Indirect Immunofluorescence and FISH for Enumerating Contaminated Site Sulfate-Reducers

A new species of sulfate-reducer, Desulfosporosinus meridiei, was recently isolated from gasoline-contaminated anaerobic groundwater in which degradation of toluene and other hydrocarbons occurred. Ground-water from inside (three sites) and outside (one site) the contaminant plume was probed with specific polyclonal antibodies raised against two strains of D. meridiei (strains T2 and S6). Molecular 16S rRNA probes designed to hybridize with cells of D. meridiei were also used. Cell counts using antistrain T2 antibodies (specific for all strains of D. meridiei and two strains of D. orientis) were similar (10³ cells/mL) both inside and outside the plume as were total DAPI counts (10⁶ cells/mL). The numbers of cells stained with antibodies specific for Group B strains of D. meridiei varied between locations. The molecular probes DSP477A and DSP477B were designed for, and were effective on, pure cultures of D. meridiei and were able to distinguish this species from Desulfovibrio desulfuricans in hybridization experiments. No cells were seen to hybridize with probe DSP477B in groundwater samples. Cell counts in groundwater using the universal eubacterial probe, EUB338, were only 8% to 29% of DAPI counts. Fluorescence intensity was poor and auto fluorescence of particles made counting difficult. This study showed that molecular probing using techniques commonly employed in many laboratories was of little use for evaluating microbial populations in this groundwater. Polyclonal antibodies were considerably more useful for identifying populations of specific cells. The lack of difference in cell numbers between contaminated and nearby uncontami-nated groundwater suggests that cell counts will not always be useful as indicators of intrinsic remediation.     

GC/MS-SCAN to follow the fate of crude oil components in bioreactors set to remediate contaminated soil

In this paper GC/MS-SCAN was used to identify the crude oil components that persist after bioremediation treatment of contaminated soil and the metabolites generated during this process. The soil was treated in bioreactors inoculated with an adapted bacterial population. In the first of two sets of conditions used, the water phase of the reactor was circulated continuously at a flow rate of 7 l day⁻¹, and in the other case, it was circulated for a short period once a day to give the equivalent of 0.5 l day⁻¹. Data showed that acyclic, n- and substituted alkanes C₁₂ were still present after one year of remediation, while the majority of substituted derivatives of polycyclic and aromatic hydrocarbons could not be detected by GC/MS-SCAN analysis. The number of components identified was about one-half of that initially observed. After treatment the same number of components was detected at the top and bottom of the reactor in which the water phase was circulated continuously, whereas a smaller number of metabolites were observed at the top rather than at the bottom of the reactor with discontinuous circulation. The analysis has pointed to the importance of n-alkanes, their substituted derivatives and polycyclic aromatic hydrocarbons as the most significant pollutants.     

Risk-Based Corrective Action of Hydrocarbon Contamination at a Former Major Urban Petroleum Storage Site in the U.K.

The former site of a major petroleum storage facility adjacent to a major urban watercourse was found to have potentially significant concentrations of hydrocarbons in soil and groundwater that needed to be addressed prior to redevelopment. A series of intrusive investigations were undertaken to collect physical and chemical data for a Quantitative Risk Assessment (QRA) of potential impacts on human health and the wider environment, in order to derive a remedial strategy for redevelopment of the site for light industrial use. A site-specific QRA methodology was devel oped using both U.K. and U.S. guidance to produce Risk-Based Clean-up Levels (RBCLs) for benzene, and other petroleum hydrocarbons. The U.K. has no nationally based guidance on risk assessment and studies are designed by the consultant for submission to the U.K. Environment Agency (EA) for their approval. It is the EA's role to determine whether the work has been undertaken satisfactorily. To achieve these RBCLs, ex situ bioremediation was identified as the best practicable remedial option. This was carried out in windrows using mechanical aeration (to achieve oxygenation with ammonia nitrate granule and woodchip addition) for a total of approximately 5291?m³ of soil. The bioremediation process was successful in achieving the site specific RBCLs for benzene and for other hydrocarbons within an average of 5 to 6 weeks. This article describes the successful implementation of Risk-Based Corrective Action (RBCA) at this petroleum release site as a demonstration of how risk-based remedial standards for contaminated sites can be achieved with regulatory approval.     

