Bioaccumulation of organic chemicals in contaminated soils: evaluation of bioassays with earthworms

Earthworms live in close contact with the soil and can thus be considered representative for the bioavailability of chemicals at contaminated sites. Bioavailability can either be assessed by analyzing earthworms from contaminated locations or by exposing laboratory-reared specimens to soil samples from the field (bioassays). In this study, we investigate the relevance of bioassays by using an extended experimental design (to identify signs of depletion of the bioavailable phase by the earthworms) and by using two species of earthworm (the standard test species Eisenia andrei and the field-relevant Aporrectodea caliginosa). Furthermore, bioassay results are compared to body residues of worms collected from the field site: a heavily polluted polder, amended with dredge spoil. We focused on telodrin, dieldrin, hexachlorobenzene, and eight PCBs. With our bioassay design, it was shown that depletion was unlikely, although more subtle effects could have occurred (e.g., changes in sorption during the experiments). E. andrei is a good choice for bioassays because its body residues correlate well to those in A. caliginosa, as well as to those in the field-collected worms. Nevertheless, E. andrei accumulated slightly more than the other species and appeared to be more sensitive to the conditions in soil from one of our sites.     

Bioaccumulation of pharmaceuticals and other anthropogenic waste indicators in earthworms from agricultural soil amended with biosolid or swine manure

Analysis of earthworms offers potential for assessing the transfer of organic anthropogenic waste indicators (AWIs) derived from land-applied biosolid or manure to biota. Earthworms and soil samples were collected from three Midwest agricultural fields to measure the presence and potential for transfer of 77 AWIs from land-applied biosolids and livestock manure to earthworms. The sites consisted of a soybean field with no amendments of human or livestock waste (Site 1), a soybean field amended with biosolids from a municipal wastewater treatment plant (Site 2), and a cornfield amended with swine manure (Site 3). The biosolid applied to Site 2 contained a diverse composition of 28 AWls, reflecting the presence of human-use compounds. The swine manure contained 12 AWls, and was dominated by biogenic sterols. Soil and earthworm samples were collected in the spring (about30 days after soil amendment) and fall (140-155 days after soil amendment) at all field sites. Soils from Site 1 contained 21 AWIs and soil from Sites 2 and 3 contained 19 AWls. The AWI profiles at Sites 2 and 3 generally reflected the relative composition of AWls present in waste material applied. There were 20 AWls detected in earthworms from Site 1 (three compounds exceeding concentrations of 1000 microg/kg), 25 AWls in earthworms from Site 2 (seven compounds exceeding concentrations of 1000 microg/ kg), and 21 AWls in earthworms from Site 3 (five compounds exceeding concentrations of 1000 microg/kg). A number of compounds thatwere present in the earthworm tissue were at concentrations less than reporting levels in the corresponding soil samples. The AWIs detected in earthworm tissue from the three field sites included pharmaceuticals, synthetic fragrances, detergent metabolites, polycyclic aromatic hydrocarbons (PAHs), biogenic sterols, disinfectants, and pesticides, reflecting a wide range of physicochemical properties. For those contaminants detected in earthworm tissue and soil, bioaccumulation factors (BAF) ranged from 0.05 (galaxolide) to 27 (triclosan). This study documents that when AWls are present in source materials that are land applied, such as biosolids and swine manure, AWls can be transferred to earthworms.     

Impact of pH on Cu accumulation kinetics in earthworm cytosol

We studied the interaction between toxic stress and accumulation in the earthworm Aporrectodea caliginosa, as induced by different soil copper pools and soil constituents (especially pH). Earthworms were exposed in quartz sand, spiked soils, and field soils with different Cu concentrations and varying soil composition. The copper content in the earthworms was determined in the following: the cytosolic fraction, a granular fraction and a fraction consisting of tissue fragments, cell membranes and intact cells. The highest amount of Cu was found in the cytosolic fraction. The other fractions varied only slightly in response to changes in any of the copper pools in soil. Cytosolic copper was the best predictor of Cu availability to earthworms collected from soils at constant pH, as statistically significant correlations were obtained with pore water pCu at constant pH in earthworms exposed in quartz sand. This correlation was lost for cytosolic Cu concentrations in earthworms exposed to spiked soils and field soils at differing pHs. Instead, cytosolic copper correlated well to Cu in either pore water or solid phase. Soil pH not only plays an important role in the availability of metals and therefore on their uptake fluxes, but internal competition of Cu2+ and H+ at physiologically active binding sites also explained these apparent contradictions and increased the predictability of body burdens significantly.     

