Spiked Soil Research Articles

Determination and Quantitation of Ten Sulfonylurea Herbicides in Soil Samples Using Liquid Chromatography with Electrospray Ionization Mass Spectrometric Detection

A multiresidue method was developed for confirmation and quantitation of ten sulfonylurea herbicides including nicosulfuron, thifensulfuron-methyl, metsulfuron-methyl, sulfometuron-methyl, chlorsulfuron, ethametsulfuron-methyl, tribenuron, bensulfuron-methyl, pyrazosulfuron-ethyl, and chlorimuron-ethyl in soil. Analytes were extracted from the soil sample with methanol-phosphate buffer (2:8, v/v) (pH 7.8) in an ultrasonic bath. The extracts were adjusted to pH 2.5 with 85% H 3PO 4 and passed, under vacuum, through a solid-phase extraction cartridge. Several types of adsorbents were evaluated, including silica-based Cleanert C 18 and two polymeric adsorbents (Oasis HLB and Cleanert HXN). Cleanert C 18 showed good cleanup effects in the study. Determination and quantitation were performed by high performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) instrumentation equipped with an ion trap mass filter. Analytes were eluted on a HPLC column of 4.6 mm × 250 mm XDB C 18, 5 × particle size, in the mobile phase of the acetonitrile (solvent A)-methanol (solvent B)-0.2% acetic acid (solvent C). The elution gradient was as follows: the mobile phase started with 10% of acetonitrile and 10% methanol, which increased linearly to 45% in 14 min, to 48% in the next 2 min and then returned to the initial condition in 2 min. The column temperature was kept at 30°C with a flow rate of 1.0 ml/min. Thus the retention time of nine herbicides was in the range of 10 to 16 minutes. Spiked soil at 0.01–1.0 mg/kg levels was checked. Average recoveries were in the range of 80.2%–104.5% with relative standard deviations (RSDs) of 0.02%–14.90%. The limit of detection (LOD) of this method was in the range of 0.6 to 3.5 μg/kg.

Determination of Triazine Herbicides and Diuron in Mud from Olive Washing Devices and Soils Using Gas Chromatography with Selective Detectors

In the present work, a method for the simultaneous determination of five herbicides, diuron, simazine, atrazine, terbuthylazine and terbutryn by GC‐electron capture detection (ECD) and GC‐thermoionic specific detector (TSD) in soil and mud samples (from olives washing devices) has been developed. Extraction of the herbicides from soil samples was carried out by liquid–solid extraction with ciclohexane/acetone under sonication. In addition, a clean‐up step by solid phase extraction (SPE) using alumina was necessary for mud samples to remove fat residues in the extracts. Spiked soil standards were used for calibration. Limit of detection (LOD) values ranged between 0.2–1.4 ng g−1 and limit of quantitation (LOQ) between 1.4–2.0 ng g−1. The precision of the method was satisfactory for all the herbicides analyzed, with RSD values ranging between 7.5%–32.3% and 8.5%–17.8% for 10 and 100 ng g−1 spiking levels, respectively. The accuracy of the method was checked at three spiking levels (10, 50, and 100 ng g−1) with recovery values ranging from 74.2%–129.1%. In the case of mud samples, mean recovery values (100 ng g−1 spiking level) were acceptable for diuron (69.5%) and more satisfactory in the case of triazine herbicides (81.0%–123.0%). Diuron and terbuthylazine were the herbicides most frequently detected in the analyzed samples.

Determination of the method detection limits for acid extractable metals in environmental solids: a comparative approach

The accurate determination of method detection limits (MDLs) for acid extractable metals in environmental solid samples (soils, sediments and solid wastes) has been shown to be difficult because not only is it difficult to obtain a representative reference soil sample but also sample spiking is difficult. The use of reagent water as the reference matrix for the determination of MDL in soils does not reflect the matrix effect of real world samples. This paper proposes a comparative approach for determining MDLs for acid extractable metals in soils by first comparing the MDL derived from environmental surface waters with the MDL estimated from the replicate analyses of real soil samples, before assigning a rational MDL values for use in soils. This comparative approach does not require spiking soil and provides more realistic MDL values than the reagent water-based MDLs because they reflect the matrix effect of soils. This paper also provides a method for quantitative description of the matrix effect, which has been a qualitative description in the literature to date. The assigned MDL is verified using the relative standard deviation (RSD) obtained from the analysis of soils of different textures.