Metabolic indicators for detecting in situanaerobic alkylbenzene degradation

Monitoring programs for intrinsic bioremediation of fuel hydrocarbonsrequire indicators that can convincingly demonstrate in situ metabolism. In this evaluation of potential indicators of in situ anaerobic alkylbenzene metabolism, laboratory and field data are reviewed for two classes of aromatic acids: (i) benzylsuccinate, E-phenylitaconate, and their methyl homologs, and (ii) benzoate, and methyl-, dimethyl-, and trimethylbenzoates. The review includes previously unpublished field data from a hydrocarbon-contaminated site in Fallon (Nevada), at which both classes of metabolites were detected in groundwater. The two classes of compounds were evaluated with respect to specificity (i.e., unique biochemical relationship to a specific alkylbenzene), stability, and generation as degradation intermediates versus dead-end products; recent developments in the biochemistry of anaerobic toluene and xylene degradation were incorporated in this evaluation. In general, benzylsuccinates/E-phenylitaconates are superior to benzoates in terms of their very high specificity to their parent hydrocarbons and their lack of commercial and industrial sources. They are also uniquely indicative of anaerobic conditions. All of the benzoates, benzylsuccinates, and E-phenylitaconates are relatively stable chemically and (with the exceptionof benzoate) biologically under anaerobic conditions, based on the limited data available. Although benzoate, benzylsuccinate, and E-phenylitaconate are intermediates of anaerobic toluene mineralization to carbon dioxide, their methyl homologs can be either mineralization intermediates or cometabolic dead-end products of alkylbenzenes, depending on the bacteria involved. Benzoates are far more commonly reported in field studies of hydrocarbon-contaminated aquifers than are benzylsuccinates and E-phenylitaconates, although it is not clear whether this is an accurate representation of the relative occurrenceof these metabolites at contaminated sites, or whether it instead reflects the limited range of target analytes used in most field studies to date.     

Bioremediation of benzene,toluene, ethylbenzene,xylenes-contaminated soil: a biopile pilot experiment

Aims: In this study, we evaluated the removal efficiency of fuel hydrocarbons from a jet fuel contaminated area using bioaugmentation treatment in biopile. Methods and Results: The hydrocarbon analysis of the sample revealed total hydrocarbons mainly constituted by benzene, toluene, ethylbenzene, xylenes (BTEX) and heavy aliphatic hydrocarbons. Enrichments of soil sample were performed with BTEX, pristane and fuel JP-5, respectively, selected hydrocarbon-degrading strains, namely Acinetobacter sp., Pseudomonas sp. and Rhodococcus sp. Three hundred litres of culture containing 10⁸ cell ml⁻¹ of each strain and nutrients sprayed on the biopile allowed a removal of 90% of total hydrocarbons in 15 days. Bioremediation process was monitored by observation of the respiration rate and the bacterial abundance and GC-MS analysis. Conclusions: The efficiency of the treatment in the biopile was considerable. The assessment of microbial activity during the experiment is necessary for interventions targeted to improve environmental parameters such as humidity, temperature, pH and nutrients for optimization of the bioremediation process. Significance and Impact of the Study: A better knowledge of microbial successions at oil-polluted sites is essential for environmental bioremediation. Data obtained in biopile study improve our understanding of processes occurring during oil pollution.     

Enhanced anaerobic biodegradation of BTEX-ethanol mixtures in aquifer columns amended with sulfate,chelated ferric iron or nitrate

Flow-through aquifer columns were used to investigate the feasibility of adding sulfate, EDTA–Fe(III) or nitrate to enhance the biodegradation of BTEX and ethanol mixtures. The rapid biodegradation of ethanol near the inlet depleted the influent dissolved oxygen (8 mg l^-1), stimulated methanogenesis, and decreased BTEX biodegradation efficiencies from >99% in the absence of ethanol to an average of 32% for benzene, 49% for toluene, 77% for ethylbenzene, and about 30% for xylenes. The addition of sulfate, EDTA–Fe(III) or nitrate suppressed methanogenesis and significantly increased BTEX biodegradation efficiencies. Nevertheless, occasional clogging was experienced by the column augmented with EDTA–Fe(III) due to iron precipitation. Enhanced benzene biodegradation (>70% in all biostimulated columns) is noteworthy because benzene is often recalcitrant under anaerobic conditions. Influent dissolved oxygen apparently played a critical role because no significant benzene biotransformation was observed after oxygen was purged out of the influent media. The addition of anaerobic electron acceptors could enhance BTEX biodegradation not only by facilitating their anaerobic biodegradation but also by accelerating the mineralization of ethanol or other substrates that are labile under anaerobic conditions. This would alleviate the biochemical oxygen demand (BOD) and increase the likelihood that entraining oxygen would be used for the biotransformation of residual BTEX.     

