Using Caenorhabditis Elegans To Assess The Ecological Health Risks Of Heavy Metals In Soil And Sediment Around Dabaoshan Mine,China

Mineral resources are indispensable to human production activities and life.However,many mining areas have been seriously polluted by heavy metals due to limited mining technology and incorrect tailings treatment,posing a threat to the health of staff and residents nearby.However,most studies focused on chemical analysis and rarely combined with biological assays for toxicity during environmental safety assessments in mining areas.The acid mine drainage with many toxic dissolved heavy metal ions generated by mining at the Dabaoshan Mine,the largest polymetallic mine in southern China,was released to the environment.Detailed regional survey for the ecological risks of this polluted area is currently in urgent need.Therefore,here we selected the Dabaoshan Mine as our study area,eight representative sampling points were set along the flow direction of wastewater and Fandong water,heavy metal concentrations in farmland soils,sediments and their extracts were determined,potential ecological risk index,health risk assessment and partial least-squares regression（PLSR）was applied to access the ecological risks of heavy metals in the Dabaoshan mining area.Caenorhabditis elegans（C.elegans）has been widely used in ecotoxicology research owning to its strong tolerance,convenient cultivation,and high homology with the human genome.Based on the pollution level of heavy metals in the Dabaoshan mining area,C.elegans biological toxicity test was used in current study to explore the biological toxic effects of water-soluble extracts from samples collected from Dabaoshan Mine,effects of different heavy metals on the biomarkers of nematodes were further clarified.The main research conclusions are as follows:（1）The concentrations of Ni,Cu,As,Pb,and Zn at each sampling point in Dabaoshan mining area were all higher than the corresponding soil background values in Guangdong Province,which were 1.21 to 4.04 times,4.65 to 112.45 times,11.72 to 194.01 times,3.10to 65.33 times,2.46 to 69.25 times of the background values,respectively.In general,the potential ecological risk of heavy metals in this polluted area was at a serious pollution level（RI=721.53）.The risk of individual heavy metal was ranked as follows:As>Cu>Pb>Zn>Ni>V>Cr>Mn.As.Cu and Pb exhibited extremely high risk,high risk and moderate risk,respectively.In addition,the carcinogenic risk of As in the farmland soils of Liangqiao Village to adults was greater than 1,while the non-carcinogenic risk of Pb to children was greater than 10^-4.（2）After exposure to the water-soluble extracts from Dabaoshan samples,the survival rate and body length of nematodes were inhibited in vary degrees.Compared with the control,the leachates of tailings wastewater channel sediment（E3）and its downstream sediment（E4）presented the most obvious effects:the survival rate of the E3（×1000）and E4（×50）exposed group was less than 50.00%（p<0.01）,and the body length of the E3（×1000）exposed group was shortened by about 10.00%（p<0.01）.Gene expression（sod-3,gst-4）and enzyme activity（SOD,CAT）related to oxidative stress were increased（p<0.05or p<0.01）,genes related to apoptosis（egl-1）and heavy metallothionein（mtl-1,mtl-2）were also promoted（p<0.05 or p<0.01）in these groups.These data indicated that the water-soluble extracts from samples collected might be toxic to nematodes through oxidative damage and apoptosis.（3）The interpretation rate of each optimal PLSR model was higher than 60.00%.In the PLSR models of physiological indicators,Pb had a significant impact on survival rate and body length of C.elegans,and body length was also affected by Cu.In the PLSR models of biochemical indicators,the main factors affecting SOD activity were Ni,As,Pb,and the main factors affecting CAT enzyme activity were Cr and Cu.In the PLSR models of molecular indicators,V and As had a significant effect on the expression of sod-3,Cr and As had a significant effect on the expression of gst-4 and egl-1.In addition,the expression of egl-1 was also affected by V,and the expression of mtl-2 was significantly affected by Pb and Cu.