Fe, Rather Than Soil Organic Matter, as a Controlling Factor of Hg Distribution in Subsurface Forest Soil in an Iron Mining Area

Abstract

To identify whether the iron (Fe) mining area in the Jiulongjiang River basin (JRB) has an influence on the mercury in the forest soil, the spatial distribution patterns of mercury’s behavior on different controlling factors were analyzed, and a potential ecological risk assessment was done. A total of 107 soil samples were collected from two forest soil profiles, one profile near the Fe mining area and the other far from it. The soil near the mining area had a moderate potential ecological risk with high Fe content rich in the upper layer of soil (<70 cm), whereas soil collected far from the mining area had a low potential ecological risk. These results indicated that the rise of iron content in the soil near the mining area was beneficial to the enrichment of mercury, probably causing damage to the forest ecosystem. Both soil organic carbon (SOC) and Fe content have strong positive correlations with THg content, controlling the mercury behavior in the upper layer (<70 cm) and a lower layer (>70 cm) of soil, respectively. The high Fe content in the upper layer of soil will compete for the adsorption of mercury by SOC, leading to the poor correlation between SOC and THg.

Suspended Sediments Quality Assessment in a Coastal River: Identification of Potentially Toxic Elements

“…The lithology of the JRB is mainly composed of clastic sedimentary and magmatic rocks, with rarely distributed limestones and metamorphic rocks. Mining areas (e.g., Fe mine) are mainly distributed in the northwest basin [ 32 ]. The upper reaches are mainly covered by forest and mountain areas, while the lower reaches are affected by different human activities, such as agriculture and industry.…”