Soil samples metal analysis

In situ densitometry has been the most preferred method for quantitative analysis of substances. The important applications of densitometry in inorganic PLC include the determination of boron in water and soil samples [38], N03 and FefCNfg in molasses [56], Se in food and biological samples [28,30], rare earths in lanthanum, glass, and monazite sand [22], Mg in aluminum alloys [57], metallic complexes in ground water and electroplating waste water [58], and the bromate ion in bread [59]. TLC in combination with in situ fluorometry has been used for the isolation and determination of zirconium in bauxite and almnimun alloys [34]. The chromatographic system was silica gel as the stationary phase and butanol + methanol + HCl -H water -n HF (30 15 30 10 7) as the mobile phase. 

Spike and bench-scale tests were performed in order to size the pilot test. For this purpose, soil samples of about 10kg each and groundwater samples (about 5kg each) were retrieved/collected both during and after the installation of the test wells in, respectively, sealed plastic bags and glass containers, and these were preserved under refrigeration. The samples were analysed for content of chlorinated solvents, sulphates, nitrates and metals (baseline analysis). 

Wide-spaced sampling was carried out in an area of approximately 150 000 km at density of one sample per 100 km (Wang et al. 2007). Soil samples were collected from the weakly cemented sandy horizon at a depth of 20-30cm. The soil samples were subjected to total analysis and selective leaching of mobile metals. Elements were determined by ICP-MS. 

The analytical use of GECE modified in situ by using bismuth solution for square wave anodic stripping voltammetry (SWASV) of heavy metals is also studied [36]. The use of this novel format is a simpler alternative to the use of mercury for analysis of trace levels of heavy metals. The applicability of these new surface-modified GECE to real samples (tap water and soil samples) is presented. 

The former UK Ministry of Agriculture and Food has also published [17] recommended soil preparation techniques for the determination of a wide range of metals and for the preparation of plant samples for analysis by dry combustion and the determination of ash. 

Because of the local inhomogeneity of the test area, the sampling and analysis of several soil samples is necessary for representative characterization of the heavy metal exposure of the total area. 

The following two examples [EINAX et al., 1990 KRIEG and EINAX, 1994] demonstrate not only the power, but also the limits of multivariate statistical methods applied to the description of polluted soils loaded with heavy metals from different origins. Case studies with chemometric description of soil pollution by organic compounds are also discussed in the literature. DING et al. [1992], for example, evaluated local sources of chlorobenzene congeners in soil samples by using different methods of multivariate statistical analysis. 

Aqueous trip blanks sometimes accompany soil samples collected into metal liners or glass jars. In this capacity they do not provide any meaningful information. Soil samples do not have the same contamination pathway as water samples because they are not collected in 40-milliliter (ml) VOA vials with PTFE-lined septum caps. In addition, soil does not have the same VOC transport mechanism as water does (adsorption in soil versus dissolution in water). There are other differences that do not permit this comparison different sample handling in the laboratory different analytical techniques used for soil and water analysis and the differences in soil and water MDLs. That is why the comparison of low-level VOC concentrations in water to VOC concentrations in soil is never conclusive. 

Unhomogenized, homogenized, and collocated soil samples collected from shooting ranges for metal analysis... 

Soil samples for VOC analysis are collected into airtight coring devices or into preserved VOA vials. Soil samples for SVOC, metal, and inorganic parameter analyses are collected into brass or stainless steel core barrel liners, acrylic liners, or into glass jars with PTFE-lined lids. The liners are capped with PTFE sheets and plastic caps. 

Common to nearly all analyses is preservation with refrigeration at 2-6°C, a practice, which minimizes the volatilization of organic compounds with low boiling points and the bacterial degradation of most organic compounds. That is why we must place samples on ice immediately after they have been collected, ship them in insulated coolers with ice, and keep them refrigerated until the time of analysis. Water samples collected for metal analysis and preserved with nitric acid are an exception to this rule as they may be stored at room temperature. The addition of methanol or sodium bisulfate solution to soil collected for VOC analysis is the only chemical preservation techniques ever applied to soil samples. 

Several existing protocols require a solvent (acetone, methanol, isopropanol) rinse as part of equipment decontamination for VOC sampling and 1 10 percent hydrochloric or nitric acid rinse for metal analysis sampling (DOE, 1996 USACE, 1994). These practices, successful as they may be in removing trace level contaminants, create more problems than they are worth. Organic solvents are absorbed by the polymer materials used in sampling equipment construction and appear as interferences in the VOC analysis. Acid destroys the metal surfaces of soil sampling equipment and induces corrosion. The use of solvents and acids is a safety issue and it also creates additional waste streams for disposal. 