Intrinsic bioremediation in a solvent-contaminated alluvial groundwater

An industrial site contaminated with a mixture of volatile organic compounds in its subsurface differed from previously reported locations in that the contamination consisted of a mixture of chlorinated, brominated, and non-halogenated aromatic and aliphatic solvents in an alluvial aquifer. The source area was adjacent to a river. Of the contaminants present in the aquifer, benzene, toluene, and chlorobenzene (BTC) were of primary concern. Studies of the physical, chemical, and microbiological characteristics of site groundwater were conducted. The studies concentrated on BTC, but also addressed the fate of the other aquifer VOCs. Gas chromatographic analyses performed on laboratory microcosms demonstrated that subsurface microorganisms were capable of BTC degradation. Mineralization of BTC was demonstrated by the release of ¹⁴CO₂ from radiolabelled BTC. In the field, distribution patterns of nutrients and electron acceptors were consistent with expression of in situ microbial metabolic activity: methane, conductivity, salinity and o-phosphate concentrations were all positively correlated with contaminant concentration; while oxidation-reduction potential, nitrate, dissolved oxygen and sulfate concentrations were negatively correlated. Total aerobes, aerotolerant anaerobes, BTC-specific degraders, and acridine orange direct microscopic microorganism counts were strongly and positively correlated with field contaminant concentrations. The relative concentrations of benzene and toluene were lower away from the core of the plume compared to the less readily metabolized compound, chlorobenzene. Hydrodynamic modeling of electron-acceptor depletion conservatively estimated that 450 kg of contaminant have been removed from the subsurface yearly. Models lacking a biodegradation term predicted that 360 kg of contaminant would reach the river annually, which would result in measurable contaminant concentrations. River surveillance, however, has only rarely detected these compounds in the sediment and then only at trace concentrations. Thus, the combination of field modeling, laboratory studies, and site surveillance data confirm that significant in situ biodegradation of the contaminants has occurred. These studies establish the presence of intrinsic bioremediation of groundwater contaminants in this unusual industrial site subsurface habitat. Received 01 December 1995/ Accepted in revised form 27 July 1996     

Anaerobic degradation of the aromatic hydrocarbon biphenyl by a sulfate-reducing enrichment culture

The aromatic hydrocarbon biphenyl is a widely distributed environmental pollutant. Whereas the aerobic degradation of biphenyl has been extensively studied, knowledge of the anaerobic biphenyl-oxidizing bacteria and their biochemical degradation pathway is scarce. Here, we report on an enrichment culture that oxidized biphenyl completely to carbon dioxide under sulfate-reducing conditions. The biphenyl-degrading culture was dominated by two distinct bacterial species distantly affiliated with the Gram-positive genus Desulfotomaculum . Moreover, the enrichment culture has the ability to grow with benzene and a mixture of anthracene and phenanthrene as the sole source of carbon, but here the microbial community composition differed substantially from the biphenyl-grown culture. Biphenyl-4-carboxylic acid was identified as an intermediate in the biphenyl-degrading culture. Moreover, 4-fluorobiphenyl was converted cometabolically with biphenyl because in addition to the biphenyl-4-carboxylic acid, a compound identified as its fluorinated analog was observed. These findings are consistent with the general pattern in the anaerobic catabolism of many aromatic hydrocarbons where carboxylic acids are found to be central metabolites.     

Applicability of the functional gene catechol 1,2-dioxygenase as a biomarker in the detection of BTEX-degrading Rhodococcus species

Aims: Catechol 1,2-dioxygenase is a key enzyme in the degradation of monoaromatic pollutants. The detection of this gene is in focus today but recently designed degenerate primers are not always suitable. Rhodococcus species are important members of the bacterial community involved in the degradation of aromatic contaminants and their specific detection could help assess functions and activities in the contaminated environments. To reach this aim, specific PCR primer sets were designed for the detection of Rhodococcus related catechol 1,2-dioxygenase genes. Methods and Results: Primers were tested with genetically well-characterized strains isolated in this study and community DNA samples were used as template for Rhodococcus specific PCR as well. The sequences of the catabolic gene in question were subjected to multiple alignment and a phylogenetic tree was created and compared to a 16S rRNA gene based Rhodococcus tree. A strong coherence was observed between the phylogenetic trees. Conclusions: The results strongly support the opinion that there was no recent lateral gene transfer among Rhodococcus species in the case of catechol 1,2-dioxygenase. Significance and Impact of the Study: In gasoline contaminated environments, aromatic hydrocarbon degrading Rhodococcus populations can be identified based upon the detection and sequence analysis of catechol 1,2-dioxygenase gene.     

