Biotoxicity Study Of Typical Urban Black-odor River Water

Since the80s of last century, the pollution of urban rivers has become more and more serious in the development of economy and city promotion. Some urban rivers display serious black-odorous water, which receives wide attention. Jiushanwai River (JS) and Shanxia River (SX) are two important tributaries of Wen-Rui Tang River in Wenzhou city. JS and SX have been seriously polluted, and are typical black-odor rivers. In the present study,10and5sampling points were respectively set along JS and SX River. Water samples were collected monthly during from October2010to October2011. The general physical and chemical indexes of sample water were checked. The main aims of this paper are to survey the biological toxicity of water of JS and SX River to Brachydanio rerio, Luminescent bacteria and Xenopus tropicalis embryoswere, to analyse seasonal and regional changes of the eco-toxicity of the two typical black-odor rivers, to explore the toxicity detection methods for black-odor rivers, and to provide references for evaluation and treatment of black-odor rivers.The main results are as follows:1. The annual temperature (T) of JS River is (22.81±5.99)℃, pH was7.50±0.54, the concentration of dissolved oxygen (DO) was (1.97±1.63) mg·L-1, ammonia nitrogen (NH3-N) was (9.52±4.23)mg·L-1, and total phosphorus (TP) was (9.75±4.27) m·L-1.The annual temperature of SX River was (22.05±6.11)℃, pH was7.53±0.53, DOwas(1.64±1.44)mg·L-1,NH3-N was (9.29±2.89)mg·L-1,and TP was (2.36±3.11) m·L-1.The temperature and pH changes of JS were almost consistent with that of SX in the monitoring year. DO of SX was significantly lower than that of JS, but TP of SX was higner than that of JS, and NH3-N of SX was higner than that of JS, especially in the summer, which reflect that pollution of SX was serious.2. Water of JS River and SX River displayed varying degrees of acute toxicity to Brachydanio rerio. The mortality of zebrafish exposed to water of JS and SX sampled during from November2010to April2011were all lower than the non-toxic standard of positive control toxicant K2Cr2O7. The five samples of SX and the JS2sample water reached a high toxic level when assayed during from June2011to September 2011. Comparatively, the toxicity of SX water was general higher than that of JS water, especially in summer during from June to September. The poisoning symptoms of zebrafish exposed to black-order water most include super-excitement following quick death and bradykinesia following coma. In the exposure process, the mortality of zebrafish was associated with pH and DO of sample water.3. Results of Luminescent bacteria test showed that toxicity of JS and SX water appeared relatively consistent seasonal changes. Their comprehensive toxicity was all low in winter and spring, but high in summer. Biotoxicity of black-odor river water assayed by Luminescent bacteria was consistent with that by zebrafish. However, inhibitory light rate of Luminescent bacteria was more sensitive than mortalty of zebrafish to check biotoxicity of black-odor water. Further analysis showed that the relative inhibitory light rate of Luminescent bacteria was positively correlative with temperature, NH3-N and TP, but negatively correlative with DO of black-odor water.4. Results of Xenopus tropicalis embiyoswere test showed that JS and SX water had different degrees of toxicity. The toxicological effects of black-odor river water were mostly indicated using percentage of hatch, body length, percentage of survival and percentage of teratogenicity of Xenopus tropicalis embryoswere. For example, percentage of teratogenicity of Xenopus tropicalis embryoswere exposed to JS and SX water sampled in October and December2010, were significantly higher than that of control group. It indicates that black-odor water is toxical to biology development. Malformations were mostly observed in head, abdomen and tail of Xenopus tropicalis. Notable malformations include abnormal eye, curved back, distorted notochord, widen ventral-finen, larged proctodaeum, skin hypopigmentation and so on.The comprehensive results of the present study indicate that typical black-odor river water displays different degrees bio-toxicity to Brachydanio rerio. Luminescent bacteria and Xenopus tropicalis embryoswere, with an example of JS and SX River. Intensity of bio-toxicity is closely relative with temperature, dissolved oxygen, ammonia nitrogen, and total phosphorus of black-odor river water. It suggests that the bioassay toxicity should be properly carried out for evaluation of water quality, in order to demonstrate ecological safety of river. In this paper, seasonal and regional bio-assay toxicity of JS and SX River provides a complete example for monitoring and evaluation of urban rivers.