水体硬度对锌的水质基准及生态风险评估的影响

为了探究水体硬度对锌水质基准及生态风险的影响，筛选了锌对我国淡水水生生物的77种急性毒性数据和20种慢性毒性数据，以及相应的水体硬度数据，采用物种敏感度分布法分别推导硬度校正前后锌的长期和短期水质基准值，并使用概率密度重叠面积法及联合概率分布法评估锌在我国八大流域水体中的急性、慢性生态风险及HC₅（保护95%生物的污染物浓度）超标率.结果表明:①校正前长期和短期水质基准值分别为11.90和71.67 μg/L；在水体硬度分别校正为50、100、150、200、250和350 mg/L后，锌的短期水质基准值分别为53.39、82.29、105.98、126.81、145.76和179.82 μg/L，锌的长期水质基准值分别为10.25、12.52、14.07、15.29、16.30和17.19 μg/L.②当硬度校正为100~350 mg/L时，长期和短期水质基准值均高于硬度校正前的水质基准值，短期水质基准值校正前后最大相差近2.5倍.③在八大流域水体中，锌的急性和慢性生态风险以及HC₅超标率随着水体硬度的增加而降低.研究显示，水体硬度对水质基准和生态风险均具有显著性影响，建议在锌水质基准和标准制修订过程中充分考虑硬度影响，为流域精细化管理提供科技支撑，以实现合理有效地保护我国水生态系统安全. 

Effect of Hardness on Water Quality Criteria and Ecological Risk Assessment of Zinc

Acute and chronic toxicity data of zinc to 77 freshwater native aquatic organisms and the corresponding water hardness data were collected and screened in this study. The species sensitivity distribution method was used to derive the water quality criteria before and after hardness correction. In addition, the probability density overlapping area method and the joint probability curve method were used to evaluate the acute and chronic ecological risks and HC₅ over-standard rates of zinc in water bodies of eight major basins in China. The results showed that: (1) The acute and chronic water criteria were 71.67 and 11.90 μg/L, respectively, before water hardness correction. When water hardness was corrected to 50, 100, 150, 200, 250 and 350 mg/L, the short-term water criteria of zinc were 53.39, 82.29, 105.98, 126.81, 145.76 and 179.82 μg/L, the long-term water criteria were 10.25, 12.52, 14.07, 15.29, 16.30 and 17.19 μg/L, respectively. (2) It is obviously that the acute and chronic HC₅ (hazardous concentration for 5% of species) values were higher than the values without water hardness corrected (100-350 mg/L). The maximum difference between the short term water criteria before and after the water hardness correction was 2.5 times. (3) The risk probability decreased with the increase of water hardness, which is basically consistent with the change trend of water quality criteria. It indicates that water hardness has a significant effect on water quality criteria and ecological risk probability. The influence of hardness should be fully considered in the revision of zinc water quality standard in order to provide scientific and technological support for watershed field-specified management and effective protection for the aquatic ecosystem safety in China.