Carbon isotope composition of dissolved humic and fulvic acids in the Tokachi River system

This study reports carbon isotopic ratios (Δ(14)C and δ(13)C) of dissolved humic and fulvic acids in the Tokachi River system, northern Japan. These acids have a refractory feature and they represent the largest fraction of dissolved organic matter in aquatic environments. The acids were isolated using the XAD extraction method from river water samples collected at three sites (on the upper and lower Tokachi River, and from one of its tributaries) in June 2004 and 2005. δ(13)C values were -27.8 to -26.9 ‰ for humic and fulvic acids. On the other hand, the Δ(14)C values ranged from -247 to +26 ‰ and the average values were -170 ± 79 ‰ for humic acid and -44 ± 73 ‰ for fulvic acid. The difference was attributed to the residence time of fulvic acid in the watershed being shorter than that of humic acid. The large variation suggested that humic substances have a different pathway in each watershed environment.     

Evaluation of toxicity of the pesticides, chlorpyrifos and arsenic, in the presence of compost humic substances in aqueous systems

An improved understanding of pesticide toxicity in natural systems can have important consequences for pesticide management and remediation strategies for contaminated areas. The interaction between humic substances extracted from compost natural organic matter and both organic and inorganic pesticides was evaluated for its effect on the toxicity of pesticides in the aqueous phase. The toxicity of contaminants was measured using the Microtox toxicological bioassay. Solutions containing concentrations ranging from 2 to 42 mg C/l of humic substance extracted from a South Texas compost were added to concentrations of the organic pesticide, chlorpyrifos, and toxicity reduction ranging from 50 to 100% was demonstrated. Different concentrations of arsenic ranging from 0.5 to 5 mg/l were also associated with three different concentrations of humic substances and the arsenic toxicity was consistently reduced by a factor of 100%. These results demonstrate a significant relationship between humic substance interactions with organic and inorganic pesticides, and pesticide toxicity in natural systems, and may also suggest a mechanism for pesticide toxicity reduction in natural waters through compost humic addition for contaminated groundwaters and surface waters.     

Dependence of the migration ability of plutonium and americium in soils on additions of natural and modified organic compounds

The nature and content of modified humic acid derivatives influence the intensity of the recovery of Pu, Am, and C_org from soddy podzolic soil with distilled water. Under the dynamic conditions, these radionuclides are recovered more intensely in the presence of carboxylated humic acids, compared to the hydroxymethylated derivatives. When soils with the introduced modified humic acid derivatives are subjected to prolonged washing with distilled water, the radionuclides undergo redistribution within the columns, suggesting their migration. Under the action of dissolved organic substances isolated from soils (low-molecular-weight nonspecific organic compounds and fulvic acids), the radionuclide migration in soils occurs still more intensely. In the course of soil column washing with an aqueous phase containing the dissolved organic matter, Pu and Am pass into the mobile state to a greater extent than in washing the soils with distilled water.     

Chlorination of organophosphorus pesticides in natural waters

Unknown second-order rate constants for the reactions of three organophosphorus pesticides (chlorpyrifos, chlorfenvinfos and diazinon) with chlorine were determined in the present study, and the influence of pH and temperature was established. It was found that an increase in the pH provides a negative effect on the pesticides degradation rates. Apparent second-order rate constants at 20 degrees C and pH 7 were determined to be 110.9, 0.004 and 191.6 M(-1) s(-1) for chlorpyrifos, chlorfenvinfos and diazinon, respectively. A higher reactivity of chlorine with the phosphorothioate group (chlorpyrifos and diazinon) than with the phosphate moiety (chlorfenvinfos) could explain these results. Intrinsic rate constant for the elementary reactions of chlorine species with chlorpyrifos and diazinon were also calculated, leading to the conclusion that the reaction between hypochlorous acid and the pesticide is predominant at neutral pH. The elimination of these pesticides in surface waters was also investigated. A chlorine dose of 2.5 mg L(-1) was enough to oxidize chlorpyrifos and diazinon almost completely, with a formation of trihalomethanes below the EU standard for drinking water. However, the removal of chlorfenvinfos was not appreciable. Therefore, chlorination is a feasible option for the removal of organophosphorus pesticides with phosphorothioate group during oxidation and disinfection processes, but not for the elimination of pesticides with phosphate moiety.     

