长江流域地表水中镉生态风险的区域差异分析

Analysis of Regional Differences in Cadmium Ecological Risk in Surface Waters of theYangtze River Basin

围绕长江流域地表水中镉(Cd)的水质基准和生态风险的区域差异展开分析.首先,根据我国《淡水水生生物水质基准——镉》推荐的方法,结合长江流域地表水的硬度分布对Cd长期水质基准值进行了校正;在此基础上,考虑长江流域的物种区系特征,进一步修正得到了Cd长期水质风险阈值,并依此阐释了长江流域的Cd长期水质风险阈值分布和风险商分布的区域差异性.结果发现,经硬度校正和物种修正后,长江流域不同城市间Cd长期水质风险阈值的最大值为0.75μg·L^(-1),最小值为0.08μg·L^(-1),二者相差近10倍;不同城市间Cd风险商的最高值为1.12,最低值为0.035,二者相差达32倍.长江流域上中游交界区和洞庭湖水系等重点区域的Cd生态风险高,尚需深入研究.

This study primarily focused on the regional disparities in both water quality criteria and ecological risks attributed to cadmium presence within the surface waters of the Yangtze River Basin.In the initial phase,the long-term water quality criteria for cadmium were recalibrated in accordance with the guidelines outlined in China's“Water Quality Criteria for Freshwater Aquatic Organisms-Cadmium,”accounting for the prevalent hardness distribution within the Yangtze River Basin's surface water.Subsequently,a more refined revision was undertaken considering the specific characteristics of the species residing within the Yangtze River Basin.This undertaking led to a comprehensive interpretation of the regional variations in both the distribution of long-term water quality criteria values and the risk quotient distribution of cadmium throughout the Yangtze River Basin.The incorporation of hardness and species-specific attributes resulted in a revised range of long-term water quality criteria for cadmium across different urban locales within the Yangtze River Basin.Notably,the recalibrated values ranged from 0.08µg·L^(-1) as the lowest threshold to 0.75µg·L^(-1) as the upper limit,signifying a tenfold differentiation.Correspondingly,the urban average annual risk quotient associated with cadmium exposure demonstrated a variation from 0.035 to 1.12,marking a significant 32-fold discrepancy between the lowest and highest values.It is essential to highlight that regions of paramount importance,such as the confluence area connecting the upper and middle stretches of the Yangtze River Basin and the intricate Dongting Lake system,exhibited noteworthy ecological risks attributed to cadmium presence.Consequently,further in-depth investigations into these critical regions are imperative for a comprehensive understanding of the associated risks.