Urban parks play an important role in the urban ecosystem and are also used by residents for recreation. The environmental quality of urban park soils might influence human health following long-term exposure. To assess potential sources and pollution risks of heavy metal(loid)s in the topsoil of urban parks, we subjected metal concentrations in soil samples from 121 parks in the Beijing urban area to geostatistical analyses, conditional inference tree (CIT) analyses, ecological risk and human health risk assessment. CIT effectively explained the influence of human activity on the spatial variation and accumulation of soil metal(loid)s and identified the contributions of natural and anthropogenic inputs. The main factors influencing the accumulation of heavy metal(loid)s, including urbanization duration, park age, per capita GDP, industrial output, and coal consumption, were evaluated by CIT. Except for Cr and Ni, the average concentrations of the metal(loid)s tested (Cu, Pb, Zn, Hg, As, and Cd) were higher than the background values. In the urban parks, Ni and Cr derived mostly from soil parent materials. Concentrations of Cu, Zn, Pb, Cd, As, and Hg were strongly associated with human influences, including industrial, agricultural, and traffic activity. After assessing health and ecological risks, we conclude that heavy metal(loid)s in the soil of Beijing urban parks pose no obvious health risk to humans, and the ecological risk is also low.

Apportioning sources of environmental pollutants is key to controlling pollution. In this study, the sources of heavy metals to 234 agricultural soils from the Jianghan Plain (JHP) (∼22454 km2) in central China were discriminated between using Cd and Pb isotope compositions and multivariate statistical analyses. Concentrations of some metals in JHP soils (0.48 ± 0.2, 48.2 ± 15.9, 0.12 ± 0.23, 48.8 ± 16.4, 36.5 ± 9.8, and 96.8 ± 42.2 mg kg−1 for Cd, Cu, Hg, Ni, Pb, and Zn, respectively) were higher than background concentrations in Chinese soil. The Cd isotope compositions for the JHP soils (δ114/110Cd values −0.76‰ to −0.25‰) were similar to Cd isotope compositions found for smelter dust and incinerator fly ash, indicating Cd was supplied to the JHP soils by ore smelting and/or refining processes. The Pb isotope compositions for the JHP soils (206Pb/207Pb 1.182–1.195 and 208Pb/206Pb 2.078–2.124) were between the Pb isotope compositions found for Chinese coal and natural sources, which a binary isotope mixing model indicated contributed 52% and 48%, respectively, of the Pb in JHP soils. Cluster analysis and positive matrix factorization indicated that the sources of heavy metals in JHP soils may consist of smelting and/or refining activities, coal combustion, agricultural activities, and natural sources (including Han River sediment and soil parent materials). The isotope fingerprints and multivariate statistical analyses together indicated that coal combustion and smelting and/or refining activities were the main anthropogenic sources of heavy metals polluting JHP soils.

Intensive human activities, in particular agricultural and industrial production have led to heavy metal accumulation in the peri-urban agricultural soils of China threatening soil environmental quality and agricultural product security. A combination of spatial analysis (SA), Pb isotope ratio analysis (IRA), input fluxes analysis (IFA), and positive matrix factorization (PMF) model was successfully used to assess the status and sources of heavy metals in typical peri-urban agricultural soils from a rapidly developing region of China. Mean concentrations of Cd, As, Hg, Pb, Cu, Zn and Cr in surface soils (0–20 cm) were 0.31, 11.2, 0.08, 35.6, 44.8, 119.0 and 97.0 mg kg−1, respectively, exceeding the local background levels except for Hg. Spatial distribution of heavy metals revealed that agricultural activities have significant influence on heavy metal accumulation in the surface soils. Isotope ratio analysis suggested that fertilization along with atmospheric deposition were the major sources of heavy metal accumulation in the soils. Based on the PMF model, the relative contribution rates of the heavy metals due to fertilizer application, atmospheric deposition, industrial emission, and soil parent materials were 30.8%, 33.0%, 25.4% and 10.8%, respectively, demonstrating that anthropogenic activities had significantly higher contribution than natural sources. This study provides a reliable and robust approach for heavy metals source apportionment in this particular peri-urban area with a clear potential for future application in other regions.