Yeongsan River Environment Research Center, National Institute of Environmental Research, Gwangju, 61011, Republic of Korea.
Yeongsan River Environment Research Center, National Institute of Environmental Research, Gwangju, 61011, Republic of Korea.
Environ Pollut. 2022 Aug 1;306:119403. doi: 10.1016/j.envpol.2022.119403. Epub 2022 May 6.
Lake sediments are important sinks of various pollutants and preserve historical pollution records caused by anthropogenic activities. Recently, the sediments of Lake Jangseong, South Korea were first detected with high concentrations of organic matter (ignition loss [IL]; total organic carbon [TOC]), nutrients (total nitrogen [TN]; total phosphorus [TP]), and some heavy metals (Zn, Cu, Cd, and Hg). Here, we identified the origins of these concentrations accumulated in the sediments using extensive surveys and various assessments. Sediment pollution assessed by sediment quality guidelines, pollution load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd. Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the high pollutant concentrations detected in 2020 were confirmed only at a certain location in the lake. Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth of 15.0 cm. The high pollutant concentrations locally occurred around a "hotspot" site that was previously frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore, chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (C and N) of organic matter suggested that the pollutants in the sediments at the "hotspot" sites had different origins than those found at other sites. Accordingly, the by-products discharged after cage fish farming, such as residual feed, fish meal, and waste, accumulated in the sediments and were then exposed to natural internal disturbances caused by the effects of climate change-induced drought. This local distribution and the phosphorus and heavy metal chemical fraction results with low elution potential indicated that the pollutants in the sediments of Lake Jangseong had negligible impact on water quality.
湖泊沉积物是各种污染物的重要汇，保留了人为活动造成的历史污染记录。最近，韩国昌城湖的沉积物首次被检测到含有高浓度的有机物（烧失量[IL]；总有机碳[TOC]）、养分（总氮[TN]；总磷[TP]）和一些重金属（Zn、Cu、Cd 和 Hg）。在这里，我们使用广泛的调查和各种评估方法，确定了这些在沉积物中积累的浓度的来源。通过沉积物质量指南、污染负荷指数和潜在生态风险指数评估的沉积物污染，对 IL、TN、TP 和 Cd 而言，情况令人严重关切。因此，我们通过空间、网格和垂直分布评估了污染源，并发现 2020 年检测到的高污染物浓度仅在湖泊的某个特定位置确认。此外，在深度为 15.0 厘米的沉积物岩芯的沉积层中也检测到了类似的结果。高污染物浓度局部出现在一个“热点”地区，该地区以前经常用于水产养殖活动，表明污染物是由于过去的笼式养鱼而积累在沉积物中，而不是由于外部来源的污染流入。此外，磷和重金属的化学形态分析以及有机物质稳定同位素（C 和 N）的评估表明，“热点”地点沉积物中的污染物与其他地点的污染物来源不同。因此，笼式养鱼后排放的副产品，如残余饲料、鱼粉和废物，在沉积物中积累，然后暴露于气候变化引起的干旱影响的自然内部干扰下。这种局部分布以及磷和重金属化学形态分析结果表明，沉积物中的污染物对水质的影响可以忽略不计。
