The risk and phytotoxicity of metal(loid)s in the sediment, floodplain soil, and hygrophilous grasses along Le’an River

Abstract

The Dexing Copper Mine, the largest open cast copper mine in China, is located along the upper reaches of the Le’an River, which flows into Poyang Lake, the largest freshwater lake in China. The spatial distribution, potential risk, and phytotoxicity of Cu, Pb, Ni, Cr, and As were investigated in sediments, floodplain soils, and two native hygrophilous grasses of the river. The results showed that 25% of the sediments were strongly polluted with Cu and As and that 50% were moderately polluted. About 33% of the sediments were slightly polluted with Pb, and there was almost no Ni and Cr pollution. Cu and As accounted for 41% and 80%, respectively, of the single ecological risk ratio (Eᵣⁱ), and for 15% and 48%, respectively, of the potential ecological hazard (RI). The high ecological risks from Cu and As occurred in the upper to middle reaches of the river. Cu concentrations in floodplain soils were 210.8–655.5 mg/kg, and As concentrations were 17.1–73.2 mg/kg. High potential Cu phytotoxicity occurs in 100% of the soils, and high potential As phytotoxicity occurs in 85% of the soils. Native hygrophilous grasses Echinochloa Crusgalli (L.) has a high potential for Cu phytostabilization and phytoextraction of Pb and As, while Polygonum Criopolitanum has a high potential for the phytoextraction of Cu and As. Metal(loid)s still pose considerable environmental risks in the Le’an River. Native grasses seem to be tolerant to metal(loids) and suitable for the extraction of metal(loid) pollution from floodplain soils.