Source apportionment, criteria derivation, and health risk assessment of heavy metals in urban green space soils

Urban green spaces play a crucial role in maintaining urban resilience and offering opportunities for outdoor activities to residents. The potential hazards of heavy metals in the soils of these green spaces have raised significant concerns. A total of 130 topsoil samples containing seven heavy metals were collected from 50 urban green spaces in Tianjin, China. The study aimed to identify and quantify the potential sources of these heavy metals, establish general assessment criteria (GAC) for the metals, and evaluate the associated human health risks based on their concentration and sources. The findings indicated minimal pollution from heavy metals in the soils of Tianjin's urban green spaces. Through the use of positive matrix factorization (PMF), correlation analysis, and spatial interpolation, the study identified four main sources of heavy metals: traffic emissions, natural sources, industrial activities, and agricultural activities. Discrepancies between the contaminated land exposure assessment (CLEA) model-derived GAC and China's soil screening values were attributed to differences in land use scenarios. Moreover, concentration-specific health risk assessments revealed that protection area green spaces posed a higher risk to human health compared to park green spaces. The study also highlighted that natural factors correlated with cobalt and agricultural activities related to arsenic significantly contributed to non-carcinogenic risks in both adults and children. Arsenic-related agricultural activities were identified as key contributors to carcinogenic risks in children. The findings of this study are valuable for establishing soil quality standards, and provide a reference for the prevention and control of heavy metal pollution in urban greenfield soils as well as for the protection of the health of urban populations.