Abstract
Assessing heavy metal pollution and delineating pollution are the bases for evaluating pollution and determining a cost-effective remediation plan. Most existing studies are based on the spatial distribution of pollutants but ignore related uncertainty. In this study, eight heavy-metal concentrations (Cr, Pb, Cd, Hg, Zn, Cu, Ni, and Zn) were collected at 1040 sampling sites in a coastal industrial city in the Yangtze River Delta, China. The single pollution index (PI) and Nemerow integrated pollution index (NIPI) were calculated for every surface sample (0–20 cm) to assess the degree of heavy metal pollution. Ordinary kriging (OK) was used to map the spatial distribution of heavy metals content and NIPI. Then, we delineated composite heavy metal contamination based on the uncertainty produced by indicator kriging (IK). The results showed that mean values of all PIs and NIPIs were at safe levels. Heavy metals were most accumulated in the central portion of the study area. Based on IK, the spatial probability of composite heavy metal pollution was computed. The probability of composite contamination in the central core urban area was highest. A probability of 0.6 was found as the optimum probability threshold to delineate polluted areas from unpolluted areas for integrative heavy metal contamination. Results of pollution delineation based on uncertainty showed the proportion of false negative error areas was 6.34%, while the proportion of false positive error areas was 0.86%. The accuracy of the classification was 92.80%. This indicated the method we developed is a valuable tool for delineating heavy metal pollution.
Highlights
Anthropogenic activities, such as urbanization processes, change the inherent properties of affected soils, such as their pH, texture, cation exchange capacity, and bulk density, and inadvertently cause harmful substances, such as heavy metals, to deposit into the soils [1,2,3]
The mean concentrations of all heavy metals in the samples were less than the mean concentrations in the national secondary standard (CEPA, 1995) [47]
The spatial distribution of heavy metals was assessed by Ordinary kriging (OK)
Summary
Anthropogenic activities, such as urbanization processes, change the inherent properties of affected soils, such as their pH, texture, cation exchange capacity, and bulk density, and inadvertently cause harmful substances, such as heavy metals, to deposit into the soils [1,2,3]. Public Health 2018, 15, 710; doi:10.3390/ijerph15040710 www.mdpi.com/journal/ijerph
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