In order to clarify the total selenium (Se) content and species of Se in the soils of Dashan Region, a typical Se-enriched area in China, 69 soil samples with different land-use purposes were collected, and the concentrations of total Se, water-soluble Se, exchangeable Se, acid-soluble Se, organic-bound Se and residual Se and the physical and chemical properties of these soils were investigated. The total Se content ranged between 0.31 and 7.65 mg kg⁻¹ (dry weight). The concentrations of water-soluble, exchangeable, acid-soluble, organic-bound and residual forms of Se were 7.71–26.8 μg kg⁻¹, 24.7–93.3 μg kg⁻¹, 112–1430 μg kg⁻¹, 26–765 μg kg⁻¹ and 1300–5330 μg kg⁻¹, respectively. The concentrations of total Se were positively correlated with the contents of clay and soil organic matter, but were negatively correlated with pH values. The contents of bioavailable Se, which consists of water-soluble Se and exchangeable Se, were negatively correlated with the contents of soil organic matter, but positively correlated with pH values. The results suggest that pH value and the content of organic matter are key factors that regulate the bioavailability of Se in soils of Dashan Region.

Miscanthus sacchariflorus (Maxim.) Benth. is a metallophyte suitable for the phytoremediation of mine wastes. The tolerance and accumulation of M. sacchariflorus to cadmium was studied by pot experiments. The results showed that O₂·⁻ generation rate, plasma membrane permeability and MDA content of M. sacchariflorus leaves increased with increasing Cd concentrations in soil, but significant effect was only observed when Cd concentrations were ≥ 50 mg·kg⁻¹. SOD and POD activities increased initially but decreased later on, whereas CAT activity only increased significantly at higher Cd concentrations, 50–100 mg·kg⁻¹. The content of photosynthetic pigment and growth of M. sacchariflorus were both not significantly affected when Cd concentration was ≤ 25 mg·kg⁻¹. In contrast, both parameters were significantly affected when Cd concentration was ≥ 50 mg·kg⁻¹. M. sacchariflorus could accumulate much Cd, but most of the Cd assimilated was retained in the belowground part, suggesting that M. sacchariflorus has poor ability to translocate Cd to the aboveground part. Our results suggested that although M. sacchariflorus was not a hyper-accumulator, it has a strong capacity to tolerate and stabilize the Cd. Therefore, M. sacchariflorus has a certain potential in the phytostabilization of Cd-contaminated soils.