Performance of AERMOD and CALPUFF models on SO2 and NO2 emissions for future health risk assessment in Tema Metropolis

AERMOD results were compared with the reported CALPUFF results to estimate the concentrations and temporal distributions of SO₂ and NO₂ from Tema Oil Refinery with particlar attention to heavy rainy season (HRS), minor rainy season (MRS), and dry season (DS). Statistical indices, including the fractional bias (FB), geometric mean variance (VG), normalized mean square error (NMSE), index of agreement (IOA), and geometric mean bias (MG), were used to assess the reliability of the models. Overall, AERMOD better predicted ambient SO₂ and NO₂ levels than the reported CALPUFF model. For SO₂, AERMOD showed a good agreement with FB, IOA, and MG while CALPUFF showed a good prediction in NMSE and VG. Also, AERMOD predicted NO₂ well with NMSE, IOA, MG, and VG compared with FB for CALPUFF. The MRS results showed higher hourly maximum concentrations (107.4 µg/m³ for SO₂ and 31.7 µg/m³ for NO₂). Maximum daily concentrations were slightly higher in HRS (37.7 µg/m³ for SO₂ and 9.6 µg/m³ for NO₂) compared to MRS and DS. The performace of the models may provide a better understanding for future epidemiological studies.     

The effect of soil‐particle size on hydrocarbon entrapment near a dynamic water table

The entrapment of residual hydrocarbon globules by water table fluctuations can produce a long‐term contamination threat to groundwater supplies that is difficult to remove. The mobilization of entrapped hydrocarbon globules depends on the balance between capillary and gravitational forces represented by the Bond number. It is important to estimate the potential for hydrocarbon entrapment at a spill site due to its influence on the effectiveness of remediation efforts. The present work focuses on the influence of particle diameter on hydrocarbon entrapment for a typical LNAPL (light nonaqueous‐phase liquid). Laboratory column tests have been conducted using a dual‐beam gamma densitometer to measure saturations of the three phases (water, air, and hydrocarbon). Soltrol 170^®, a solvent manufactured by Phillips 66 Co., is used as the hydrocarbon. Residual saturation of the Soltrol is measured after fluctuations in water table level to establish the distribution and consistency of hydrocarbon entrapment below the water table. Glass particles of nearly uniform size were used to represent a sandy soil. In the experiments, average particle sizes ranged from 210 to 6000 μm. Data were also taken using the synthetic soil matrix approved by the U.S. Environmental Protection Agency (EPA) for contamination studies. Results show that the distribution of trapped LNAPL is quite uniform and that the average residual saturation is about 13% up to a particle diameter of 710 μm. Above this diameter, residual saturation decreases with particle size. The corresponding critical Bond number, determined experimentally, agrees well with the predicted value of 1.6.     

The effect of interfacial tension on hydrocarbon entrapment and mobilization near a dynamic water table

The entrapment of residual hydrocarbon ganglia during water table fluctuations can produce a long‐term contamination threat to groundwater supplies that is difficult to remove. The mobilization of entrapped hydrocarbon ganglia depends on the balance between capillary and gravitational forces represented by the Bond number. The present work focuses on the influence of the interfacial tension between the hydrocarbon and the surrounding water on the entrapment and mobilization of the residual ganglia. Laboratory column tests using glass beads as the porous medium have been conducted to determine the residual saturation of a hydrocarbon (Soltrol 170) trapped during vertical displacements due to a rising water table and the necessary decrease in interfacial tension to mobilize these trapped ganglia. The interfacial tension was decreased by the addition of isopropyl alcohol to the water phase. Saturations of the three phases (water, hydrocarbon, and air) were measured with a dual‐beam y‐densitometer. The results for residual hydrocarbon saturation at various interfacial tensions were combined with previous results for different particle diameters to provide a general relationship between residual saturation and Bond number. The relationship is expressed in an empirical correlation valid for Bond numbers between 0.001 and 1.2.     

地下水微生物功能群及生物地球化学循环

地下水系统是地球关键带的重要组成部分,为微生物提供了特殊的栖息环境和复杂的生存条件,进而演化出复杂的生物地球化学过程.随着多技术、多学科的交叉融合及发展,近几十年地下水微生物功能群及生物地球化学循环研究取得了引人瞩目的 重要进展.本文从地下水中的微生物群功能分区、微生物介导的地球化学元素循环、污染与修复中的生物地球化学...     

