The analysis of soil-metal concentrations and selection of extraction methods
Comparative analysis of soil-metal concentration data is often limited by inherent differences in extraction techniques, because the extent of soil-metal dissolution is controlled significantly by the selected extraction schemes. In this work, to study complicated aspects of extraction methods, the soil-metal concentrations were determined on a set of soil samples using two different techniques: the Korean Standard Method (KSM) and the US EPA 3050A Method (UEM). The former method involves dissolution of metals via treatment of weak acid (0.1 M HCl), while the latter consists of strong acid digestion to extract the dominant portion of soil-bound metals. These two contrasting methods were applied to the soil samples selected to represent diverse environmental settings. The results of our analyses indicated that the absolute concentrations were substantially different between the two methods. Whereas most metals (including Pb, Mn, Cu, Zn, Co, Cd, Ni) exhibited UEM/KSM ratios in the range 3.4-9.3, Cr and Fe showed the extremely high ratios of 20 and 83, respectively. When these metal concentration data were compared with respect to the geographical characteristics, large differences were apparent. The metals analyzed by the KSM generally showed a pattern in which concentration change occurred in a predictable manner. However, for those of the UEM, the maximum concentrations were most frequently seen from the clean grassland site which we expected to be the least contaminated. According to this study, it appears that KSM can be used to distinguish different type of pollution processes. By contrast, interpretation of UEM data may require more caution, as the method itself is more suitable for diagnosing large-scale pollution sources.
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Document Type: Research Article
Publication date: March 1, 2000