Field-contaminated Soils Research Articles

Serological detection of spore balls of Spongospora subterranea and quantification in soil

A polyclonal antiserum produced against spore balls of Spongospora subterranca f.sp. subterranea prepared from potato tubers was able to detect as little as 0·02 spore balls in an enzyme‐linked immunosorbent assay (ELISA). In spiked soil samples, the antiserum detected 100 spore balls per g soil. However, the different spore ball contamination levels were discriminated better in ELISA tests al concentrations above 2000 spore balls per g soil than at lower concentrations. In contrast, a bioassay test based on baiting soils with tomato seedlings gave good discrimination of spore ball contamination levels in spiked soils containing <1000 spore balls per g soil and poor discrimination of levels in spiked soils containing >2000 spore balls per g soil. Tests on a limited number of field soils suggested ELISA may be capable of predicting disease levels on tubers group in such soils better than the bioassay. The antiserum did not react with 30 other micro‐organisms tested, including many that are saprophytes or pathogens on potatoes and resting spores of the taxonomically related Plasmodiophora brassicae. It detected spore balls of different cultivar origin equally well. It also detected spores from different geographical origins. An attempt to improve the sensitivity of the serological detection through concentrating spore balls from held soils by sieving was unsuccessful. Cross‐absorption of the antiserum with uncontaminated field soil increased the sensitivity of detection of spore balls in spiked soil samples four‐fold. The ability of the antiserum to discriminate contaminated field soils from an uncontaminated soil was much improved by using the gamma‐globulin fraction or cross‐absorbed serum. Western blot analysis revealed that the antiserum detected a member of different proteins the most distinct of which had a molecular weight of slightly less than 6.5 kDa. A technique was developed to suppress autofluorescence of spore balls, allowing immunofluorescence studies to be carried out. Using this technique in conjunction with indirect FITC immunofluorescence discrete bright fluorescent spots were visualized using the specific serum. With the non‐specific serum, only a very dull background fluorescence was evident.

Electrokinetic Remediation of Mercury-Contaminated Soils Using Iodine/Iodide Lixiviant

In-situ remediation of mercury-contaminated soils, by electrokinetic or other means, is difficult because of the low solubility of mercury and its compounds. In this research, enhanced electrokinetic remediation of HgS-contaminated soils using I2/I- lixiviant was investigated using bench-scale electrokinetic cells. The thermodynamic conditions under which the lixiviant could be effective were determined by constructing a pE−pH diagram for the Hg−S−I system. Introduced near the cathode, the lixiviant migrated through the soil to the anode by electromigration. Mercury, released by the oxidation of HgS compounds by I2, was complexed as HgI42-. The negative complex continued to electromigrate toward the anode. Up to 99% of the Hg present in laboratory-contaminated soils could be removed. Electrokinetic treatment of a field-contaminated soil, containing more organic matter than the laboratory-contaminated soil, occurred much slower. The critical issues in determining the efficacy of the process are the oxidation of reduced Hg by I2 and I3- and the transport of the resultant HgI42- complex.

Holding-time estimates for soils containing explosives residues: Comparison of fortification vs. field contamination

Maximum acceptable preextraction analytical holding times (MHTs) were estimated by spiking aqueous solutions of two nitramines, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and three nitroaromatics, 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (2,4-DNT), into three soils. Nitramines were stable over an 8-week test period at all storage temperatures, but nitroaromatics, which were reasonably stable when frozen, degraded rapidly at room temperature and more slowly under refrigeration. In contrast, both nitroaromatics and nitramines were quite stable under refrigeration for four field-contaminated soils. When three of these field-contaminated soils were subsequently fortified with TNT and TNB, rapid degradation under refrigeration was again observed for the added nitroaromatics. The rates of degradation were quite different in the three soils, further emphasizing the uncertainties in MHT estimates derived from fortified soils. We conclude that fortified soils can produce very different estimates of MHTs, recoveries, treatability, etc., compared to field-contaminated soils even when spiking is done in aqueous media.