Predicting the Effect of Deep-Rooted Hybrid Poplars on the Groundwater Flow System at a Large-Scale Phytoremediation Site

Estimating the effect of phreatophytes on the groundwater flow field is critical in the design or evaluation of a phytoremediation system. Complex hydrogeological conditions and the transient water use rates of trees require the application of numerical modeling to address such issues as hydraulic containment, seasonality, and system design.

In 1999, 809 hybrid poplars and willows were planted to phytoremediate the 317 and 319 Areas of Argonne National Laboratory near Chicago, Illinois. Contaminants of concern are volatile organic compounds and tritium. The site hydrogeology is a complex framework of glacial tills interlaced with sands, gravels, and silts of varying character, thickness, and lateral extent. A total of 420 poplars were installed using a technology to direct the roots through a 25--ft (8--m)-thick till to a contaminated aquifer.

Numerical modeling was used to simulate the effect of the deep-rooted poplars on this aquifer of concern. Initially, the best estimates of input parameters and boundary conditions were determined to provide a suitable match to historical transient ground-water flow conditions. The model was applied to calculate the future effect of the developing deep-rooted poplars over a 6 year period. The first 3 years represent the development period of the trees. In the fourth year, canopy closure is expected to occur; modeling continues through the first 3 years of the mature plantation. Monthly estimates of water use by the trees are incorporated. The modeling suggested that the mature trees in the plantation design will provide a large degree of containment of groundwater from the upgradient source areas, despite the seasonal nature of the trees' water consumption. The results indicate the likely areas where seasonal dewatering of the aquifer may limit the availability of water for the trees. The modeling also provided estimates of the residence time of groundwater in the geochemically altered rhizosphere of the plantation.     

Measurement of Oxygen Demand of Petroleum Hydrocarbon-Contaminated Groundwater

The standard biological oxygen demand (BOD) test was modified for application to petroleum hydrocarbon-contaminated groundwater. The goal was to assess the potential oxygen demand of plume constituents as part of a field trial investigating oxygen-enhanced in situ bioremediation. Modifications to standard BOD protocol included the use of an adapted microbial population developed from site groundwater and methods to minimize both the loss of volatile compounds and the exposure of samples to air. Results from this study indicated that the measured oxygen demand was significantly greater than the oxygen demand estimated solely by stoichiometric calculations from the concentrations of the analytes of typical regulatory concern, that is, benzene, toluene, ethylbenzene, and xylenes (BTEX). This is not surprising, because the petroleum hydrocarbon sources typically contain many organic contaminants other than BTEX, as well as potentially oxidizable natural dissolved organic matter and inorganic species typically present in hydrocarbon plumes. However, in practice, estimation of the total oxygen demand of a contaminated groundwater by exhaustive analyses of all oxidizable or aerobically degradable species typically will be infeasible. The modified BOD test may be a simple, low-cost, useful tool when assessing the potential for natural attenuation by aerobic biodegradation or designing methods to supply oxygen for enhanced aerobic bioremediation.     

Lab-Scale Biodegradation Study of BTEX under the Unsaturated Condition and Its Effect on Soil Matric Potential

Benzene, toluene, ethylbenzene, and xylene are collectively known as BTEX which contributes to volatile environmental contaminants. This present study investigates the microbial degradation of BTEX in batch and continuous soil column experiments and its effects on soil matric potential. Batch degradation experiments were performed with different initial concentrations of BTEX using the BTEX tolerant culture isolated from petroleum-contaminated soil. In batch study, the degradation pattern for single substrate showed that xylene was degraded much faster than other compounds followed by ethylbenzene, toluene, and benzene with the highest μ_max = 0.140 h^?1 during initial substrate concentration of 100 mg L^?1. Continuous degradation experiments were performed in a soil column with an inlet concentration of BTEX of about 2000 mg L^?1 under unsaturated flow in anaerobic condition. BTEX degradation pattern was studied with time and the matric potential of the soil at different parts along the length of the column were determined at the end of the experiment. In continuous degradation study, BTEX compounds were degraded with different degradation pattern and an increase in soil matric potential was observed with an increase in depth from top to bottom in the column with applied suction head. It was found that column biodegradation contributed to 69.5% of BTEX reduction and the bacterial growth increased the soil matric potential of about 34% on an average along the column height. Therefore, this study proves that it is significant to consider soil matric potential in modeling fate and transport of BTEX in unsaturated soils.     

