Contaminated Field Sites Research Articles

Anaerobic biotransformation of carbon tetrachloride under various electron acceptor conditions

The biotransformation of carbon tetrachloride (CT) under various electron acceptor conditions was investigated using enrichment cultures developed from the anaerobic digester sludge of Thibodaux sewage treatment plant. The results indicated that CT was biotransformed under sulfate-reducing, methanogenic, nitrate-reducing, iron-reducing, fermenting, and mixed electron acceptor conditions. However, the rates of CT removal varied among the conditions studied. The fastest removal of CT (100% removal in 12 days) was observed under mixed electron acceptor conditions followed in order by sulfate-reducing, methanogenic, fermenting, iron-reducing, and nitrate-reducing conditions. Under mixed electron acceptor conditions, the CT was converted to methyl chlorides, which was further metabolized. Under sulfate, iron, nitrate-reducing, and methanogenic conditions, the major metabolite produced from CT metabolism was chloroform (CF). Under fermenting conditions, methylene chloride was produced from CT metabolism. This study showed evidence for CT metabolism in a mixed microbial population system similar to many contaminated field sites where a heterogeneous microbial population exists.

A COMBINED MICROCOSM AND FIELD APPROACH TO EVALUATE THE AQUATIC TOXICITY OF AZINPHOSMETHYL TO STREAM COMMUNITIES

We evaluated the potential effects of the organophosphate insecticide azinphosmethyl (AZ) in a combined microcosm and field approach. The upper regions of the Lourens River, South Africa, are free of contamination (control site), whereas the subsequent stretches flowing through a 400-ha orchard area receive transient insecticide pollution (e.g., 0.82 μ/L AZP, 344 μg/kg chlorpyrifos) following spray drift and runoff (contaminated site). Stones taken from the control site were transferred to outdoor microcosms (1.5 × 0.2 × 0.2 m), providing 12 core species and approximately 350 individuals per microcosm. Microcosms were contaminated for 1 h with AZP (control, 0.2, 1, 5, and 20 μ/L; three replicates each), and acute effects on survival were evaluated 6 d following exposure. The two strongest treatments (measured concentrations: 19.2 ± 1.0 and 4.9 ± 0.3 μ/L, respectively) resulted in a significantly (analysis of variance) reduced invertebrate density, attributed mainly to various insect taxa, such as Demoreptus sp., Castanophlebia sp., Simuliidae, and Chironomidae. In contrast, Aeshna sp., Dugesia sp., Ceratopogonidae, and Cheumatopsyche sp. were unaffected. In parallel, we conducted a quantitative macroinvertebrate survey at the control site and the contaminated site of the Lourens River after the seasonal pesticide application period. The two sites contained a similar number of species but differed considerably in their species composition and abundances. Five of the eight species that were affected by AZP in the microcosm study occurred in the field at significantly lower densities at the contaminated than at the control site or were absent at the contaminated site. All of the four species that were unaffected in the microcosm occurred at significantly higher densities at the contaminated field site. Only 3 of the 12 species reacted differently in the microcosm and the field study. We conclude that microcosm studies employing a field-relevant design could be linked successfully to field studies and our results suggest that transient pesticide contamination affects the aquatic communities of the Lourens River.

Terrestrial natural sources of trichloromethane (chloroform, CHCl3) - An overview

The widespread use of volatile chlorinated compounds like chloroform, trichloroethene and tetrachloroethene in industrialized societies causes a large annual release of these compounds into the environment. Due to their role as a source for halogen radicals involved in various catalytic atmospheric reaction cycles, including the regulation of the stratospheric and tropospheric ozone layers, these compounds also constitute a risk for drinking water resources as they can be transported to the groundwater from contaminated field sites or even from atmospheric deposition. Therefore, identification and investigation of sources and sinks of volatile chlorinated compounds are of particular interest. Chloroform, a major contributor to natural gaseous chlorine, was found to be emitted by several anthropogenic and natural sources including the oceans and terrestrial areas. The origin of chloroform in the terrestrial environment can be anthropogenic point sources, atmospheric deposition, release by vegetation and production directly in the soil. The calculated annual biogenic global chloroform emission is 700 Gg, and marine and terrestrial environments are nearly equal contributors. The estimated emissions from anthropogenic sources account for less than 10% of the estimated total emissions from all sources. Among terrestrial sources, forests have recently been identified as contributing to the release of chloroform into the environment. With the data available, annual emissions of chloroform to the atmosphere from forest sites were calculated and compared to other natural sources. At present knowledge, forests are only a minor source in the total biogenic flux of chloroform, contributing less than 1% to the annual global atmospheric input. However, it should be noted that data are available for Northern temperate forests only. The large tropical forest areas may provide a yet unknown input of chloroform.

