Characteristics, Source Apportionment, and Ecological and Human Health Risk Assessment of Heavy Metals in Cultivated Soils from the Jiamusi Section of the Lower Songhua River

The Jiamusi section of the lower Songhua River is an important commodity grain production area in China, and the environmental quality of its cultivated soils is directly linked to regional food security and ecosystem stability. To clarify the status of heavy metal pollution in soils in this area, identify pollution sources, and assess potential risks, this study established sampling units in typical cultivated land in the Jiamusi section in 2023, collected 276 topsoil samples (0-20 cm), and determined the contents of eight heavy metals, namely As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, as well as physicochemical indicators such as soil pH. Correlation analysis and principal component analysis were used to identify heavy metal sources; the single-factor pollution index method, Nemerow comprehensive pollution index method, and geo-accumulation index method were used to evaluate pollution levels; and a human health risk assessment model was used to assess carcinogenic and non-carcinogenic risks for adults and children. The results showed that the average soil pH in the study area was 6.51. The average concentrations of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were 10.38, 0.23, 53.77, 22.83, 0.09, 21.63, 29.17, and 83.89 mg/kg, respectively, all of which are below the soil background values of the region. Compared with the soil pollution risk screening values for agricultural land, Cd exceedance was the most prominent, with 63 sampling sites exceeding the standard. As, Cr, Cu, Pb, and Zn each had 1-6 sites exceeding the standard, while Hg and Ni had no exceedance sites. Correlation and principal component analyses showed that soil heavy metals mainly originated from natural parent materials (Cr, Ni), industrial activities (Zn, Cu), traffic activities (Pb, Cd), and a composite source associated with other anthropogenic activities (Hg). Pollution assessment results indicated that the soils in the study area generally ranged from unpolluted to mildly polluted: 72.82% of the sampling sites were unpolluted, 11.23% were at the warning level, 11.59% were slightly polluted, and 4.34% were moderately to heavily polluted. Health risk assessment showed that oral ingestion was the main pathway of heavy metal exposure, and the non-carcinogenic risk to children (mean HI 0.87, 19.93% of sampling sites with HI>1) was higher than that to adults (mean HI 0.15). The carcinogenic risk indices at all sampling sites were less than 10‒4, within the acceptable range. These results provide a scientific basis for the prevention and control of heavy metal pollution in cultivated soils, green agricultural development, and ecological and environmental protection in the Jiamusi section of the lower Songhua River.