Study On The Influence Of Lead-naphthalene Combined Pollution On Lead Speciation And Its Microbial Effects

The continuous mining of non-ferrous metal mines has led to the concentration areas of non-ferrous metal mines becoming a huge source of pollution with high concentrations of heavy metals and organic beneficiation chemicals,which caused serious harm to the surrounding ecological environment.As the simplest polycyclic aromatic hydrocarbons(PAHs)in structure,naphthalene is widely used in hydrometallurgy of non-ferrous metal mines.Lead(Pb)is one of the most common heavy metal pollutants in non-ferrous metal mines.Both of them coexist in the mine and form combined pollution of the mine environment.Based on the three-step extraction method of BCR,microcalorimetry and 16 S r RNA sequencing technology,this study is aimed to explore the influence of lead-naphthalene combined pollution on lead speciation and microbial effects.The main research conclusions are as follows:The speciation of lead mainly exists in the residue state and the reducible state.The combination of lead and naphthalene has not changed the situation that the speciation of lead is mainly the residue state and the reducible state.With the increase of culture time,the speciation of lead changed from a reducible state to a more stable residue state.Lead is complexed with soil organic matter so that lead exists in a higher proportion of reducible state in the sample group containing 200 mg/kg lead.Lead combined with naphthalene to form a reducible state so that the reducible state of lead was less converted into other speciation as the culture time increased.The single and combined pollution of lead and naphthalene promoted the soil microbial metabolic activity in the early stage of culture,and show an inhibitory effect at the end of culture.The effects of naphthalene on microbial metabolic activity at lower concentrations(200 mg/kg)are stronger than those at higher concentrations(400 mg/kg).The combined pollution of lead and naphthalene has a synergistic effect on the microbial metabolic activity.In the combined pollution of lead and naphthalene,the activity of microorganisms is related to the oxidizable state and reducible state of lead.Lead and naphthalene had higher relative abundance to the resistant bacteria,and the combined pollution had synergistic effect on them.The influence of naphthalene on the composition of the microbial community weakened with its dissipation,but the influence of lead and the combined pollution with naphthalene on the composition of the microbial community increased with time.The single and combined pollution of lead and naphthalene reduced the diversity,uniformity and richness of samples,and the combined pollution mainly played an antagonistic effect.As the culture time increases,the diversity,uniformity and richness of soil microorganisms increased.The addition of lead and naphthalene failed to change the composition of the main soil species.Lead and naphthalene had a higher relative abundance to the resistant bacteria,and the combined pollution had a synergistic effect on them.The influence of naphthalene on the composition of the microbial community weakened with its dissipation,but the influence of lead and the combined pollution with naphthalene stronger with time increased.In summary,this study clarified the effects of lead-naphthalene combined pollution on lead speciation and microbial metabolic activity and diversity,and provided a theoretical basis for the prevention and control of heavy metals and organic flotation reagent compound pollution in non-ferrous metal mining areas.