Microbial activity in soils following steam treatment.

Steam enhanced extraction (SEE) is an aquifer remediation technique that can be effective at removing the bulk of non-aqueous phase liquid (NAPL) contamination from the subsurface, particularly highly volatile contaminants. However, low volatility compounds such as polynuclear aromatic hydrocarbons (PAHs) are less efficiently removed by this process. This research evaluated the effects of steam injection on soil microbial activity, community structure, and the potential for biodegradation of contaminants following steam treatment. Three different soils were evaluated: a laboratory-prepared microbially-enriched soil, soil from a creosote contaminated field site, and soil from a chlorinated solvent and waste oil contaminated field site. Results from field-scale steaming are also presented. Microbial activity before and after steam treatment was evaluated using direct epifluorescent microscopy (DEM) using the respiratory activity dye 5-cyano-2,3, ditolyl tetrazolium chloride (CTC) in conjunction with the fluorochrome 5-(4,6-dichlorotriazinyl) aminofluorescein (DTAF) to yield a quantitative assessment of active and total microbial numbers. DEM results indicate that steamed soils that were analyzed while still hot exhibited microbial activity levels that were below detection. However, soil samples that were slowly cooled, more closely reflecting the conditions of applied SEE, exhibited microbial activity levels that were comparable to presteamed soils. Samples from a field-site where steam was applied continuously for 6 weeks also showed high levels of microbial activity following cooling. The metabolic capabilities of the steamed communities were investigated by measuring cell growth in enrichment cultures on various substrates. These studies provided evidence that organisms capable of biodegradation were among the mesophilic populations that survived steam treatment. Fluorescent in situ hybridization (FISH) analysis of the soils with domain-level rRNA probes suggest that both Archaea and Bacteria survived steam exposure.

Decreased glutathione S-transferase expression and activity and altered sex steroids in Lake Apopka brown bullheads ( Ameiurus nebulosus)

A number of freshwater lakes and reclaimed agricultural sites in Central Florida have been the receiving waters for agrochemical and municipal runoff. One of these sites, Lake Apopka, is also a eutrophic system that has been the focus of several case studies reporting altered reproductive activity linked to bioaccumulation of persistent organochlorine chemicals in aquatic species. The present study was initiated to determine if brown bullheads ( Ameiurus nebulosus) from the north marsh of Lake Apopka (Lake Apopka Marsh) exhibit an altered capacity to detoxify environmental chemicals through hepatic glutathione S-transferase (GST)-mediated conjugation as compared with bullheads from a nearby reference site (Lake Woodruff). We also compared plasma sex hormone concentrations (testosterone, 17-β estradiol, and 11 keto-testosterone) in bullheads from the two sites. Female bullheads from Lake Apopka had 40% lower initial rate GST conjugative activity toward 1-chloro-2,4-dinitrobenzene (CDNB), 50% lower activity towards p-nitrobutyl chloride (NBC), 33% lower activity toward ethacrynic acid (ECA), and 43% lower activity toward Δ5-androstene-3,17-dione (Δ 5-ADI), as compared with female bullheads from Lake Woodruff. Enzyme kinetic analyses demonstrated that female bullheads from Lake Apopka had lower GST-catalyzed CDNB clearance than did female Lake Woodruff bullheads. Western blotting studies of bullhead liver cytosolic proteins demonstrated that the reduced GST catalytic activities in female Lake Apopka bullheads were accompanied by lower expression of hepatic GST protein. No site differences were observed with respect to GST activities or GST protein expression in male bullheads. Female Lake Apopka bullheads also had elevated concentrations of plasma androgens (testosterone and 11-ketotestosterone) as compared with females from Lake Woodruff. In contrast, male Lake Apopka bullheads had elevated levels of plasma estrogen but similar levels of androgens as compared with male bullheads from Lake Woodruff. Collectively, our studies indicate the presence of reduced GST protein expression, reduced GST conjugative capacity and altered sex steroid homeostasis in female bullheads from a contaminated field site in Central Florida. The implications of these physiological alterations in terms of pollutant biotransformation and reproduction are discussed.