Bioaccumulation of Inorganic Chemicals from Soil by Plants: Spiked Soils vs. Field Contamination or Background

ABSTRACT Risk assessors are often cautioned against the use of tests of highly bioavailable salt solutions added to soil to estimate the bioaccumulation of chemicals from waste site soils by plants. In this investigation, a large number of laboratory and field studies that measured the bioaccumulation of inorganic chemicals in plants were reviewed. The objective was to discern whether or not the relationship between the concentration of the element in aboveground vegetation and that in soil was different if the contamination was aged in the field rather than freshly added to soil in salt solution. For two of the eight elements, selenium and cadmium, salt solution experiments were associated with greater soil-plant uptake ratios than field measurements. Thus, these are not reliable data for use in the derivation of plant uptake regressions for screening-level ecological risk assessments at field sites. In contrast, the plant uptake of arsenic, copper, lead, mercury, nickel, and zinc, when added in salt solutions, was generally within the 95% prediction limit of regressions derived from field data. Chemical form, plant taxon, soil type, experimental methodology, and aging may be as important as the source of the chemical in predicting plant uptake of inorganic chemicals from soil.

Degradation of nonylphenol in spiked soils and in soils treated with organic waste products

Widespread application of sewage sludge to agricultural soils in Denmark has led to concern about the accumulation and effects of nonylphenol (NP) in the soil ecosystem. We have thus studied the degradation of NP and possible uptake in agricultural plants in greenhouse pot experiments. Different waste products including anaerobic and aerobic sludge, compost, and pig manure were incorporated into a sandy soil. In addition, NP was used to spike soil to known concentrations. Rape (Brassica napus L. cv Hyola 401) was sown in the pots and harvested after 30 d. In order to investigate the influence of plant growth on the degradation, plant-free pots were established. The concentrations in the soil were between 13 and 534 ppb dry weight. No plant uptake was observed above the detection limit at 100 ppb dry weight. When NP was added as waste to the soil, plant growth significantly stimulated the degradation. In experiments with anaerobic and aerobic sludge, respectively, 13 and 8.3% of NP remained in the soil from pots planted with rape compared with 26 and 18% in soil without plant growth. When NP was added as a spike to soil, the degradation was more complete and plant growth did not influence the degradation. Percentages of 2.2 and 1.8 were still in the soil at harvest for planted and plant-free pots, respectively. The degradation of NP was more extensive in sludge-amended soil compared with compost.

Microwave-assisted solvent extraction of the herbicide methabenzthiazuron from soils and some soil natural organic and inorganic constituents. Influence of environmental factors on its extractability.

A microwave-assisted solvent extraction (MASE) method for the determination of methabenzthiazuron (MBT) in soil samples by HPLC-DAD (diode array detection) was evaluated. Spiked soil samples having different physico-chemical properties, and selected soil-derived matrices with diverse MBT adsorption capacity, characterized by their Freundlich equation Kf values, were used to verify the method applicability to a broad range of different soils. The spiking procedure was considered a crucial point to reproduce as closely as possible the solute-soil adsorption taking place in the natural environment. Ageing effects, where the compound could diffuse into inaccessible locations within the soil matrix in view of its great stability, were considered of particular concern. In spite of the heterogeneous physico-chemical properties of soils under study, recoveries were greater than 90%. Performance of the MASE procedure correlated highly with the adsorption capacity of soil-derived matrices: the lowest recoveries were for illite (67-73%), among the mineral surfaces, and for a humic acid (67-72%), among the organic fractions. Intra-assay variation for each type of sample soil range from 0.40 to 3.89%(RSD). Limits of detection and quantification were 0.047 and 0.15 microg g(-1), respectively. Analyte residence time was not a very significant factor on the extractability.