Interaction of pesticides with humic compounds and their metal complexes

The interaction of pesticides with humic compounds (humic and fulvic acids) and with their metal complexes was studied potentiometrically and radiometrically, using the pesticides Aldicarb and Methomyl, and the herbicide Ametryne. The metal humate or fulvate complexes were prepared by precipitation of the complexes using Co²⁺, Zn²⁺, or Sr²⁺. The results indicated that Aldicarb, Methomyl, and Ametryne form stable complexes with humic acid (HA) and fulvic acid (FA). The complexation strength increases in the order Aldicarb ≤ Methomyl < Ametryne. The complexes of Aldicarb and Methomyl with HA and FA are stronger than the metal humate/fulvate complexes with Co²⁺, Zn²⁺, and Sr²⁺, and these pesticides displace the metal ions. Ametryne adds to the metal humate/fulvate by physical adsorption or ligand exchange. The complexation of Aldicarb and Methomyl with humic compounds causes the release of radionuclides (⁶⁰Co, ⁶⁵Zn, ⁹⁰Sr) from the soil organic matter to the solution. The pH exerts a decisive effect on the complexation of the pesticides with humic compounds. Published in Russian in Radiokhimiya, 2006, Vol. 48, No. 4, pp. 377–383. The text was submitted by the authors in English.     

Equilibrium sampling of freely dissolved alkylphenols into a thin film of 1-octanol supported on a hollow fiber membrane

A new negligible depletion extraction procedure was proposed for equilibrium sampling of 4-tert-octylphenol (OP) and 4-nonylphenol (NP) into a thin film of 1-octanol supported on a hollow fiber membrane. This thin liquid film extraction technique was directed at the determination of (1) freely dissolved concentrations, (2) distribution coefficients to 1-octanol (D(ow)), and (3) binding to dissolved organic matter (DDOC). The sampling device was prepared by dipping pieces of polypropylene microporous hollow fiber membrane (10-mm length, 30-microm wall thickness, 240-microm inner diameter) into 1-octanol for a few seconds to impregnate the pores of the hollow fiber wall. After stirring in 100 mL of sample solution for 24 h, the sampling device was harvested and desorbed with 30 microL of methanol, of which 20 microL was injected for HPLC analysis. With the measured D(ow) of a chemical and its equilibrium concentration in the 1-octanol sampling phase (C(octanol)), the freely dissolved concentration (Cfree) was calibrated based on Cfree = C(octanol)/D(ow). Measured log Dow values of OP (4.32 +/- 0.06) and NP (4.79 +/- 0.02) were independent of the chemical concentration, only minimally affected by the environmentally relevant pH, buffering capacity, and salinity of samples, and agreed well with reported values. Log DDOC values of OP (4.89 +/- 0.43) and NP (5.14 +/- 0.37), determined in Aldrich humic acid solution, agreed with reported partition coefficients to organic carbon (log Koc) for particles in river water and effluent wastewater. Short equilibration times and high enrichment factors were obtained for both analytes due to the high surface to volume ratio of the new sampler. The technique was successfully applied to determine Cfree of OP and NP in real water samples and to study their association with humic acids and bovine albumin.     

碳纳米管吸附腐植酸的动力学、热力学及机理研究

针对天然水中腐植酸(HA)类溶解性有机物去除问题, 采用多壁碳纳米管为吸附剂, 在不同的pH值、吸附剂量、初始HA浓度下进行吸附动力学实验, 用准二级速率方程拟合了动力学数据, 其线性相关度在0.99以上, 拟合得到的平衡吸附量为27mg/g,与实验结果(25.5 mg/g)基本一致. 在25~50℃下进行了碳纳米管吸附腐植酸的等温吸附实验, 以Langmuir模型拟合的平衡吸附量为29.7mg/g, 与实验结果相近. 用Clapeyron-Clausius与Gibbs- Helmholtz方程计算的自由能(Δ G)、焓(Δ H)、熵(Δ S)皆为负值, 说明碳纳米管对腐植酸的吸附为放热熵减过程. 碳纳米管的表面、管间隙、管内腔及管束之间形成的束聚孔为其有效吸附点位, 腐植酸与碳纳米管间的π-π作用也是吸附的主要原因之一.     

