of a set of diverse organic compounds, and a predictive model for this endpoint has been developed. The model was evaluated in terms of possible anaerobic metabolic steps. The most important fragments linked to biodegradability (biophores) were aromatic and aliphatic thiol, methoxy, and alcohol groups and the carboxylic ester group. Fragments that can possibly inhibit anaerobic biodegradation were also identified but were not significant. A metabolic transformation step is proposed for all identified fragments. Our results are therefore such that the most likely transformation under anaerobic conditions is anticipated when biophores are present in the molecule, while nonbiodegradability is assumed when none of these fragments are present. The number of correct classifications by the model is over 93%. When predictions for all compounds were generated using cross-validation of the model, 84% of the overall predictions were correct. However, when only the predictions of possible biodegradability under anaerobic conditions are considered, the number of correct predictions is over 89%, whereas the percentage of correct predictions for nonbiodegradability is only 64%. It is therefore concluded that the analysis given in this contribution yields a model that can predict anaerobic biodegradability, but the assumption that the absence of a biophore leads to nonbiodegradability is not valid. Predictions of nonbiodegradability of compounds are therefore unreliable, probably due to the limited amount of data on anaerobic biodegradation available for use in this study.
Fluctuating asymmetry and mentum gaps in populations of the midgeChironomus riparius(diptera: Chironomidae) from a metal-contaminated river
Authors: Groenendijk Dick , Zeinstra Lidy W.M , Postma Jaap F
Published: March 2010

The developmental stability of both metal-exposed and nonexposed Chironomus riparius populations from the lowland River Dommel was investigated using fluctuating asymmetry (FA) and the incidence of mentum gaps. It was hypothesized that larval development was affected by the influx of metals, directly by chemical stress, as well as through inbreeding of metal-adapted and nonadapted specimens. Morphological parameters were therefore assessed in field-collected larvae and in clean, laboratory-cultured, first-generation (F1) larvae. Fluctuating asymmetry values and mentum gap incidence at contaminated field sites were significantly higher than at clean, upstream locations. Furthermore, FA values of clean, laboratory-cultured F1 larvae generally fell to reference values, indicating the direct effect of metal pollution on developmental aberrations. Mentum gaps were not observed in clean F1 cultures. Slightly elevated FA values were, however, still observed in clean F1 larvae from polluted locations downstream from the metal input. This residual disturbance was thought to reflect genetic stress emerging from interbreeding between metal-adapted and nonadapted specimens. Fluctuating asymmetry and mentum gaps together serve as a useful ecotoxicological marker for metal stress and, when combined with in situ studies and F1 cultures, allow for analysis of the response of animal populations to spatial and temporal gradients in metal exposure.
Genetic variation in red raspberries (Rubus idaeus L.; rosaceae) from sites differing in organic pollutants compared with synthetic tandem repeat DNA probes
Authors: Keane Brian , Smith M Kate , Rogstad Steven H
Published: March 2010

Two synthetic tandem repetitive DNA probes were used to compare genetic variation at variable-number-tandem-repeat (VNTR) loci among Rubus idaeus L. var. strigosus (Michx.) Maxim. (Rosaceae) individuals sampled at eight sites contaminated by pollutants (N = 39) and eight adjacent uncontaminated sites (N = 38; distances separating sites ranged from 5 to 350 m). For the 77 plants analyzed, the mean number of bands scored per individual was 16.5 (SD = 3.5). Mean genetic similarity (0.51) and heterozygosity (0.62) across all plants from contaminated sites did not differ significantly from that among all plants from uncontaminated sites (mean similarity = 0.52; mean heterozygosity = 0.63). Nor did similarity and heterozygosity differ between contaminated and uncontaminated sites when estimates of these values within each of the 16 sites were compared. Estimates ofFst (0.01-0.04) indicated little genetic differentiation between plants from contaminated and uncontaminated sites. However, relative to plants from uncontaminated sites, plants from contaminated sites possessed significantly fewer private alleles (1 vs 18; p < 0.001) and alleles per individual (mean = 15.2 vs 17.9; p = 0.0002). Considering the 16 sites individually, uncontaminated sites possess significantly more population bands (p = 0.015), private alleles (p = 0.01), and alleles per individual (p = 0.027). These differences were distributed across sites rather than resulting from large, idiosyncratic differences attributable to one or a few outlier sites. The findings of this study suggest that a loss of genetic variation among R. idaeus individuals growing in impacted areas has occurred at all eight sites, and that VNTR markers may be useful biological indicators of plant populations under stress from human perturbations. In addition, extensive clonal spread of this species, previously documented for other species of Rubus, was not detected.
Impact of azadirachtin on Glomus intraradices and vesicular-arbuscular mycorrhiza in root inducing transferred dna transformed roots of Daucus carota
Authors: Wan Michael T , Rahe James E
Published: March 2010

