土壤中有机氯农药残留分析用标准样品的制备

介绍了土壤中有机氯农药残留分析用标准样品的制备方法。土壤样品经风干、研磨、筛分、混匀后装瓶。样品经索氏提取、弗罗里硅土小柱净化后,采用气相色谱-质谱法对残留的有机氯农药进行测定。结果表明,采自沈阳地区的土壤中的有机氯农药含量分布较为均匀,是一种理想的环境标准样品候选物样品。该研究为土壤中有机氯农药残留分析用标准样品的研制奠定了基础。     

重金属有效态与土壤环境质量标准制订

制订合适的土壤环境质量标准是评价土壤健康质量及食品安全的核心问题,而土壤重金属有效态对制定土壤环境质量标准具有重要意义。土壤重金属有效态主要指植物有效态,它与重金属形态关系密切。影响土壤重金属有效态的因素很多,主要包括:土壤pH值、氧化还原电位、CEC、有机质含量、粒径组成(黏粒含量)、铁铝锰氧化物含量、植物种类、土壤微生物、土壤温度的高低、重金属来源等。化学试剂浸提法是测量重金属生物有效性的常用方法,所用化学试剂主要有三类:弱(稀)酸、络合剂和中性盐,中性盐由于对土壤pH值影响小而受到重视。我国现行土壤质量标准采用土壤重金属总量和pH两个因素为依据,但是不少学者认为,该标准仅适用于重金属有效态较高的土壤,而不能反映重金属有效态含量较低土壤的实际状况。     

Molecular biological access to the chemistry of unknown soil microbes: a new frontier for natural products

Cultured soil microorganisms have provided a rich source of natural-product chemistry. Because only a tiny fraction of soil microbes from soil are readily cultured, soil might be the greatest untapped resource for novel chemistry. The concept of cloning the metagenome to access the collective genomes and the biosynthetic machinery of soil microflora is explored here.     

Use of chemometrics methods and multicriteria decision-making for site selection for sustainable on-site sewage effluent disposal

This paper presents a study undertaken to evaluate site suitability for sewage effluent renovation based on physico-chemical characteristics of the soil. The results obtained showed that as the soil becomes acidic, the phosphorus concentration in the soil reduces accordingly. The chloride ion concentration was found to be a reliable indicator for evaluating the soil capacity to remove nitrogen. A high cation exchange capacity (CEC) can enhance the renovation of sewage effluent. Soils with high quartz content had a low CEC with high organic matter content (OM) being able to compensate. Therefore, an understanding of the micro-nutrients in the soil, organic matter content and chloride ion concentration are important.To facilitate a multi-variate approach for site selection, multicriteria decision-making (MCDM) methods, PROMETHEE and GAIA, were applied for analysis of a sequence of three matrices consisting of 8, 16, and 48 soil site objects, respectively, and seven soil property parameters. Matrix models and the interpretation of results are discussed in detail. From these analyses, PROMETHEE II net outranking flows, ?, found that two sites were always among the top three ranks of the three matrix models, which suggested that they were the most suitable for sewage effluent renovation. The criteria CEC and OM, were particularly important for the selection of these better sites, but pH and Cl⁻ attributes discriminated the weaker performing sites from the better ones; as well the PO₄³⁻ and the NH₃-N criteria were in general opposition to CEC, OM, pH and Cl⁻ but were much less effective as discriminators. Consideration of net outranking flows suggested an approach method for the selection of other possibly suitable sites for sewage effluent renovation.     

A preliminary screening technique for selected metals at waste sites

Fast neutron activation analysis (FNAA) was investigated as a possible on-site preliminary screening technique for metal contamination of soil. Two metals, Cu and Zn, were used in a laboratory setting to evaluate the possibility of detecting metal contamination of soil at or below the maximum permissible metal concentration in soil. Varying quantities of compounds of the selected metals were mixed into a prepared soil column for analysis of signal intensity as a function of concentration in the soil. Experiments were conducted with a sealed tube neutron generator and a germanium gamma-ray detector. Both metals produced signal levels distinguishable from background soil concentrations at the maximum permissible level.     