Novel model describing trace metal concentrations in the earthworm, Eisenia andrei.

We developed a novel model describing Eisenia andrei body concentrations for Cd, Cu, Pb, and Zn as a function of pH, metals, and soluble organic carbon (SOC) in soil extracts for potential use in predicting values in contaminated field sites. Data from 17 moderately contaminated Dutch field soils in which earthworms were cultured were used in model development. Model parameters quantify biological phenomena important for metal bioavailability, and soil variables quantify relevant soil chemistry characteristics. Earthworm body concentration (EBC) was modeled so that soil metal soluble at bulk soil pH was considered available for dermal exposure, and gut exposure was due to soil metal in solution near neutral regulated gut pH. The efficiency parameter values indicated that metals are biologically regulated in the following order (most to least): Zn - Cu > Pb > Cd. The values determined for the exposure-route constant indicate that Cd, Cu, and Pb EBCs are almost exclusively (>96%) due to dermal exposure and that only 18% of Zn EBC was due to gut exposure. The minimum healthful EBCs determined were Zn > Cu > Pb > Cd, and the values for Pb and Cd were near zero. The Cu model was normalized by soluble organic carbon to be meaningful. The model was most accurate in describing Zn behavior.

Removal of volatile and semivolatile organic contamination from soil by air and steam flushing

A soil core, obtained from a contaminated field site, contaminated with a mixture of volatile and semivolatile organic compounds (VOC and SVOC) was subjected to air and steam flushing. Removal rates of volatile and semivolatile organic compounds were monitored during flushing. Air flushing removed a significant portion of the VOC present in the soil, but a significant decline in removal rate occurred due to decreasing VOC concentrations in the soil gas phase. Application of steam flushing after air flushing produced a significant increase in contaminant removal rate for the first 4 to 5 pore volumes of steam condensate. Subsequently, contaminant concentrations decreased slowly with additional pore volumes of steam flushing. The passage of a steam volume corresponding to 11 pore volumes of steam condensate reduced the total VOC concentration in the soil gas (at 20°C) by a factor of 20 to 0.07 mg/l. The corresponding total SVOC concentration in the condensate declined from 11 to 3 mg/l. Declines in contaminant removal rates during both air and steam flushing indicated rate-limited removal consistent with the persistence of a residual organic phase, rate-limited desorption, or channeling. Pressure gradients were much higher for steam flushing than for air flushing. The magnitude of the pressure gradients encountered during steam flushing for this soil indicates that, in addition to rate-limited contaminant removal, the soil permeability (2.1×10 −9 cm 2) would be a limiting factor in the effectiveness of steam flushing.

The relation between extrapolated risk, expressed as potentially affected fraction, and community effects, expressed as pollution‐induced community tolerance

The results of toxicity tests can be used to calculate the potentially affected fraction (PAF) of species in an ecosystem at a given pollutant concentration using statistical extrapolation methods. The PAF curve indicates the fraction of species from the original community that may become inhibited at each elevated pollutant concentration and is a measure of the ecotoxicological risk. Pollution-induced community tolerance (PICT) is a true community response that is measured under controlled conditions in the laboratory, using organisms from contaminated field sites. Microorganisms from experimental field plots with added Zn were exposed to various concentrations of Zn in the laboratory and the mineralization of 14C acetate was monitored. Microorganisms from plots with Zn concentrations above 124 mg/kg showed a significant increase in the effect concentration 10% (EC10) and, therefore, had a significant PICT. The pore-water concentrations of Zn in these field soils were in the same magnitude as the EC10 of the microorganisms from these soils. The PAF curve was calculated from previously reported toxicity tests with five different microbial species using the average and the standard deviation of the logarithmically transformed EC10 values. The average sensitivity of this PAF curve was similar to the EC50 of the acetate mineralization curve from the field plot without added Zn2+, but the PAF curve was less steep. Our experiments indicated that 27 to 84% of the original microbial species were inhibited at Zn concentrations from 334 to 1,858 mg/kg soil, respectively. Our results suggest that the PICT method can now also be used to quantify the fraction of the original species composition that is inhibited at a specific pollutant concentration.

