[Application of multiple lines of evidence analysis technology in the assessment of sites contaminated by heavy metals].

A multiple lines of evidence analysis technology was applied to assess whether sites were contaminated by heavy metals (HMs). Firstly, the baseline upper limit concentration for As and Cr6+ were derived for the two investigated sites based on the analysis of the relative cumulative probability plots of the two metals and their spatial distribution in the soil. The results indicated that the baseline upper limit concentrations for As and Cr6+ at site 1 were 29. 8 mg x kg(-1) and 76. 1 mg x kg(-1), respectively, which were much higher than those reported for the local area by others. But at site 2, the baseline upper limit concentrations for As and Cr6+ were 10.6 mg x kg(-1) and 33 mg x kg(-1), respectively, which were only a little higher than the reported values. Taken the derived baseline concentrations as the assessment criteria, both sites were contaminated by the heavy metals to some degree, which is consistent with the site historical activities review results and element correlation analysis results. At site 1, the As concentration in 3.8% samples exceeded the derived baseline concentration, while the Cr6+ concentration in 6.0% samples exceeded the baseline concentration. At site 2, only the concentration of As in 5.2% samples exceeded the derived baseline value. All the above exceeding rates were much lower than those based on the reported baseline values, which were 77.7% and 96.7% for As and Cr6+ at site 1, respectively and 41.9% for As at site 2. The difference indicates that for a specific site, the baseline concentrations for heavy metals reported in literatures should not be directly applied as the criteria to assess whether the site is contaminated or not, which may cause the results to lose the objectivity and leading to the misallocation of lots of rare resource to remediate soil that maybe not contaminated.