Supercritical-fluid extraction as a method for investigating the fate of the organic contaminants in soil

Supercritical fluid extraction (SFE) has proven to be a method for the extraction of pollutants from the soil having serious difficulties to be standardized. A new possibility to use SFE for investigate the fate of pollutants in the soil structure is suggested. The recovery of the analyte from the soil matrix depends on the mass transfer. This includes the desorption of the analyte from the soil surface, its diffusion through the interior of the soil structure, and its transport within the bulk flow of supercritical fluid through the interstitial pores of the soil. The mass transfer can be expected to depend on both the different types of soil and the different location of the analyte in the soil structure. The analyte extraction is also controlled by thermodynamic factors such as the sorption/desorption equilibrium from the soil. On this basis, a mathematical model based on the supercritical fluid extraction conditions (viz, temperature, pressure, fluid flow, modifier,...), which are directly linked to the status of the analyte in the soil, is developed. The elaboration of the kinetical results using our model would permit to approximate the distribution of the contaminant to a non porous- or to a deep porous-soil structure model as a function of a fresh contamination or an aged contamination. These conditions can be described by spiked or native contaminant extraction time profiles, respectively.     

EUROSOILS - A set of CRMs for comparability of soil-measurements

An overview is given on the development, properties, and application of the European reference soil set--the EUROSOILS. The introduction of this new type of reference material has, for the first time, enabled comparison of data related to the interaction of chemical substances with the soil, and thus, improvement of soil quality. Because of their unforeseen success, a second generation of EUROSOILS had been produced and the range of application extended to other types of measurement related to the soil matrix--soil pH, carbon and nitrogen content, particle-size distribution and cation-exchange capacity. Other fields of application include analytical method development or testing of soil decontamination techniques. On the basis of the success of the EUROSOIL concept and the need for a common basis for comparison of soil-related data in Europe and beyond, the European Commission's Institute for Reference Materials and Measurements decided to certify several properties of the second EUROSOIL-generation, thus establishing a common QA/ QC system for soil-related data. The main features of the EUROSOILS, their origin, the necessary field and laboratory work, and some interesting background information about the project are presented in this paper.     

A novel method for the study of the biophysical interface in soils using nano-scale secondary ion mass spectrometry

The spatial location of microorganisms and their activity within the soil matrix have major impacts on biological processes such as nutrient cycling. However, characterizing the biophysical interface in soils is hampered by a lack of techniques at relevant scales. A novel method for studying the distribution of microorganisms that have incorporated isotopically labelled substrate ('active' microorganisms) in relation to the soil microbial habitat is provided by nano-scale secondary ion mass spectrometry (NanoSIMS). Pseudomonas fluorescens are ubiquitous in soil and were therefore used as a model for 'active' microorganisms in soil. Batch cultures (NCTC 10038) were grown in a minimal salt medium containing 15N-ammonium sulphate (15/14N ratio of 1.174), added to quartz-based white sand or soil (coarse textured sand), embedded in Araldite 502 resin and sectioned for NanoSIMS analysis. The 15N-enriched P. fluorescens could be identified within the soil structure, demonstrating that the NanoSIMS technique enables the study of spatial location of microbial activity in relation to the heterogeneous soil matrix. This technique is complementary to the existing techniques of digital imaging analysis of soil thin sections and scanning electron microscopy. Together with advanced computer-aided tomography of soils and mathematical modelling of soil heterogeneity, NanoSIMS may be a powerful tool for studying physical and biological interactions, thereby furthering our understanding of the biophysical interface in soils.     

Preparation of artificially spiked soil with polycyclic aromatic hydrocarbons for soil pollution analysis.

To confirm the method for preparing artificially spiked soil with polycyclic aromatic hydrocarbons (PAHs), we tested the homogeneity of PAHs in spiked soils, which were prepared by three different procedures, by using kaolin and ando soil. When the slurry of kaolin and acetone containing PAHs were evaporated by a rotary evaporator at 30 - 35 degrees C, the most homogeneous distribution of PAHs was obtained in the spiked soil. This procedure was applied to the preparation of PAH-spiked soil for natural soil (ando soil). Such spiked soils can be useful as the standard materials for standardization of the analytical methods for PAHs in the soil and sediment samples.     

