Effects Of Cl^-,NO₃^- On Pyrite Biooxidation And Migration Behavior Of AMD Contaminants In Calcareous Soil

In this paper,the effect of density and nutrition supply of Acidithiobacillus ferrooxidans on the release of typical pollutants during pyrite biooxidation process have been investigated;the influence of Cl-and NO3-on the biooxidation of pyrite and the production of acid mine drainage(AMD)have been further studied;Finally,the migration behavior of the contaminants(H+,Fe2+,Fe3+,SO42-)after acid mine drainage entered calcareous cinnamon soil also has been revealed.The results indicated that:(1)compared with the increase of the density of Acidithiobacillus ferrooxidans,increasing the nutrition supply was easier to promote the release of typical pollutants during pyrite oxidation.(2)there was no significant differences of pyrite biooxidation efficiency between the treatment without Cl-addition and with 8.2 mmol/L of Cl-addition.The biooxidation efficiency of pyrite was promoted when the initial Cl-concentration was 16.5 mmol/L.The biooxidation efficiency of pyrite was obviously inhibited when the initial Cl-concentration reached 49.4-65.8 mmol/L.However,compared to the black control system(without NO3-addition),when the NO3-concentrations were 8.2 mmol/L and 16.5 mmol/L,the biooxidation rate of pyrite was significantly improved,and the NO3-system with 8.2 mmol/L was significantly higher than the concentration of 16.5 mmol/L.As for the higher concentrations(32.9-65.8 mmol/L)of NO3-,the more pronounced the inhibition of pyrite biooxidation with increasing concentrations.And the biologically oxidized pyrite surface has obvious microbiological erosion pits.(3)after 20 batches of AMD contaminated soil experiments confirmed that the AMD of pH 2.22-2.49 entered the 0-20 cm calcareous cinnamon soil,the pH of filtrate just changed to 6.40-7.81,and the total Fe ions retention efficiency reached 99.90%-99.99%,the SO42-ions retention efficiency reached 81.67%-93.59%,meanwhile,the Cu2+ ions retention efficiency was as high as 98.74%.Compared with the original soil pH(8.24),the pH of soil0-10 cm and soil10-20 cm were 3.65-7.51 and 6.21-7.91,respectively.Element Fe and S were mainly distributed in the soil 0-10 cm,and soil pH had a great influence on the migration efficiency of element Cu.Then,element Ca can enter the lower soil layer from the surface by leaching and bind with SO42-in the lower layer formed CaSO4,so that element S vertical migration rate was significantly higher than element Fe.The CaCO3 in contaminated had a tendency to converted to CaSO4.The outcomes of this study will provide scientific significance for clarifying the formation rules of acid mine drainage.In addition,the revelation of AMD contaminants migration behavior of acid mine drainage in calcareous soil can provide the necessary parameter support for the remediation of the contaminated site.The research results have great practical significance.