Assessment of toxicity of two nitroaromatic compounds in the freshwater fish Cyprinus carpio

This study was conducted to evaluate the toxicological response ofp-nitrotoluene and p-nitroaniline to the key fish species, Cyprinus carpio. A freshwater fish bioassay based on the 96 h LC50 was used to estimate the single and joint toxicity of the two chemicals. The toxicity of p-nitrotoluene was greater than that of pnitroaniline based on 96 h LCso values of 40.74 mg.L^-1 and 48.99mg.L^-1, respectively. Both compounds had moderate toxicity toward Cyprinus carpio, and this toxicity increased with the exposure duration and con- centration. Binary mixtures of the compounds were more toxic than the individual compounds at 96 h, and they acted upon partial addition. When the exposure time was longer, the toxicity increased for mixtures of compounds with the same concentration or toxicity. The results of this study suggest that exposure to a combination of these chemicals would result in a higher environmental risk in aquatic systems than exposure to either compound alone. Further research is needed to investigate the combined effects and sublethal toxicity of p-nitrotoluene and p- nitroaniline, since they are both still used in China.

Joint effects of Penta-BDE and heavy metals on Daphnia magna survival,its antioxidant enzyme activities and lipid peroxidation

The joint toxicity of Penta-BDE(Pe-BDE)and heavy metals including cadmium and copper on Daphnia magna(D.magna)was evaluated on the basis of determining the 48 h survival,antioxidative enzyme responses,and lipid peroxidation.The response was classified as additive,greater than additive,or less than additive by comparing the measured“toxic units,TU”with one.Based on the survival of D.magna,less-than-additive interactions were found in most of mixtures treatments.This may be attributed to the different toxicity mechanism between Pe-BDE and metals.Cu and Cd played a greater role in toxicity than what Pe-BDE did.As for the superoxide dismutase(SOD)and catalase(CAT)activity,most response was less than additive.For the glutathione S-transferases(GST)activity,most of the greater-thanadditive responses were found in the Cu plus Pe-BDE treatments,but the additive responses occurred in Cd plus Pe-BDE treatments and binary metal treatments.For lipid peroxide levels,which were measured as malondialdehyde(MDA)levels,less-than-additive response occurred in the 50%Cd plus 50%Cu and ternary mixture treatments.Results suggested that Pe-BDE,Cd,and Cu could induce different patterns of antioxidant enzyme responses,such as antioxidant/prooxidant responses,depending on their capability to produce reactive oxygen species and antioxidant enzymes to detoxify them.

Inhibition character of crotonaldehyde manufacture wastewater on biological acidification

This work aims to investigate the inhibitory effect of crotonaldehyde manufacture wastewater(CMW)on biological acidification.To reveal the inhibitory effect of wastewater to the anaerobic granular sludge(AnGS),variations of the specific acidogenic activity(SAA)and activities of key enzymes were investigated.The results indicated that the dosage of CMW causing a 50%effect concentration(EC50)on the activity of total volatile fatty acids(TVFA)production was 380 mg COD/g VSS.The inhibitory effect of individual toxicants in CMW on the activity of TVFA production were in the order of crotonaldehyde>ethyl sorbate>(E,E)-2,4-hexadienal,and their inhibitory degrees on individual VFA productions were acetic acid(Ac)>n-butyric acid(n-Bu),which could correspond to the variations in the activities of acetate kinase(AK)and butyrate kinase(BK).Furthermore,the combined effect of three toxicants on the activity of TVFA production was significantly higher than that of any individual toxicant,and the contribution of the relative toxicity to CMW was 77.27%.Additionally,the biodegradation products of the main toxicants indicated that the removal of crotonaldehyde and(E,E)-2,4-hexadienal was primarily due to the hydrogenation of alkene and aldehyde and the oxidation of aldehyde.Nevertheless,the removal of ethyl sorbate was primarily based on adsorption.In conclusion,biological acidification has a limited ability to treatment CMW,therefore,a further pretreatment technology should be used to remove the main toxicant of wastewater.