Release of Cr(III) from Cr(III) picolinate upon metabolic activation

Hexavalent and trivalent chromium are released into the environment from a number of different industrial activities. It is known that Cr(VI) can be reduced and subsequently complexed by humic acids to produce Cr(III) humic acid complexes in the soil and aquatic environments. The metabolic fate of Cr(III) humic acid complexes and other Cr(III) organic complexes in mammalian systems is unknown. Therefore, Cr(III) picolinate was chosen as a model complex for Cr(III) humic acid complexes and other environmentally relevant Cr(III) complexes. Both human hepatocyte microsomes and primary cultures of chick hepatocytes were used to generate metabolites of Cr(III) picolinate. The results from both of these treatments show that a significant amount of Cr(III) is released (66 and 100%, respectively) and that N-1-methylpicotinamide is the primary organic metabolite from this compound. These data suggest that the populations of humans who are exposed Cr(III) picolinate or other environmentally relevant organic Cr(III) complexes, such as Cr(III) humic acid complexes, are potentially accumulating high levels of Cr(III) intracellularly. This intracellular accumulation of Cr(III) can result in the formation of covalent bonds between Cr(III) and DNA and/or other macromolecules, causing genotoxic effects. These data should be considered when assessing the risk of an area contaminated with chromium.     

Applicability of cloud point extraction coupled with microwave-assisted back-extraction to the determination of organophosphorous pesticides in human urine by gas chromatography with flame photometry detection

A procedure for the determination of organophosphorous pesticides (OPPs) - phorate, diazinon, parathion-methyl, fenthion and quinalphos - in human urine was developed using the cloud point extraction of nonionic surfactant (Triton X-114) coupled with microwave-assisted back-extraction prior to gas chromatography with flame photometry detection (GC-FPD) analysis. The upper organic solution obtained from back-extraction was centrifugated simply for further cleanup for the sake of automatic injection. A preconcentration factor of 50 was obtained for these five OPPs extracted from only 10 mL of a sample. The limits of detection (LODs) were 0.07 ng mL(-1) for phorate, fenthion and quinalphos, 0.04 ng mL(-1) for diazinon and 0.08 ng mL(-1) for parathion-methyl. The limits of quantification (LOQs) were 0.21, 0.12, 0.24, 0.21 and 0.21 ng mL(-1), respectively. Accuracy of the method was evaluated by bias, which ranged from +6.85 to -14.68%. Precision was also good; the relative standard deviations (R.S.D.s) were less than 9%. The method showed to be potential for biological monitoring.     

Montmorillonite functionalized with pralidoxime as a material for chemical protection against organophosphorous compounds

Montmorillonite K-10 functionalized with α-nucleophilic 2-pralidoxime (PAM) and its zwitterionic oximate form (PAMNa) is introduced as a versatile material for chemical protection against organophosphorous (OP) compounds such as pesticides and chemical warfare agents (CWA). Upon inclusion into the montmorillonite interlayer structure, the pyridinium group of PAMNa is strongly physisorbed onto acidic sites of the clay, leading to shrinking of the interplanar distance. Degradation of diethyl parathion by PAMNa-functionalized montmorillonite in aqueous-acetonitrile solutions occurred primarily via hydrolytic conversion of parathion into diethylthio phosphoric acid, with the initial stages of hydrolysis observed to be pseudo-first-order reactions. Hydrolysis catalyzed by the clay intercalated by PAMNa was 10- and 17-fold more rapid than corresponding spontaneous processes measured at 25 and 70 °C, respectively. Hydrolytic degradation of diisopropyl fluorophosphate (DFP), a CWA simulant, was studied on montmorillonite clay functionalized by PAMNa and equilibrated with water vapor at 100% relative humidity by 31P high-resolution magic angle spinning NMR and was observed to be rather facile compared with the untreated montmorillonite, which did not show any DFP hydrolysis within 24 h. The incorporation of the functionalized clay particles into elastomeric film of polyisobutylene was shown to be a means to impart DFP-degrading capability to the film, with clay particle content exceeding 18 wt %.     

