Vertical Distribution and Contamination of Soil Mercury in Karst Catchment, Southwest China: Land‐Use Type Influence

Abstract The policy‐driven “Grain for Green Programme” (GGP) has resulted in large‐scale land conversion from agricultural land to natural land in the karst area. One research surrounding the GGP is focused on evaluating its ecological implications for total mercury (THg) enrichment in Yinjiang County, Guizhou Province, Southwest China. Results show that 1) THg content in agricultural land (201.85 ± 57.23 µg kg −1 ) is lower compared to the forest (1048.62 ± 306.19 µg kg −1 ) and shrub (2582.60 ± 614.76 µg kg −1 ). 2) The THg content shows a good correlation with Fe (agricultural land: R = 0.75, p < 0.01; shrub: R = 0.88, p < 0.01), pH (shrub: R = 0.87, p < 0.01), and sand proportion (forest: R = −0.65, p < 0.01), rather than soil organic carbon (SOC). In the shrub, the increased pH and iron (Fe) content correspond to THg content between 1804 and 3743 µg kg −1 ; below the depth of 80 cm of the forest soil, the increased sand proportion correlates to THg content between 1223 and 748 µg kg −1 . 3) The risk index of the THg exceeds 320 in the soil and imposes a very high ecological risk to this area.