Vertical distribution characteristics of soil mercury and its formation mechanism in permafrost regions:A case study of the Qinghai-Tibetan Plateau

Continuing permafrost degradation is increasing the risk of mercury(Hg) exposure in the permafrost regions on the Qinghai-Tibetan Plateau(QTP),but related studies are still limited,especially the ones on the detailed Hg migration processes in permafrost.The vertical distribution characteristics of soil Hg were investigated in three ecosystems in the Beiluhe area on the QTP,and its influencing factors and formation mechanism were investigated.The results indicate that the total soil mercury(THg)concentration in the Beiluhe area remains at an extremely low level(6.33±2.45 ng/g).In the vertical profile,the THg concentration of the shallow soil layer(0-50 cm)(5.96±2.22 ng/g)is significantly lower than that of the deep layer(50-400 cm)(7.44±2.71 ng/g)(p<0.05).Within the upper 50 cm,the THg concentration decreases with soil depth,and the peak THg concentration occurs at 100-300 cm on the entire profile.Although the THg concentration is slightly affected by the organic matter in the shallow soil layer,in general,the soil parent material is the dominant factor affecting the THg concentration.Intense weathering results in a low THg concentration in the shallow soil layer because the soil Hg is carried downward with the soil moisture.To a certain depth,the impermeable frozen soil layer intercepts the flow of the soil Hg,and it forms a Hg enrichment layer.This paper presents the distinctive pattern of the soil Hg distribution in the permafrost regions of the QTP.

Mercury transportation in soil via using gypsum from flue gas desulfurization unit in coal-fired power plant

The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization （FGD） units of coal- fired power plants. Studies have been carried out in confined greenhouses using FGD gypsum treated soils. Major research focus is uptakes of mercury by plants, and emission of mercury into the atmosphere under varying application rates of FGD gypsum, simulating rainfall irrigations, soils, and plants types. Higher FGD gypsum application rates generally led to higher mercury concentrations in the soils, the increased mercury emissions into the atmosphere, and the increased mercury contents in plants （especially in roots and leaves）. Soil properties and plant species can play important roles in mercury transports. Some plants, such as tall fescue, were able to prevent mercury from atmospheric emission and infiltration in the soil. Mercury concentration in the stem of plants was found to be increased and then leveled off upon increasing FGD gypsum application. However, mercury in roots and leaves was generally increased upon increasing FGD gypsum application rates. Some mercury was likely absorbed by leaves of plants from emitted mercury in the atmosphere.

Remediation effect of compost on soluble mercury transfer in a crop of Phaseolus vulgaris

We studied the dynamics of mercury（Hg） transfer in Phaseolus vulgaris plants grown in soil with Hg-doped compost at the maximum levels permitted by Colombian law on organic amendments. Quantitative evaluation of transfer was made in different plant organs： roots,stem, leaves, pods and seeds. Matrix effect was determined in doped soil assays, using soil with and without addition of compost. Results showed that the use of organic matter reduced Hg transfer to the plant and the amount transferred was differentially distributed to the organs. We observed an inverse relationship between concentration and distance from the body to the root. It was evident that transfer was mediated by quantitative factors;the greater the presence of mercury in soil, the larger the amount that will be transferred.Results also indicate the remedial effect of compost and the presence of a barrier, at the root level, against mercury translocation to the plant aerial parts.