Contents
Chapter 1 Pollution of Acid Mine Drainage in The Mining Area 1
1.1 Acid Mine Drainage and Its Occurrence 1
1.2 Mechanism of AMD Generation 3
1.3 AMD Prevention and Control Techniques 6
1.3.1 Oxygen Barrier 6
1.3.2 Bactericide 8
1.3.3 Co-Disposal and Blending 8
1.3.4 Passivation 9
1.3.5 Passive Treatment Techniques 9
1.4 Main Points of Interest in This Book 10
1.4.1 Sulfur Cycle in AMD-Affected Watershed 10
1.4.2 Fe Cycling and Nano-Fe(III) secondary minerals in AMD-Affected Watershed 12
1.4.3 Main Points of Interest inOurWork 14
1.5 The Dabaoshan Mine 15
1.5.1 Mineral Resources of The Dabaoshan Mine 15
1.5.2 Solid Waste Disposal in the Mine Area 16
1.5.3 AMD Control and Its Treatment in Mine Area 18
1.5.4 AMD Pollution in the Dabaoshan Mine Area 20
1.5.5 General Sampling Sites Arrangement 21
Chapter 2 Sulfate Migration and Geochemical Behaviors in the AMD-Affected River 23
2.1 Physicochemical Characteristics of the Affected River Watershed 23
2.1.1 Acidic Watershed Environments 24
2.1.2 High Turbidity 25
2.1.3 Steep Riverbed Upstream 26
2.1.4 Oxidative Water Condition 29
2.1.5 High Salinity 29
2.2 Sulfur Element Distribution in the Watershed 30
2.2.1 Dissolved Sulfur in Water Phase 30
2.2.2 Sulfur Distributions in Sediments 31
Chapter 3 Metallic Elements’ Fate and Migration Mechanisms in the AMD-Affected River 37
3.1 Metallic Elements in the Watershed 37
3.1.1 Dissolved Metallic Elements in the Water Phase 37
3.1.2 Metallic Elements in Sediment Phase 38
3.2 Migration Mechanisms for Metallic Elements in the Affected Watershed 44
3.2.1 Potential Mobility 44
3.2.2 Oxidative Leaching and Re-Adsorption 45
3.2.3 Hydraulic Transportation 46
3.2.4 Precipitation/ Co-Precipitation 47
3.3 Relations of Sulfur， Iron， and Metallic Elements in the Watershed 48
3.3.1 Relationship Argumentation by SPSS Analysis 48
3.3.2 Relationship Argumentation by Mineralogy Analysis 50
3.3.3 Relationship Argumentation via Isotope Analysis 54
Chapter 4 Microbial Community Composition in AMD-Polluted Watershed and Paddy Soil 59
4.1 Microbial Community Shifts in Response to AMD Pollution in the Hengshi River Watershed 59
4.1.1 Materials and Methods 60
4.1.2 Physicochemical Characterization of the Watershed 61
4.1.3 Alpha Diversity Analyses 61
4.1.4 Beta Diversity Analyses 66
4.1.5 Spatiotemporal Dynamics of Microbial Communities 68
4.2 Microbial Community Responses to AMD-Laden Pollution in Rice Paddy Soils 81
4.2.1 Investigating the Effect of Pollution inAMD-Affected Paddy Soil 81
4.2.2 Microbial Community and Soil Properties 82
4.2.3 The Spatial Pattern of Microbial Community 91
Chapter 5 Chemical Transformations of Secondary Minerals in the AMD-Affected Area: Induced by Dissolved Organic Matter 95
5.1 Role of L-Tryptophan in the Release of Chromium from Schwertmannite 96
5.1.1 Experimental Setting 96
5.1.2 Results and Discussion 99
5.1.3 Possible Mechanism 109
5.2 Fulvic Acid Induction of the Liberation of Chromium From CrO24 -Substituted Schwertmannite 111
5.2.1 Release of Total Fe， Cr， and SO24- from Schwertmannite 111
5.2.2 Cr Speciation Analysis 122
5.2.3 Proposed Schematic Illustrating Fate of Fe and Cr 123
5.3 Elucidation of Desferrioxamine B on the Liberation of Chromium from Schwertmannite 124
5.3.1 Dissolution Kinetics 124
5.3.2 Effects of DFOB and pH on the Dissolution of Cr-Schwertmannite 125
Chapter 6 Chemical Transformations of Secondary Minerals in AMD-Affected Area: Induced by Inorganic Substance 139
6.1 Effect of Cu(II) on the Stability of Oxyanion-Substituted Schwertmannite 140
6.1.1 Schwertmannite Synthesis 140
6.1.2 Stability Experiments 141
6.1.3 Effect of Cu(II) on the Stability of Oxyanion-Substituted Schwertmannite 142
6.2 Transformation of Cadmium-Associated Schwertmannite and Subsequent Element Repartitioning Behaviors 159
6.2.1 Cd-associated Schwertmannite Synthesis 159
6.2.2 Surface Complexation Model Simulations 159
6.2.3 Cd-associated Schwertmannite Transformation Experiments 160
6.2.4 Transformation Mechanism of Cadmium-associated Schwertmannite 160
6.3 The Behavior of Chromium and Arsenic Associated with Redox Transformation of Schwertmannite in AMD Environment 173
6.3.1 Schwertmannite Synthesis 173
6.3.2 Transformation Experiments 173
6.3.3 The Behavior of Chromium and Arsenic Associated with Redox Transformation of Schwertmannite In AMD Environment 174
6.4 Thiocyanate-Induced Labilization of Schwertmannite: Impacts and Mechanisms 188
6.4.1 The Inducing Transformation of Schwertmannite 188
6.4.2 TheMechanismofThiocyanate-InducedTransformation 189
6.4.3 pH-Controlled Transformation 200
6.4.4 Ligand-Promoted Transformation 201
Chapter 7 The Microbial Transformation of Schwertmannite 203
7.1 Schwertmannite Transformation Led by Iron-Reducing Bacte

Chapter 1 Pollution of Acid Mine Drainage in the Mining Area