EN CORE® Sampler Performance: Storing Soil for VOC Analysis

The En Core® sampler is designed to collect and store soil samples in a manner that minimizes loss of contaminants due to volatilization and/or biodegradation. Use of this device is described in American Society for Testing and Materials (ASTM) Practice D 6418, Standard Practice for Using the Disposable En Core Sampler for Sampling and Storing Soil for Volatile Organic Analysis. Two studies were performed to evaluate the performance of the En Core sampler to store VOC-contaminated soil for analysis. One study involved spiking soil samples with low concentrations of VOCs (less than 200 µg/kg) and storing them under various conditions prior to analysis. Results from this study show that the En Core sampler gives 80% or greater recoveries of low concentrations of VOCs from soil samples stored under a number of conditions. The second study was performed to generate data on the performance of the 25-g En Core sampler to store soil samples spiked with EPA Method 1311, Toxicity Characteristic Leaching Procedure (TCLP), volatile organic analytes. Results show that the En Core device gives 80% or greater recoveries of most of the Method 1311 volatile organic analytes from soil stored under various conditions for 14 days.

Effect of moisture on the extraction efficiency of polycyclic aromatic hydrocarbons from soils under atmospheric pressure by focused microwave-assisted extraction

The effects of the moisture content in the original, air-dried and re-moistened matrices as well as solvent have been studied on the recovery of polycyclic aromatic hydrocarbons (PAHs) from soil by a focused microwave-assisted extraction (FMAE) method. Solvents selected for the extractions were cyclohexane–acetone (1:1), hexane–acetone (1:1) and dichloromethane. On the extraction of 20-day aged spiked soil, the highest recovery was found by applying hexane–acetone mixture. Spiked soil sample, quality control sample and real soil sample were used for the evaluation of moisture effect. It indicated that the presence of water in the soil is important for the recovery enhancement of PAHs and with this presence it is possible to avoid drying step with the FMAE technique. A comparison between microwave and 16-h Soxhlet methods has been made. It evidenced that the microwave-assisted extraction under ambient atmospheric pressure is a suitable alternative to Soxhlet extraction for the analysis of PAHs in soils.

Changes in sorption/bioavailability of imidacloprid metabolites in soil with incubation time

Changes in sorption/bioavailability of two metabolites, imidacloprid-urea {1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinone} and imidacloprid-guanidine {1-[(6-chloro-3-pyridinyl)methyl]-4,5-dihydro-1H-imidazol-2-amine} of the insecticide imidacloprid {1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine} with aging in different soils were determined. Soil moisture was adjusted to –33 kPa and 14C- and analytical-grade imidacloprid-urea and imidacloprid-guanidine were added to the soil at a rate of 1.0 mg kg–1. Spiked soils were incubated at 25°C for 8 weeks. Replicate soil samples were periodically extracted successively with 0.01 N CaCl2, acetonitrile, and 1 N HCl. Imidacloprid-urea sorption, as indicated by sorption coefficient values, was highest in the soil with highest organic C content, and increased by an average factor of 2.6 in three soils during the 8-week incubation period. Imidacloprid-guanidine sorption increased by a factor of 2.3 in the same soils. The increase in sorption was the result of a decrease in the metabolite extractable with CaCl2 (solution phase); the amount of metabolite extractable with acetonitrile and HCl (sorbed phase) did not significantly change with incubation time. It appears the increase in sorption was because the rate of degradation in solution and on labile sites was faster than the rate of desorption from the soil particles. It may have also been due to metabolite diffusion to less accessible or stronger binding sites with time. Regardless of the mechanism, these results are further evidence that increases in sorption during pesticide aging should be taken into account during characterization of the sorption process for mathematical models of pesticide degradation and transport.

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.

The Importance of Nickel Phytoavailable Chemical Species Characterization in Soil for Phytoremediation Applicability

ABSTRACT In this work Ni speciation in natural and spiked soils (with similar total concentration) was studied. Spiked soils were prepared by addition of NiSO4.6H2O to obtain concentration similar to the one in natural soils. In soils mobile species were determined with a simplified sequential extraction as follows: H2O for water-soluble metal, KNO3 for exchangeable species, DTPA for complexed/adsorbed species. Results show that in spiked soils the exchangeable and adsorbed Ni concentrations are considerably higher than in natural soils. A study of plant uptake was carried out in order to evaluate the relation between mobile species and phyto-availability. Alfalfa (Medicago sativa L.), even though it is not a hyperaccumulator, was selected for its tolerance to high metal concentrations in soil. Preliminary results show a very high correlation between Ni mobile species and Ni uptake by alfalfa. Significant differences were found between spiked and natural soils. In the latter, high levels of total Ni did not correspond to relevant uptake as in the case of spiked soil. Results stress the importance of evaluating preliminarly heavy metal speciation in soil before planning phytoremediation procedures.