Uptake, bioavailability and elimination of hydrophobic compounds in earthworms (Eisenia andrei) in field‐contaminated soil

AbstractUptake, accumulation, and elimination of hydrophobic organic chemicals in earthworms (Eisenia andrei) exposed to field‐contaminated Volgermeerpolder soil was studied Earthworms were able to take up chlorobenzenes and polychlorobiphenyls (PCBs), but body burdens did not exceed concentrations measured in the soil For the chlorobenzenes, steady state concentrations in the worms and biota to‐soil accumulation factor (BSAF) values were much smaller than expected based on earlier experiments, suggesting a decreased bioavailability in the Volgermeerpolder soil Comparison of the PCB accumulation pattern in worms to the pattern in soil showed that biotransformation of the studied PCBs is of minor importance in this species Elimination of all chemicals studied was monophasic, with the exception of hexachlorobenzene, which showed a biphasic elimination The elimination half life for the initial fast phase of this compound is comparable to the elimination measured in previous studies Elimination rate constants decreased with increasing log Kow

Reductive dechlorination of chloroalkenes in microcosms developed with a field contaminated soil

Static microcosms were constructed with a low organic carbon content, field-contaminated soil containing (in μmol/kg wet soil) tetrachloroethylene (PCE; 69.1), trichloroethylene (TCE; 18.1) and cis-1,2-dichloroethylene (cDCE; 2.3). Incubation at 20°C resulted in reductive dechlorination of PCE and TCE to cDCE under both sulfate-reducing and fermentative/methanogenic conditions. Low levels of vinyl chloride (VC) were also produced. Addition of electron donors (such as ethanol, acetate and lactate) was necessary for reductive dechlorination to occur. However, less than 0.25% of the electron equivalents potentially made available by the electron donor(s) were actually used for the dechlorination of the target chlorinated alkenes. More than 99% of the soil PCE was dechlorinated in less than 200 days of incubation under either sulfate-reducing or methanogenic conditions when external electron donors were added to these microcosms. Nitrate reduction conditions led to a much lower rate and extent of PCE dechlorination.

Comparison of analytical methods for determination of volatile organic compounds in soils

This study compares aqueous extraction headspace/gas chromatography and purge-and-trap gas chromatography/mass spectrometry (EPA SW-846, method 8240) for the determination of four volatile organic compounds (VOCs) in soil. Comparisons were performed on two fortified soils and two soils obtained from sites where hazardous waste had been spilled or disposed. In only two of the cases studied were significant differences consistently found; for the two most hydrophobic compounds in a high organic carbon soil and for TCE in a field-contaminated soil that had previously shown slow aqueous VOC desorption. The findings strongly suggest that aqueous extraction/headspace GC using a portable instrument can be used to screen soils on site for VOCs, providing rapid same-day results, that will consistently identify the presence of these analytes and provide quantitative results which are generally not significantly different from slower more expensive, laboratory-based purge-and-trap analysis. 29 refs., 3 figs., 7 tabs.

Estimating the equilibrium aqueous concentrations of polynuclear aromatic hydrocarbons in complex mixtures

By use of a two-phase liquid-liquid equilibrium model, the distribution of nonpolar solutes between water (polar phase) and soil organic matter (nonpolar phase) was related to principles of equilibrium chemistry. Batch equilibrium experiments were conducted with field-contaminated soils. Aqueous concentrations were measured directly, predicted through the use of organic cosolvents, and calculated from Raoult's law, thereby providing a three-way comparison of solute behavior in water. Results showed that composition of the nonpolar phase strongly influences the solute concentrations in the polar phase, suggesting that Raoult's law is applicable to complex mixtures

Liquid Chromatographic Method for Determination of Explosives Residues in Soil: Collaborative Study

Abstract A collaborative study of a sonic extraction/liquid chromatographic method for determining nitroaromatic and nitramlne explosives In soil was conducted at 8 participating laboratories. Analytes HMX, RDX, TNB, DNB, tetryl, TNT, and 2,4-DNT were measured In duplicate for 4 field-contaminated soils and 4 spiked standard-matrix soils. Concentrations ranged from detection limits of about 1 μg/g to nearly 1000 μg/g. Results were evaluated with and without data Identified as outliers, which were often caused by electronic integrator miscalculation of chromatographic peak response. When outliers are excluded, method repeatability (within-laboratory relative standard deviation) for all analytes except tetryl Is less than 5% for spiked soils and less than 18% for fieldcontaminated soils. Relative standard deviation generally decreases as analyte concentration Increases. Reproducibility (between-laboratory relative standard deviation), except for tetryl and DNT, Is less than 7% for spiked soils and 26% for fleld-contamlnated soils. Thus, collaborators have nearly equivalent performance on spiked samples. For fleld-contamlnated soils, some additional Imprecision seems to result from the variability of extraction recoveries. Analyte recoveries from spiked soils are 95-97% for HMX, RDX, TNT, and DNT (similar to recoveries from aqueous samples); 92-93% for DNB and TNB; and 70% for tetryl. Poor results for tetryl (due to thermal degradation) are correctable If sonic bath temperatures are maintained near ambient. The method has been approved Interim official first action by AOAC.