Enhanced Biotransformation of Trichloroethylene Under Mixed Electron Acceptor Conditions

The biotransformation of trichloroethylene (TCE) under various electron acceptor conditions was investigated by using enrichment cultures developed from the anaerobic digester sludge of Thibodaux sewage treatment plant. The results indicated that TCE was biotransformed under sulfate reducing, methanogenic, nitrate reducing, iron reducing, and fermenting conditions. However, the rates of TCE removal varied among the conditions studied. The fastest removal of TCE (100% removal in 9 days) was observed under mixed electron acceptor conditions, followed in order by methanogenic, fermenting, iron reducing, sulfate reducing, and nitrate reducing conditions. Under mixed electron acceptor conditions, the TCE was converted to ethene, which was further metabolized. Under sulfate and nitrate reducing conditions, the major metabolites produced from TCE metabolism were cis and trans dichloroethylene (DCE). Under methanogenic, iron reducing, and fermenting conditions, cis and trans DCE and ethene were produced from TCE metabolism. This study showed evidence for TCE metabolism in a mixed microbial population system similar to any contaminated field sites, where heterogeneous microbial population exists.

THE RELATION BETWEEN EXTRAPOLATED RISK, EXPRESSED AS POTENTIALLY AFFECTED FRACTION, AND COMMUNITY EFFECTS, EXPRESSED AS POLLUTION-INDUCED COMMUNITY TOLERANCE

The results of toxicity tests can be used to calculate the potentially affected fraction (PAF) of species in an ecosystem at a given pollutant concentration using statistical extrapolation methods. The PAF curve indicates the fraction of species from the original community that may become inhibited at each elevated pollutant concentration and is a measure of the ecotoxicological risk. Pollution-induced community tolerance (PICT) is a true community response that is measured under controlled conditions in the laboratory, using organisms from contaminated field sites. Microorganisms from experimental field plots with added Zn were exposed to various concentrations of Zn in the laboratory and the mineralization of 14C acetate was monitored. Microorganisms from plots with Zn concentrations above 124 mg/kg showed a significant increase in the effect concentration 10% (EC10) and, therefore, had a significant PICT. The pore-water concentrations of Zn in these field soils were in the same magnitude as the EC10 of the microorganisms from these soils. The PAF curve was calculated from previously reported toxicity tests with five different microbial species using the average and the standard deviation of the logarithmically transformed EC10 values. The average sensitivity of this PAF curve was similar to the EC50 of the acetate mineralization curve from the field plot without added Zn2+, but the PAF curve was less steep. Our experiments indicated that 27 to 84% of the original microbial species were inhibited at Zn concentrations from 334 to 1,858 mg/kg soil, respectively. Our results suggest that the PICT method can now also be used to quantify the fraction of the original species composition that is inhibited at a specific pollutant concentration.

Enhanced biodegradation of cyclotetramethylenetetranitramine (HMX) under mixed electron-acceptor condition

The biodegradation of cyclotetramethylenetetranitramine, commonly known as `high melting explosive' (HMX), under various electron-acceptor conditions was investigated using enrichment cultures developed from the anaerobic digester sludge of Thibodaux sewage treatment plant. The results indicated that the HMX was biodegraded under sulfate reducing, nitrate reducing, fermenting, methanogenic, and mixed electron accepting conditions. However, the rates of degradation varied among the various conditions studied. The fastest removal of HMX (from 22 ppm on day 0 to <0.05 ppm on day 11) was observed under mixed electron-acceptor conditions, followed in order by sulfate reducing, fermenting, methanogenic, and nitrate reducing conditions. Under aerobic conditions, HMX was not biodegraded, which indicated that HMX degradation takes place under anaerobic conditions via reduction. HMX was converted to methanol and chloroform under mixed electron-acceptor conditions. This study showed evidence for HMX degradation under anaerobic conditions in a mixed microbial population system similar to any contaminated field sites, where a heterogeneous population exists.

Effects of copper on reproduction of two collembolan species exposed through soil, food, and water