The impact of azadirachtin, neem extracts, and their products, Eneem 3G and Neemix® 4.5E, on the symbiotic vesicular-arbuscular mycorrhizal fungus Glomus intraradices was assessed by short-term subacute toxicity tests using root inducing transferred DNA (Ri T-DNA) transformed roots of Daucus carota as the host in the minimal medium system. The concentration causing 50% inhibition of growth and development was determined, and effects of these test materials on carrot roots and colonization by G. intraradices were also evaluated. The inhibitory effect of azadirachtin and neem compounds was compared with that of several reference pesticides (benomyl, chlorothalonil, copper sulfate, dimethoate, glyphosate, and its metabolite aminomethyl-phosphonic acid). Azadirachtin, neem extracts, Eneem 3G, and Neemix 4.5E, including their carriers and solvents, have low short-term toxicity to G. intraradices when compared with reference pesticides. As well, neither D. carota nor the vesicular-arbuscular mycorrhizal colonization was affected by these compounds. The potential ecotoxicological impact of azadirachtin, a new botanical insecticide, on the terrestrial environment is evaluated and discussed.
Mercury and plants in contaminated soils: 2. Environmental and physiological factors governing mercury flux to the atmosphere
Authors: Leonard Todd L , Taylor George E , Gustin Mae S , Fernandez George C.J
Published: March 2010

The objective of this study was to evaluate the role of physiological and environmental factors in governing the flux of elemental mercury from plants to the atmosphere. Five species (Lepidium latifolium, Artemisia douglasiana, Caulanthus sp., Fragaria vesca, and Eucalyptus globulus) with different ecological and physiological attributes and growing in soils with high levels of mercury contamination (34 to 54 μg/g) were examined. Studies were conducted in a whole-plant, gas-exchange chamber providing precise control of environmental conditions, and mercury flux was estimated using the mass balance approach. Mercury flux increased linearly as a function of temperature within the range of 20 to 40°C, and the mean temperature coefficient (Q10) was 2.04. The temperature dependence of mercury flux was attributed to changes in the contaminant's vapor pressure in the leaf interior. Mercury flux from foliage increased linearly as a function of irradiance within the range of 500 to 1,500 μmol m/s, and the light enhancement of mercury flux (flux ratio at 1,500:500 μmol m/s) was within a factor of 2.0 to 2.5 for all species. Even though the leaf-to-atmosphere diffusive path for mercury vapor from foliage is similar to that of water vapor, stomatal conductance played a secondary role in governing mercury flux. In a quantitative comparison with other studies in both laboratory and field settings, a strong linear relationship is evident between mercury vapor flux and the natural logarithm of soil mercury concentration, and this relationship may have predictive value in developing regional- and continental-scale mercury budgets. The most critical factors governing mercury flux from plants are mercury concentration in the soil, leaf area index, temperature, and irradiance.
Linking teratogenesis, growth, and DNA photodamage to artificial ultraviolet b radiation in Xenopus laevis larvae
Authors: Bruggeman Douglas J , Bantle John A , Goad Carla
Published: March 2010

The frog embryo teratogenesis assay—Xenopus (FETAX) was used to illustrate sublethal endpoints indicative of ultraviolet B (UV-B) radiation exposure in Xenopus laevis larvae. Xenopus laevis embryos were covered with plastic cutoff filters to manipulate UV dose, and irradiated under a light carriage consisting of two UV-B and three UV-A bulbs. At the end of day 2, 20% of the tadpoles from all treatments were removed, and DNA was extracted. Frequency of pyrimidine dimers was estimated by quantifying single-strand breaks after incubating DNA with an endonuclease specific for cyclobutane pyrimidine dimers. Remaining tadpoles were sacrificed on day 5, and mortality, malformations, and growth data were recorded. Teratogenesis and growth inhibition were positively correlated with increasing UV-B dose in all tests. Photodamage to DNA in experiment 1 increased with higher UV-B doses. Teratogenesis positively correlated with the frequency of pyrimidine dimers. In experiment 2, significant variation with DNA photodamage in egg clutches was observed and no treatment effect was found. Usage of these sublethal endpoints in the field or laboratory would be helpful in discerning adaptational responses of developing amphibians to UV-B radiation, and interactive effects between UV and photosensitive chemicals.
Toxicity of chlorobenzenes to alux-marked terrestrial bacterium,Pseudomonas fluorescens
Authors: Boyd Elaine M , Meharg Andrew A , Wright Julian , Killham Ken
Published: March 2010

Insertion of lux genes, encoding for bioluminescence in naturally bioluminescent marine bacteria, into the genome of Pseudomonas fluorescens resulted in a bioluminescent strain of this terrestrial bacterium. The lux-marked bacterium was used to toxicity test the chlorobenzene series. By correlating chlorobenzenes 50% effective concentration (EC50) values against physiochemical parameters, the physiochemical properties of chlorobenzenes that elicit toxic responses were investigated. The results showed that the more chlorinated the compounds, the more toxic they were to lux-marked P. fluorescens. Furthermore, it was shown that the more symmetrical the compound, the greater its toxicity to P. fluorescens. In general, the toxicity of a chlorobenzene was inversely proportional to its solubility (S) and directly proportional to its lipophilicity (Kow). By correlating lux-marked P. fluorescens EC50 values, determined for chlorobenzenes, with toxicity values determined using Pimephales promelas (fathead minnow), Cyclotella meneghiniana (diatom), and Vibrio fischeri (marine bacterium), it was apparent that lux-marked P. fluorescens correlated well with freshwater species such as the diatoms and fathead minnow but not with the bioluminescent marine bacterium V. fischeri. The implications of these findings are that a terrestrial bacterium such as P. fluorescens should be used for toxicity testing of soils and freshwaters rather than the marine bacterium V. fischeri.
Physicochemical characterization of residual mineral oil contaminants in bioremediated soil
Authors: Angehrn Daniel , Gälli René , Zeyer Josef
Published: March 2010