Application of cyclodextrins in environmental bioassays for soil

Based on our former experience on contaminant solubilisation and mobilisation in the process of soil remediation we used cyclodextrins as additives in environmental bioassays, for improving solubility and bioavailability of the contaminant in soil and as a consequence sensitivity of the bioassay. In this article we introduce the findings on the application of RAMEB (randomly methylated ??-cyclodextrin) for testing PCP (pentachlorophenol) in soil, in three bioassays: bacterial luminescence-inhibition test with Vibrio fischeri, protozoon growth inhibition test with Tetrahymena pyriformis, and Ames mutagenicity test. We applied RAMEB which has a high solubilising capacity on many typical soil contaminant and PCP, because contradictory results were published for its toxicity and mutagenicity. The RAMEB-aided Ames test, gave a sudden and expressed increase in the mutagenicity of PCP, however, Ames mutagenicity was negative without cyclodextrin (CD). Based on these results we tried to apply RAMEB for increasing sensitivity of other bioassays, such as acute toxicity tests with different test organisms. According to our results the effect of RAMEB on bioavailability and toxic effect depends not only on the K _ow value (octanol?Cwater partition coefficient) of the chemical substances, but also on the test organism, the water-content of the test-matrix and the applied concentration of RAMEB, as well as its ratio to PCP. We collected all the characteristics of the bioassays applied for PCP and some other contaminants and showed the measured effect data in comparison with each other. We found that in the complex system of soil and soil suspension, used in the bioassays, the interactions between soil solid, water and gaseous phases, as well as between the test organism and RAMEB result in K _ow dependent partition of the contaminant between solid and water phases of soil, RAMEB, and the test organism. The conclusion is that RAMEB undoubtedly has an influence on the fate and behaviour of the contaminant in soil and soil suspensions, and the direction of the RAMEB-induced changes depends on the effective concentration of the RAMEB in the bioassay, the time of contact, the type of test organism, and the characteristics of the RAMEB?Ccontaminant complex. In those cases, when RAMEB increased the effect of a contaminated environmental sample, this CD-induced increase can be considered as a ??realistic worse case?? situation, which can be very useful in risk assessment, resulting in a moderate overestimate in the value of environmental risk.     

Systematic Identification of Analytical Indicators to Measure Soil Load on Plants for Safety Assessment Purposes

Abstract

Contaminants in soil can be transferred to humans and other biota when soil dust on plants is ingested as food. Measuring how much soil is on plants, in the absence of artificial tracers or contaminants, is difficult because of the very small amounts involved and the confounding effect of absorption of elements through roots. However, measurements of soil load are essential for assessment modelling. We compared the ability of several analysis strategies, involving naturally occurring elements, to predict the soil load on plants. Large samples of 12 vegetable and fruit crops were collected, along with corresponding soil samples. An independent measure of soil load on the crop samples was derived from a combination of gravimetric measurements, including loss on washing and the acid-insoluble ash content. The best agreement between the elemental-abundance and the gravimetric methods was for Sr in the plant acid-insoluble ash. Through a systematic process of elimination, we conclude that analyses of the acid-insoluble ash fraction of the plant samples for Al, Ba, Fe, Si, Sr and Ti are most reliable. If analyses are to be restricted to the full plant ash, then the choice of analytes is restricted to Al, Fe, Si and Ti. Soil loads in our study averaged 20 mg soil kg^?1 dry plant for leafy tissues and 2 mg soil kg^?1 for fruits, and washing decreased soil loads about 1.5 fold.     

Soil characterization by energy dispersive X-ray fluorescence: sampling strategy for in situ analysis.

This work describes a sampling strategy that will allow the use of portable EDXRF (energy dispersive X-ray fluorescence) instruments for "in situ" soil analysis. The methodology covers a general approach to planning field investigations for any type of environmental studies and it was applied for a soil characterization study in the zone of Campana, Argentina, by evaluating data coming from an EDXRF spectrometer with a radioisotope excitation source. Simulating non-treated sampled as "in situ" samples and a soil characterization for Campana area was intended. "In situ" EDXRF methodology is a powerful analytical modality with the advantage of providing data immediately, allowing a fast general screening of the soil composition.     