AbstractExtrapolation of laboratory toxicity data to the field is hampered by differences in bioavailability, among other factors. Often, chemical availability of substances in the soil pore water is considered equivalent to bioavailability. However, for collembolans, which are not closely connected with the water phase of the soil, the situation may be different since other routes of exposure may also be of importance. In the present study, two species of Collembola, Folsomia candida Willem and Folsomia fimetaria L., were exposed to copper sulfate in different ways, for example, in aqueous solutions, in spiked soil, in soil from a copper‐contaminated field site, and via the food supply (yeast). Reproduction of the collembolans was inhibited at elevated soil or yeast copper concentrations. The 10% effective concentration (EC10) values for freshly spiked soil were 50 [0.03–13,095] and 141 [20–1,001] mg/kg for F. candida and F. fimetaria, and the corresponding values for yeast exposure were 2,900 [613–13,877] and 361 [0.1–972,864] mg/kg (95% confidence limits in square brackets). Soil from the contaminated field site had no effects on reproduction at copper concentrations up to 2,500 mg/kg. Internal copper concentrations were constant up to a soil copper concentration between 400 and 800 mg/kg in newly spiked soil and up to between 1,400 and 2,500 mg/kg in field soil. Copper accumulation in the animals from freshly spiked soil was higher than from yeast, and accumulation from both routes appeared to be additive. Spiked soil resulted in higher accumulation than soil from a contaminated field site. Addition of clean yeast to spiked soil resulted in a decrease in copper accumulation. The two collembolan species accumulated comparable concentrations from soil, whereas F. candida accumulated more copper from contaminated yeast placed on top of unpolluted soil than F. fimetaria. Male F. fimetaria accumulated more copper from contaminated soil than females. When exposed through yeast, the two sexes accumulated similar concentrations. A link between internal copper concentrations and effects on reproduction was difficult to establish because of large variations in both parameters and because effects seemed to begin at soil and yeast copper concentrations where internal concentrations were still regulated. Consequently, the establishment of a fixed internal threshold was uncertain.

Selection favours low hsp70 levels in chronically metal-stressed soil arthropods

Abstract Thirty-eight populations of woodlice (Oniscus asellus, Porcellio scaber) and millipedes (Julus scandinavius) from 28 differently metal-polluted field sites were analysed for their 70-kDa stress protein (hsp70) level. Although ANOVA revealed significant dependence of the hsp70 level on the concentrations of water-soluble lead, cadmium and zinc and the soil pH, each of these parameters accounted for at most 18% of the intersite variability of the stress protein level only. A multivariate model based on multiple regression analysis explained more than 96% of hsp70 variance and revealed both the pollution history of a site (strong metal contamination for more than 70 years) and invertebrate species identity to act as the most important parameters. The model accounted for the observation that most of the populations from long-term polluted sites exhibited comparatively low stress protein levels in response to their own (contaminated) habitats. In contrast, isopods (O. asellus) from a control site were not able to maintain a low hsp70 level when they were exposed to either an artificial metal cocktail or soil taken from one of the contaminated field sites. They did not acclimatize to the exposure conditions within 3 months. We propose that selection of insensitive phenotypes in long-term polluted soils has taken place so as to minimize the stress protein level which, in turn, is indicative of high intracellular protein integrity. Long-term selection for a high hsp70 level to compensate for adverse metal impact was not observed, which suggests that such a strategy may trade off against other fitness consequences. In this context, insensitivity to metal stress involved increased selectivity in food choice and reduced variability in stress response. Multiple regression models showed species-specificity in those abiotic factors which determined (1) high hsp70 levels in sensitive populations as well as (2) low hsp70 levels in insensitive ones. Therefore, abiotic factors can be assigned to act as the main components of selection: lead and cadmium for J. scandinavius and O. asellus, zinc for P. scaber.

Field and in vitro evidence for in-situ bioremediation using compound-specific 13C/ 12C ratio monitoring

This work describes the use of δ 13C values of residual hydrocarbons as a method for demonstrating in-situ biodegradation. Microbial growth, hydrocarbon loss and increase in δ 13C values were demonstrated in vitro using benzene and styrene as carbon substrates. Isotope evidence of biodegradation were subsequently sought in four field sites contaminated with a wide variety of hydrocarbons. Analysis of residual hydrocarbons in the field indicated that an overall increase in the δ 13C generally accompanied loss of hydrocarbons, an observation consistent with in-situ biodegradation. The field samples were analyzed using vapor or soil extracts, and the increases in δ 13C were observed using both types of samples. Vapor sampling is of practical interest because stable isotope ratio monitoring of soil vapor could dramatically reduce the number of wells required for monitoring of ongoing remediation efforts. Our preliminary studies of contaminated field sites allude to the potential of compound-specific isotopic monitoring techniques as a cost-effective measure of in-situ biodegradation.

