Polluted soils characterisation

The extraction step can be made either in aqueous or organic medium. Before extraction, the soil sample is pretreated (drying, grinding and sieving) according to the first steps of the classical procedure [3]. The solid/liquid ratio used for the extraction is 1 g soil/10 mL solvent. 

Two PAH-contaminated soils of different origins have been studied. Soil A (sandy soil) comes from an ancient coking plant, and soil B (clay soil), from a rather recent creosote production site. Spectra have been acquired after mechanical agitation with deionised water for 1 and 24 h (Fig. 9). Direct examination of aqueous sample spectra leads to the following observations 

UV-visible spectrophotometry enables giving indications about the pollution maturation level in contaminated soils. Stabilised leachates from old contaminated soils are characterised by a monotonous decreasing spectrum (soil A), while younger ones show a specific spectrum where additional compounds are responsible for visible accidents (soil B). 

In order to avoid huge interferences from the matrix (humic-like substances), extraction by sonication using acetonitrile has been tested on the two previous contaminated soils. After 1 h of sonication, UV spectra of the supernatant have been acquired (Fig. 10). 

From a qualitative point of view, direct examination of UV spectra shows approximately the same shape for the two soils, with many visible accidents due to the presence of specific compounds such as PAHs. Moreover, because of the dilution factor, it can be assumed that acetonitrile extraction is more efficient than water extraction, especially for nonpolar compounds such as PAHs. As expected, the two specific peaks located at 254 and 288 nm can be noticed on the two UV spectra. 

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Thermoanalysis methods such as pyrolysis-gas chromatography-mass spectrometry [GC-MS] and thermogravimetry mass spectrometry have been used to characterise hydrocarbon sludges from petrochemical plants and polluted soils [26,27]. In combination with conventional extraction and supercritical fluid extraction followed by [ GC-MS ], over 100 constituents were identified in samples. White et al. [28] also applied pyrolysis-[GC-MS] to the determination of hydrocarbons and showed that the analysis can be complicated by the presence of natural organic matter. White [28] inferred the presence of biogenic compounds in Alaskan soil. 

Enzyme induction and/or isoenzyme variation have been used to characterise widely different phenomena. These enzymatic parameters were shown to be useful criteria for monitoring air pollution (Keller, 1974 Fliickiger et al., 1978 Rabe and Kreeb, 1979), for ecogenetic characterisation of plant populations (Verkleij et al, 1980 Triest, 1991), for the study of callus tissue differentiation (Coppens and Gillis, 1987) and plant development and differentiation (Scandalios, 1974). The evaluation of phytotoxicity of metal-polluted soils and other substrates can also be realised by enzymatic parameters. 

Leachates are produced by percolation of rain water through a solid matrix, such as solid wastes from urban or industrial landfills, or polluted soils, for example (Fig. 1). Leachates are highly polluted solutions (or suspensions) characterised by a high salinity and organic content. Consequently, they are rather complex to study or analyse, as huge interferences may occur and affect results. 

In another AT study, Terrado et al. [15] characterised pollution patterns in different parts of the Ebro catchment. In the upper part of the Ebro, pollution was found to be mainly in the form of heavy metals (Zn, Cu, Cr, Pb, Cd and Hg), polycyclic aromatic hydrocarbons (PAHs), hexachlorocyclohexanes (HCHs) and trichlorobenzenes (TCBs). Etrophic conditions were also found. Pollution was found to source mainly from industry and urbanisation. The central Ebro was characterised by nutrient pollution such as the accumulation of Ca, Na, Mg and K, which highlighted the importance of salinisation effects from intensive irrigation and soils with high salt content. In the lower Ebro, organic [DDTs, hexachlorobenzene (HCB) and hexachlorobutadiene (HCBu)] and heavy metal (Hg, Cd, Zn and As) contamination was found to derive mainly from industrial and agricultural activities. 

In conclusion, PAH and soil evolution indexes are simple and rapid tools for the characterisation of PAH-contaminated soils in terms of level and repartition of pollution and for the prediction of their potential biotreatability. From an environmental point of view, they permit pointing out sensitive zones and defining priorities in terms of decontamination. 

Characterisation of exposure. This process intends to estimate how much of a harmful chemical substance is for how long in contact with a specified organism. Exposure characterisation is usually a complex process that should consider physico-chemical properties of pollutants and the site (e.g. to estimate influencing factors such as the availability of contaminants), as well as naturally occurring pollutant degradation. For contaminated soils, exposure is usually estimated with measurement of toxicant concentrations by chemical analysis... 

Avidano L., Elisa G., Paolo C. G., Elisabetta C., Characterisation of soil health in an Italian polluted site by using microorganisms as bioindicators, Appl. Soil Ecol., 30, 21-33, 2005. 

The proposed procedure is a compact, yet mathematically simple and comprehensive approach to a risk-based assessment of soil and groundwater pollution by hazardous substances found at anthropogenic sites of urban and industrial environments. It is important to note that this procedure requires a thorough and spatially highly resolved field site characterisation to exhaustively describe the pedofacies representative for a particular site. 

Alliksaar, T. J.-M. Punning, 1998. The spatial distribution of characterised fly-ash particles and trace metals in lake sediments and catchment mosses Estonia. Wat. Air. Soil Pollut. 106 219-239. 

Watt, J., 1998. Automated characterisation of individual carbonaceous fly-ash particles by computer controlled scanning electron microscopy Analytical methods and critical review of alternative techniques. Wat. Air Soil Pollut. 106 309-327. 

Data about the imperviousness of a faultless liner system under defined boundary conditions for as large a number of pollutants and soil materials as possible form an important component of the characterisation of the efficacy of this liner for instance in comparison to equivalent alternative liner systems. Therefore, in the following, a parameterization will be discussed for the permeation rate (or the permeability) and the induction time for diffusive mass transport in the composite liner consisting of a geomembrane and a compacted clay liner (or more generally a porous mineral material). Quantities, which refer to the geomembranes, will be denoted with index 1, such as thickness d and diffusion coefficient D, and quantities referring to the mineral liner will have index 2 such as thickness d2 and effective diffusion coefficient D2. The porosity of the water-saturated mineral liner is denoted with 0 as above. 

It can be inferred that all discussed techniques calorimetry, temperature-programmed techniques, as well as TG, DSC, DTA and coupled techniques, have important place in the domain of environment science in characterisation of materials used for the abatement of pollutants in investigation of processes of pollutant removal or degradation and generally in monitoring the processes that include numerous environment pollutants. Having in mind the versatility of possible atmospheric, water or soil pollutants, we can estimate that these techniques will be further developed and adjusted for the applications in domain of environment protection. 

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