Most of the pollutants discharged into the water will deposit at the bottom of the river and may cause biological toxicity. Daphnia magna-elutriate toxicity bioassay was usually applied to evaluate sediment toxicity. However, the loss of hydrophobic pollutants during the elutriating will lead to the underestimation of sediment toxicity. The purpose of this study is to apply the optimized immobilized sediments to D. magna test, so it can be directly exposed to the sediments and get accurate sediment toxicity results. The optimized immobilized sediment was prepared by mixing 1 g sediment with 7.5 mL 3% (w/v) alginate and hardened in a 4% (w/v) CaCl₂ solution. Based on D. magna acute toxicity test, the median lethal concentration values (LC₅₀) of the spiked Cu and diuron measured by using immobilized sediment were both lower than that of using the elutriate, in which the difference of Cu-LC₅₀ reached a significant level. The toxicity changes of sediment in the polluted rivers before and after dredging were then be evaluated by using the immobilized sediment. The toxicity of the sediments at four sites decreased from acute-toxic (pro-dredging) to slight-acute-toxic and nontoxic (post-dredging).

排放到水中的大多数污染物将沉积在河底，并可能引起生物毒性。大型蚤（Daphnia magna- elutriate）毒性生物测定法通常用于评估沉积物毒性。但是，淘析过程中疏水性污染物的损失会导致沉积物毒性的低估。这项研究的目的是将优化的固定化沉积物应用于D. magna试验，以便它可以直接暴露于沉积物并获得准确的沉积物毒性结果。通过将1 g沉淀物与7.5 mL 3％（w / v）海藻酸盐混合并在4％（w / v）CaCl ₂溶液中硬化来制备优化的固定沉淀物。基于D. magna急性毒性试验中，固定化沉淀物测得的加标Cu和Diuron的中位致死浓度值（LC ₅₀）均低于浸提液，其中Cu-LC ₅₀的差异达到了显着水平。然后通过固定化沉积物评估疏dr前后污染河流中沉积物的毒性变化。四个地点的沉积物的毒性从急性毒性（前挖泥）降低到轻微急性毒性和无毒（挖泥后）。