The acute and chronic toxicity effects of ammonia nitrogen were studied using Daphnia magna as the test organism. The toxicity response of the offspring born by pregnant individuals during chronic exposure to ammonia nitrogen was further studied. The acute toxicity test showed that the 24 h LCso and 48 h LCso of ammonia nitrogen to this organism were 165.97 and 69. 54 mg/L,respectively. The results of 21 d chronic toxicity testing showed that the number of exuviations, one of the growth parameters, was the most sensitive indicator, from which the values of Lower Chronic Limit (LCL) and Upper Chronic Limit (UCL) were determined to be 1.88 and 3.75 mg/L, respectively. The Chronic Value (CHV) was calculated as 2.66 mg/L using the LCL and UCL. All the data allowed us to obtain the Acute-to-Chronic Ratio (ACR) as 26. 14. In contrast with the control, the 48 h LCso of ammonia nitrogen to the offspring born by the pregnant individual during the chronic test exposure were greater ( increased by 13.7％ -56.2％ ), which suggested that maternal exposure to ammonia nitrogen could improve the adaptability of the offspring to the same chemical.%采用大型溞(Daphnia magna)作为受试生物,在测定了氨氮对大型溞的急慢性毒性效应的基础上,进一步研究了在慢性毒性试验中暴露于氨氮环境下的母溞所产子代对氨氮的毒性响应.急性毒性试验结果表明,氨氮对大型溞的24 h和48 h的LC50分别为165.97和69.54 mg/L.21 d慢性试验结果表明:大型溞的生长指标--脱皮数是对氨氮最为敏感的毒性参数;其慢性毒性下限值(LCL)和慢性毒性上限值(UCL)分别为1.88和3.75 mg/L;据此计算出的慢性毒性值(CHV)为2.66 mg/L,急慢性比(ACR)为26.14.在慢性试验中,暴露于毒物的母体所产的子代幼溞,与对照组相比,其48 h LC50都有所增大(增幅为13.7%～56.2%),说明对毒物的适应性有所增强.
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