Content and fractionation of heavy metals in soils of two contaminated sites in Taiwan

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Abstract
The rice paddies near Taoyuan County, Taiwan, were contaminated with trace metals by the effluent from two plasticizer plants in the seventies. A study was conducted to: (i) determine the total metal contents, (ii) compare the extraction strength of different solutions, and (iii) investigate the metal speciation. Total soil metals at site 1 ranged from: lead = 201 to 1955 mg Kg−1; cadmium = 18 to 205 mg Kg−1; and zinc = 131 to 282 mg Kg−1. Total soil metals at site 2 ranged from: lead = 80 to 148 mg Kg−1; cadmium = 8 to 82 mg Kg−1; and zinc = 55 to 65 mg Kg−1. Five different extractants (4 N HNO3, aqua regia, 0.1 N HCl, 0.002 M EDTA, and 0.002 M NTA) were utilized and compared. Sequential extraction was conducted to assess the metal speciation in soil systems. Lead was found to be predominantly organic‐bound or oxide‐bound. The exchangeable fraction was the dominant form of cadmium in both sites. Zinc was mostly oxide‐bound. The potential impacts on groundwater quality by cadmium were assessed.