Surfactants differentially impact p,p'-DDE accumulation by plant and earthworm species

The effect of four surfactants (Triton X-100, Tween-80, rhamnolipids, cyclodextrin) at 100-1000 mg/L on p,p'-DDE phytoextraction by Cucurbita pepo (zucchini) under field conditions and p,p'-DDE bioaccumulation by earthworm species (Eisenia fetida, Lumbricus terrestris) under laboratory conditions was investigated. Abiotically, surfactants (except cyclodextrin) increased contaminant desorption from soil by 4-fold, with higher concentrations generally promoting greater release. Cyclodextrin had no effect on DDE desorption. DDE concentrations in unamended zucchini roots and stems were 30- and 7.8-fold greater than soil levels, respectively, and 1.6% of the contaminant was extracted from the soil. The surfactant effects were cultivar specific. Triton X-100 increased DDE uptake in "Costata" by 2.6-fold, yielding 5% contaminant phytoextraction. In "Goldrush", DDE accumulation decreased by 69% across all surfactants. Surfactants significantly increased DDE bioaccumulation by earthworms. For E. fetida with all surfactants and L. terrestriswith Triton X-100 and cyclodextrin, DDE accumulation increased 2.5-7.2-fold, paralleling abiotic desorption. However, Tween-80 and rhamnolipids increased DDE accumulation in L. terrestris by 74 and 36 fold, respectively. These dramatic increases in contaminant bioaccumulation do not correlate with the increased availability observed abiotically. Surfactant-mediated increases in contaminant bioavailability are an unexpectedly complex process and clearly present unanticipated concerns over pollutant exposure to nontarget organisms.     

Phylogenetic and functional biomakers as indicators of bacterial community responses to mixed-waste contamination

Few studies have demonstrated changes in community structure along a contaminant plume in terms of phylogenetic, functional, and geochemical changes, and such studies are essential to understand how a microbial ecosystem responds to perturbations. Clonal libraries of multiple genes (SSU rDNA, nirK, nirS, amoA, pmoA, and dsrAB) were analyzed from groundwater samples (n = 6) that varied in contaminant levels, and 107 geochemical parameters were measured. Principal components analyses (PCA) were used to compare the relationships among the sites with respect to the biomarker (n = 785 for all sequences) distributions and the geochemical variables. A major portion of the geochemical variance measured among the samples could be accounted for by tetrachloroethene, 99Tc, No3, SO4, Al, and Th. The PCA based on the distribution of unique biomarkers resulted in different groupings compared to the geochemical analysis, but when the SSU rRNA gene libraries were directly compared (deltaC(xy) values) the sites were clustered in a similar fashion compared to geochemical measures. The PCA based upon functional gene distributions each predicted different relationships among the sites, and comparisons of Euclidean distances based upon diversity indices for all functional genes (n = 432) grouped the sites by extreme or intermediate contaminant levels. The data suggested that the sites with low and high perturbations were functionally more similar than sites with intermediate conditions, and perhaps captured the overall community structure better than a single phylogenetic biomarker. Moreover, even though the background site was phylogenetically and geochemically distinct from the acidic sites, the extreme conditions of the acidic samples might be more analogous to the limiting nutrient conditions of the background site. An understanding of microbial community-level responses within an ecological framework would provide better insight for restoration strategies at contaminated field sites.     

