Investigation Of Metal Pollution Of Lhasa River And The Toxicity Of Hg,Cd And Cu On Schizopygopsis Younghusbandi

The Lhasa River is called the“Mother River”by the people of Lhasa,and it is the main source of drinking water,agricultural irrigation,industrial water,and ecological water in the Lhasa River Basin.However,with the development of the city and the rise of the mining industry,a large amount of domestic sewage and industrial wastewater have flowed into the river.The Lhasa River is facing heavy metal pollution.At present,there are limited data on the status of heavy metal pollution in Lhasa River.Research on the toxic effects of heavy metals on the native Lhasa fish is even more scarce.Therefore,the study carried out a survey on the heavy metals of As,Hg,Cd,Cu,Pb,Cr,Zn,Ni in Lhasa River and the native Lhasa fish.Then we took the Schizopygopsis younghusbandi larvae as the research object,to explore the effects of Hg²⁺,Cd²⁺and Cu²⁺on the developmental toxicity,thyroid interference and antioxidant system of larvae.Finally,the toxicity of heavy metals to larvae was evaluated quantitatively by Integrated Biomarker Response?IBR?.Our research conducted a comprehensive analysis of the heavy metal content in the Lhasa River and the native fish,desmontrated the biological toxicity of heavy metals to the Schizopygopsis younghusbandi larvae,and evaluated the ecological risk of the Lhasa River heavy metals from an overall level.Scientific basis and reference opinions for resource protection can be provided after the study.The main results are as follows:Health risk assessment from heavy metals in water and fish showed that the water quality in most parts of the Lhasa River meets the Class I water quality requirements of Chinese“Surface Water Environmental Quality Standards”.However,Cu and Cr in the water from Mozhugongka-Lhasa section only met Class III water quality requirements.As a drinking water source,it might bring carcinogenic risk to residents.We deduced the reason might be due to sewage discharge from domestic and mining in Mozhugongka-Lhasa section.The analysis of heavy metal in fish showed that the enrichment factor of heavy metals was generally low in muscle.While Schizopygopsis younghusbandi,Oxygymnocypris stewartii,Schizothorax waltoni and Ptychobarbus dipogon were slightly contaminated by Hg.The correlation analysis of heavy metal sources shows that Cr,Pb,Ni and Hg are more likely to have the same source,and Cu and Zn have the same source.After exposure to Cu²⁺,Cd²⁺and Hg²⁺,the body T3 and T4 concentrations and the expression of genes related to thyroid hormone synthesis,transport,metabolism and binding were significantly changed in Schizopygopsis younghusbandi larvae.The results showed that Cu²⁺,Cd²⁺and Hg²⁺caused thyroid destruction.In addition,the malformation rate of the larvae after heavy metal exposure were significantly increased,and the survival rate and body length were significantly reduced,indicating that Hg²⁺,Cd²⁺and Cu²⁺caused the developmental toxicity of larvae.The oxidative stress experiment of Hg²⁺,Cd²⁺and Cu²⁺on Schizopygopsis younghusbandi larva was carried out.The results showed that Hg²⁺,Cd²⁺and Cu²⁺significantly changed the expression of oxidative stress-related genes,and significantly affected CAT,SOD and GR enzyme activities,resulting in the decrease of GSH content and the increase of MDA content in vivo.The results indicated that Hg²⁺,Cd²⁺and Cu²⁺exposure caused oxidative damage and lipid peroxidation.The results of IBR analysis showed that the various indicators?such as T4,GSH and MDA?to Hg²⁺,Cd²⁺and Cu²⁺stress were sensitive,which could be used as an effective biomarker to monitor and evaluate heavy metal pollution in Lhasa River.In addition,Schizopygopsis younghusbandi larvae seem to be more sensitive to Cd²⁺,which caused toxic effect as low as 2.5ug/L.Considering the Cd²⁺dose in Lhasa River,Schizopygopsis younghusbandi larvae are facing the biological toxicity by Cd²⁺.In short,the water quality of most parts of the Lhasa River is generally well,but some river sections faced the ecological risks of heavy metals.At environment concentrations,heavy metals caused developmental toxicity,thyroid disturbance,and oxidative stress to Schizopygopsis younghusbandi larvae.All these should arouse attention from the government and departments concerned...