Abstract:
Guangze County is situated in the northern section of the Wuyi Mountains, a typical red soil distribution area within the hilly and mountainous regions south of the Yangtze River. This county has abundant natural resources, including mountains, rivers, forests, farmlands, lakes, and grasslands. Additionally, it serves as a major grain-producing county at the provincial level in Fujian Province. Agricultural activities affect the soil quality of agricultural land to varying degrees. To investigate the current status of heavy metal pollution in soils across different land use types in Guangze County, 75 soil samples were collected from five land use types within the county: vegetable field (SC), paddy field (SD), Chinese fir forestland (SM), secondary broad-leaved forestland (KY), and bamboo forestland (ZL). The contents of eight heavy metals — cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), chromium (Cr), nickel (Ni), mercury (Hg), and arsenic (As) — were analyzed. Pollution risks were assessed using several indexes: single-factor pollution index, Nemero comprehensive pollution index, geoaccumulation index, and potential ecological risk index. The results indicated that the average soil contents of Cd, Pb, Hg, and Zn across different land use types in Guangze County exceeded the background values of these elements in Fujian Province. Notably, high levels of Cd and Pb were observed, with 9% and 25% sampling points, respectively, exceeding the screening values set by the GB 15618—2018 (Soil Environmental Quality — Risk Control Standard for Soil Environment of Agriculture Land). The single-factor index (
Pi) of Pb in the soil was higher than those of the other heavy metals, and the geoaccumulation indexes (
Igeo) of Pb and Cd in the soil were relatively high, indicating an average pollution level ranging from none to moderate. The Cd content in the soil of the study area exhibited a significantly positive correlation with soil pH (
P<0.01), whereas the Pb content showed a significantly positive correlation with altitude (
P<0.01). The Cd contents in the soils of SC and SD was significantly higher than that in non-agricultural land types at the same latitude (
P<0.05), with 27% and 20% of the sampling points exceeding the screening values set by the GB 15618—2018 (Soil Environmental Quality — Risk Control Standard for Soil Environment of Agriculture Land). The potential ecological risk of heavy metals in the soil of SC and SD was classified as moderate risk, which was obviously higher than that for KY, SM, and ZL. No significant difference was found in the Pb content between agricultural and non-agricultural soils or in the
Pi or
Igeo values. However, different proportions of slight potential ecological risks were noted. Therefore, agricultural utilization is likely the primary source of Cd pollution in the soil of Guangze County. Targeted agricultural improvement measures, such as increasing soil pH and applying organic fertilizers, should be implemented for prevention and control. The sources of Pb pollution in soil may involve a combination of natural and agricultural origins.