Earthworm sublethal responses to titanium dioxide nanomaterial in soil detected by ¹H NMR metabolomics

1H NMR-based metabolomics was used to examine the response of Eisenia fetida earthworms raised from juveniles for 20-23 weeks in soil spiked with either 20 or 200 mg/kg of a commercially available uncoated titanium dioxide (TiO(2)) nanomaterial (nominal diameter of 5 nm). To distinguish responses specific to particle size, soil treatments spiked with a micrometer-sized TiO(2) material (nominal diameter, <45 μm) at the same concentrations (20 and 200 mg/kg) were also included in addition to an unspiked control soil. Multivariate statistical analysis of the (1)H NMR spectra for aqueous extracts of E. fetida tissue suggested that earthworms exhibited significant changes in their metabolic profile following TiO(2) exposure for both particle sizes. The observed earthworm metabolic changes appeared to be consistent with oxidative stress, a proposed mechanism of toxicity for nanosized TiO(2). In contrast, a prior study had observed no impairment of E. fetida survival, reproduction, or growth following exposure to the same TiO(2) spiked soils. This suggests that (1)H NMR-based metabolomics provides a more sensitive measure of earthworm response to TiO(2) materials in soil and that further targeted assays to detect specific cellular or molecular level damage to earthworms caused by chronic exposure to TiO(2) are warranted.     

Monitoring of landfill leachate dispersion using reflectance spectroscopy and ground-penetrating radar

The utility of ground-penetrating radar and reflectance spectroscopy in the monitoring of landfill sites has been investigated. Strong correlations between red edge inflection position and chlorophyll and heavy metal concentrations have been demonstrated from grassland species affected by leachate contamination of the soil adjacent to the landfill test site. This study demonstrated that reflectance spectroscopy can identify vegetation affected by leachate-contaminated soil at a range of spatial resolutions. To identify the vegetation affected by leachate contamination, the spectroradiometer must have contiguous bands at sufficient spectral resolution over the critical wave range that measures chlorophyll absorption and the red edge (between 650 and 750 nm). The utility of ground-penetrating radar data to identify leachate escaping from breakout points in the contaminant wall has also been demonstrated. An integrated approach using these techniques, combined with field and borehole sampling and contaminant migration modeling, offers a possible cost-effective monitoring approach for landfill sites.     

CO2-efflux measurements for evaluating source zone natural attenuation rates in a petroleum hydrocarbon contaminated aquifer

In order to gain regulatory approval for source zone natural attenuation (SZNA) at hydrocarbon-contaminated sites, knowledge regarding the extent of the contamination, its tendency to spread, and its longevity is required. However, reliable quantification of biodegradation rates, an important component of SZNA, remains a challenge. If the rate of CO(2) gas generation associated with contaminant degradation can be determined, it may be used as a proxy for the overall rate of subsurface biodegradation. Here, the CO(2)-efflux at the ground surface is measured using a dynamic closed chamber (DCC) method to evaluate whether this technique can be used to assess the areal extent of the contaminant source zone and the depth-integrated rate of contaminant mineralization. To this end, a field test was conducted at the Bemidji, MN, crude oil spill site. Results indicate that at the Bemidji site the CO(2)-efflux method is able to both delineate the source zone and distinguish between the rates of natural soil respiration and contaminant mineralization. The average CO(2)-efflux associated with contaminant degradation in the source zone is estimated at 2.6 μmol m(-2) s(-1), corresponding to a total petroleum hydrocarbon mineralization rate (expressed as C(10)H(22)) of 3.3 g m(-2) day(-1).     

Monitoring network design for phytoremediation systems using primary and secondary data sources

Phytoremediation, or contaminant removal using plants, has been deployed at many sites to remediate contaminated soil and groundwater. Research has shown that trees are low-cost, rapid, and relatively simple-to-use monitoring systems as well as inexpensive alternatives to traditional pump-and-treat systems. However, tree monitoring is also an indirect measure of subsurface contamination and inherently more uncertain than conventional techniques such as wells or soil borings that measure contaminant concentrations directly. This study explores the implications for monitoring network design at real-world sites where scarce primary data such as monitoring wells or soil borings are supplemented by extensive secondary data such as trees. In this study, we combined secondary and primary data into a composite data set using models to transform secondary data to primary, as primary data were too sparse to attempt cokriging. Optimal monitoring networks using both trees and conventional techniques were determined using genetic algorithms, and trade-off curves between cost and uncertainty are presented for a phytoremediation system at Argonne National Laboratory. Optimal solutions found at this site indicate that increasing the number of secondary data sampled resulted in a significant decrease in global uncertainty with a minimal increase in cost. The choice of the data transformation model had an impact on the optimal designs and uncertainty estimated at the site. Using a data transformation model with a higher error resulted in monitoring network designs where primary data were favored over colocated secondary data. The spatial configuration of the monitoring network design was similar with regard to the areas sampled, irrespective of the data transformation model used. Overall, this study shows that using a composite data set, with primary and secondary data, results in effective monitoring designs, even at sites where the only data transformation model available is one with significant error.     