After bioremediation of mineral oil—contaminated soils, residual contaminants can remain in the soils. In this article, an analytical concept to determine the physicochemical properties of residual contaminants that can be used to assess the environmental fate and potential environmental hazards of these chemicals is presented and discussed. This concept can serve as a tool to characterize unknown compounds within a complex mixture on the basis of basic analytical data. The volatility of the residual contaminants was determined by headspace analyses, but no volatile organic compounds (with a boiling point of <280°C) were present. Soxhlet extraction using tetrachloromethane was found to be the most efficient method to obtain the total solvent extractable material (TSEM). Information about the polarity of the contaminants in TSEM was obtained by flash chromatography. It was found that the majority of the residual contaminants are present in the fractions containing nonpolar components, such as branched or cyclic aliphatics and alkylated aromatics. A minor fraction consisted of compounds with polar functional groups, such as long-chain alkanals, alkanols, and alkanoic acids. Information about the octanol/water partition coefficient (Kow) of the contaminants within the TSEM was obtained with use of a combination of two independent chromatographic separation steps, reverse-phase high-performance liquid chromatography, followed by high-resolution gas chromatography. Depending on the compound classes, Kow values varied accordingly but were above 106. Considering these Kow values, the mobility of the residual contaminants in bioremediated soils is expected to be very low.
Evidence for differential effects of 2,4,6-trinitrotoluene and other munitions compounds on specific subpopulations of soil microbial communities
Authors: Fuller Mark E , Manning John F
Published: March 2010

The effects of 2,4,6-trinitrotoluene (TNT) and other munitions compounds on indigenous microbial communities in several soils were examined. Culturable heterotrophs, concentrations of phospholipid fatty acid (PLFA), and basal respiration rates exhibited slight negative correlations with high TNT and 1,3,5-trinitrobenzene (TNB) levels. Heat-shock-resistant culturable heterotrophs, percentage of gram-positive soil isolates, mole percent of branched PLFA, and 10Me18:0 (tuberculostearic acid) were observed to be significantly lower in highly contaminated soils. Total soil nitrogen levels were positively correlated with high TNT and TNB concentrations, whereas total soil carbon exhibited no significant correlation with either compound. Multivariate analysis of PLFA data resulted in distinct separation of soils with respect to their degree of contamination, with specific signature PLFAs for gram-positive bacteria, fungi, and protozoa being negatively associated with high contaminant levels. Apparent concentrations of TNT resulting in 50% reductions in indicators of gram-positive populations were much higher than values from pure culture experiments, possibly as a result of low bioavailability due to sorption onto clay and soil organic matter. Few effects of other munitions compounds were observed. Closer examination of a highly contaminated soil revealed that the number of culturable heterotrophs growing on 0.3% molasses plates decreased by 50% when 67 μg TNT/ml was added to the medium; a 99% decrease was observed for soil contaminated with less than 20 μg TNT/g. Highly contaminated soil harbored a greater number of organisms that were able to grow on plates amended with greater than 10 μg TNT/ml. Gram-positive isolates from both soils demonstrated marked growth inhibition when greater than 8-16 μg TNT/ml was present in the culture medium. These results indicate that chronic exposure to munitions compounds can dramatically alter soil microbial communities.
Rapid method for assessing pollution-induced community tolerance in contaminated soil
Authors: Rutgers Michiel , Verlaat Ilse M van't , Wind Bea , Posthuma Leo , Breure Anton M
Published: March 2010

Using the pollution-induced community tolerance (PICT) concept, this article presents a rapid method for detecting toxic effects of contaminated soil on soil microbial communities and for elucidating the causal relationship between exposure history and toxic effects in exposed microbial communities. The method is based on the use of multiwell plates (Biolog®) for producing concentration versus effect relationships for (maximally) 95 different microbial metabolic activities. For this, artificial exposure in the multiwell plate is established to the contaminant supposedly causing toxic effects in the field. The method was tested in a gradient of zinc-contaminated field plots by studying community tolerance to zinc. For most substrates the metabolic activities showed an increased community tolerance for zinc with increased zinc concentration in the field. Consequently, PICT has evolved after 2.5 years of zinc exposure under field conditions. The perspectives for future use of the PICT concept in combination with the multiwell technique for demonstrating ecotoxicological effects at contaminated sites is exemplified by the comparison of Dutch soil quality criteria for zinc with the collected data. This comparison showed that the evolution of microbial-PICT for zinc has occurred at environmental concentrations near the Dutch intervention value, a quality criterion linked to remediation urgency.
Monitoring aquatic environments receiving industrial effluents using small fish species 1: Response of spoonhead sculpin (Cottus ricei) downstream of a bleached-kraft pulp mill
Authors: Gibbons Wade N , Munkittrick Kelly R , Taylor William D
Published: March 2010

