| 梯级拦河堰对典型山地城市河流重金属元素的滞留效应:以重庆市梁滩河为例 |
| 摘要点击 4587 全文点击 558 投稿时间：2021-11-04 修订日期：2021-12-14 |
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| 中文关键词 山地城市河流 梯级拦河堰 沉积物 重金属元素 生态风险 来源解析 |
| 英文关键词 mountainous urban river cascade weirs sediment heavy metals ecological risk source analysis |
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| 中文摘要 |
| 梯级拦河堰通过改变水力条件的方式将大量重金属元素滞留到河底沉积物中，滞留在沉积物中的重金属会长期影响地表水质和水生态.在2020年5月采集位于重庆市主城区、布设有梯级拦河堰的典型山地城市河流——梁滩河干流河底沉积物，并监测各河段内沉积物累积量和样品中重金属元素含量以及其它基本理化指标.结果表明，梁滩河干流沉积物ω（As）、ω（Cd）、ω（Cu）、ω（Hg）、ω（Ni）和ω（Pb）均值分别为（4.66±4.78）、（0.361±0.256）、（32.30±14.38）、（0.069±0.039）、（33.47±15.37）和（26.34±11.52） mg·kg-1，由于污染源空间分布不均和梯级拦河堰对河流连通性的破坏，各点位沉积物重金属含量有着较大的空间变异系数.改进的地累积指数（Im）显示，Cd是沉积物中污染水平最高的重金属元素；有12.50%的监测点位处于偏中度或中度污染水平，污染主要分布于建设用地集中的上下游区域.潜在生态风险评价指数法（RI）和沉积物质量基准法（SQGs）显示，除污染水平较高、毒性强的Cd和Hg外，流域内背景值含量较高的Ni也对地表水生态风险形成威胁.在梯级拦河堰的影响下，干流沉积物中滞留As、Cd、Cu、Hg、Ni和Pb总量分别为446.10、47.28、4997.80、10.81、5135.68和4048.16 kg，其中Cd、Ni和Pb会长期威胁地表水生态安全.由于较高的重金属滞留总量和更易形成厌氧环境，各级拦河堰上游附近河段也是重金属内源释放所需关注的重点区域.利用主成分分析和聚类分析解析沉积物中重金属元素来源：Cd、Cu和Pb主要源于居民/工业点源污染；Hg主要源于农业面源污染；As和Ni主要源于自然土壤侵蚀. |
| 英文摘要 |
| Contaminants such as heavy metals in rivers are partially retained in the sediments at the bottom as a result of the altered water regime within the cascade weirs. The associated heavy metals in the sediments can affect surface water quality and ecology for a long period. In May 2020, sediments were collected in a typical mountainous river (Liangtan River) with cascade weirs in the main urban area of Chongqing. The accumulation of sediments in each river section, the content of heavy metals, and other basic physicochemical indicators in the samples were monitored. The results showed that the average ω(As), ω(Cd), ω(Cu), ω(Hg), ω(Ni), and ω(Pb) in the sediments of the main stream of Liangtan River were (4.66±4.78), (0.361±0.256), (32.30±14.38), (0.069±0.039), (33.47±15.37), and (26.34±11.52) mg·kg-1, respectively. A large coefficient of spatial variation regarding the content of heavy metals in the sediments across the sampling sites was observed owing to the uneven spatial distribution of pollution sources and the destruction of river connectivity by cascade weirs. The modified geoaccumulation index (Im) showed that Cd was the most polluted heavy metal element in the sediments. Of the monitored river sections, 12.50% approached or were at moderate pollution levels, and these sections were mainly found in the upstream and downstream reaches of Liangtan River with relatively concentrated construction lands. The potential ecological risk assessment index method (RI) and the sediment quality guideline method (SQGs) showed that, in addition to Cd and Hg with a high pollution level and strong toxicity, Ni in the sediments also posed a potential threat to the ecological safety of surface water due to its high background content in the watershed. The total amounts of As, Cd, Cu, Hg, Ni, and Pb retained in the sediments by cascade weirs were estimated to be 446.10, 47.28, 4997.80, 10.81, 5135.68, and 4048.16 kg, respectively, in which Cd, Ni, and Pb were identified to be the major threats to the ecological safety of surface water over a long period. The upper reaches prior to the weirs with the most retained heavy metals and the easier formation of an anaerobic environment are suggested to be the key areas for investigation of the endogenous release of heavy metals. Source apportionment of heavy metals in river sediments through the combination of principal component analysis and cluster analysis revealed that Cd, Cu, and Pb mainly originated from residential/industrial point source pollution. Hg mainly originated from agricultural non-point source pollution, whereas As and Ni mainly originated from natural soil erosion. |
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