Pattern Optimization And Red Mud Bioremediation For The Reclamation Of Mining Area

The large scale of mining resources exploration can result in serious land damage,dramatic landscape pattern changes,biological diversity damage,soil pollution,etc.Conservation of landscape ecology and soil remediation should be considered in land reclamation.Although considerable research has been done on land reclamation and vegetation restoration,biodiversity survey,reasonable landscape planning from the perspective of connectivity,and reclamation scenarios simulation are still absent to date.In addition,there is still a lack of approach to alleviate soil pollution caused by mine tailings in the post-mining landscape.In order to address these issues,through using landscape ecology and soil science theory,first,we analysed the landscape pattern dynamic changes of mining process in a typical open cast coal mine.Then we introduced combined landscape model and land use changing model to conduct connectivity analysis and reclamation scenarios simulation of abandoned mined land(AML).Finally,we developed a bioremediation method with the addition of organic matter and calcium to reduce soil pollution and improve soil structure.Results of this study provide a theoretical basis and technical guide for restoring the damaged environment,reasonably plotting reclamation schemes,and recovering the contaminated soil in post-mining areas.The main results and conclusions are in the following.Firstly,the rapid exploitation of opencast coal causes land damage and landscape pattern changes in mining areas.Conservation of landscape ecology should be considered in land reclamation plan and during implementation.Landscape indices can quantitatively describe landscape pattern changes.This study took Weijiamao opencast coal mine,located in the farming-pastoral transitional zone with low ecological vulnerability in northern China,as a case study.Landscape ecology theory and traditional statistical methods were used to analyse the landscape pattern changes during the three stages(i.e.,before exploitation,after exploitation and after reclamation).10 landscape indices were selected to evaluate the landscape pattern of three stages and principal component analysis was used to determine the weights of all landscape indices.The results showed compared with the scores of stage of before exploitation,the scores of stage of after exploration were decreased from 0.93 to 0.24.The scores of stage of after reclamation were increased from 0.24 to 0.42.The findings from this study are helpful for further analysis of multi-stage,multi-modal landscape pattern which provides a better ground for a further guide to its implementation of land reclamation planning and conservation of landscape ecology in the opencast coal mine.Secondly,AML not only possesses large land resources but also has resulted in high levels of soil pollution,soil siltation,and landslides,among other detrimental effects.In order to eliminate the negative effects,priorities should be given to the concentrated abandoned mine land to alleviate negative environmental pollution.The purpose of this study was to set up a quantifying guideline system for assessing the spatial connectivity of reclaimed AML and the surrounding land-use types.Methods of landscape ecology analysis and Fragstats software were employed to determine the guideline system.Five indicators were selected based on their ecological meanings:numbers of patches,largest patch index,shape index,proximity index,and Shannon's diversity index and their weights were gained through expert evaluation method.Finally,a case study of the program of reclaiming abandoned mine land in Xuyong County,Sichuan Province,China was taken.Three scenarios were set:scenario of all the abandoned mine land was reclaimed to cultivated land(S1),scenario of all the abandoned mine land was reclaimed to forest land(S2),and scenario of all the abandoned mine land was reclaimed to grassland(S3)to calculate the spatial connectivity of reclaimed abandoned mine land and the surrounding land-use types after reclamation.The results indicated that the spatial connectivity of reclaimed AML and the surrounding land-use types of S1 was the highest among the three scenarios.This study's findings can be used to better understand the guideline system for assessing the spatial connectivity of reclaimed abandoned mine land and provide scientific support for the optimization of spatial structure and alleviating the negative effects of abandoned land reclamation.Thirdly,connectivity modelling approaches for AML patches are limited for post-mining landscape design,especially where large changes in land use might be expected due to large-scale land reclamation.This study presents a novel approach combining AML patch sizes with a proximity index to characterise patch-scaled connectivity for determining the spatial positions of patches with huge sizes and high connectivity;according to land-use policy in China,such sites should have priority for reclamation.We then propose a scenario-based method coupled with landscape-scale metrics for quantifying landscape-scaled connectivity,which aims at exploring the optimal reclamation scheme with the highest connectivity.Using the Mentougou District in Beijing,China,as a case study,we confirmed which patches should be reclaimed first to meet the pre-determined reclamation numbers;we then tested three different reclamation scenarios(i.e.,cultivated land-orientated,forest-orientated,and construction land-orientated scenarios)to describe the impact of the different development strategies on landscape connectivity.We found the forest-orientated scenario increased connectivity quantitatively,as shown an increase in the integral index of connectivity(IIC)and other landscape-scale metrics.Therefore,we suggest that future land-use policy should emphasise converting AML into the forest to blend in with surrounding land-use categories.The findings presented here can be used to better understand quantitative analyses of the connectivity of AML patches at both the patch scale and the landscape scale and to incorporate connectivity modelling into reclamation plans,thus providing scientific support for AML management in mine-site rehabilitation.Fourthly,understanding abandoned mine land AML changes during land reclamation is crucial for reusing damaged land resources.This study combines the linear programming model and the CLUE-S model to simulate land-use dynamics in the Mentougou District(Beijing,China)from 2007 to 2020 under three reclamation scenarios,that is,the planning scenario based on the general land-use plan in study area(scenario 1),maximal comprehensive benefits(scenario 2),and maximal ecosystem service value(scenario 3).Nine landscape-scale graph metrics were then selected to describe the landscape characteristics.The results show that the coupled model presented can simulate the dynamics of AML effectively and the spatially explicit transformations of AML were different.New cultivated land dominates in scenario 1,while construction land and forest land account for major percentages in scenarios 2 and 3,respectively.Scenario 3 has an advantage in most of the selected indices as the patches combined most closely.To conclude,reclaiming AML by transformation into more forest can reduce the variability and maintain the stability of the landscape ecological system in the study area.These findings contribute to better mapping AML dynamics,optimizing land use structures,and providing policy support for the sustainable management of AML.Finally,mine tailings induced pollution is one of the main types of soil pollution.Bauxite residue(red mud)has the attributes of high pH and concentrations of salts,which cause poor soil structure and hamper the plant rooting.This study investigated the effects of organic matter(Sugarcane mulch,SH and Lucerne hay,LH)and calcium amendment on the soil structure improvement and pH reduction in the red mud bioremediation experiment.The results showed the combined organic addition and Ca2+can help improve soil aggregates and lower the contents of sodium,meeting the demand of promoting sodium leaching.Gammaproteobacteria takes a relatively higher percentage in the microbial composition in all treatments.The SC and LH amendments increased the relative abundance of Firmicutes,Actinobacteria,bacteroidetes,and fungi,which are critical to organic matter decomposition and soil development.The SC and LH amendments in the red mud increased the abundance of microbial species,including organic matter decomposing bacteria(e.g.,Lysobacter defluvii,Nocardiopsis sp),tolerant bacteria(e.g.,Alkalibacterium sp.and Stenotrophomonas sp.),and fungi.The research results can lay a basis for soil bioremediation of mine tailings.