Larger fish species may not always be suitable for monitoring the response to industrial effluents because they are mobile and capable of extensive movement beyond effluent exposure areas. Spoonhead sculpin (Cottus ricei) was collected upstream and downstream of a large bleached-kraft pulp mill on the Athabasca River, Alberta, Canada, during fall and spring periods to determine whether small, sedentary fish species demonstrate responses reflecting local exposure conditions. During the fall sampling period, exposed fish were older and larger than upstream fish and showed increases in condition, gonad size, egg weight, liver weight, and hepatic mixed function oxygenase activity (7-ethoxyresorufin O-deethylase [EROD]). Sculpin collected from the opposite river bank, where exposure was reduced, showed condition factors, gonad size, egg weight, liver weight, and EROD activity that were not significantly different from reference sites or intermediate between reference and downstream values. In the spring after a prolonged overwinter exposure to higher effluent concentrations, exposed fish were larger, showed increased size-at-age, condition, liver weight, ovary size, and EROD activity. Far-field collections showed that most responses persisted downstream for at least 48 km. The general response of exposed spoonhead sculpin was consistent with a nutrient enrichment effect described in studies investigating water quality, algal growth, and benthos communities at this site but also may be related to reduced competition associated with the loss of older fish observed in the spring. The use of small species for sentinel monitoring provided a viable alternative to use of larger, more mobile species.
Monitoring aquatic environments receiving industrial effluents using small fish species 2: Comparison between responses of trout-perch (Percopsis omiscomaycus) and white sucker (Catostomus commersoni) downstream of a pulp mill
Authors: Gibbons Wade N , Munkittrick Kelly R , McMaster Mark E , Taylor William D
Published: March 2010

To further evaluate the suitability of small fish species for sentinel monitoring, a comparison was made between the responses of trout-perch (Percopsis omiscomaycus) and the larger white sucker (Catostomus commersoni) under similar conditions of pulp mill effluent exposure and mobility. Fish were collected upstream and downstream of a thermomechanical pulp mill on the Kapuskasing River, Ontario, Canada, where the presence of a hydro dam restricts the movement of fish between reference and exposure areas. Trout-perch collected downstream of the mill were shorter, lighter, and younger than upstream fish, whereas exposed white sucker were longer, heavier, and, for male sucker, older than reference fish. Only male trout-perch showed induced hepatic mixed function oxygenase activity (7-ethoxyresorufin-O-deethylase). Both forskolin-stimulated in vitro production of 17 β-estradiol in trout-perch and plasma concentrations of 17 β-estradiol in sucker were significantly depressed in exposed fish. The inconsistency in responses between species made it difficult to determine how the opposing responses were related and which species was most sensitive to instream conditions. Despite the discrepancies, use of an interpretation framework indicated that both species identified similar potential problems (e.g., size-selective mortality and recruitment problems), suggesting that either species could be used as a sentinel species at this site.
Validation of hsp70 stress gene expression as a marker of metal effects in Deroceras reticulatum (pulmonata): Correlation with demographic parameters
Authors: Köhler Heinz-R , Belitz Beatrix , Eckwert Helga , Adam Ralf , Rahman Basim , Trontelj Peter
Published: March 2010

The presence of a stress gene comprising a motif homologous to the hsp70 consensus sequence was proven for the grey garden slug, Deroceras reticulatum (Müller). The induction of stress gene transcription (including mRNA stability) and the accumulation of the corresponding stress protein, Hsp70, was quantified in slugs exposed to cadmium- or zinc-enriched food for 2 to 3 weeks. To validate the suitability of these two aspects of the cellular stress reponse to act as early-warning markers for metal effects on life-history parameters, fecundity, offspring number, longevity, and mortality of slugs were recorded in life-cycle experiments. Quantitative reverse transcription-polymerase chain reaction and a standardized immunoblotting technique revealed higher sensitivity of changes in hsp70 transcription than stress protein accumulation in response to both metals. The elevation of the hsp70-mRNA level caused by short-term (14 d) metal exposure coincided with both diminished fecundity and reduced offspring production due to chronic metal exposure in terms of threshold concentrations for cadmium (˜0.2 mg/kg) and zinc (˜200 mg/kg) effects. As well, accumulation of Hsp70 after 3 weeks of exposure can be considered an early-warning signal for increased mortality when cadmium (threshold concentration ˜0.3-2 mg/kg) or zinc exposure (threshold concentration ˜0.4-2 g/kg) is throughout the entire lifetime of the slugs.
Transformaton of 2,4,6-trinitrotoluene by the aquatic plantMyriophyllum spicatum
Authors: Pavlostathis Spyros G , Comstock Kelly K , Jacobson Myrna E , Saunders F Michael
Published: March 2010

