Soil Quality Evaluation And Improvement Effects Of Reclaimed Land Of Sirong Manganese Mine Area In Guangxi

The open-pit manganese mining leads to serious ecological damage around the mining area.The reclamation of abandoned land and the improvement of soil quality are the main measures to improve the environment of the mining area.The high geological background characteristics of heavy metals lead to poor environmental quality of reclaimed soil,and the heterogeneity of reclaimed soil significantly affects its productivity.Based on the quality evaluation of the reclaimed soil of Sirong open-pit manganese mine in Guangxi,this paper selects the appropriate reclaimed soil conditioner and studies the improvement effect.The main results are as follows:1、Effects of different reclamation methods on soil fertility quality: p H value range is 3.85 ～7.03.The order of comprehensive fertility quality is: control farmland > citrus > vegetable field >sugarcane > Eucalyptus > elephant grass > corn > ore washing soil.Impact on environmental quality: the content of Mn in reclaimed soil is 1066 ～ 4558 mg/kg,which is 1.01 ～ 4.48 times of the background value of soil in Liujiang.The results of pollution load index and potential risk assessment show that Mn is heavily polluted,the reclaimed soil is at slight risk,and the pollution of sugarcane and vegetable fields is the most serious.The morphological distribution of soil Mn is quite different,and the proportion of residual Mn increases.Reclamation methods such as citrus,vegetable field and sugarcane can significantly improve soil nutrients and reduce the availability of Mn in soil.2、Effects of Different Reclamation Years on soil fertility quality: p H value ranges from 3.85 to 6.63,and the order of comprehensive fertility quality: control farmland > 30 years > 22 years >9 years > 6 years > 3 years.Impact on environmental quality: the content of Mn in reclaimed soil is 1308 ～ 4578 mg/kg,which is 1.01 ～ 4.48 times of the background value in Liujiang.The results of pollution load index and potential risk assessment show that Mn is heavily polluted,the reclaimed soil is at slight risk,and the heavy metal pollution is the heaviest in 30 years and 22 years.The morphological distribution of soil Mn is quite different,and the proportion of residual manganese in reclaimed soil increases.Different reclamation years can improve soil nutrients and reduce the availability of Mn in soil to a certain extent.3、The results of modifier screening test showed that the four modifiers : iron modified biochar(C),activated phosphate rock powder(HL),iron modified biochar + phosphate rock powder(C+L),iron modified biochar + bentonite(C+P)could improve soil nutrients and corn biomass in varying degrees and reduced the accumulation of Mn in the underground and aboveground parts of corn.C,C+L and C+P had relatively good improvement effects.4、Further improvement effect test results showed that the p H value,total nitrogen and organic carbon content increased significantly followed by lime(SH),peat(CT),iron modified biochar(C),activated phosphate rock powder(HL),iron modified biochar + phosphate rock powder(C+L),iron modified biochar + bentonite(C+P)when 0.1% lime was applied as the substrate.CT and C could significantly increase the content of soil organic matter.C Treatment was the best for soil nutrient improvement.The root length and plant height of HL 0.6% were significantly higher than those of other improvers.C treatment had the largest increase in maize biomass,while HL had the smallest increase in maize biomass.C treatment significantly decreased the transport coefficient of Mn from maize roots to stems and leaves.Generally speaking,iron modified biochar is an ideal improver for soil remediation of manganese ore.