Liquid Chromatographic Method for Determination of Extractable Nitroaromatic and Nitramine Residues in Soil

Abstract An analytical method was developed to determine the concentration of nitroaromatic and nitramine residues in soil. Air-dried soil samples are ground with a mortar and pestle and extracted with acetonitrile in an ultrasonic bath. A portion of extract is diluted with aqueous CaCh to flocculate suspended particles, filtered, and analyzed by liquid chromatography. The method provides linear calibration curves over a wide range of concentration. Detection limits ranged from 0.03 to 1.27 ng/g. Recovery of spiked analyte was better than 80% for all analytes tested. Each step in the analytical procedure was optimized using spiked and field-contaminated soils. This optimization included tests to (1) assess the effectiveness and kinetics associated with various extraction methods, solvents, and soil-to-solvent ratios; (2) compare separations achievable using various combinations of reverse-phase columns and eluants; (3) assess analyte recovery and ease of use for various procedures to remove particles from extracts; and (4) document stability of soil extracts and analytical stock and working standards. A ruggedness test and a preliminary assessment at 2 other laboratories indicated that the method was sufficiently rugged to justify a full-scale collaborative test. A comparison of extraction kinetics for spiked soil vs field-contaminated soil revealed very different kinetic behavior, indicating it is unwise to develop extraction procedures based solely on spiked soils.

Soil microbial biomass estimates in soils contaminated with metals

The validity of the chloroform fumigation-incubation procedure for measuring soil microbial biomass in field soils contaminated with metals (e.g. Cu, Ni, Zn, Cd) was assessed. The metal contamination was the result of past sewage sludge additions and the contaminated field soils now contain metals at about current maximum U.K. recommended levels. The decomposition of native soil biomass or microbial material added after fumigation was little affected by the presence of metals and it was concluded that fumigation-incubation is a reliable procedure for measuring biomass in soils contaminated with moderate amounts of metals. This conclusion was confirmed by direct microscopy: similar soil biomass estimates were obtained by both methods.

The Chemistry and Phytotoxicity of Arsenic in Soils: I. Contaminated Field Soils

The Chemistry and Phytotoxicity of Arsenic in Soils: I. Contaminated Field Soils

The Chemistry and Phytotoxicity of Arsenic in Soils: I. Contaminated Field Soils

AbstractArsenic (As) residues on 58 surface soil samples taken from soils with a history of As application averaged 165 ppm As, while nearby soils not treated averaged 13 ppm As. Most of the residual As was found as Fe‐As (0.1N NaOH extractable) by a modified soil P procedure. Water‐soluble As (1N NH4Cl extractable) was detected in soils from two states. Other forms, Al‐ and Ca‐As (0.5N NH4F and 0.5N H2SO4 extractable As, respectively), may predominate if the amount of “reactive” Al or Ca is high and reactive Fe is low. Bioassay of the contaminated and uncontaminated soils showed a correlation of 0.74 between growth reduction and total As and 0.82 with a summation of As fractions. Plants were tolerant to large As applications (670 ppm As) to soils which were high in reactive (1N NaOH extractable) Al.

Comparison of Several Methods for Extracting Chlordane Residues from Soil

Abstract Residues of chlordane were extracted from a field-contaminated clay loam soil with various solvents under a variety of conditions. Mixtures of hexane-acetone and hexane-2-propanol recovered only 1.93–2.64 ppm total chlordane residues from the air-dried soil as compared to 3.88–4.10 ppm (highest recovery) when 20% water was added to the soil prior to extraction by these solvents. Effects of the amount of water in the soil at the time of extraction, contact time with solvent or water, and extraction methods were also studied.