Toxicity Studies Of Several Pollutants On Four Indigenous Aquatic Organisms Of China

With the rapid development of China's economy, large quantities of pollutants had been discharged into the environment and caused serious harm on ecosystems. In order to accurately evaluate the toxicity of pollutants on indigenous aquatic organisms and to provide data for deriving the water quality criteria to protect aquatic organisms in China, several conventional pollutants such as nitrobenzene,2,4,6-trichlorophenol, Cr (â…¥), and ammonia were selected to study their acute and chronic toxic effects on four indigenous aquatic organisms of China (Rana chensinensis tadpoles, Macrobrachium nipponense, Cipangopaludina cahayensis, and Daphnia magna). Meanwhile, two emerging pollutants (acetaminophen (PATA) and p-aminobenzoic (PABA)) were also investigated to evaluate their acute and chronic toxicity on Daphnia magna as well as their combined toxic effects with nitrobenzene.The results of acute toxicity test showed that 96h(48h)-LC50 of Cr (VI) on Rana chensinensis tadpoles, Cipangopaludina cahayensis, Macrobrachium nipponense, and Daphnia magna were 31.72mg/L,7.28mg/L,0.04 mg/L and 0.16mg/L respectively; 96h (48h)-LC5o of ammonia on the four aquatic organisms were 129.46mg/L, 126.55mg/L,87.22mg/L,69.54mg/L, respectively; 96h (48h)-LC50 of Nitrobenzene on the four aquatic organisms were 117.04mg/L,104.23mg/L,0.033mg/L and 55.69mg/L respectively; 96h (48h)-LC50 of 2,4,6-trichlorophenol on the four aquatic organisms were 0.52mg/L,8.98mg/L,0.25mg/L and 1.41mg/L respectively. Compared with the other two aquatic organisms, Macrobrachium nipponense and Daphnia magna were more sensitive to these four pollutants.Chronic exposure of Cipangopaludina cahayensis to different concentrations of pollutants (e.g. nitrobenzene) showed different effects on its fat and protein contents, glutathione and lipid peroxidation activity, weight increase rate and survival rate. Overall, high concentration of nitrobenzene lead to the reduction of weight increase rate and survival rate, increasing protein and fat contents, and significantly induced activity of glutathione. Higher exposure concentrations of Cr (â…¥) could increse the mortality, decrease growth rate or even inhibit its growth, and significantly induce glutathione and lipid peroxidation. Considering the great variation of the above indicators over exposure time and concentration, they are not recommended as the indexes for deriving criteria.The tadpoles'growth toxicity tests showed that toxic substances could inhibit its growth, shorten the length of its body and tail, decrease the weight and the survival rate, inhibit growth of hind legs and metamorphosis growth, and prolong growth time. Calculated by development indicator, the lower chronic level(LCL), upper chronic level(UCL) of Cr (VI) and nitrobenzene are 0.04 and O.1mg/L,6.25 and 12.5mg/L, respectively. Chronic toxicity values are 0.06,8.84mg/L, respectively.The 21d chronic toxicity test of the pollutants with Daphnia magana showed that pollutants could inhibit its growth, reduce the number of peeling, prolong the pregnancy and spawning, and decrease the fecundity. Although the sensitivity of toxic indexes varied with different substance, the breeding index of Daphnia magana was a good indicator on the whole. The LCL, UCL of ammonia and nitrobenzene were 1.88 and 3.75mg/L,2.50 and 5.00mg/L respectively; Chronic toxicity values were 2.66 and 3.54mg/L respectively. The offspring acute toxicity test showed that the offspring born by pregnant individual during the chronic test exposure, were significantly more tolerant to the contamination. For ammonia (<30mg/L), the higher concentration the mothers exposed to, the stronger tolerance their offspring had. For nitrobenzene, the offspring born by the mother from the minimum concentration exposure had the highest tolerance.The toxicity results of two emerging pollutants on Daphnia magna showed that 48h-LC50 of PATA was 49.36mg/L, and 95% confidence limits were 41.87-58.18 mg/L. According toxicity grading standards to Daphnia magna, PATA was a moderate toxic substance.48h-LCso of PABA to Daphnia magna exceeded 100mg/L, which implied that PABA was a low toxic substance. The LCL, UCL of PATA and PABA on Daphnia magna were 0.75 and 1.50mg/L,6.25 and 25.00mg/L, respectively, and the chronic toxicity values were 1.06 and 12.50mg/L respectively. Breeding index is a good sensitivity indicator for the toxicity test of medicines. The combined toxicity effects of PATA and nitrobenzene mainly showed partly additive or antagonistic. The high concentration of PABA (> 63.8mg/L) had antagonistic effect with nitrobenzene, while showed partly additive effect at the low concentration of PABA (<58.1 mg/L). The types of combined toxicity effects were different due to different evaluation methods, which might be related with the change of medicine toxicity and the perfectibility of the evaluation method.