Spatial distribution and sources of trace elements in surface soils, Changchun, China: Insights from stochastic models and geostatistical analyses

- Distributions of trace elements all fit with binary mixture distribution.
- The cut-off values could be identified by finite mixture distribution models.
- Moderate Pb pollution and severe Hg pollution are found.
- The abilities of atmospheric diffusion of Pb and Hg are strong.
- Sources of trace elements are identified.

Trace elements As, Cd, Cu, Hg, and Pb in soils originate from both natural and anthropogenic sources, and intense anthropogenic activity can lead to excessive trace element levels, which are harmful to the environment. We investigated the trace elements in the topsoil of Changchun, China, using stochastic models and the indicator kriging method. The influence of anthropogenic and natural variables on the distribution of trace elements was evaluated, with the proportions of background and anthropogenic sources identified using stochastic models. High-risk maps were constructed using indicator kriging. The results showed that the anthropogenic variables significantly influenced the spatial variations of trace elements. The relative influence of natural variables differed for the different elements. The median values of background As, Cd, Cu, Hg, and Pb were 10.55 mg kg− 1, 0.114 mg kg− 1, 21.80 mg kg− 1, 0.036 mg kg− 1, and 25.88 mg kg− 1, respectively; while the threshold values were 12.90 mg kg− 1, 0.200 mg kg− 1, 29.40 mg kg− 1, 0.046 mg kg− 1, and 29.49 mg kg− 1, respectively. The relative contributions of background values to total values of As, Cd, and Cu were greater than 95%, while those for Pb were 91%. In contrast, Hg showed serious pollution, with less than 75% of the total Hg derived from background sources. The geographically extensive Hg pollution is likely influenced by emissions from coal-fired plants and boilers, while other trace elemental pollutants primarily originate from factory emissions. Furthermore, the atmospheric diffusion of Pb and Hg is significant, resulting in their migration to agricultural areas.