Key Laboratory of Karst Dynamics, MNR&GZAR, Institute of Karst Geology, CAGS, Guilin 541004, China.
The Second Engineering Investigation Institute of Guizhou Bureau of Geology and Mineral Exploration and Development, Zunyi 563000, China.
Int J Environ Res Public Health. 2021 Apr 10;18(8):3986. doi: 10.3390/ijerph18083986.
The bioavailability of heavy metals (HMs) in sediments is closely related to the security of the aquatic environment, but their impacts are poorly researched, particularly in karstic rivers. Therefore, Liujiang River Basin was taken as an example in this study. Seven HMs were analyzed to determine the bioavailability and speciations of HMs in sediments. Moreover, the impacts of environmental factors on HMs were identified. The obtained results suggested that HMs in the sediments are all within their permissible exposure limit (PEL), but Cd and Zn are significantly higher than the soil baseline. Most HMs were found to be in a residual fraction, while their exchangeable fraction was found to be in an extremely low ratio. HMs in bioavailable parts are significantly higher than in the exchangeable and carbonate-bound phases but lower than in the non-residual phase, which demonstrated that HM bioavailability is not confined to the exchangeable and carbonate-bound phases. The correlation coefficients commonly decreased with decreasing speciation ratios, which suggested that the overall bioavailability of metals should be determined by speciation ratios instead of speciations themselves. Noteworthily, most HMs in the residual form were found to be significantly correlated with their overall bioavailability, which highlighted the potential bioavailability of residual form. The non-correlations between pH, electrical conductivity (EC), total dissolved solids (TDS), and HM bioavailability suggested that HMs in the carbonate-bound phase are stable and unsusceptible to environmental variations, while the significant correlations between redox potential (Eh), turbidity, organic matter (OM), main grain size (Mz), and HM bioavailability suggested that HMs in the reducible and oxidizable forms are susceptible to environmental fluctuations. Therefore, the variation of HM bioavailability in karstic rivers is largely regulated by their reducible and oxidizable forms instead of their carbonate-bound form.
重金属（HMs）在沉积物中的生物可利用性与水环境保护的安全性密切相关，但对其的研究却很少，尤其是在喀斯特河流中。因此，本研究以柳江流域为例，分析了 7 种重金属，以确定沉积物中重金属的生物可利用性和形态。此外，还确定了环境因素对重金属的影响。结果表明，沉积物中的重金属均在其可接受的暴露限值（PEL）范围内，但 Cd 和 Zn 明显高于土壤基线。大部分重金属存在于残渣态，而其可交换态的比例极低。可利用部分的重金属明显高于可交换态和碳酸盐结合态，但低于非残渣态，这表明重金属的生物可利用性不仅限于可交换态和碳酸盐结合态。相关系数通常随形态比值的降低而降低，这表明金属的整体生物可利用性应由形态比值决定，而不是形态本身。值得注意的是，大部分残渣态重金属与整体生物可利用性呈显著相关，这突出了残渣态重金属的潜在生物可利用性。pH、电导率（EC）、总溶解固体（TDS）与重金属生物可利用性之间无相关性，表明碳酸盐结合态重金属稳定，不易受环境变化的影响；而氧化还原电位（Eh）、浊度、有机物（OM）、主要粒径（Mz）与重金属生物可利用性之间存在显著相关性，表明可还原态和可氧化态重金属易受环境波动的影响。因此，喀斯特河流中重金属生物可利用性的变化主要受其可还原态和可氧化态的调节，而不是碳酸盐结合态。