The ability of the aquatic plant Eurasian Watermilfoil (Myriophyllum spicatum) to transform 2,4,6-trinitrotoluene (TNT) was investigated in a series of batch assays. The TNT was added to plant cultures in single and multiple consecutive additions, at various initial concentrations, to determine its transformation kinetics, identify products formed, evaluate phytotoxic effects, and to determine the effect of light deprivation on the TNT transformation process. Rapid disappearance of TNT from the plant culture media was observed. The TNT disappearance rate was a function of both plant and TNT concentration (i.e., followed mixed, second-order kinetics). The TNT transformation occurred only in the presence of plants and was inhibited by the addition of sodium azide. Phytotoxicity leading to plant chlorosis was observed in batch plant cultures with an initial TNT concentration above 5.9 μM. Reductive transformation of TNT to aminodinitrotoluenes and lower levels of hydroxylaminodinitrotoluene and diaminonitrotoluenes detected in the plant culture media accounted for less than 10 to 20% of the total TNT mass added. Extraction of plant material at the end of batch incubations when all TNT was depleted from the media yielded low levels of TNT and aminodinitrotoluenes and accounted for only 3.4% of the initially added TNT mass. Light deprivation decreased both the rate and extent of the reductive transformation of TNT.
Growing food crops on sludge-amended soils: Problems with the U.S. Environmental Protection Agency method of estimating toxic metal transfer
Authors: McBride Murray B
Published: March 2010

The use of sewage sludges as farm fertilizers, encouraged in recent years by changes in U.S. Environmental Protection Agency (U.S. EPA) policy, has raised concerns among some scientists regarding food safety and long-term soil productivity. The U.S. EPA risk assessment for entry into the human diet of three of the most toxic metals, cadmium (Cd), mercury (Hg), and lead (Pb), utilized uptake coefficients (UCs) to calculate the amount of each metal that could enter food crops from the soil. Each UC was calculated as the increment of metal concentration in the edible part of the crop per unit increase of metal loading to the soil. However, the final UC estimates employed in the risk assessment are biased toward low values by a number of factors. These include the use of geometric means to obtain single-point averages of UCs for each crop group evaluated, rather than using arithmetic means or probabilistic methods, a systematic analytical or contamination error apparent in the reported metal concentrations of the control crops, and the fact that most of the UC values were derived for soils with pH 6 or higher. For more than 50% of all the soil and cropping conditions represented in the risk assessment, the geometrically averaged Cd UC values used by the U.S. EPA underestimated the actual risk posed by uptake into crops. The UC values for Pb and Hg are uncertain because of analytical or contamination errors, and because of the few data available for a number of crops. These uncertainties and biases in the risk assessment would advise a more cautious approach to agricultural and home garden use of sewage sludge than is permitted by the U.S. EPA 503 rule.
Selection of optimal measures of growth and reproduction for the sublethal Leptocheirus plumulosus sediment bioassay
Authors: Gray Brian R , Emery Vallen L , Brandon Dennis L , Wright Rachel B , Duke B Maurice , Farrar J Daniel , Moore David W
Published: March 2010

This article describes the selection process used to identify optimal measures of growth and reproduction for the proposed 28-d sublethal sediment bioassay with the estuarine amphipod Leptocheirus plumulosus. We used four criteria (relevance of each measure to its respective endpoint, signal-to-noise ratio, redundancy relative to other measures of the same endpoint, and cost [i.e., of labor, training, and equipment]) to evaluate nine growth and seven reproductive measures. Optimal endpoint measures were identified as those receiving relatively high scores for all or most criteria. Measures of growth scored similarly on all criteria, except for cost. The cost of the pooled (female plus male) growth measures was substantially lower than the cost of the female and male growth measures because the latter required more labor (by approx. 25 min per replicate). Pooled dry weight was identified as the optimal growth measure over pooled length because the latter required additional labor and nonstandard software and equipment. Embryo and neonate measures of reproduction exhibited wide differences in labor costs but yielded similar scores for other criteria. In contrast, brooding measures of reproduction (females carrying embryos in the brood pouch) scored relatively low on endpoint relevance, signal-to-noise ratio, and redundancy criteria. We recommend neonates/survivor as the optimal measure of L. plumulosus reproduction because it exhibited high endpoint relevance and signal-to-noise ratios, was redundant to other reproductive measures, and required minimal time.
Relation of lead exposure to sediment ingestion in mute swans on the Chesapeake Bay, USA
Authors: Beyer W Nelson , Day Daniel , Morton Anna , Pachepsky Yakov
Published: March 2010

Although wildlife risk assessments are generally based on the accumulation of environmental contaminants through food chains, wildlife may also ingest contaminants incidentally with sediment. Forty-two mute swans (Cygnus olor) were collected from unpolluted portions of central Chesapeake Bay, Maryland, USA, in spring 1995, and their intestinal digesta were analyzed for 13 metals (aluminum [Al], boron, barium, cadmium, copper [Cu], iron, magnesium, manganese, nickel, lead [Pb], strontium, vanadium, and zinc) and for acid-insoluble ash, a marker of sediment. Swan livers and sediment samples also were analyzed for the same metals. Group method of data handling demonstrated that the digesta Al, which is associated with clays, was the best predictor of digesta Pb. Adding concentrations of other metals as predictors did not improve the accuracy of the estimates of Pb concentrations from Al concentrations. The r2 of the equation relating the log of digesta Pb to the log of digesta Al was 0.86, whereas the r2 of the equation relating the log of digesta Pb to the log of digesta acid-insoluble ash was 0.50. Accounting for the sediment ingested was critical to determining the exposure of mute swans to Pb, as well as to some of the other metals, and sediment ingestion should be considered in ecotoxicological risk assessments of waterfowl. The mean of 7.4% acid-insoluble ash in the digesta corresponded to an estimated 3.2% sediment in the diet. The Pb concentrations in the digesta were two to three times the concentration that would have been predicted from sediment Pb concentrations; presumably, the swans had ingested clays high in Pb that had settled on the vegetation. The swans were probably not exposed to high Cu concentrations but nevertheless had hepatic Cu concentrations that would be considered very high if found in other species.
Model for trace metal exposure in filter-feeding flamingos at Alkaline Rift Valley Lake, Kenya
Authors: Nelson Yarrow M , Thampy Ramesh J , Motelin Gideon K , Raini Jackson A , DiSante Cynthia J , Lion Leonard W
Published: March 2010

