Mercury speciation, distribution, and bioaccumulation in a river catchment impacted by compact fluorescent lamp manufactures

Mercury uptake by Paspalum distichum L. in relation to the mercury distribution pattern in rhizosphere soil

Paspalum distichum L. was tested to evaluate their phytoremediation capacity for Hg contaminated soil through analyzing the dissipation of Hg in soil through a greenhouse study by using self-made rhizos box. Original soil samples were collected at Hg mining site with serious Hg contamination and a control site, respectively. Planting of P. distichum. L last for 60 days. Soil and plant samples were collected from four periods (0 d, 20 d, 40 d, and 60 d) and soil samples were collected from five different rhizosphere distance in horizontal direction (0-2 cm, 2-4cm, 4-6cm, 6-8cm, 8-10cm). The results showed that the presence of P. distichum. L significantly accelerated the Hg dissipation in soil compared with control. Hg concentration in the rhizospheric soil was affected by the plant growth period and the distance to the plant roots. The closer of soil to the root of P. distichum. L, the lower mercury concentration in soil. During the 60-day growing period, the concentrations of total Hg (THg) and methylmercury (MeHg) reduced by 45% and 64%, respectively, in the rhizosphere (0-2cm) of Hg contaminated soil. However, MeHg concentration was increased near the roots (0-4 cm) during the initial growing period (0-20 d), which may be attributed to the influence of root exudates. Root is the major part for Hg accumulation in P. distichum. L. The low ratio between Hg concentrations in underground and aboveground tissues indicated that it seemed difficult for Hg translocation from root to shoot. The highest THg (9.71 ± 3.09 μg·g^-1) and MeHg (26.97 ± 0.98 ng·g^-1) value in root of P. distichum. L were observed at the 20^th day when P. distichum. L grown in Hg contaminated soil. The results of chemical fractions analyses showed that elemental Hg and residual Hg were the two major speciations followed by organic bound Hg in the Hg contaminated soil, which indicated the high bioavailability and ecological potential risk of Hg in Hg contaminated soil.

Contamination Features and Source Apportionment of Heavy Metals in the River Sediments around a Lead-Zinc Mine: A Case Study in Danzhai, Guizhou, China

The spatial patterns, ecological risks, and sources of heavy metals (HMs), including Pb, Zn, Mn, Cu, Cd, Hg, and As in river sediments, were identified around a lead-zinc mine of Danzhai, Guizhou, China. The concentrations of selected HMs and their coefficient variations indicated that the river sediments around this typical lead-zinc mine were obviously contaminated with HMs. Anthropogenic activities had further enhanced the accumulation of HMs. The higher contents of the most common selected HMs were mainly distributed in the area close to the lead-zinc mine. Based on the combined evaluations of the single factor pollution index, geo-accumulation index, and potential ecological risk index, it indicated that the ecological risks of Hg, Cd, Zn, and Pb were high or extremely high, and of Mn, Cu, and As were slight or none in the sediments around this lead-zinc mine. It was found that lead-zinc mining and smelting activities, coal mining activities, and agricultural activities (livestock and poultry breeding) are the primary sources of selected HMs, based on the results of correlation analysis together with principal component analysis (PCA) and positive matrix factorization (PMF) model. The pollution of HMs in the river sediments around a lead-zinc mine was predominantly caused by lead-zinc mining and smelting activities. Therefore, for environmental persistence, lead-zinc mining and smelting activities should be given careful consideration and under close surveillance.

Responses of the grass Paspalum distichum L. to Hg stress: A proteomic study

Paspalum distichum L. was tested to evaluate its ability to phytoremediate mercury (Hg) contaminated soil over a 60-d period by analysis of the total Hg concentrations in roots and leaves. Hg concentration in Hg-contamination soil decreased by 70.0 μg g^-1 after 60 day of grass cultivation and Hg was readily taken up by the roots (4.51 ± 1.90 μg g^-1) rather than the leaves (0.35 ± 0.02 μg g^-1). In addition, a comparative proteomic study was performed to unravel the protein expression involved in the Hg stress response in P. distichum L. A total of 49 proteins were classified as differentially proteins in the roots by the 'top three' proteomic analysis, of which 32 were up-regulated and 17 down-regulated in response to Hg stress. These changed proteins were classified by gene ontology analysis into five complex molecular functions involving photosynthesis and energy metabolism (31%), oxidative stress (14%), protein folding (16%), sulfur compound metabolism (10%), metal binding, and ion transport (29%). Moreover, the protein expression patterns were consistent with the metabolism pathway results. Overall, the results contribute to our understanding of the molecular mechanisms of the Hg response in P. distichum and we propose a theoretical basis for the phytoremediation of Hg-contaminated soils.

Soil Mercury Accumulation and Emissions in a Bamboo Forest in a Compact Fluorescent Lamp Manufacturing Area

The role of bamboo forest in soil Hg accumulation and emissions was evaluated by analyzing Hg concentration in soil and plant samples as well as Hg flux between soil and air. THg concentrations in soil samples ranged widely from 28.5 to 860 ng g^-1 with a mean value of 153 ± 17.3 ng g^-1. Methylmercury concentrations in soil samples from forest soil (FS, 0.94 ± 0.20 ng g^-1) were significantly higher (p < 0.05) than from bare soil (BS, 0.54 ± 0.07 ng g^-1). The mean foliar THg concentration (178 ± 16.8 ng g^-1) was significantly higher (p < 0.05) than those in branches (63.1 ± 7.27 ng g^-1) and roots (73.1 ± 16.9 ng g^-1), indicating that the major source of Hg in bamboo might be from air deposition. Hg flux from FS (25.6 ng m^-2 h^-1) was significantly lower (p < 0.05) than that from BS (32.2 ng m^-2 h^-1). The annual decline in Hg emissions due to the presence of the bamboo forest may reach 6.94 kg.