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随着城市化和工业化的快速发展,大量来自人为来源的重金属被排放到水生环境中[1-5]。水生环境中的金属是不可生物降解的。而重金属可以通过物理、化学和生物过程在沉积物和悬浮颗粒中积累[6]。然而,当沉积物中的环境条件发生变化时,化学和生物过程可能会使累积的重金属再循环回水柱,从而将沉积物变成内部污染源[7]。因此,研究沉积物重金属对评价人类活动对水环境的影响具有重要意义。重金属主要来源于自然输入或人为活动。通过多元统计分析,可以追踪这些重金属的来源。地质累积指数和潜在生态风险指数被广泛用于评估它们所构成的风险[8]。然而,以往的研究表明,不同评估方法的结果有时并不一致[9]。因此,采用多种方法对沉积物质量进行评价,以获得更全面、更准确的信息是十分必要的。
海河流域是一个农业、工业和城市化迅速发展的流域,在我国的国民经济发展中占有举足轻重的地位。其水生态环境受到广泛的关注[10-11]。漳卫河水系多年平均水资源总量为5.36×109 m3,是海河流域水资源量最大的子流域,主要由漳河、卫河两大支流组成。其水环境和水生态安全对海河具有重要影响。近年来,河流沉积物中的重金属污染已得到广泛研究[12]。Tang等对海河流域的滦河等9个主要子流域的表层沉积物的重金属污染、风险、毒性进行了综合评价[13],Cao等也对海河干流的有毒金属污染进行评价[14],结果均表明,人为输入是金属富集的一个重要贡献者,其中沉积物中Cd的污染程度较高。Zhang等对海河流域的大中型城市河流沉积物中的重金属(Cr、Cu、Ni、Pb、Zn)污染及其危害进行了评价,表明城市化水平的提高会导致城市河流沉积物中Cr、Zn的污染加剧[15]。赵海萍等对漳河上游水质及污染进行分析,浊漳南源的有机污染物污染程度远大其他河段[16]。郝红等对海河流域的漳河、卫河、卫运河、南运河及漳卫新河的表层沉积物中的 As、Hg、Cd、Cu、Cr、Pb、Zn 等重金属进行了评价,结果表明多数河段都具有较高的生态风险[17]。多数学者主要以海河及其流域内主要河流为研究对象开展重金属分析及污染评价的相关研究,但是针对漳河上游流域的重金属相关研究较少。
认识沉积物重金属的污染特征和潜在生态风险,以及确定可能的来源和控制因素,对于污染预防和生物多样性保护管理至关重要。因此,研究漳河沉积物中重金属的污染水平对保障海河流域水资源安全具有重要影响。Cr、Cu、Ni在人体代谢过程中发挥着重要作用,过度接触这些金属会对人体健康产生有害影响,并增加慢性中毒的可能性。Pb虽然不参与人体代谢,但在非常低的水平上具有毒性作用。本研究选取这4种常见的重金属对地球化学基线及其生态风险进行评价。
漳河上游流域沉积物中重金属生态风险评价
Ecological risk assessment of heavy metals in sediments of the upper reaches of Zhanghe River
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摘要: 海河流域人口密集,大中城市众多,在我国政治经济中具有重要地位。漳河,属海河流域漳卫南运河水系,是漳卫河的一大支流。本研究以漳河上游流域表层沉积物为研究对象,采用相对累积频率法和归一化法建立了4种重金属(Cr、Ni、Cu、Pb)的区域地球化学基线。根据区域地球化学基线值定量计算了漳河上游流域沉积物中重金属污染的人为贡献率。根据不同背景参考值(土壤背景值、重金属浓度中值和区域地球化学基线值)采用地质累积指数和潜在生态风险指数对沉积物中重金属的污染水平和生态风险进行评价。沉积物中Cr、Ni、Cu、Pb的平均含量分别为91.51、43.33、21.93、18.30 mg·kg−1,接近中国土壤背景值。计算的区域地球化学基线值略低于沉积物中重金属的平均含量。Cr、Ni、Cu、Pb的平均人为贡献率为17.14%、11.16%、50.92%、29.35%,表明人为影响较小。此外,Igeo和EI结果表明,沉积物重金属处于无污染至轻度污染状态,具有较低的生态风险。Abstract: Haihe River Basin plays an important role in China's politics and economy. Zhanghe River is the largest tributary of Zhangwei River, which belongs to Zhangweinan Canal in Haihe River Basin. In this study, the regional geochemical baselines of four heavy metals (Cr, Ni, Cu, Pb) were established by relative cumulative frequency and normalization methods. The anthropogenic contribution rate of sediment in the upper reaches of Zhanghe River was quantitatively calculated by using the baseline value of regional geochemistry. The geological accumulation index (Igeo) and potential ecological risk index (EI) were used to evaluate the pollution level and ecological risk of heavy metals in sediments according to different background reference values (soil background value, median concentration of heavy metals and regional geochemical baseline value). The average contents of Cr, Ni, Cu and Pb in sediments are 91.51 mg·kg−1, 43.33 mg·kg−1, 21.93 mg·kg−1 and 18.30 mg·kg−1, respectively, which are close to the background values of soil in China. The calculated regional geochemical baseline value is slightly lower than the average content of heavy metals in sediments. The average anthropogenic contribution rates of Cr, Ni, Cu and Pb are 17.14%, 11.16%, 50.92% and 29.35%, indicating that the anthropogenic influence is relatively small. In addition, the results of Igeo and EI show that heavy metals in sediments are in a state of no pollution to slight pollution, and the ecological risk is low.