Design and Validation of ureC-based Primers for Groundwater Detection of Urea-Hydrolyzing Bacteria

Polymerase chain reaction primers based on the ureC gene are described for use in detecting diverse groundwater urea-hydrolyzing bacteria. Six degenerate primers were designed and evaluated for their ability to detect the gene encoding the large catalytic subunit of urease, ureC. Five combinations of these primers were tested pair-wise and displayed an overlapping detection range for bacterial isolates. Pair L2F/L2R exhibited the greatest detection range for described bacterial species and for bacterial isolates from groundwater samples belonging to the bacterial divisions Firmicutes, Actinobacteria, and the α , β , and γ subdivisions of Proteobacteria. Primers L2F/L2R exhibited a greater detection range than previously described ureC-specific primers, and amplified novel ureC sequences from groundwater isolates in the genera Hydrogenophaga, Acidovorax, Janthinobacterium, and Arthrobacter. A comparative phylogenetic analysis of ureC and 16S rRNA genes was performed to determine the utility of groundwater ureC sequence information as a phylogenetic marker for ureolytic species. Our results were consistent with previous analyses of urease genes which demonstrated that the ureC gene has undergone lateral transfer and is not a robust phylogenetic marker. However, the ureC-specific primers, L2F/L2R, demonstrate a broad detection range for ureolytic species, and can serve to enhance functional diversity analyses of ureolytic bacteria.     

Modeling of a Field Experiment on Bioremediation of Chlorobenzenes in Groundwater

The aquifer below an abandoned chemical plant in Hamburg, Germany, is heavily contaminated with chlorinated aromatic compounds, mainly chlorobenzenes. Preliminary evaluations made evident that pump-and-treat remediation of the site would be inefficient due to adsorption of the contaminants and the possible presence of dense nonaqueous phase liquid (DNAPL) in the aquifer. Other preliminary studies indicated that benzenes with a low degree of chlorination, which account for the bulk of the contamination in the aquifer, were aerobically degradable. Thus, in situ bioremediation using dissolved oxygen as an oxidant was proposed as an alternative to pump-and-treat remediation.

To assess the feasibility of bioremediation at this site, a pilot study was conducted on a 55 m x 30 m test plot that was equipped with two injection wells, six extraction wells, and 18 observation wells. Water saturated with oxygen using pure oxygen gas was injected for a period of 433 days.

Application of the three-dimensional reactive transport model, Transport, Biochemistry, and Chemistry (TBC), allowed the distinction between transport and reactive processes and the evaluation of oxygen consuming processes. Preliminary mass balance considerations had indicated that a significant portion of the injected oxygen was used for oxidation of inorganic compounds instead of the contaminants. The model calculations allowed quantification of these effects. Simulation results suggested that in situ bioremediation occurred at the site, but with an unacceptably low efficiency. Only 2% of the injected oxygen was used for contaminant degradation, while 63% was consumed by inorganic reductants, presumably mainly pyrite. Approximately 32% of the injected oxygen was extracted by the extraction wells and approximately 3% remained in the aquifer after the pilot study was completed.     

Effects of oil shale waste disposal on soil and water quality: hydrogeochemical aspects

Abstract

Environmental pollution from solid waste landfillings (SWLs) is of major concern to both the environmentalists and to individual citizens. The necessity for studying on contaminant generation and control is becoming more urgent in view of the risks associated with such sites.

An oil shale tailing at Maoming, South China, was chosen as our study case. Soil samples, water samples and oil shale tailings were collected from the site and analyzed for their compositions. The analytical results revealed that the soil and groundwater were contaminated to various degrees by several chemicals or pollutants from the oil shale tailings. The major environmental problems associated with the site were acidification of soil and groundwater, high content of heavy metals and sulfate in soil and groundwater and organic contamination of soil, in particular, finding of carcinogenous benzo[a] pyrene other PAHs.

Statistical and geochemical methods were applied to reveal the sources of contaminants. Soil and groundwater contamination were correlated obviously with the oil shale waste disposal. The nearer the sampling sites to the tailing, the heavier the soil and groundwater were contaminated. The different water samples composition had same chemical characteristics. The soil and water samples were analyzed for 16 PAHs (USEPA priority pollutants). It indicated that PAHs were retained mostly in the soil, which consisted of mainly naphthalene, fluorene, phenanthrene and anthracene. Analysis for PAHs source revealed that they were also from the oil shale tailing.