Chemical interferences may be produced by overlapping spectra of different elements or as the result of x-ray absorption or enhancement. Either effect is common in soil contaminated with heavy metals. Chemical interferences may be substantially reduced through a mathematical correction, but they cannot be completely eliminated. Other factors that affect the accuracy of XRF analysis are the instrument settings and the operator technique, especially in in situ measurements. A correlation of XRF results with laboratory analysis by other analytic techniques should be always established in the early stages of the project implementation and confirmed, if changes in the nature of soil samples have been observed. 

Species distribution studies have shown that trace element (e.g. metals) concentrations in soils and sediments vary with physical location (e.g. depth below bed surface) and with particle size. In these speciation studies the total element content of each fraction was determined using a suitable trace element procedure, for example, solid sample analysis by X-ray emission spectroscopy or neutron activation analysis, or alternatively by dissolution of sample and analysis by ICPOES, AAS or ASV. The type of sample fraction analysed can vary, and a few... 

Method Blank. A method blank is carried through all the steps of sample preparation and analysis as if it were an actual sample. This is most important from the sample preparation prospective. The same solvents/reagents that are used with the actual samples are used here. For example, in the analysis of metals in soil, a clean soil sample may serve as a method blank. It is put through the extraction, concentration, and analysis steps encountered by the real samples. The method blank accounts for contamination that may occur during sample preparation and analysis. These could arise from the reagents, the glassware, or the laboratory environment. 

The lead contents of 206 soil samples determined by AAS indicated that such determination provides a useful parameter for soil comparison and discrimination in forensic science (Chaperlin 1981). Soil investigations near a former smelter in Colorado revealed that historic use of arsenical pesticides has contributed significantly to anthropogenic background concentrations of arsenic on certain residential properties. A variety of forensic techniques including spatial analysis, arsenic speciation and calculation of metal ratios were successful in the separation of smelter impacts from pesticide impacts (Folkes, Kuehster, and Litle 2001). 

The other popular sequential extraction procedure is the protocol proposed by the Community Bureau of Reference, Commission of the European Community (known as the BCR protocol). The method was proposed on the basis of interlaboratory smdies undertaken in order to harmonize conditions for soil and sediment sample analysis. Based on the research data, in 1992 it was stated that application of EDTA or acetic acid solution is appropriate and sufficient for elimination of the bioaccessible fi action of metals from soil samples [62]. In the case of other samples, best results were achieved after application of a three-stage procedure with the following extractants ... 

Reductive co-precipitation of noble metals with a suitable collector (Te, Se, As, Hg, and Cu) may provide uncertainty when examining complex environmental samples as a result of difficulties with complete separation of high amounts of common metals, which can partially pass into the precipitate, and possible loss of PGMs. Recovery of Pt from soil samples was reported to be 55-87 % after its separation by co-precipitation with Te [88]. Long analysis time is a disadvantage of such a procedure. 

The Qixiashan lead-zinc deposit is a hydrothermal lead-zinc mineralisation in a cataclastic fault zone in limestone. The ore body is 300 m below surface, and the overburden comprises 30 m of Quaternary alluvium. Soil samples were collected along a traverse over the mineralisation in three successive years and analysed for CO2 (Fig. 4-4). The samples from Year 1 yielded the highest CO2 concentrations and broadest anomaly, but contrast is poor. In Year 2 the anomaly is about 200 ppm CO2 and is best developed around a fault that cuts the mineralisation at depth. Anomaly contrast is put at 4.2. Samples were taken from a depth of 80 cm in Year 3, compared to 30 cm in earlier years the resulting CO2 pattern, however, is closely similar to that found in Year 2. Analysis of bore hole samples for CO2, Hg, Pb, Zn, Cu and Ag showed that the Qixiashan deposit is vertically and horizontally zoned (Fig. 4-5). The highest CO2 concentrations are found close to the richest ore. The CO2 halo extends upward on the hangingwall side of the deposit and spreads laterally. This halo is much better developed above the mineralisation than those of the base and precious metals only the Hg halo extends as far upward, and it is also rather wider. 

Langenkamp, H., and Marmo, L. (eds.) (2001). Workshop on Harmonisation of Sampling and Analysis Methods for Heavy Metals, Organic Pollutants and Pathogens in Soil and Sludge Summary and Conclusions, Feb. 8-9, 2001, Stresa, Italy, European Commission. EUR 198909 EN. 

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