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Key words:
- Zhanghe River /
- sediments /
- heavy metals /
- regional geochemical baseline /
- pollution assessment
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表 1 表层沉积物重金属浓度汇总统计
Table 1. Summary statistics of the heavy metal concentrations of the surface sediments
Cr Ni Cu Pb 最小值/(mg·kg−1) 44.23 35.78 12.49 10.00 最大值/(mg·kg−1) 175.57 53.62 63.41 35.77 均值/(mg·kg−1) 91.51 43.33 21.93 18.30 中值(mg·kg−1) 88.43 43.08 18.64 18.47 标准偏差/(mg·kg−1) 24.30 4.64 10.48 5.43 相对标准偏差/% 0.27 0.11 0.48 0.30 表 2 其他区域沉积物重金属含量的比较(mg·kg−1)
Table 2. Comparison of heavy metal content in sediments of other regions (mg·kg−1)
位置
LocationCr Cu Ni Pb 参考文献
References漳河上游流域
The upper reaches of Zhanghe River91.51 21.93 43.33 18.30 本研究 中国淮河流域
Huaihe River, Anhui, China— 31.30 32.79 53.43 [6] 中国白洋淀
Baiyangdian Lake,china62.50 26.50 29.10 23.10 [23] 长江和淮河流域中下游浅水湖泊
Freshwater lakes in the middle and lower reaches of the Yangtze and Huai River Basins74.60 47.60 38.30 37.7 [3] 中国胶州湾
Jiaozhou Bay, China86.17 27.31 32.35 38.54 [7] 东阳江
Dongyang River71.90 86.20 28.10 79.10 [24] 三峡库区支流汝溪河
Ruxi Tributary of the Three Gorges Reservoir79.60 32.69 41.34 29.12 [25] 宝鸡市渭河
Weihe River in Baoji City57.57 48.89 31.80 15.70 [26] 长江中下游底泥
Middle and lower reaches of the Yangtze River77.20 46.47 — 37.75 [27] 柳江中下游流域
The middle and lower reaches of Liujiang River53.70 21.60 22.50 32.70 [28] 印度喀拉拉邦
Kerala, India— 18.20 50.40 21.60 [29] 埃及红海海岸
Coastal sediments, Red Sea, Egypt— 9.43 17.52 11.43 [30] 越南西贡河
Saigon River, Vietnam— — 4.02 1.27 [31] 沙特阿拉伯红海
Red Sea, Saudi Arabia— 2.10 2.16 2.75 [32] 韩国西南沿海河流
River sediments of southwestern coastal Korea62.20 29.70 26.10 32.10 [33] 山西省土壤背景值
Soil background value ,Shanxi Province61.8 32.0 26.9 15.8 [34] 中国土壤背景值
Soil background value,china66.8 25.5 33.8 21.9 [34] 表 3 表层沉积物的区域地球化学基线
Table 3. Regional geochemical baseline of surface sediments
重金属
Heavy metal地球化学基线函数
Geochemical baseline functions地球化学基线值/(mg·kg−1)
Geochemical baseline valueR2 Cr Cr(mg·kg-1)=60.75+6.69 Al(%)$ \times $ 85.56 0.89 Ni Ni(mg·kg-1)=35.29+1.62 Al(%)$ \times $ 41.46 0.98 Cu Cu(mg·kg-1)=16.76+0.47 Al(%)$ \times $ 18.39 0.84 Pb Pb(mg·kg-1)=11.95+1.28 Al(%)$ \times $ 16.33 0.96 表 4 淡水沉积物质量指南的汇总统计
Table 4. Summary statistics of the and guideline freshwater sediment quality values
重金属
Heavy metalCr Ni Cu Pb TEL/(mg·kg−1,干重) 43.3 22.7 31.6 35.8 PEL/(mg·kg−1,干重) 111.0 48.6 149.0 128.0 <TEL/% 0 0 87.50 100 TEL – PEL/% 84.37 81.25 12.50 0 >PEL/% 15.63 18.75 0 0 TEL:阈值效应水平Threshold effects level;PEL:可能影响水平Probable effects level[39]. -
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