Acute Toxicity of 2,4,6-Trinitrotoluene in Earthworm (Eisenia andrei)

2,4,6-Trinitrotoluene (TNT) is an worldwide recalcitrant environmental contaminant and is toxic to a number of organisms including humans. This study examines the acute effects (lethal and biomass changes) of TNT on the oligochaetes species Eisenia andrei, using the 3-day filter paper, and the 7- and 14-day direct contact spiked soil (OECD artificial and forest soil) toxicity tests. Studies using the filter paper test indicated that the lethality of TNT could be detected in the range 1.5 to 14.2 μg/cm2, with significant biomass (body weight) changes occurring at the lowest concentration. Acute effects (lethality) could not be measured when earthworms were placed on filter paper containing a saturated aqueous solution of TNT. This may indicate that with these exposure conditions, TNT may have been adsorbed to the filter paper, and that this matrix should be saturated with TNT before becoming available to the earthworms. Spiked soil toxicity tests indicated that the E. andrei lethality by TNT was >1.5 times higher when earthworms were exposed to TNT-spiked forest soil (LOEC:260 mg/kg; LC50 14 days 222.4 mg/kg) than to spiked OECD artificial soil (LOEC:420 mg/kg; LC50 14 days: 364.9 mg/kg). The sublethal effect on biomass change at the selected TNT concentrations in soil was not significant compared to controls. Results indicate that the bioanalytical methods described in this article could be used as TNT toxicity assessment tools. This soil quality test method gives valuable information for the screening of soil toxicity.

Ecotoxicological Characterization of Energetic Substances Using a Soil Extraction Procedure

The acetonitrile-sonication extraction method (US EPA SW-846 Method 8330) and aquatic-based toxicity tests were used on laboratory and field samples, to characterize the ecotoxicity of soils contaminated with energetic substances. Spiked soil studies indicated that 2,4,6-trinitrotoluene (TNT)-dependent soil toxicity could be measured in organic extracts and aqueous leachates using the 15-min Microtox (Vibrio fischeri, IC50=0.27 to 0.94 mg TNT/liter incubation medium) and 96-h Selenastrum capricornutum growth inhibition (IC50=0.62 to 1.14 mg/liter) toxicity tests. Analyses of leachates of composite soil samples [containing TNT and some TNT metabolites, 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX)] from an explosives manufacturing facility, indicated toxicities similar to those found in the TNT-spiked soil studies and pure TNT in solution, and suggested that TNT was the major toxicant. Using TNT as a model toxicant in soils having different moisture contents (20% vs dry) and textures (sandy vs clayey–sandy) but similar organic matter content (3–4%), multi-factorial analyses of Microtox test data revealed that these soil factors significantly influenced the TNT extractability from soil and subsequent toxicity measurements. Taken together, data indicate that the modified Method 8330 may be used in conjunction with ecotoxicity tests to reflect the toxic potential of soils contaminated with energetic substances.

Determination of Mecoprop and Dichlorprop in Aqueous Soil Solutions by HPLC with DAD

A reverse phase high performance liquid chromatographic method was developed for the direct determination of mecoprop (MCPP) and dichlorprop (DCPP) in the presence of soil and peat constituents. Spiked aqueous soil or soil/peat samples were directly injected after centrifugation and filtration. The analytical sensitivity, 0.35 and 0.24 ng L-1, detection limit, 1.02 and 0.70 ng L-1, and precision, 1.28 and 0.80%, for MCPP and DCPP respectively, are very appropriate. The concentration ranges studied 0.0–94.2 ng L-1 for MCPP and 0.0–103.1 ng L-1 for DCPP are suitable for adsorption/desorption and mobility studies of these herbicides in soil. The two tests used to demonstrate the purity or otherwise of every chromatographic peak give valuable information.

