CONTENT AND FRACTIONATION OF HEAVY-METALS IN SOILS OF 2 CONTAMINATED SITES IN TAIWAN

The rice paddies near Taoyuan County, Taiwan, were contaminated with t race metals by the effluent from two plasticizer plants in the seventi es. 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 zin c = 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 e xtraction 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 qua lity by cadmium were assessed.