Source and health risk assessment of heavy metals in farmland soil of Tianjin City

To reveal the heavy metal risks in the soil of vegetable and grain planting areas around the city, and to address the current lack of research on human health risks caused by hand mouth intake, respiratory pathways, and skin contact exposure pathways, as well as to estimate the health risks of adults and children from different sources, the surface soil of farmland in Xiqing District, Tianjin City was taken as the research object, and the concentrations of 8 heavy metals including Cr, Cu, Ni, Pb, Zn, As, Hg, and Cd were analyzed. Principal component analysis (PCA), positive definite matrix factorization (PMF), and health risk assessment model (PMF-HRA) were used to evaluate the degree, sources, and health risks of soil heavy metal pollution, and to identify the main heavy metal pollutants and their exposure pathways. The results show that Cd and Hg pollution is the most severe among the 8 heavy metals in agricultural soil in Tianjin City, with the average exceeding the background values by 151.9% and 324.1%, respectively. About 15% of the points are at moderate to severe pollution levels. The main sources of heavy metal pollution in the soil of the research area include natural soil formation processes, agricultural production, transportation, coal burning, and pesticide use. Cd (pesticide sources) and Hg (coal-fired sources) are important elements of soil pollution in agricultural land in the study area. There is no significant non-carcinogenic health risk in three exposure pathways: ingestion of crops, hand and mouth ingestion, and skin contact. The total carcinogenic risk index (TCR) of natural sources is the highest, with Cr being the main contributor to childhood total non-carcinogenic risk indices (HI) and childhood TCR in the source contribution; Hg contributes the most to HI in coal-fired sources, while Cu and Zn contribute to HI from mixed sources of pesticides and transportation. The contributions of the above heavy metal elements are closely related to the industrial, agricultural, and transportation activities of surrounding residents, and should be taken seriously.