基于植被指数的藏北牧区土壤湿度反演

土壤湿度的遥感动态监测在农牧业生产中具有重要意义。近年来,多种基于遥感指数的土壤湿度监测方法被提出并得到广泛关注,但当前对不同深度土壤湿度的反演及植被指数反映土壤湿度滞后性的研究较少。该文针对遥感指数反演土壤湿度的精度问题,对MODIS(moderate resolutionimaging spectroradiometer)的2种植被指数产品归一化差异植被指数(normalized difference vegetation index,NDVI)和增强型植被指数(enhanced vegetation index,EVI)与土壤湿度实测值进行相关分析,并利用在其中一个样点得到相关系数最高的回归模型对距离较远的其它点进行土壤湿度值估算,最后用土壤湿度实测值对模型的精度进行验证。结果表明,2种植被指数均与土壤湿度值呈现出较强的相关性,且利用植被指数估算土壤湿度的延迟天数为5～10 d。在相同气候模式、土壤类型和植被类型的条件下,高程为影响回归模型精度的主要因素。该研究可为牧区多层深度土壤湿度反演方法的选择和监测提供参考依据。     

Field-scale evaluation of the passive flux meter for simultaneous measurement of groundwater and contaminant fluxes

A new method, passive flux meter (PFM), has been developed and field-tested for simultaneously measuring contaminant and groundwater fluxes in the saturated zone at hazardous waste sites. The PFM approach uses a sorptive permeable medium placed in either a borehole or monitoring well to intercept contaminated groundwater and release "resident" tracers. The sorbent pack is placed in a groundwater flow field for a specified exposure time and then recovered for extraction and analysis. By quantifying the mass fraction of resident tracers lost and the mass of contaminant sorbed, groundwater and contaminant fluxes are calculated. Here, we assessed the performance of PFMs at the Canadian Forces Base Borden field site in Ontario, Canada. Two field tests were conducted under imposed groundwater flow fields: (1) radial flow to a well and (2) linear flow in a test channel confined by sheet pile walls on three sides. Both tests demonstrate that the local fluxes measured by PFM and averaged overthe screen interval were within 15% of imposed groundwaterflow and within 30% of measured contaminant mass flux. Patterns in depth variations in groundwater and contaminant fluxes, determined by the PFM approach, allow for site characterization at a higher spatial resolution. These results support the PMF method as a potential innovative alternative for measuring groundwater and contaminant fluxes in screened wells.     

Herbicide runoff along highways. 2. Sorption control

Controversy remains about the importance of nonlinear sorption isotherms, desorption rate limitations, and aging effects, collectively referred to as nonideal sorption processes, in controlling the fate and transport of organic contaminants. Herbicide runoff from highway soils represents a good test case for assessing the relative importance of nonideal sorption because runoff flow rates are often high, soil-water contacttimes are short, and significant time is available for contaminant aging after application. This study examines the sorption and desorption of five herbicides with a wide range of properties (isoxaben, oryzalin, diuron, clopyralid, and glyphosate) on soil samples from two roadsides in northern California and uses the results to examine field runoff data from multiple rainy seasons. Nonideal sorption processes do not appear to be significant in determining herbicide runoff at the field sites because (i) sorption isotherms were linear or slightly nonlinear for all compounds but glyphosate, (ii) field runoff concentration ratios between isoxaben and oryzalin were consistent with linear partitioning predictions, (iii) runoff leaving the site appeared to be in equilibrium with local soil concentrations, and (iv) desorption distribution coefficients for aged herbicides on soil samples collected from the field site did not differ substantially from those obtained in short-term laboratory adsorption experiments. Collectively, these findings indicate that linear equilibrium models are adequate for predicting the concentration of herbicides in runoff in these field settings and that more complicated nonideal models do not need to be invoked. Vegetated slopes effectively reduced the herbicide loads, with average removals of 35-80% occurring as runoff traversed a 3-m segment 1 m from the edge of the spray zone.     