A New Calibration Free pH‐Probe for In Situ Measurements of Soil pH

A new pH‐probe was developed for in situ determination of soil pH. It consists of a stainless steel tube with a plastic inset containing the indicator electrode, the reference electrode and a temperature sensor at the end of the tube. The indicator electrode is a quinhydrone composite electrode that does not need to be calibrated, because it acquires almost the theoretical predicted potential and has a constant formal potential and slope under all fabrication conditions. The pH‐probe has a low standard deviation (±4 mV or 0.07 pH units). The response time is short (5 s). To characterize its function the soil pH‐probe was used to analyse pond and arable soil samples. The results were compared with those obtained with a conventional combined glass electrode. To evaluate the results, measurements were performed (i) in natural wet soil samples (in situ conditions), (ii) after drying and moistening the soil samples (moistened samples) and (iii) after drying the soil samples and mixing with bidistilled water (soil solutions; generally accepted method in laboratories). The minimum water content required to obtain stable potentials in soil samples was 10%. The influence of S^2?, NO and Fe³⁺ as naturally available reducing and oxidising agents on the potential response of the pH‐probe was investigated. All the obtained results demonstrate that the developed pH‐probe is a powerful tool to measure the pH of a soil sample under in situ conditions without a calibration step.     

An intercomparison of sampling techniques for measurements of radiocaesium in upland pasture and soil

An intercomparison of sampling procedures used by five laboratories for the determination of radiocaesium in vegetation and peaty soil was carried out at two locations in Cumbria. The multiple sampling has given information on the homogeneity of the parameters studied at each location. The parameters comprise soil bulk densities, total deposition of¹³⁷Cs, deposition of¹³⁷Cs in three soil layers, biomass densities, concentrations of¹³⁷Cs in pasture, and activity ratios (¹³⁴Cs/¹³⁷Cs) in soil and vegetation. The determination of total deposition of¹³⁷Cs gave no indication of differences between the laboratories. The results from the soil profiles do indicate significant differences between laboratories. One laboratory using a coring technique observed difficulties during sampling due to compression of the soil. The coring technique should thus be avoided or applied with extreme care for the sampling of depth profiles in peaty soil. The results from the sampling of pasture show no indication of differences between the laboratories. For the parameters studied the observed variabilities across soil depths and locations range from 10% to 81% in terms of relative standard deviations. A comparison across all results at the two locations indicate a 50% higher field variability at one of the sites relative to the other.     

Electroanalytical procedure and sorption studies for imazaquin in different soils

The objective of the present work is to determine sorption coefficients of the herbicide imazaquin using the differential pulse polarography in the major soil classes occurring in the State of São Paulo, Brazil. This study contributes to the predictions of pesticide fate and transport mechanisms in the environment as well as its exposure and interactions with different soil materials. Imazaquin was analysed directly in soil samples (scan rate 2 mV s^–1, mercury drop size 0.37 mm, and pulse height 50 mV) and the detection limits varied from 42 to 58 g L^–1 for different soils. Imazaquin showed the K_F values varying from 0.8 (for the sandy soil) to 35.5 L kg^–1 (for the medium textured soil), with a significant dependence on the soil pH, organic matter content, and clay minerals. The study demonstrates the practical utilisation of the electroanalytical methodology to determine the imazaquin adsorption in soil and consequently assess the impact of this herbicide in the environment, especially for the evaluation of the potential risk of surface and groundwater contamination.     

A Chemical Test for Determining Biological Availability of Aged Chemicals in Soil

Abstract

Aging is one of several processes that are known to affect exposure of chemicals to organisms by decreasing the available fraction of chemical contaminants in soil. This phenomenon has important implications in the assessment of the hazards of chemicals and regulations for soil cleanup. Passive sampling devices (PSDs) are potentially direct chemical indicators for assessing bioavailability of pesticides (and other chemicals). PSDs consist of lipophilic material within a semi-permeable membrane, similar to biological systems. In this study, a pesticide mixture was aged in soil for up to eight months. Earthworms and PSDs were placed in soil and chemical uptake into both was determined over time. Uptake rates into PSDs and maximum concentrations were observed to positively correlate with uptake rates and maximum concentrations in earthworms for both of the soil types studied (sandy loam, silt loam). These results indicate that PSDs may be used as a surrogate for earthworms and provide a chemical technique for assessing the availability of aged chemical residues in soil.     

