Historical soil samples

Carbon turnover in production fields can be determined, using non-isotopic techniques, by combining historical soil samples, current soil samples, and whole field yield monitor data. Sensitivity analysis of such data shows that the amount of above-ground biomass that could be harvested decreases with root to shoot ratio (Table 8.1). For example, if root biomass is ignored, analysis suggests that only 20-30% of the above-ground biomass can be harvested, whereas if the root to shoot ratio is 1.0, then between 40% and 70% of the residue could be harvested. 

Information about the soil in its natural state is thus an essential part of any soil sampling. This information may be available from previous soil analysis, that is, before contamination took place. This type of information is commonly available from the state s land grant university and the areas soil survey. Another option would be to obtain historical soil samples. Historical soil samples are samples of the soil taken before contamination has occurred and thus can be used to ascertain the natural levels of components of interest in that soil. These contain information that may not be readily available otherwise. Caution must be used because storage of soil samples can change analyte composition including the most prominent species present (see Table 7.1 and Reference 2). 

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). 

Rost, H., Loibner, A.P., Hasinger, M., Braun, R. Szolar, O.H.J. (2002) Behaviour of PAHs during cold storage of historically contaminated soil samples. Chemosphere, 49(10), 1239-1246. 

Sediment samples are used to study the historical phthalate contamination and for the determination of local contamination and biodegradation. Concentration levels of phthalates largely depend on the sampling site. The average concentrations are of the same order of magnitude as the soil samples (see Table 28.1 OB). 

The notable human tolerance toward dioxin probably lias its roots in histoiy. Dioxin was found in 8000-year old sediments in Japan and dioxin levels of 30 ppt were detected in 170-year old soil samples from Rothamsted, England (90 ppt was the measured level in 1995). Industrial development obviously increased the amounts of dioxin, but its origin in the early or pre-historical samples is a much more interesting question. In 1977, evidence was found that dioxins are formed regularly in combustion processes. Wood contains about 0.2% of chlorine in the form of chloride salts, some of which is transformed into dioxins during burning. About 5 billion t of wood are burnt annually on Earth, which may form about 551 of dioxin. The human body has learnt to tolerate dioxins in small amoimts. 

The country-wide dataset of stream sediment analyses in Austria consists of 36,136 samples analyzed for 34 chemical elements (Fig. 1), (Thalmann et al. 1989). Complemented by local surveys of hydrochemistry, whole rock geochemistry, soil chemistry and mineralogical phase analyses, these data are used to derive natural background levels of different rock units, investigate chemical fluxes between soil, rock and groundwater, and evaluate the emission risks of historical mine waste. 

Dibromoethane has been widely released to the environment mainly as a result of the historical use of the compound as a gasoline additive and a fumigant (Fishbein 1979). The compound has also been released from industrial processing facilities. For example, 1,2-dibromoethane was found in air, water, soil, and sediment samples taken near industrial bromine facilities in El Dorado and Magnolia, Arkansas, in 1977 (Pellizzari et al. 1978). 

Because historical data for the soil is not available, to estimate the number of samples for the stockpile characterization, we collect four preliminary samples and analyze them for lead. The concentrations are 120, 60, 200, and 180 mg/kg, with the average concentration of 140 mg/kg and the standard deviation of 63 mg/kg. We use Equation 11, Appendix 1, for the calculation of the estimated number of samples. Using a one-tailed confidence interval and a probability of 0.05, we determine the Student s t value of 2.353 for 3 degrees of freedom (the number of collected samples less one) from Table 1, Appendix 1. 

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