Toxic trace metals have been implicated as a potential cause of recent flamingo kills at Lake Nakuru, Kenya. Chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) have accumulated in the lake sediments as a result of unregulated discharges and because this alkaline lake has no natural outlet. Lesser flamingos (Phoeniconaias minor) at Lake Nakuru feed predominantly on the cyanobacterium Spirulina platensis, and because of their filter-feeding mechanism, they are susceptible to exposure to particle-bound metals. Trace metal adsorption isotherms to lake sediments and S. platensis were obtained under simulated lake conditions, and a mathematical model was developed to predict metal exposure via filter feeding based on predicted trace metal phase distributions. Metal adsorption to suspended solids followed the trend Pb ≫ Zn > Cr > Cu, and isotherms were linear up to 60 μg/L. Adsorption to S. platensis cells followed the trend Pb ≫ Zn > Cu > Cr and fit Langmuir isotherms for Cr, Cu and Zn and a linear isotherm for Pb. Predicted phase distributions indicated that Cr and Pb in Lake Nakuru are predominantly associated with suspended solids, whereas Cu and Zn are distributed more evenly between the dissolved phase and particulate phases of both S. platensis and suspended solids. Based on established flamingo feeding rates and particle size selection, predicted Cr and Pb exposure occurs predominantly through ingestion of suspended solids, whereas Cu and Zn exposure occurs through ingestion of both suspended solids and S. platensis. For the lake conditions at the time of sampling (1.2 g/L suspended solids, 0.23 g/L S. platensis), predicted ingestion rates based on measured metal concentrations in lake suspended solids were 0.71, 6.2, 0.81, and 13 mg/kg-d for Cr, Cu, Pb, and Zn, respectively. Higher exposure doses are predicted when metal concentrations are determined from sediment concentrations rather than suspended solids concentrations. Also, decreases in the S. platensis population would increase the clearing rate of the flamingos and increase predicted metal exposure via ingestion of suspended solids. For example, with metal concentrations calculated based on average metal concentrations in lake sediments and S. platensis concentration of 0.06 g/L, exposure rates would be 13, 10, 4.4, and 38 mg/kg-d for Cr, Cu, Pb, and Zn, respectively. These ingestion rates, except for Cu, are significantly higher than the no observable adverse effects levels.
Chronic retene exposure causes sustained induction of CYP1A activity and protein in rainbow trout (Oncorhynchus mykiss)
Authors: Fragoso Nuno M , Parrott Joanne L , Hahn Mark E , Hodson Peter V
Published: March 2010

The removal of persistent chlorinated organic compounds from pulp mill effluents has not eliminated mixed function oxygenase (MFO) induction by these effluents. Therefore, continuous MFO induction downstream of pulp mills may be due to exposure to more labile compounds, such as retene (an alkyl-substituted phenanthrene), which typically cause transient induction after a single brief exposure. Because fish are exposed continuously to pulp mill effluents, we have tested, and rejected, the null hypothesis that continuous exposure of fish to retene does not cause sustained MFO induction. Rainbow trout exposed continuously to retene, a component of some pulp mill effluents and sediments downstream of pulp mills, showed concentration-dependent increases in hepatic ethoxyresorufin-O-deethylase (EROD) activity. The increase in EROD activity was sustained over 32 d of continuous exposure, but it diminished to background levels within 4 d after transfer to clean water. The enzymatic response was confirmed by measuring changes in the content of immunodetectable cytochrome P4501A (CYP1A) protein. These data support a role for labile, nonhalogenated compounds in chronic effects of pulp mill effluents on fish.
Species selection for an ecological risk assessment of the Columbia River at the Hanford Site, Washington, USA
Authors: Becker James , Brandt Charles , Dauble Dennis
Published: March 2010