Vadose Zone Characterization at a Contaminated Field Site Using Partitioning Interwell Tracer Technology

The partitioning interwell tracer test (PITT) has been demonstrated to be effective in determining volume and spatial distribution of residual nonaqueous phase liquids (NAPLs) in the saturated subsurface. Use of PITT technology in the vadose zone has been limited to this point. Two PITTs were completed in the vadose zone of a NAPL contaminated site at Kirtland Air Force Base in Albuquerque, NM. The PITTs were completed before and after a thermally enhanced soil vapor extraction remediation effort, to provide performance assessment. Methane was used as a nonpartitioning tracer. Four perfluorocarbons (perfluoromethylcyclohexane, perfluoro-1,3-dimethylcyclohexane, perfluoro-1,3,5-trimethylcyclohexane, and perfluorodecalin) were utilized as air−NAPL partitioning tracers. Difluoromethane was used as an air−water partitioning tracer to estimate water saturation. The complex light NAPL (LNAPL) consisted of hydrocarbon fuels ranging from approximately 12−70 carbons in size. Laboratory experimental data and thermodynamic modeling were used to characterize compositional changes in the NAPL due to the remediation effort. About 260 kg of NAPL were removed from the subsurface by the remediation effort. The PITT assessment of the remediation was compared favorably to the results from soil borings taken at the site. The PITT has been shown to be a useful technology for both NAPL characterization and remedial performance assessment in the vadose zone.

Changes in soil microbial communities over time resulting from one time application of zinc: a laboratory microcosm study

Soil microcosms each consisting of approximately 20 kg soil were set up in the laboratory. Three microcosms were amended with 6000 mg zinc kg −1, a concentration chosen to approximate the quantities of total zinc found at a contaminated field site. Three control microcosms received no zinc amendment. Three pH control microcosms received H 2SO 4, adequate to result in the same pH decrease as occurred in the zinc amended soil. Mean soluble zinc contents were 4660 mg kg −1 (amended soils), 1.08 mg kg −1 (unamended soils), and 2.10 mg kg −1 (pH adjusted soils). Biological community assessments included culturable bacteria (plate counts), microbial biomass (chloroform fumigation), dehydrogenase activity, proportion of zinc resistant bacteria (plate counts on zinc amended agar), and changes in community structure (BIOLOG and phospholipid fatty acid (PLFA) analysis). After 15 d of incubation, zinc amendment resulted in an 87% decrease in viable counts and a 47% decrease in microbial biomass. Dehydrogenase activity decreased by 95%, and the proportion of zinc resistant bacteria increased from 0.08% to 0.75%. Microbial community structure alteration resulting from zinc amendment was indicated by shifts in both BIOLOG metabolic profiles and PLFA profiles. Effects of zinc on PLFA profiles included relative decreases in indicator fatty acids for arbuscular mycorrhizal fungi and actinomycetes. Some adaptation of the microbial communities to the zinc amendment was suggested by the fact that after 420 d incubation there were no significant differences in culturable bacterial populations or microbial biomass of the control and zinc amended systems. However, other microbial properties measured in this study showed that zinc still affected microbial community structure and activity after 420 d. Dehydrogenase activity of the zinc treated communities remained 93% lower than the controls. The percentage of zinc resistant populations was still significantly higher for the zinc treated communities. Similarly, the BIOLOG and PLFA profiles continued to show differences in the structure of the zinc treated and control microbial communities. Effects of zinc on PLFA profiles at day 420 included a relative decrease in an indicator fatty acid for arbuscular mycorrhizal fungi and a relative increase in an indicator fatty acid for fungi. The comparison of PLFA profiles also showed mixed results for several fatty acid indicators for actinomycetes. The pH control treatment showed similar effects on population size and activity as the zinc treatment, although in most cases there was a much stronger effect with the zinc treatment. In addition, the pH treatment caused changes in BIOLOG and PLFA profiles which were different than the changes seen with zinc treatment.

DNA adducts in perch ( Perca fluviatilis) from a creosote contaminated site in the River Ångermanälven, Sweden

