The Mercury Behavior and Contamination in Soil Profiles in Mun River Basin, Northeast Thailand

To determine the geochemical characteristics and contamination of soil mercury in the Mun River basin, northeast Thailand, the vertical mercury distribution patterns and mercury contamination levels in six soil profiles under different land uses are studied. A total of 240 soil samples collected from agricultural land, abandoned agricultural land, and woodland were analyzed by an RA-915M mercury analyzer to determine the total mercury (THg) content, which ranged from 0.13 to 69.40 μg∙kg(−1) in the study area. In the soil cultivation layer (0–30 cm), the average content of THg in the woodland (15.89 μg∙kg(−1)) and the agricultural land (13.48 μg∙kg(−1)) were higher than that in the abandoned agricultural land (4.08 μg∙kg(−1)), indicating that the plants or crops could increase the content of mercury in the surface soil layer. The total organic carbon (TOC) and iron content with high positive correlations with the THg content significantly contributed to the adsorption of soil mercury. Moreover, a higher pH value in the soil and a finer grain size in soil texture can be beneficial for the enrichment of mercury. A geoaccumulation index was used to evaluate the contamination of mercury, showing that this area had a slight contamination, and a few soil sites were moderate contamination.