We describe a two-tier screening methodology used to select receptor species for an ecological risk assessment of the Columbia River at the Hanford Site in south-central Washington state. This approach was developed and implemented under the guidance of the Columbia River Comprehensive Impact Assessment Management Team (CRCIA Team), a public steering committee comprised of members of regulatory agencies, native American tribes, and other stakeholders. Three hundred sixty-eight species that occur in the riverine and riparian communities of the Columbia River were reduced to 52 using criteria identified by an independent panel of biologists (tier I) and by scoring and ranking species based on their potential exposure to contaminated media (tier II). This two-tier screening methodology could be implemented at other locations where the number of species present must be reduced for an ecological risk assessment and where receptor species with relatively high potential contaminant exposures need to be evaluated. Participation of the CRCIA Team in the species selection process facilitated agreement between risk assessors, regulators, and stakeholders as to the number and kinds of organisms to be evaluated in our risk assessment. It is critical that regulators and stakeholders be involved in the selection of receptors to ensure that species of public interest as well as ecologically relevant species are evaluated in ecological risk assessments. This approach will increase the likelihood that such risk assessments will be used in management decisions.
Distribution and composition of polycyclic aromatic hydrocarbons within experimental microcosms treated with creosote-impregnated Douglas fir pilings
Authors: Bestari K T Jim , Robinson Richard D , Solomon Keith R , Steele Tracey S , Day Kristen E , Sibley Paul K
Published: March 2010

Temporal changes in the concentration and relative composition of 15 priority polycyclic aromatic hydrocarbons (PAHs) in water, sediment, and polyvinylchloride (PVC) strips were assessed to evaluate the fate of creosote leached from impregnated wood pilings in aquatic environments. The study consisted of single microcosms containing one of 0.5, 1, 2, 3, 4, or 6 creosote-impregnated pilings and two microcosms containing untreated pilings. Quantitative analyses of PAHs were performed using high-performance liquid chromatography equipped with a fluorescence detector. For each treatment, total PAHs(∑ PAH) in water increased rapidly up to 7 d posttreatment yielding a clear dose-dependant concentration gradient ranging from 7.3 (0.5 pilings) to 97.2 μg/L (6 pilings). Total PAHs declined exponentially after 7 d and was reduced close to background concentrations (0.8–6.7 μg/L) by the end of the study (84 d). No increase in ∑ PAH was observed in sediments at any treatment, nor was there any relationship between sediment PAHs and distance from each piling cluster. However, a slight increase in PAHs was observed on PVC liner strips that exhibited a concentration gradient similar to that in water. The PVC-bound ∑ PAH ranged from 0.3 to 2.4 μg/cm2 and 0.2 to 2.2 μg/cm2 at 31 and 58 d posttreatment, respectively. Based on these data, we estimated a rate loss of creosote from the pilings of approximately 50 μg/cm2/d (273 mg/piling/d). The low concentration of PAHs on the PVC, along with the absence of accumulation of PAHs in sediments, suggests that creosote was lost primarily from water via degradative pathways such as photolysis and microbial decomposition and adsorption onto PVC. The rapid loss of creosote from water in conjunction with the slow rate of leaching from the pilings suggests that risks associated with the use of creosote-impregnated pilings in aquatic environments may be minimal.
Effect of wetting and drying on the bioavailability of organic compounds sequestered in soil
Authors: White Jason C , Quiñones-Rivera Antonio , Alexander Martin
Published: March 2010

A study was conducted to determine whether cycles of wetting and drying alter the availability of organic compounds that have aged in soil. Subjecting soil to wetting-and-drying cycles during periods of aging <60 d decreased the biodegradability, extractability, and uptake by earthworms of phenanthrene and reduced the extractability of di(2-ethylhexyl) phthalate (DEHP) sequestered in soil compared with soil aged at constant moisture. The mineralization of sequestered DEHP was greater in soil that was wet and dried during a 41-d period of aging than in soil incubated at constant moisture. Wetting and drying soil during periods of aging of 100 or more days had no effect on the biodegradability or assimilation by Eisenia foetida of sequestered phenanthrene and DEHP. Subjecting soil containing previously sequestered phenanthrene to one, three, or four wetting-and-drying cycles increased the biodegradability of the compound. The extractability of sequestered phenanthrene was greater in soil that was wet and dried once after aging than in soil maintained at constant moisture, but three wetting-and-drying cycles did not affect extractability. The biodegradability of sequestered DEHP was unaffected by wetting and drying. We suggest that wetting and drying may be useful in the remediation of contaminated soils.
Investigation of naphthalene sorption in soils and soil fractions using batch and column assays
Authors: Bayard Rémy , Barna Ligia , Mahjoub Borhane , Gourdon Rémy
Published: March 2010

The adsorption–desorption of naphthalene on several soil fractions and model soils has been studied in batch and column experiments to investigate the complementarity between the two methods. Batch experiments, in which the sorbents were suspended in aqueous solutions of naphthalene at different initial concentrations, were used to determine the states of apparent equilibrium and approach the kinetics of adsorption and desorption. Apparent equilibrium was reached in batch within 10 to 15 h and could be described with simple linear isotherms in the ranges of concentrations studied. A significant fraction of naphthalene was found to be adsorbed almost instantaneously, the rest being adsorbed more progressively, following first-order kinetics. Adsorption of naphthalene mainly takes place on the organic matter of the soils or soil fractions. Adsorption is directly related to the organic content of the soil fractions and not to the size of the particles with which the organic matter is associated. Naphthalene adsorption was found to be well reversible when the pollutant–sorbent contact time was short (24 h) and the sorbed concentration was relatively low. At higher sorbed concentrations, a slight hysteresis effect was observed in batch studies. Data obtained from soil column experiments conducted with water as mobile phase were in good agreement with the results obtained in batch. The adsorption was described using a double-compartment model, considering a nonuniform distribution of the adsorption sites (organic matter) between the external surface of soil microaggregates (with instantaneous adsorption) and the internal compartment inside the microaggregates (with rate-limited adsorption). The site distribution depends on the nature and degree of humification of the soil organic matter.
Effects of pentachlorophenol on survival of earthworms (Lumbricus terrestris) and phagocytosis by their immunoactive coelomocytes
Authors: Giggleman Marina A , Fitzpatrick Lloyd C , Goven Arthur J , Venables Barney J
Published: March 2010