Ligand-assisted extraction for separation and preconcentration of gold nanoparticles from waters

A new two-step extraction procedure is proposed for separation and preconcentration of gold nanoparticles (Au-NPs) from aqueous samples. First, Au-NPs are loaded onto a reversed phase C-18 (RP-C18) column, and then ligand-assisted extraction into chloroform is performed. 1-Dodecanethiol (1-DDT, 5 mM) was used as selective ligand for quantitative extraction under ultrasonic condition. Parameters of the extraction procedure, such as sample volume, organic solvent, concentration and nature of the ligand, ultrasonication time, pH of the sample, and different coating as well as sizes of Au-NPs were investigated in regard to the extraction efficiency of Au-NPs. The optimized procedure allows separation and preconcentration of the Au-NPs with an enrichment factor of up to 250 assuring no changes in size and/or shape of the NPs. This was proved by investigation of the particles by UV-vis spectrometry and transmission electron microscopy (TEM). Furthermore, the presence of potentially interfering other metal nanoparticles (M-NPs) and dissolved organic matter (DOM) was studied. Observed minor recoveries of Au-NPs in DOM model solutions were overcome by hydrogen peroxide pretreatment up to a DOM concentration of about 4 mg/L. Feasibility of the proposed method was proved by application of the optimized procedure to 5 real water samples. Recoveries of Au-NPs in the real waters spiked in a concentration range from 0.15 to 5100 μg/L obtained by this method varied from 68.4% to 99.4%. Consequently, the proposed approach has great potential for the analysis of M-NPs in environmental waters.     

Measuring binding and speciation of hydrophobic organic chemicals at controlled freely dissolved concentrations and without phase separation

The binding and speciation of hydrophobic organic chemicals (HOCs) in aqueous solutions were determined by controlling chemical activity and measuring total concentrations. Passive dosing was applied to control chemical activities of HOCs in aqueous solutions by equilibrium partitioning from a poly(dimethylsiloxane) polymer preloaded with the chemicals. The HOC concentrations in the equilibrated solutions [C(solution(eq))] and water [C(water(eq))] were then measured. Free fractions of the HOCs were determined as C(water(eq))/C(solution(eq)), whereas enhanced capacities (E) of the solutions for HOCs were determined as C(solution(eq))/C(water(eq)). A mixture of polycyclic aromatic hydrocarbons served as model analytes, while humic acid, sodium dodecyl sulfate, hydroxypropyl-β-cyclodextrin, and NaCl served as model medium constituents. The enhanced capacities were plotted versus the concentrations of medium constituents, and simple linear regression provided precise partition ratios, salting out constants, and critical micelle concentrations. These parameters were generally in good agreement with published values obtained by solid phase microextraction and fluorescence quenching. The very good precision was indicated by the low relative standard errors for the partition ratios of 0.5-8%, equivalent to 0.002-0.03 log unit. This passive dosing approach allows binding and speciation of HOCs to be studied without any phase separation steps or mass balance assumptions.     

Sample preparation based on dynamic ion-exchange solid-phase extraction for GC/MS analysis of acidic herbicides in environmental waters

The newly established enrichment technique, dynamic ion-exchange solid-phase extraction (DIE-SPE), was studied for sample preparation for GC/MS analysis of 16 acidic herbicides in environmental waters. C18 bonded silica was the solid-phase material used. The optimal sample pH was weakly acidic to neutral. However, for common tap water and surface water, which run pH 6-9, all the acidic herbicides except for Chloramben could be effectively extracted from a sample of 1,000-mL volume without pH adjustment. The humic acid could be concurrently extracted from water, but most of it was separated from the sample by using 3 mL of 10% methanol in acetone as the eluent, which would completely elute the analytes and leave a large part of the humic acid on the cartridge. The selective elution reduced the interference of humic acid and made the DIE-SPE an effective approach for the analysis of the acidic herbicides in surface water. Comparing DIE-SPE with conventional reversed-phase SPE (RP-SPE), the former gave higher recoveries for the acidic herbicides and was less affected by sample matrixes. A tandem-cartridge system combining RP- and DIE-SPE in sequence was set up for the simultaneous isolation of the acidic herbicides and removal of the interfering substances. Despite some minimal retention on the upper RP-SPE cartridge, most of the acidic herbicides could be extracted on the lower DIE-SPE cartridge with recovery over 80% except for Chloramben (50%), fenoprop (73%), MCPB (67%), and 2,4-DB (70%) when a 500-mL aqueous sample of pH 9.5 was percolated through the tandem-cartridge system. The effectiveness of the system in removing the long carbon chain fatty acids as well as the basic and neutral organic interfering substances from the sample was also demonstrated.     