Comparison of subcellular partitioning, distribution, and internal speciation of Cu between Cu-tolerant and naïve populations of Dendrodrilus rubidus Savigny

When considering contaminated site ecology and ecological risk assessment a key question is whether organisms that appear unaffected by accumulation of contaminants are tolerant or resistant to those contaminants. A population of Dendrodrilus rubidus Savigny earthworms from the Coniston Copper Mines, an area of former Cu mining, exhibit increased tolerance and accumulation of Cu relative to a nearby non-Cu exposed population. Distribution of total Cu between different body parts (posterior, anterior, body wall) of the two populations was determined after a 14 day exposure to 250 mg Cu kg(-1) in Cu-amended soil. Cu concentrations were greater in Coniston earthworms but relative proportions of Cu in different body parts were the same between populations. Cu speciation was determined using extended X-ray absorption fine structure spectroscopy (EXAFS). Cu was coordinated to O atoms in the exposure soil but to S atoms in the earthworms. There was no difference in this speciation between the different earthworm populations. In another experiment earthworms were exposed to a range of Cu concentrations (200-700 mg Cu kg(-1)). Subcellular partitioning of accumulated Cu was determined. Coniston earthworms accumulated more Cu but relative proportions of Cu in the different fractions (cytosol > granular > tissue fragments, cell membranes, and intact cells) were the same between populations. Results suggest that Coniston D. rubidus are able to survive in the Cu-rich Coniston Copper Mines soil through enlargement of the same Cu storage reservoirs that exist in a nearby non-Cu exposed population.     

Arsenic influence on genetic variation in grain trace-element nutrient content in Bengal delta grown rice

It has previously been shown that across different arsenic (As) soil environments, a decrease in grain selenium (Se), zinc (Zn), and nickel (Ni) concentrations is associated with an increase in grain As. In this study we aim to determine if there is a genetic element for this observation or if it is driven by the soil As environment. To determine the genetic and environmental effect on grain element composition, multielement analysis using ICP-MS was performed on rice grain from a range of rice cultivars grown in 4 different field sites (2 in Bangladesh and 2 in West Bengal). At all four sites a negative correlation was observed between grain As and grain Ni, while at three of the four sites a negative correlation was observed between grain As and grain Se and grain copper (Cu). For manganese, Ni, Cu, and Se there was also a significant genetic interaction with grain arsenic indicating some cultivars are more strongly affected by arsenic than others.     

基于代谢组学分析青枯病烟田土壤代谢标志物

【目的】分析青枯病烟田和健康烟田土壤代谢物组成的差异,筛选青枯病烟田土壤代谢标志物。【方法】以青枯病烟田和健康烟田的烟株根围土壤为研究对象,采用非靶向代谢组学LC-MS/MS分析技术,对3个时期（未发病、发病中期、发病后期）土壤代谢物组成进行研究。【结果】（1）在未发病时、发病中期和发病后期,青枯病烟田和健康烟田土壤代谢物有显著差异的代谢物分别为115种、159种和105种。（2）3个时期共同差异代谢物有63种,其中正离子模式代谢物有49种,负离子模式代谢物有14种。49种正离子模式代谢物可以聚为2个大类和7个小类。（3）筛选出8种代谢标志物,分别为环巴胺（Cyclopamine）、麦芽四糖（Maltotetraose）、麦黄酮（Tricine）、凯林（Khellin）、6-(alpha-D-glucosaminyl)-1D-myo-inositol、茄啶（Solanidine）、贝磷地尔（belfosdil）、硅雄酮（Silandrone）。【结论】青枯病烟田和健康烟田土壤代谢物组成上存在较大差异,筛选出8种代谢标志物可为判别土壤感烟草青枯病状况提供一定参考。     

Metal distributions in New Orleans following hurricanes Katrina and Rita: A continuation study

In late October 2005, twenty-seven metals were determined in soils and sediment layers deposited by floodwaters (flood sediments) within New Orleans, Louisiana. Samples originated from 43 sites along four transects, at an industrial canal, and near the Superdome. The sampling design encompassed flooded and nonflooded areas as well as differing economic strata within the city. Results from this effort confirmed findings of our previous study designed to quantify contaminant profiles in the aftermath of Hurricane Katrina. The expanded sampling from this most recent investigation revealed that arsenic (As) and lead (Pb) concentrations exceeded United States Environmental Protection Agency (USEPA) soil screening criteria indiscriminately throughout the city. However, As and Pb concentrations were lower along St. Charles Avenue, an area largely unaffected by hurricane related flooding. Toxicant concentrations did not exceed soil screening criteria values for lead within any flood sediments or for 32 of 37 soil samples, but arsenic concentrations in 40 of 43 samples exceeded screening criteria.     

