南水北调中线总干渠水中重金属含量及风险评价

CONTENTS AND RISK ASSESSMENT OF HEAVY METALS IN SURFACE WATER IN THE MAIN CANAL OF MIDDLE ROUTE OF THE SOUTH-TO-NORTH WATER DIVERSION PROJECT

于2018年5月—2020年6月对南水北调中线总干渠11个采样点表层水中18种重金属的浓度进行周期性采样监测,并分别利用USEPA推荐的健康风险评价模型和物种敏感性分布(SSD)法评估常见重金属的人体健康风险水平和水生态风险水平。化学分析结果显示,18种重金属均被普遍检出,平均浓度大小排序为:Fe>Sr>Ba>Zn>Ti>Ni>Mn>Cu>V>Cr>As>U>Rb>Se>Pb>Bi>Co>Cd,均未超出《地表水环境质量标准》(GB 3838—2002)Ⅰ类水标准和《生活饮用水卫生标准》(GB 5749—2006)限值。健康风险评价结果显示,南水北调中线总干渠表层水中8种常见重金属(Cr、Cd、As、Cu、Pb、Zn、Ni、Mn)对儿童和成人的总健康风险值处于10^(-8)级别。基于构建的8种常见重金属(As、Ni、Pb、Cr、Zn、Se、Cd、Cu)的SSD曲线,计算重金属对本土淡水生物5%危害浓度(HC5)和潜在影响比例(PAF),结果显示,南水北调中线总干渠水中目标重金属对全体水生生物种群的影响比例小于5%,但Cu和Zn分别可对8.54%和16.77%的藻类种群造成影响,Cr可对6.44%的甲壳类种群造成影响。上述结果表明,南水北调中线总干渠水中重金属的当前含量不高,不会对人体造成潜在健康风险;以保护95%的生物物种为标准,个别重金属对总干渠中藻类、甲壳类种群可能具有一定潜在风险,尚有待进一步关注。

The concentrations of 18 heavy metals were detected in surface water from 11 sampling sites along the Main Canal of Middle Route of the South-to-North Water Diversion Project from May, 2018 to June, 2020, and the health risk assessment model recommended by USEPA and Species sensitivity distributions(SSD) method were used to estimate the human health hazard risk levels and ecological risk levels, respectively. The results showed that all the heavy metals were frequently detected, and the average concentrations ranked as Fe>Sr>Ba>Zn>Ti>Ni>Mn>Cu>V>Cr>As>U>Rb>Se>Pb>Bi>Co>Cd, with concentrations of all heavy metals not exceeding the class I water standard of Quality Standard for Surface Water(GB 3838-2002) and the limit of Standard for Drinking Water Quality(GB5749-2006). The health risk assessment showed that the mean values of the total health risk of adults and children caused by 8 common heavy metals(Cr, Cd, As, Cu, Pb, Zn, Ni and Mn) were at 10^(-8) range in surface water from the Main Canal of Middle Route of the South-to-North Water Diversion Project. Based on the SSD curves of 8 heavy metals(AS, Ni, Pb, Cr, Zn, Se, Cd and Cu), the hazardous concentrations for 5% of species(HC5) and the potential affected fractions(PAF) were calculated. The results demonstrated that the percentage of the whole aquatic organisms affected by the investigated heavy metals were below 5% in surface water of the Main Canal of Middle Route of the South-to-North Water Diversion Project, but Cu and Zn affect 8.54% and 16.77% of the algal population, respectively,and Cr affect 6.44% of the crustacean population. Overall, our results indicated that the current contents of heavy metals remain low in surface water of the Main Canal of Middle Route of the South-to-North Water Diversion Project,posing no potential health risks to humans, and that several heavy metals may pose potential risks to the population status of algal and crustaceans, which needs further investigations.