Earthworms, Lumbricus terrestris, exposed for 96 h to filter paper saturated with five nominal concentrations of pentachlorophenol (PCP: 5–50 μg PCP/cm2), exhibited a 50% lethal concentration (LC50) of 25.0 μg PCP/cm2 (95% confidence interval [CI]: 22.8–27.2) and corresponding whole worm body burden-based 50% lethal dose (LD50) of 877.7 μg PCP/g dry mass (95% CI: 828.5–927.0). Linear regression modeling showed that worms increased body concentrations (BC = μg PCP/g dry tissue mass) with increasing exposure concentrations (EC) according to BC = 113.5 + 29.5EC (r2 = 0.94, p = 0.03). Phagocytosis of yeast cells by immunoactive coelomocytes was suppressed only at body concentrations (863.3 μg PCP/g dry mass) that approximated the calculated LD50 and overlapped those demonstrating lethality, indicating a sharp transition between sublethal and lethal toxicity. An exposure concentration of 15 μg PCP/cm2 produced significant suppression of phagocytosis of yeast cells by immunoactive coelomocytes. However, the average measured body burden from this group (863.3 μg PCP/g dry mass) approximated the estimated LD50, indicating a sharp toxic response slope. Exposure to 10 μg PCP/cm2 with a corresponding body concentration of 501.3 μg PCP/g dry mass did not affect phagocytosis. The importance of body burden data is emphasized.
Influence of nutrient additions on cadmium bioaccumulation by aquatic invertebrates in littoral enclosures
Authors: Currie Robert S , Muir Derek C G , Fairchild Wayne L , Holoka Morris H , Hecky Robert E
Published: March 2010

Cadmium distribution and bioaccumulation were examined over a 2-year period (1991–1992) in two nutrient-enriched and two control littoral enclosures and in the littoral zone in Lake 382 (L382). Lake 382, a small oligotrophic lake, is located within the Experimental Lakes Area in northwestern Ontario, Canada, and received experimental Cd additions from 1987 to 1992. In the second year of this study, chlorophyll a and suspended C concentrations in the nutrient-enriched enclosures increased by 6.6 and 3.4 times, respectively, compared to the controls. As a result of increased particulate produced by the nutrient additions, Cd concentrations in water from the nutrient-enriched enclosures were higher (46–114 ng/L) compared to the controls (23–84 ng/ L). Estimated Cd/C concentrations in water were lower in the nutrient-enriched enclosures relative to the controls because of higher particle concentrations. Effects on Cd bioaccumulation were limited even though mesotrophic to eutrophic conditions were reached in the nutrient-enriched enclosures. Trends for lower Cd concentrations in mussels and crayfish from the nutrient-enriched enclosures compared to the controls were observed; however, significant differences were rarely detected. Zooplankton and immature Chironomidae from the nutrient-enriched enclosures had consistently higher Cd concentrations compared to the controls, but significant differences were not detected. Enhanced accumulation of Cd-rich particulate matter by these organisms may account for this trend. Mussels and crayfish accumulated significantly more Cd when exposed in the lake compared to the enclosures. This observation is due to elevated Cd water concentrations in the lake compared to the enclosures because of continued Cd additions to the lake. These results suggest that the water route of exposure is an important pathway for Cd accumulation by these organisms.
Relative role of pore water versus ingested sediment in bioavailability of organic contaminants in marine sediments
Authors: Forbes Thomas L , Forbes Valery E , Giessing Anders , Hansen Rikke , Kure Liv K
Published: March 2010

Experimental data for fluoranthene and feeding selectivity in combination with reaction-diffusion modeling suggest that ingestion of contaminated sediment may often be the dominant uptake pathway for deposit-feeding invertebrates in sediments. A dietary absorption efficiency of 56% and accompanying forage ratio of 2.4 were measured using natural sediment that had been dual-labeled (14C:51Cr) with fluoranthene and fed to the marine deposit-feeding polychaete Capitella species I. Only 3 to 4% of the total absorption could be accounted for by desorption during gut passage. These data were then used as input into a reaction-diffusion model to calculate the importance of uptake from ingested sediment relative to pore-water exposure. The calculations predict a fluoranthene dietary uptake flux that is 20 to 30 times greater than that due to pore water. Factors that act to modify or control the formation of local chemical gradients, boundary layers, or dietary absorption rates including particle selection or burrow construction will be important in determining the relative importance of potential exposure pathways. From a chemical perspective, the kinetics of the adsorption and desorption process are especially important as they will strongly influence the boundary layer immediately surrounding burrowing animals or irrigated tubes. The most important biological factors likely include irrigation behavior and burrow density and size.