New evaluation scheme for two-dimensional isotope analysis to decipher biodegradation processes: application to groundwater contamination by MTBE

Compound-specific analysis of stable carbon and hydrogen isotopes was used to assess the fate of the gasoline additive methyl tert-butyl ether (MTBE) and its major degradation product tert-butyl alcohol (TBA) in a groundwater plume at an industrial disposal site. We present a novel approach to evaluate two-dimensional compound-specific isotope data with the potential to identify reaction mechanisms and to quantify the extent of biodegradation at complex field sites. Due to the widespread contaminant plume, multiple MTBE sources, the presence of numerous other organic pollutants, and the complex biogeochemical and hydrological regime atthe site, a traditional mass balance approach was not applicable. The isotopic composition of MTBE steadily changed from the source regions along the major contaminant plume (-26.4% to +40.0% (carbon); -73.1% to +60.3% (hydrogen)) indicating substantial biodegradation. Constant carbon isotopic signatures of TBA suggest the absence of TBA degradation at the site. Published carbon and hydrogen isotope fractionation data for biodegradation of MTBE under oxic and anoxic conditions, respectively, were examined and used to determine both the nature and the extent of in-situ biodegradation along the plume(s). The coupled evaluation of two-dimensional compound-specific isotope data explained both carbon and hydrogen fractionation data in a consistent way and indicate anaerobic biodegradation of MTBE along the entire plume. A novel scheme to reevaluate empiric isotopic enrichment factors (epsilon) in terms of theoretically based intrinsic carbon (12k/13k) and hydrogen (1k/2k) kinetic isotope effects (KIE) is presented. Carbon and hydrogen KIE values, calculated for different potential reaction mechanisms, imply that anaerobic biodegradation of MTBE follows a SN2-type reaction mechanism. Furthermore, our data suggest that additional removal process(es) such as evaporation contributed to the overall MTBE removal along the plume, a phenomenon that might be significant also for other field sites at tropic or subtropic climates with elevated groundwater temperatures (25 degrees C).     

Analysis of polychlorinated biphenyls in concurrently sampled Chinese air and surface soil

Polychlorinated biphenyl (PCB) concentrations were measured in a concurrent air and surface soil sampling program across China. Passive air samples were collected for approximately 3 months from mid-July to mid-October, 2005 using polyurethane foam (PUF) disk type samplers at 97 sites and surface soil samples were collected in a subset of 51 sites in the same year. As expected, the air concentrations (pg m(-3)) were highest at urban sites (mean of 350 +/- 218) followed by rural (230 +/- 180) and background sites (77 +/- 50). The PCB homologue composition was similar across China, with no distinction among site types, and reflected the profile of Chinese transformer oil with a greater proportion of lower molecular weight (LMW) congeners, particularly the tri-PCBs. This differs from the profile in Chinese soil that was shifted toward the higher molecular weight (HMW) congeners and likely attributed to numerous years of deposition and accumulation in this reservoir. The PCB profile in surface soil also reflects an "urban fractionation effect" with preferential deposition of HMW congeners near sources. The profile of PCBs in Chinese air was shown to be different than reported for Europe and for the Great Lakes Area (GLA) in North America. European and GLA air samples show a distinction between urban and rural/V background sites, with urban sites dominated by tetra- and penta-PCBs, whereas rural and background sites are shifted toward LMW congeners. European and GLA samples also exhibit much higher PCB concentrations at urban sites. This may be attributed to the use of PCBs in building materials in European and North American cities. In China, the difference between urban and rural/background sites is less pronounced. Strong soil-air correlations were found for the LMW PCBs at the background and rural sites, and for the HMW PCBs at the urban sites, a strong evidence of the urban fractionation effect. To our knowledge, this is the first national-scale study in China investigating PCBs in both air and surface soil samples.