Study of the Degradation of Polydimethylsiloxanes on Soil

The degradation of polydimethylsiloxanes (silicones) on a spiked standard soil matrix has been studied. Spiked soil was extracted to recover silicones, and the extract was examined by several analytical techniques, including gel permeation chromatography and high-pressure liquid chromatography with an inductively coupled plasma emission spectrometer as the detector. Silicones were found to degrade rapidly to low molecular weight α,ω-siloxanediol oligomers. Within 4-6 weeks, more than half of the initial spiked silicone is converted to a water-soluble fraction consisting mostly of 1,1-dimethylsilanediol. Implications of this finding relative to the ultimate environmental fate of silicones is discussed.

TPH and BTEX Quantitation in Gasoline and Diesel Contaminated Soils by Capillary Gas Chromatography-Mass Spectrometry

A manual gas chromatographic-mass spectrometric (GC-MS) method for the analysis of total petroleum hydrocarbon (TPH), benzene, toluene, ethyl benzene, o-xylene, m-xylene, and pxylene (BTEX), and naphthalene in gasoline and diesel contaminated soils is described. Multiple groups of ions are monitored to retain the high sensitivity of selected ion monitoring while permitting identification of solutes. Spiked soil samples containing gasoline and diesel with TPH concentrations in the range of 0.5 to 5000 parts per million are used to evaluate the method. The extraction efficiency of different solvents and solvent mixtures is evaluated. Ethyl ether and methylene chloride give quantitative recoveries for both TPH and BTEX from spiked soils. TPH or BTEX analysis by GC-MS provides excellent sensitivity, linearity of quantitation, and peak identification. The method presented here also eliminates time-consuming sample preconcentration steps for diesel-range components

Comparative study of various size-exclusion chromatographic columns for the clean-up of selected pesticides in soil samples

A comparative study was carried out using various types of size-exclusion chromatographic (SEC) columns (Bio-Beads SX-3, SX-8 and SX-12, Phenogel polystyrene and Zorbax PSM 60S, silica based) for the isolation of the pesticides monuron, linuron, monolinuron, isoproturon, propanil, fenitrothion, molinate, alachlor, bensulfuron, chloridazon, trifluoralin and atrazine from soil samples. Spiked soil samples (10 μg/g) were Soxhlet extracted and fractionated with SEC columns using different mobile phases. The SEC extracts were analysed either by liquid chromatography with diode-array detection or gas chromatography with nitrogen-phosphorus detection. Recoveries varying from 70 to 82% were found for all the analytes. With the low-resolution polystyrene columns better results were found using columns with a high size-exclusion range. The Phenogel column was more efficient than the Bio Beads columns for phenylurea herbicides. The method developed was applied to the determination of linuron and atrazine in a candidate reference material and was applied to investigate the decay of molinate in real soil samples at ng/g levels.

On the metabolism of phenylurea-herbicides: X. Movement and behaviour of a glucoside conjugate in plant and soil

A comparative study was carried out using various types of size-exclusion chromatographic (SEC) columns (Bio-Beads SX-3, SX-8 and SX-12, Phenogel polystyrene and Zorbax PSM 60S, silica based) for the isolation of the pesticides monuron, linuron, monolinuron, isoproturon, propanil, fenitrothion, molinate, alachlor, bensulfuron, chloridazon, trifluoralin and atrazine from soil samples. Spiked soil samples (10 μg/g) were Soxhlet extracted and fractionated with SEC columns using different mobile phases. The SEC extracts were analysed either by liquid chromatography with diode-array detection or gas chromatography with nitrogen-phosphorus detection. Recoveries varying from 70 to 82% were found for all the analytes. With the low-resolution polystyrene columns better results were found using columns with a high size-exclusion range. The Phenogel column was more efficient than the Bio Beads columns for phenylurea herbicides. The method developed was applied to the determination of linuron and atrazine in a candidate reference material and was applied to investigate the decay of molinate in real soil samples at ng/g levels.