Hot phosphate-buffered water extraction coupled on-line with liquid chromatography/mass spectrometry for analyzing contaminants in soil

We evaluated the feasibility of analyzing rapidly traces of polar and medium polar contaminants in soil by coupling on-line a hot phosphate-buffered water extraction apparatus to a liquid chromatography/mass spectrometer system. Coupling was accomplished by using a small C-18 sorbent trap for collecting analytes and two six-port valves. The efficiency of this device was evaluated by extracting 13 selected pesticides from 200 mg of laboratory-aged soils by varying the extraction temperature, the extractant volume, and the flow rate at which the extractant passed through the extraction cell and the sorbent trap. In terms of extraction efficiency, robustness of the method, and extraction time, the best compromise was that of using 8 mL of extractant at 90 degrees C and 0.5 mL/min flow rate. Under these conditions, recoveries of 11 out of 13 analytes ranged between 82 and 103%, while those of the least hydrophilic pesticides, i.e., neburon and prochloraz, were 73 and 63%, respectively. By increasing the extractant volume to 60 mL, additional amounts of the two latter compounds could be recovered. Under this condition, however, the most hydrophilic analytes were in part no more retained by the C-18 sorbent trap. From a naturally 1.5-year aged soil, hot phosphate-buffered water removed larger amounts of three herbicides and hydroxyterbuthylazine (a terbuthylazine degradation product) than pure water and Soxhlet extraction. This result seems to confirm that hot phosphate buffer is also able to remove from soil those fractions of contaminants that, on aging, are sequestered into the humic acid framework.     

Electrokinetic removal of 2,6-dichlorophenol and diuron from kaolinite and humic acid-clay system

This paper presents the results of a study on the electrokinetic treatment of kaolinite and humic acid kaolinite complexes spiked with 2,6-dichlorophenol or 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron). In particular, the attention was paid to the interaction between solid surface and dissolved organics: the effects of contaminant sorption as well as the physicochemical reactions on the efficiency of electrokinetic remediation were investigated. Using a 3V/cm voltage gradient, approximately 90% of diuron was removed from kaolinite after one water pore volume was collected in the cathode reservoir, but much lower efficiency was obtained in the electrokinetic removal of this compound from humic acid-coated kaolinite. The results also showed that partial degradation of the contaminant occurred during electrokinetic treatment of kaolinite clay spiked with 2,6-dichlorophenol: the contamination in the clay could be remediated by the combination of electrokinetic extraction and electrochemical reactions.     

Effects of humidity and soil organic matter on the sorption of chlorinated methanes in synthetic humic-clay complexes.

Vapor-phase sorption is the most influential process governing the transport and the fate of volatile organic compounds in soil. To understand the influence of both soil organic content and the humidity of soil on the vapor sorption is an important process for degradation processes. The single-pellet moment technique was used to investigate sorption and diffusion of trichloromethane (TCM) and carbon tetrachloride (CTC) at varying relative humidities (0-80%) of synthetic humic-clay complex pellets consisting of clay (montmorillonite) and different amounts of organic matter (humic acid). The effective diffusivities of TCM and CTC did not show a noticeable change with moisture and humic acid content. On the other hand, with increasing humic acid content of clay at 0% relative humidity, an appreciable decrease of the equilibrium sorption constants of the tracers (TCM, CTC) was found because of the blockage of some sites of the mineral surfaces and especially micropores by the humic acid. The presence of water also reduced dramatically the sorption of TCM and CTC on synthetic humic-clay complexes. Above 20% relative humidity, the sorption coefficient of TCM and CTC varied only slightly with humic acid content. It was concluded that the sorption of TCM and CTC in synthetic humic-clay complexes was strongly effected by the moisture and humic acid content.     

