Multi-scale analysis of heavy metals sources in soils of Jiangsu Coast, Eastern China

Since the development of Jiangsu Coast was proposed as a national strategy by the Chinese Government in 2009, Jiangsu Coast has been experiencing rapid and intensive development in industry and tidal flat reclamation, which has inevitably led to the accumulation of heavy metals in its soils. A total of 239 samples (0-20 cm) were collected from topsoils of Jiangsu Coast, and their concentrations of Cd, Cr, Cu, Hg, Ni, Pb, and Zn were determined. Factorial kriging was applied to examine the scale-dependent correlations between heavy metals and to generate the spatial components at multiple scales, and multivariate stepwise regression was used to explore the relationships between the spatial multi-scale components of heavy metals and environmental factors. Linear model of co-regionalization (LMC) fitting indicated that the multi-scale variation comprised a nugget effect, an exponential structure with a range of 15 km (local scale), and a spherical structure with a range of 135 km (regional scale). The spatial correlations of seven heavy metals depended on their spatial scales, and their correlations increased with the increasing scales. Spatial variations in Cr and Ni were associated with natural geochemical sources on both local and regional scales. Parent material influenced the basic spatial variations in Cd, Cu, Pb and Zn on both local and regional scales, but human activity also contributed to the spatial variations in these four metals. The human inputs of Cd, Cu, Pb, and Zn differed on these two scales. Hg was dominated by industrial emissions and agricultural practices on both scales.