Abstract
The Chinese project, better known as the Grain for Green Project (GGP), has changed the land-use type in the karst area of Puding county, Guizhou province, southwest China, and this study is aimed at evaluating the Hg distribution and determining factors in soils after the land-use change. A total of ten soil profiles were selected in the typical karst region, and the land-use types were divided into native vegetation land (NVL), farmland (FL), and abandoned farmland (AFL). Total Hg concentration under different land-use types increased in the order: NVL (average 63.26 μg∙kg−1) < FL (average 71.48 μg∙kg−1) < AFL (average 98.22 μg∙kg−1). After agricultural abandonment for four to five years with a cover of native vegetation in the AFL, a higher concentration of Hg compared to the other two land-use types indicate that the Hg accumulation in soil results from vegetation restoration of AFL due to land-use change. Soil organic carbon (SOC) and macro-aggregates were highly correlated to Hg concentration in this study. Macro-aggregates can provide a stable condition for Hg due to the thin regolith and high porosity in the karst region. A high proportion of macro-aggregates can reduce the mobility of Hg in the karst area. Intense tillage can significantly reduce the formation of macro-aggregates in FL, but the macro-aggregates in AFL were recovered as well as those in NVL, resulting in the accumulation of Hg.
Highlights
Mercury (Hg) has been identified as a bioaccumulative and toxic contaminant due to its global distribution [1,2] and neurotoxic properties [3]
Elemental mercury emitted by natural processes and anthropogenic activities tends to be transported long-distance through the atmosphere, causing widespread problems like Minamata disease and negative effects on the intelligence of newborns [7,8,9]
The study area is dominated by a sub-tropical monsoonal climate, and the annual average temperature is approximately 15.1 ◦ C, the annual average rainfall is approximately 1400 mm, and the rainy season is from May to October [36]
Summary
Mercury (Hg) has been identified as a bioaccumulative and toxic contaminant due to its global distribution [1,2] and neurotoxic properties [3]. Inorganic Hg has an adverse effect on the normal metabolism of cells [4], while organic Hg can destroy brain function and cause cardiovascular diseases [5]. Elemental mercury emitted by natural processes and anthropogenic activities tends to be transported long-distance through the atmosphere, causing widespread problems like Minamata disease and negative effects on the intelligence of newborns [7,8,9]. The persistence, high toxicity, and bioaccumulation of heavy metals in the soil have become more and more significant hazards and cause adverse effects on the quality of soil and human health [13,14,15,16]
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