Heavy metal pollution is a serious concern due to the potentially harmful long-term effects for both the environment and human health. The elevated level of toxic elements in aquatic and terrestrial environments is mainly related to past and ongoing mining activities. China has many large-scale mineral resources， which account for about 12% of the total mineral resources in the world (Li et al.， 2014). According to estimates， only 0.02 t of useful material can be obtained for every 1 t of ore mined， and 0.42 t of abandoned rock， 0.52 t of tailings， and 0.04 t of smelting waste residue are left in the waste (Ripley et al.， 1995). Mining has generated about 1 500 000 ha of wasteland， and this figure is increasing by a rate of 46 700 ha per year in China (Zhuang et al.， 2009). The wastewater produced from mining operations from mine waste dumps， known in academics as acid mine drainage (AMD)， is often acidic and enriched with metallic elements， and is considered to be one of the main pollution problems that are due to historic or current mining activities (Anawar， 2015; Schaider et al.， 2014). The generation， release， mobility， and attenuation of AMD involve complex processes governed by a combination of physical， chemical and biological factors (Simate et al.， 2014). In this chapter， we review the current study work performed in recent years on AMD occurrence， effects， and generation mechanisms and summarize the approaches taken so far to prevent the AMD generation. At the end of the chapter， the research site-a classical polymetallic mining area， the Dabaoshan Mine-is introduced， and the main points of interest in the past and present study work of our team are listed.
1.1 Acid Mine Drainage and Its Occurrence
Tailings piles or ponds， mine waste rock dumps， and coal spoils are the main sources of AMD. Solid wastes of mining frequently contain significant concentrations of sulfides， such as pyrite (FeS2)， pyrrhotite (Fe1-xS)， and chalcopyrite (CuFeS2) (Naidu et al.， 2019). When the wastes are exposed to water and atmospheric oxygen， and thus are subject to weathering or rapid oxidation， the sulfide metals involved tend to become more chemically active， resulting in the generation of AMD. Water percolating through waste dumps becomes acidic， unless there are sufficient basic minerals to counterbalance the acidity (Dettrick et al.， 2019). In mining areas， AMD formation is often more extensive after mine closure and can persist for hundreds or even thousands of years. Because the pumps used to keep the water table low to facilitate mining activities are turned off after the mine is abandoned， the groundwater levels rise， making it easier for sulfide minerals to be exposed to water， oxygen， and bacteria. AMD has resulted in multiple pressures on freshwater and soil ecosystems， with severe loss of biodiversity and ecological function， and is considered a worldwide environmental problem (Steyn et al.， 2019; Park et al.， 2018).
One classic case is the Iberian Pyrite Belt， located in the southwest of Spain， which is an area heavily affected by AMD that originated from historical mining activities. In the catchment of the Odiel River， pyrite (FeS2) is the main mineral present， and other minerals such as sphalerite (ZnS)， galena (PbS)， chalcopyrite (CuFeS2)， and arsenopyrite (FeAsS) are found in minor concentrations. These minerals have been extracted since the days of the Roman Empire， although nowadays most of the mining activities have been disrupted. AMD is continuously produced from the dumps and tailings and discharged into the Odiel River even though mining activities have stopped (Sarmiento et al.， 2018; Amils et al.， 2002). In the Odiel River estuary， heavy metals have accumulated in the sediments due to the abrupt increase of pH provoked by the mixture of river water and seawater. According to Manjón et al. (2019)， the heavy metals transported to the estuary were about 8.2 t/yr of arsenic， 4 431 t/yr of zinc， 17.3 t/yr of cadmium， 53.8 t / yr of lead， and 1 647 t / yr of copper. The water located in the Cobica River basin polluted by AMD was found to have extremely low pH with an average negative pH of -1.56， which had never before been found in open-air environments contaminated by AMD. Concentrations up to 59 g/L of Fe， 2.4 g/L of Al， 740 mg/L of As， 4.3 mg/L of Co， 5.3 mg/L of Ge， and 4.8 mg / L of Sb were dissolved in the polluted waters (Sarmiento et al.， 2018).
It is estimated that more than 100 000 kilometers of river and stream systems worldwide are affected by AMD and the resultant poor water quality (Dettrick et al.， 2019). More than 6 000 kilometers of streams are polluted due to AMD from coal mines in the eastern United States. Meanwhile， in the western United States， forest lands are exposed to acid discharge from 20 000–50 000 mines， affecting about 8 000–16 000 kilometers of streams (Naidu et al.， 2019). USEPA