Abstract: Natural freshwater sediment and water column samples were collected from Wuhan section along the Yangtze River and Zhengzhou section along the Yellow river in Oct. 2000. These sediment samples were spiked with Cu, Pb, Zn, Cd. The water column and the interstitial waters were spiked with Cu, Pb, Zn, Cd, Ni in the laboratory. The Vibrio qinghaiensis sp. Q-67 and the cladoceran Daphnia magna were introduced as test species in both solid- and liquid- phases toxicity bioassays. Based on the EC₅₀/LC₅₀measured and calculated in bioassays, the toxicity differences of the sediment and water column samples between the representative sections along the Yangtze and Yellow rivers were evaluated. The natural water column and the natural interstitial waters from both sections have no acute toxicity effects on the Vibrio qi nghaiensis sp. Q-67, however, the 96 h acute toxicity effect of natural sediment from the Yangtze river on Daphnia magna is evident. The acute toxicity effects of all the five heavy metals-spiked interstitial waters collected from the Yangtze river are lower than the Yellow river counterparts, however, the acute to xicity effects of Zn-spiked and Ni-spiked overlying water samples collected from the Yangtze river are higher than the Yellow river counterparts. As for the heavy metals-spiked sediments from the Yangtze river, the toxicity differences amo ng the four heavy metals on Daphnia magna are Cd, Cu, Zn, Pb(in descending order).

Key words: water column, interstitial waters, sediment, heavy metal

摘要： 采用Q67发光菌和大型蚤为试验生物，在实验室条件下对长江武汉段、黄河花园口段的河水及表层沉积物和孔隙水及其加标样品(Cu、Pb、Zn、Cd、Ni)进行了毒性测试，通过测定样品对受试生物的EC₅₀和LC₅₀值，评价了2河段水体重金属毒性和对毒性的屏蔽效应。结果表明长江武汉段和黄河花园口段的上覆水和沉积物孔隙水均未对Q67发光菌产生毒性，但是长江沉积物样品在96h内对大型蚤产生明显的急性毒性。加标重金属后，长江孔隙水中观察到的毒性均小于黄河孔隙水；而在上覆水中，加标后毒性增加，其中加入相同质量浓度Zn和Ni，长江表现出的毒性反而大于黄河；对加标的长江沉积物，不同重金属对大型蚤的毒性大小顺序是Cd, Cu, Zn, Pb。

关键词: 上覆水, 孔隙水, 沉积物, 重金属