Levels of hepatic DNA adducts, analysed by 32P-postlabelling, histopathological lesions and organosomatic indices, were measured in perch ( Perca fluviatilis). The fish were caught at five sites in the river Ångermanälven, Sweden: one site known to be contaminated with creosote, sites downstream from the contaminated site and a reference site upstream. Perch were also caught at a long-distance reference site. The level of DNA adducts in fish from the creosote-contaminated site was 6.8±4.1 nmol mol −1 nucleotides compared to 0.21±0.21 nmol mol −1 nucleotides in fish from the long-distance reference site. The adduct level was also significantly increased compared to adduct levels in fish from the local reference site. Hepatocellular degeneration and macrophage aggregates were observed but did not correlate with a specific site in the river. No effects on organosomatic indices that correlated with distance from the contaminated site were observed. In the laboratory, perch were exposed to an organic solvent extract prepared from sediment collected at the creosote-contaminated site or to benzo(a)pyrene (BaP) by oral administration. Perch treated with the extract had adduct patterns very similar to those observed in perch from the contaminated field site. Two diagonal zones including 10–12 adduct spots were observed on the autoradiograms. One adduct was tentatively identified by co-chromatography with a 32P-labelled standard of 7 R,8 S,9 S-trihydroxy, 10 R-( N 2-deoxyguanosyl 3′-phosphate)-7,8,9,10-tetrahydrobenzo(a)pyrene (BaPDE-dG-3′p) in two different solvent systems. Autoradiograms derived from the BaP-exposed perch showed one major adduct and several less intense spots. The major BaP adduct had the same chromatographic properties as the standard BaPDE-dG-3′p adduct. This study shows that 32P-postlabelling analysis of DNA adducts in perch can be used as a sensitive indicator of exposure to genotoxic polycyclic aromatic hydrocarbons, and that comparison of DNA adduct patterns of fish exposed in the field and laboratory can be used to determine the responsible source of pollutants.

Surfactant enhanced removal of PCE in a nominally two-dimensional, saturated, stratified porous medium

Although surfactant enhanced remediation of nonaqueous phase liquids (NAPLs) by pump-and-treat technology has been studied extensively in the laboratory with one-dimensional columns, very few multi-dimensional investigations have been reported. In this study we focus on the removal of perchloroethylene (PCE) from a two-dimensional, saturated porous medium containing a low permeability sand layer situated in an otherwise high permeability sand. A PCE spill was applied at the surface of the porous medium and allowed to redistribute until static equilibrium was achieved. The porous medium was then flushed with various surfactant and co-solvent formulations injected at the PCE source location and extracted at the bottom of the porous medium using a configuration similar to that of Abdul and Ang [Abdul, S.A., Ang, C.C., 1994. In situ surfactant washing of polychlorinated biphenyls and oils from a contaminated field site: Phase II. Pilot study. Ground Water 32, 727–734]. Effluent samples were analyzed for dissolved PCE concentrations. Volumetric water and PCE content values were determined at a number of locations by means of dual-energy gamma radiation measurements. Once surfactant flushing had started, PCE moved as a distinct separate phase ahead of the surfactant front. Most of this downward moving PCE accumulated on top of the low permeability sand layer. Some PCE, however, passed quickly through this layer and subsequently through the high permeability sand below it. Movement of some of the PCE into and through the low permeability sand layer was attributed to local heterogeneities combined with reduced interfacial tensions associated with the surfactant formulation. Clean-up of PCE in most of the high permeability sand was considered to be effective. PCE accumulated on top of the fine layer, however, posed a significant challenge to remediation and required several pumping configurations and surfactant/co-solvent formulations before most of it was removed.

Fluctuating asymmetry and mentum gaps in populations of the midge Chironomus riparius (diptera: Chironomidae) from a metal‐contaminated river

AbstractThe 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.

Metapopulation dynamics: Indirect effects and multiple distinct outcomes in ecological risk assessment

AbstractA toxicant‐dosed metapopulation model was used to explore the range of possible dynamics of populations in contaminated field sites. A single species metapopulation model was developed that is discrete, deterministic, and incorporates doseresponse curves and biotic growth rates to describe the effects of contamination on a metapopulation. The distribution of the chemical contamination is assumed limited to one patch and contagious within that patch. Both persistent and degradable toxicants were modeled. Five principal conclusions resulted from our simulation studies. (1) Mortality in one subpopulation has ecologically significant effects on nondosed subpopulations. This hypothesis we term “action at a distance” because no direct contact with a toxicant has occurred except in the dosed patch. (2) Because uncontaminated sites connected to the contaminated site by migration of the biota are affected, these uncontaminated sites cannot be reference sites. (3) The arrangement of the patches is critical to the dynamics of the system and the overall impact of a toxicant. (4) Due to the contagious distribution of the toxicant and the stochastic function describing exposure effect, multiple discrete outcomes often are possible from the same initial conditions. These outcomes can range from extinction to the reaching of the carrying capacity for a patch. (5) If sufficient cleanup is not possible, it may be necessary to isolate the contaminated patch, allowing the formerly connected patches to regain more typical population dynamics.