Influence Of Acid Mining Drainage On The Chemical Composition Of Pore Water In Soil Profile Of Farmland And Its Mechanism

The sulfide mineral of mining with the characteristics of low pH,low nutrition,high sulfate and heavy metals,which contact with air and water,producing the Acid mine drainage by redox reaction.It makes pollution through irrigation,surface runoff,water infiltration into the soil and water.In this research,the field soil pore water polluted by the Acid mine drainage in the city of Tongling in Anhui province was studied,which analyzed the characteristics of physical and chemical properties of soil pore water in different depth of profile and discussed the effect of the Acid mining drainage on soil pore water by field sampling and simulation research in laboratory,in order to explain the harm of the acidic mining drainage on soil scientifically,and provide theoretical basis for the pollution risk assessment and soil bioremediation in polluted areas in Tongling.The main findings are as follows:1.Plant growth,profile depth and time changes all affect the content of pore water components in soils contaminated by the Acidic mining drainage,especially the content of nutrients and metals in pore water.(1)The contents of pH and HCO3-in pore water polluted by the Acidic mining drainage did not change significantly in the depth of profile.Both the contents of total carbon in July and October and F in December gradually increased with the increase of the depth of the section in the soil pore water in the two test areas(planted and unplanted plants),while EC in October decreased and didn't affect by planting.However,the contents of NH3-N?Fe2+?Fe?Mn in July,the HSiO3-?Cu?Ti in October,and the EC?NO3--N?Ca2+?Cl-?SO42-?HSiO3-?S2-?Al?Mn in December was significantly influenced by planting.(2)In sampling time,the contents of pH and NH3-N in pore water polluted by the Acidic mining drainage didn't change significantly in the depth of each section.The contents of EC?NO3--N?Cl-?Al?Cu in soil pore water in the two test areas(planted and unplanted plants)increased gradually,while the TC decreased and didn't affect by planting.In addition,the contents of Ca2+?F-?SO42-?HSiO3-?HCO3-?S2-?Fe?Mn in soil pore water in the two test areas(planted and unplanted plants)have a completely different trend with the change of sampling time.2.The effects of the Acid mining drainage on physical and chemical properties of soil pore water were preliminarily revealed by field test and laboratory soil column test simulation.The leaching of the Acidic mining drainage reduced the pH value of soil pore water in profile,which leads to the changes of nutrient and main mineral elements in pore water.In addition,The leaching of the Acidic mining drainage increased the contents of H+ and salt ions in soil environment,decreased the pH value of pore water and increased the EC of pore water.The NH3-N and K+ of pore water are mainly distributed in the profile layer 0-20 cm,and their contents decreased significantly with the increase of profile depth,and the reduction rate of NH3-N of pore water was greater than K+ The content of SO42-in pore water increased significantly with the increase of the leaching time of Acid mining drainage,and the content of SO42-in pore water in the profile layer 0-60cm was higher and the growth rate was higher.The Fe and Mn in pore water were enriched in profile layer 0-20 cm and 20-40 cm respectively,and the section area was also the main active area of the crop rhizosphere.Therefore,the long-term pollution of the Acidic mining drainage will inevitably lead to soil nitrogen and potassium leaching,soil compaction,serious shortage of soil fertility and plant heavy metal enrichment,which is similar to the characteristics of farmland soil contaminated by the Acidic mining drainage in Tongling.