三峡库区典型农村型消落带沉积物风险评价与重金属来源解析

本研究以三峡库区核心区——忠县典型农村型消落带为对象,于2011年7月,采集大坝水位回落后消落带沉积物样品,分析重金属含量,评价沉积物潜在风险,解析三峡库区农村型消落带重金属来源,为库区流域面源污染物控制提供基础数据.结果表明,消落带沉积物中As、Cd、Co、Cr、Cu、Mn、Ni、Pb和Zn的变化范围分别为155~160 m:5.17~14.81、0.06~0.57、8.55~20.56、62.79~93.04、15.38~60.97、425.72~782.32、21.34~48.5、23.03~43.39、57.78~130.10 mg·kg-1;170~175 m:7.05~12.57、0.17~0.33、10.71~18.89、65.22~92.89、18.89~42.91、74.06~774.41、22.47~42.49、24.17~29.23、55.67~103.18 mg·kg-1.地累积指数(I geo)表明,155~160 m消落带沉积物重金属累积顺序为Cd>Co>Mn>As>Cu>Pb>Zn,170~175m消落带累积程度大小为Co>Mn>Cd>As.沉积物污染指数(SPI)说明,155~160 m消落带沉积物潜在风险高于170~175 m沉积物,忠县城区下游155~160 m消落带沉积物风险达到峰值.统计分析结果显示,155~160 m消落带重金属Cr、Cu、Pb和Zn主要来源于自然背景,As、Ni、Cd、Co和Mn则来源于上游来水;170~175 m消落带沉积物重金属Cr、Ni、Pb和Zn主要来自自然背景,Cd、As、Co、Mn和Cu则极有可能来源于农田面源和上游.

Sediment Risk Assessment and Heavy Metal Source Analysis in Typical Country Water Level Fluctuated Zone (WLFZ) of the Three Gorges

Typical country WLFZ in Zhongxian located in the core region of the Three Gorges Reservoir was chosen as research subject in this study. In July 2012, sediment samples of WLFZ were collected after dam water level dropped. Heavy metals were analyzed for sediment potential risk assessment and then applied for sources analysis in this area, which supplied basic data for non-point pollutants control. The results showed that As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn ranged in 155-160 m:5.17-14.81, 0.06-0.57, 8.55-20.56, 62.79-93.04, 15.38-60.97, 425.72-782.32, 21.34-48.5, 23.03-43.39 and 57.78-130.10 mg·kg^-1, and 170-175 m:7.05-12.57, 0.17-0.33, 10.71-18.89, 65.22-92.89, 18.89-42.91, 74.06-774.41, 22.47-42.49, 24.17-29.23, 55.67-103.18 mg·kg^-1, respectively. Index of geo-accumulation (Igeo) suggested the accumulation orders were Cd>Co>Mn>As>Cu>Pb>Zn in 155-160m WLFZ and Co>Mn>Cd>As in 170-175 m WLFZ. Sediment pollution index (SPI) showed that sediments in 155-160 m WLFZ had higher potential risk than that of 170-175 m with the highest risk appeared in 155-166 m WLFZ site located downstream of Zhongxian. In 155-160 m WLFZ, Cr, Cu, Pb and Zn were mainly originated from natural resources, while As, Ni, Cd, Co and Mn were possibly sourced from upland water. In contrast, in 170-175 m WLFZ, Cr, Ni, Pb and Zn in the sediment came from natural resources, while Cd, As, Co, Mn and Cu were probably rooted from both agricultural non-point source and upland water.