Extracting Syringe for determination of organochlorine pesticides in leachate water and soil-water slurry: a novel technology for environmental analysis

The Extracting Syringe (ESy), a novel membrane-based sample preparation technique directly coupled as an autosampler to gas chromatography, has been employed for the analysis of organochlorine pesticides (OCPs) in raw leachate water. The ESy has also been applied for extraction of OCPs from contaminated soil samples and its performance has been compared to liquid-solid extraction (LSE) and accelerated solvent extraction (ASE). Extraction of 3-mL leachate sample at the optimised conditions resulted in enrichment factors from 32 (Endrin aldehyde) to 242 (Endrin) and detection limits from 1 to 20 ng/L. The inter-day and intra-day repeatability (% RSD) at 100 and 500 ng/L were <6% and <24%, respectively. The relative recovery at 100 and 500 ng/L ranged from 68% (Aldrin) to 116% (Endrin aldehyde); except Heptachlor that showed 51 and 60%, respectively. The ESy extraction of the slurry-made soil samples revealed occurrence of Endosulfan I (18.2 microg/g soil), 4,4'-DDE (2.6 ng/g soil), Endosulfan II (8.7 microg/g soil) and Endosulfan sulfate (1.1 microg/g soil); showing good agreement with LSE results. The total ESy consumption of organic solvents was 4.2 mL from which only 0.6 mL n-undecane was used during the extraction step (7 microL for the extraction per se), while in the LSE and ASE, it was 420 and 18.1 mL, respectively. The ESy extraction time (0.5 h) was comparable to the ASE time (0.6 h); and the time required for the LSE was 3.75 h. To sum up, the ESy has shown its competency to LSE and ASE technologies, demonstrating its applicability for environmental analysis of organic pollutants, towards green techniques for green environment.     

A disposable amperometric biosensor for rapid screening of anticholinesterase activity in soil extracts

A disposable amperometric biosensor for the determination of anticholinesterase activity in soil extracts is described. The sensitive membrane was obtained by co-crosslinking acetylcholinesterase and choline oxidase with bovine serum albumin using glutaraldehyde. The anticholinesterase activity of the soil extract was measured using chronoamperometry at 650 mV vs. Ag/AgCl to monitor the biocatalytically produced H2O2 before and after the inhibition step. An inhibition percentage of 38 +/- 4% was recorded for soil extracts spiked with 10 ppb of ethyl parathion. The device has the potential to be used as a gross sensor for the assessment of anticholinesterase activity in soil extracts.     

Effect of Sorbents Added on Adsorption Capability of Soil for Nano-TiO2

The adsorption capability of loam soil for nano-TiO2 affected by the amount and intensity of leached water has been investigated by simulating the natural rainfall process under the leaching condition.The results show that the amount and the intensity of leached water are two important factors affecting the adsorption capability of loam soil for nano-TiO2.The results indicate that the depth of the loam soil containing a maximal amount of nano-TiO2 is proportional to the amount of leached water,while it is i...     

Direct competitive ELISA for the determination of polychlorinated biphenyls in soil samples

A direct competitive ELISA for determination of polychlorinated biphenyls (PCB) in soil samples was described. The standard calibration curve based on Delor 103 (Aroclor 1242) was constructed in the dynamic range of 10-1000 micro g L(-1) and a detection limit of 5.0-12.9 micro g L(-1) (or 0.5-1.29 micro g g(-1) soil) was achieved. When spiked soil samples were extracted with methanol recoveries were 90.6-106.3 %. The effect of methanol and DMSO on assay signal and sensitivity was established. Eight PCB-contaminated soil samples were analyzed by ELISA and gas chromatography (GC). The ELISA results from Soxhlet extraction were in a good agreement with those of GC (correlation coefficient 0.9866; n=8). Except for one soil sample the results from ELISA with methanol extraction were not significantly different from those from GC.