Sequential fractionation and plant uptake of As, Cu, and Zn in a contaminated riparian wetland

Sediment serves as a sink for metals, thus it is critical to assess its contamination and associated risk. A typical riparian wetland close to a Zn-smelting operation in karst areas in southwest China was investigated. Sediment and reed plant (Phragmites australis) samples from wet and dry seasons were analyzed for total As, Cu, and Zn concentrations. Metal pollution in the sediment was assessed based on geo-accumulation index (Igeo). Further, metals in the sediment were fractionated into exchangeable, water and acid- soluble, reducible, oxidizable, and residual fractions based on the BCR sequential extraction. The results showed that the As, Cu, and Zn concentrations in the sediment were significantly higher than the background values (740-4081, 96-228, and 869-3331 vs. 10, 22, and 70 mg kg(-1)). With the I-geo being 10-17, the data indicate that the sediment was highly-polluted. While total As, Cu and Zn in the sediment increased from dry to wet season, their available concentrations decreased except Cu. With 62-94% of As, Cu, and Zn being in the residual fraction, metal availability in the sediment was low based on fractionation data. The data are consistent with low metal uptake by reed as their concentration ratios in plant roots to the sediment were 0.01-0.32. The results suggest that the riparian sediment was highly-polluted with As, Cu and Zn, but showing low metal availability and limited plant uptake. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study investigated a riparian wetland near a Zn-smelting operation in karst areas in southwest China, revealing high contamination levels in the sediment with low metal availability and limited plant uptake.