National Engineering Laboratory for Lake Pollution Control and Ecological Restoration, Chinese Research Academy of Environmental Sciences, Beijing100012, China.
National Engineering Laboratory for Lake Pollution Control and Ecological Restoration, Chinese Research Academy of Environmental Sciences, Beijing100012, China.
J Environ Sci (China). 2020 Nov;97:169-179. doi: 10.1016/j.jes.2020.04.036. Epub 2020 Jun 3.
Total contents of metals in soil and sediments on the Tibetan Plateau of China have been widely analyzed, but existing information is insufficient to effectively evaluate metal ecological risk because of a lack of metal bioavailability data. In this study, distribution, potential risk, mobility and bioavailability of metals in sediments of Lake Yamdrok Basin in Tibet of China were explored by combined use of total digestion, sequential extraction and the diffusive gradient in thin-films (DGT). Average concentrations of Cr, Ni, Cu, Zn, As, Cd and Pb in surface sediments were 31.25, 30.31, 22.00, 45.04, 31.32, 0.13 and 13.39 mg/kg, respectively. Higher levels of metals were found near the inflowing rivers. Residual form was dominant in Cr, Ni, Zn, Cd and Pb, and reducible form was dominant in As and Cd. Metals in surface sediments showed a low enrichment degree overall, but Cd and As had higher ecological risk levels than the other metals. Furthermore, there was a larger average proportion of exchangeable form of As (20.4%) and Cd (9.0%) than the other metals (1.7%-3.3%), implying their higher mobility and release risk. Average DGT-labile concentrations of Cr, Ni, Cu, Zn, As, Cd and Pb were 0.5, 4.5, 0.7, 25.1, 60.0, 0.22 and 1.0 µg/L, respectively. The DGT-labile As was significantly correlated with extractable As forms (p< 0.01), suggesting that extractable As in sediments acts as a "mobile pool" for bioavailable As. These results suggest potential risks of As and Cd, especially As, deserve further attention in Lake Yamdrok Basin.
中国青藏高原的土壤和沉积物中的金属总量已被广泛分析，但由于缺乏金属生物有效性数据，现有的信息不足以有效评估金属的生态风险。本研究采用全消解、连续提取和扩散梯度薄膜（DGT）相结合的方法，探讨了西藏羊卓雍错流域沉积物中金属的分布、潜在风险、迁移性和生物可利用性。表层沉积物中 Cr、Ni、Cu、Zn、As、Cd 和 Pb 的平均浓度分别为 31.25、30.31、22.00、45.04、31.32、0.13 和 13.39mg/kg。在流入河流附近发现了更高水平的金属。Cr、Ni、Zn、Cd 和 Pb 以残渣态为主，As 和 Cd 以可还原态为主。总体而言，表层沉积物中的金属富集程度较低，但 Cd 和 As 的生态风险水平高于其他金属。此外，As（20.4%）和 Cd（9.0%）的可交换态平均比例大于其他金属（1.7%-3.3%），这意味着它们具有更高的迁移性和释放风险。Cr、Ni、Cu、Zn、As、Cd 和 Pb 的平均 DGT-可溶浓度分别为 0.5、4.5、0.7、25.1、60.0、0.22 和 1.0µg/L。DGT-可溶 As 与可提取 As 形态显著相关（p<0.01），表明沉积物中的可提取 As 是生物有效 As 的“移动库”。这些结果表明，羊卓雍错流域存在 As 和 Cd 的潜在风险，尤其是 As 值得进一步关注。
