Study On Molecular Mechanism Of Genetic Damage Of SD Rats By Surface Water And Groundwater Around Bayan Obo Mining Area

The mining of the rare earth mining area will directly or indirectly cause peripheral water and soil pollution,groundwater and surface water are also an important environmental receptor that is contaminated with water leakage in the mining area.Once contaminated,it will cause immeasurable harm to the surrounding organisms and even human health.Our study has confirmed that biological detection methods from macroscopic individuals to microscopic cells can be used to quantitatively evaluate genetic damage to model animal SD rats caused by surrounding groundwater pollution caused by leakage of rare earth metal tailings ponds.Based on this,in order to further determine the biological monitoring method is used to evaluate whether water surrounding the mining area environment quality has universality,and the possible molecular mechanisms of toxicological damage to organisms,this study is based on the Bayan Obo mining area as the research area.Firstly,the core pollution components in groundwater and surface water in 13 mining areas were investigated,and 5 seriously polluted sample sites were selected for subsequent analysis.Then,the genetic damage to SD rats was explored from the level of"individual-tissue-cell-chromosomal-protein oxidative damage"respectively.Finally,the molecular mechanism of genetic damage to SD rats by core pollution factors in groundwater in mining areas was further analyzed.This paper aims to determine the ecological correlation characteristics between pollutants and sensitive organisms based on the biological monitoring methods from individual to gene level,so as to provide a more scientific and effective method for quantitative risk assessment of groundwater.The main results are as follows:1.The results of water quality analysis showed that:The contents of most trace elements（heavy metals and rare earth elements）of S1 and S2 sample in 13 surface water and groundwater samples of Bayan Obo mining area were significantly higher than those in other surface water.The main pollutants（except rare earth elements）in groundwater are Mn,Ni and anions F^-,NO₃^-,SO₄^2-,and the main pollutants in surface water are F^-,NO₃^-,SO₄^2-.The results of Nerome comprehensive index evaluation showed that the water quality of Bayan Obo mining area was polluted to different degrees,especially the water samples of S1,S2,S3 and S4 were seriously polluted（F value>7.2）.The pollution degree of each water sample was S1>S2>S3>S4>S5>S13>S6>S7>S12>S9>S8>S11>S10.The difference analysis of S,S1-S5 water samples showed that the contents of metal elements（Mn,Cr,Co,Ni,Zn,Cd,Pb）and rare earth elements（Sc,Y,Pr,Sm,Dy）in S1 and S2 groups were significantly higher than those in the control group（p<0.05）,especially the content of Mn was far beyond the groundwater quality standard（GradeⅢ）.2.The comprehensive analysis results using biological monitoring methods showed that:the polluted water in Bayan Obo mining area inhibited the growth of SD rats,and had significant effects on liver and kidney organs.Histopathological sections and cytomorphological observations showed that inflammatory cell infiltration in liver and kidney tissues and central varicose veins,bile duct hyperplasia,and nuclear plasma aggregation were observed in liver tissue.Gglomerular atrophy,cell necrosis,granule degeneration and other pathological features were found in renal tissue.Further enrichment analysis and correlation analysis confirmed that this might be caused by infiltration of metal ions.Comet test and micronucleus test showed that the DNA damage rate and micronucleus rate increased with the proximity of sample sites to the main mining area,and the closer to the main mining area,the more serious the damage.The results of protein oxidation damage showed that the polluted water in mining area also caused significant lipid peroxidation damage for SD rats’liver and kidney.Further analysis showed that the trace elements of Mn,Co,Ni,Sc,Nb,La,Ce,Pr,Dy and Y in the six samples were significantly positively correlated with tail DNA%（p<0.01）.The comprehensive results indicated that single or combined effects of these trace elements could cause significant DNA damage in SD rats.3.Transcriptome sequencing and qPCR were used to further analyze the molecular mechanism of genetic damage.A total of 114 DEGs were screened in liver tissue,among which 56 genes were up-regulated and 58 genes were down-regulated.A total of 137 DEGs were screened in kidney tissue,among which 67 genes were up-regulated and 70 genes were down-regulated.The GO enrichment analysis,KEGG signaling pathway analysis and protein network co-expression analysis of DEGs showed that the genes related to toxicological damage caused by water pollution were mainly Mpo,Slpi,Mmp8,Elane,Gadd45g,Gadd45b,and Ddit4 in liver tissue.These genes are involved in immune responses and DNA damage,which suggesting a possible risk of cancer;In kidney tissues,the genes associated with toxicological damage caused by water pollution are mainly Serpine,Ccl5,Cxcl10,Cdkn1a,Lck,and Cd4,which are involved in immune response,DNA damage,as well as the toxicological processes of cell cycle and apoptosis.Comprehensive results show that the main pollution factor of Bayan Obo mining area is some metal elements（Mn,Zn,Co,Ni）and rare earth elements（Sc,Nb,La,Ce,Pr,Dy and Y）,which may result in significant DNA genetic damage.In addition,different gene expression profiles showed that Mpo,Slpi,Mmp8,Elane,Mpo,Gaddd45g,Gadd45b,Ddit4,Serpine,Ccl5,Cxcl10,Cdkn1a,Lck,Cd4 are involved in immune diseases,DNA damage,cancer,cell cycle and apoptosis.These genes may be used as novel prognostic and predictive biomarkers for biosafety assessment.Therefore,this study explored the possible molecular mechanism of genetic damage in SD rats caused by polluted water in Bayan Obo mining area,and also provided a general method for scientific and effective evaluation of water pollution risk in other mining areas.