Isolation and quantification of dissolved lignin from natural waters using solid-phase extraction and GC/MS

Solid-phase extraction (SPE) was tested for the isolation of dissolved lignin from diverse natural waters (fresh, estuarine, and marine) in preparation for CuO oxidation. Capillary GC coupled to selected-ion monitoring mass spectrometry (SIM-MS) of CuO oxidation products provides the high sensitivity and precision required for the identification and quantification of trace levels of lignin in seawater. The low blanks and quick cleanup of C18 cartridges support SPE for processing such samples. Comparison of SPE with other isolation procedures (direct dry-down and ultrafiltration) has shown that this method quantitatively recovers dissolved lignin and preserves its compositional parameters. The concentration and nature of dissolved organic matter appear to be primary factors that constrain the amount of water that should be processed to obtain quantitative and reproducible recoveries of dissolved lignin using SPE. Highest recoveries of dissolved lignin were obtained at low pH (1.5-4.0) with substantial decreases at pH > 4. Extraction efficiencies were independent of flow rate within a range of five to fifteen bed volumes per minute (50-150 mL min(-1)), and both refrigeration and freezing were appropriate long-term storage methods for processed cartridges prior to elution of retained dissolved lignin.     

气相色谱法测定大黄鱼中多种农药残留的研究

建立了用一种前处理方法同时检测大黄鱼中多种有机氯、拟除虫菊酯和有机磷农药残留量的分析方法。试样经乙腈水提取,离心分层后用中性氧化铝填料和ENVI-18柱净化,然后用GC-μECD和GC-FPD测定,外标法定量。14种农药在0.01～0.5 mg/L范围内线性良好,相关系数r〉0.999,样品添加量为0.001～0.01...     

Double-disk solid-phase extraction: simultaneous cleanup and trace enrichment of herbicides and metabolites from environmental samples

Phenylurea and triazine herbicides, including some metabolites, were isolated from water and soil extracts by solid-phase extraction using a layered system of two extraction disks, a method called double-disk solid-phase extraction. The first disk consisted of strong anion exchange (SAX) of 10-micron styrene divinylbenzene (SDB) particles embedded in Teflon, and the second disk was a C18 disk of 10-micron particles also embedded in Teflon. A volume of 500 mL of water or aqueous soil extract is passed through the layered system with the SAX disk first. The purpose of the SAX disk is to remove the humic and fulvic acids from the water or aqueous soil extract by ion exchange through their carboxyl groups. Even during methanol elution of herbicides, the humic substances remain bound to the SAX disk with > 85% retention. Elution with methanol results in more than 90% recovery of the herbicides from the layered extraction disks. Removal of the humic and fulvic acids results in greater sensitivity for diode array detection quantitation (0.05 micrograms/L for herbicides) by substantially reducing the absorbance of the humic peak on the LC chromatogram. The herbicides adsorb to the SAX disk either through hydrogen bonding to the anion-exchange sites or by hydrophobic interaction with the SDB surface of the anion-exchange disk. The method was tested for the analysis of natural water samples from the Mississippi Embayment, a cotton-growing area of the southeastern United States.     

Effect of humic substances on Cu(II) solubility in kaolin-sand soil

The type and amount of organic matter present in industrially contaminated soils will influence the risk they pose. Previous studies have shown the importance of humic and fulvic acids (FAs) (important components of soil organic matter) in increasing the solubility of toxic metals but were not carried out using toxic metal levels and the pH range typical of industrially contaminated soils. This study investigated the influence of three humic substances (HSs: humates, fulvates and humins) on the solubility of copper(II) ions in kaolinitic soil spiked with Cu at levels representative of industrially contaminated soil. Humates, fulvates and humin were extracted from Irish moss peat, and controlled pH batch leaching tests were conducted on an artificial kaolin-sand soil that was spiked with each. Further leaching tests were conducted on soil spiked with each HS and copper nitrate. Dissolved organic contents were determined by titration and total and free aqueous copper concentrations in the leachate were measured using AAS and ion selective electrode (ISE) potentiometry respectively (dissolved complexed copper levels were determined by difference). It was found that humates and fulvates are partially sorbed by the soil, probably by chemisorption on positively charged gibbsite (Al-hydroxide) sites in the kaolinite. The addition of 340 mg/kg Cu(II) ions did not significantly affect the amount of humate or fulvate sorbed. Dissolved humates and fulvates form soluble complexes with copper over the pH range 3-11. However, in the presence of kaolinite, soluble copper humates and fulvates are unable to compete with the kaolinite for Cu ions at pH 6-7. Above pH 8, humate and fulvate complexes are the only forms of dissolved Cu. Humin is largely insoluble and has little effect on Cu mobility between pH 2 and 12. The implication of this study is that measurement of total soil organic content and water leaching tests should be a standard part of contaminated site investigation.