Study On The Pollution Mechanism Of Nitrogen,Phosphorus,Lead And Cadmium Of Mianyuan River In Sichuan Province And Pb²⁺Removal Technology Of Wastewater

The Mianyuan River Basin is an important production base of phosphate fertilizer and chemical industry in Sichuan Province.It has as many as 1000 factories and enterprises along the coast and the river runs through many densely populated areas.Upstream phosphate mining;agricultural irrigation in the middle reaches,the production of phosphorus and fertilizer;the discharge of domestic sewage from downstream urban residents,and so on,have jointly caused serious pollution in the Mianyuan River,seriously endangering the health of residents living on both sides of the river,and also seriously affecting the growth of crops on both sides of the river.The comprehensive influence of all kinds of industrial and agricultural pollution and domestic pollution has increased the difficulty of river pollution source tracing and pollution control.Therefore,how to effectively evaluate the pollution status,mechanism and source of pollution and explore reasonable pollution control technology is the key problem of pollution control in Mianyuan River area.Based on the National Natural Science Foundation project"Phosphorus-rich Water Uranium Occurrence Forms and Distribution Research"?No.41373120?,the physical and chemical properties of river water and the contents of TP?total phosphorus?and TN?total nitrogen?were determined in detail.Risk assessment of pollution of river sediments,determination of the geochemical characteristics of hydrogen and oxygen isotopes in river water,exploration of effective extraction methods for phosphate in river water,determination of oxygen isotope values in phosphates,exploration of factors affecting oxygen isotopes,and their application Traced the source of P and explored a new technology for removing lead ions in wastewater.The results show that:The range of water body pH?acid-base?in Mianyuan River was 7.9?8.7,the mean value was 8.41,and the water body was alkaline.The range of water Ec?conductivity?was 34?81,the mean value was 45.7,and the concentration of soluble salt in water was high.The range of water Eh?redox potential?was 114?213m V,the mean value was154.2m V,and the Eh value of water body was low.The range of water Do?dissolved oxygen content?was 5.28?9.01 ppm,the mean value was 7.85 ppm,and the water quality had improved on the dissolved oxygen index.The range of TN content in water was 0.17?10.20 mg/L,the mean value was 2.34,which exceeded the national class III water quality standard.The range of water TP content was 0.01?0.29 mg/L,and the mean value was 0.10 mg/L.Water body belonged to eutrophic water body.Water system sediment Cd content ranged 0.41?1.07 mg/kg,mean 0.60 mg/kg.Pb content ranged 11.8?36.80 mg/kg,mean 17.30 mg/kg.The pollution index?C_fⁱ?of Cd in water system sediments ranged from 0.91?2.38,with a mean of 1.33,and belonged to moderate pollution.The Pb pollution index?C_fⁱ?ranged from 0.44?1.37,with a mean of 0.65,and belonged to low pollution.The ranged of effective P content in water sediments 3.6?99.8 mg/kg,mean 22.89 mg/kg.The variation range of single factor potential ecological risk index Cd water system sediment was 27.3?71.4,and the mean value was 39.8;the variation range of single factor potential ecological risk index was 2.2?6.85,and the mean value was 3.23.Cd and Pb single-factor potential ecological risk index maximum appeared in Lianshan Town.Meanwhile,Lianshan Town also was a town with high potential ecological risk degree Cd single factor,while the potential ecological risk degree Pb single factor was low in all sampling sites.The range of?D?absolute variation of deuterium?in the river water of Mianyuan River was-11.30?-10.36‰,and the mean value was-10.83‰.The range of?¹⁸O(absolute variation of ¹⁸O)was-87.47?-79.07‰,and the mean value was-83.27‰.?D from upstream to downstream,relatively stable,while?¹⁸O from upstream to downstream,showing a change from high to low to high.The range of?¹⁸O test values in water PO₄^3-was 9.72‰?20.00‰,and the mean value was 20.59‰.From the middle reaches to the downstream,the water temperature increased gradually,while the?¹⁸O_p value showed the trend of first rising and then decreasing,which was not related to the change of water temperature,which indicated that the?¹⁸O_p value from the middle reaches to the downstream was almost unaffected by the water temperature.The effect of microbial action on the?¹⁸O_p value in water PO₄^3-was more intense.The higher the?¹⁸O_p value in water PO₄^3-,the larger the water TP/TN ratio,the greater the?¹⁸O_p value.The O isotope exchanged between river PO₄^3-and H₂O did not reach equilibrium.The above all revealed that the?¹⁸O_p values of PO₄^3-in the water body retained P original source information.From this,it could be inferred that the P pollution of the Mianyuan River came mainly to four parts:the upper reaches were phosphate mining and smelting;the middle reaches were the sewage discharged by industrial enterprises and the use of phosphate fertilizer in agricultural irrigation areas;and the lower reaches were the discharge of domestic sewage from urban residents.A novel adsorbent PVP/Fe₃O₄/GO composite with good water dispersion was synthesized in this study.As the as-prepared composited for removal of Pb²⁺with high selectivity and efficiency and easy reuse.Furthermore,it could selectively removed Pb²⁺.In the presence of coexisting metal ions with higher separation factors the Pb²⁺removal rate could reach more than 90%when PVP/Fe₃O₄/GO the composited materials to treat different wastewater samples.The Pb²⁺ions in the river could be reduced to 0.4ppb,after sample treatment.Therefore,the composite material can be used to deal with the removal of water Pb²⁺in acid water and reduce the pollution Pb water bodies.