A resilience-based approach in managing the closure and abandonment of large mine tailing ponds

Mining tailing ponds are large infrastructure objects whose life cycle spans over several decades.They are indispensable for certain types of mines where technological process produces and rejects mud.They also have potential to generate risks for human life,property and environment.For that reason,it is essential to adequately manage them throughout all the stages of their life cycle.The phase of their closure and abandonment is less studied and understood.The paper proposes a holistic resilience-based approach for analyzing this phase of their life cycle.The proposed methodology is validated through a case study at an actual surface iron ore mine in Bosnia and Herzegovina.

Chemical weathering profile in the V–Ti–Fe mine tailings pond:a basalt-weathering analog

The(ultra-)mafic mine tailings pond revealed a weathering discrepancy in the tailings profile,which provided a valuable analog to assess the role of carbonate and silicate weathering of the basalt.In this study,drill-cores samples were selected from the Wanniangou V–Ti–Fe mine tailings pond(Sichuan province,China)to investigate the mineralogicand geochemical characteristics in the tailings profile.The results reveal(1)the tailings pond profile consist of upper and lower layers.The upper layer is composed of carbonate weathering(1.4%),which was formed in the initial stages of tailings exposure and represented a minimal weathering degree.(2)The lower layer was primarily observed at the aquifer zone of the tailings pond,and was consistent with 0.45%carbonate weathering and 48.4%silicate weathering.(3)The weathering discrepancy in the tailings profile could be due to the sulfide oxidation and aerobic/flowing aquifer,which facilitate the water-tailings reactions.The tailings profile provides an analog to studying basalt weathering,as it spans both carbonate and silicate weathering.This research reinforces the idea that silicate weathering is predominant in basaltic areas and plays a crucial role in regulating atmospheric CO_(2)(carbon dioxide)levels on Earth.

Early Warning of Heavy Metal Pollution after Tailing Pond Failure Accident

Heavy metal pollution is a major issue after tailing pond failure accident.It is important to predict pollution trends for limited data of pollution sources.A simple phase separation heavy metal model was built for early warning simulation of heavy metal pollution accidents.Based on this,a new simulation framework has been developed to predict the pollution trends of the downstream according to the measured data at upstream sections.By setting the upstream monitoring date as the inflow boundary condition,the changing processes of heavy metal manganese(Mn) with different phases in the downstream can be accurately simulated and forecasted.Results showed that the concentration of the suspended phase in the downstream was larger than that in the aqueous phase and sediment phase.With this,the early warning of pollution trends after accidents could be made a few days ahead.It indicates that the impact of sediment on heavy metal should not be ignored in the early warning of tailing pond failure accidents.

Safety assessment of waste rock dump built on existing tailings ponds

The construction of waste rock dumps on existing tailing ponds has been put into practice in China to save precious land resources. This work focuses on the safety assessment of the Daheishan molybdenum mine waste rock dump under construction on two adjoining tailings ponds. The consolidation of the tailings foundation and the filling quality of the waste rock are investigated by the transient electromagnetic method through detecting water-rich areas and loose packing areas, from which, the depth of phreatic line is also estimated. With such information and the material parameters, the numerical method based on shear strength reduction is applied to analyzing the overall stability of the waste rock dump and the tailings ponds over a number of typical cross sections under both current and designed conditions, where the complex geological profiles exposed by site investigation are considered. Through numerical experiments, the influence of soft lenses in the tailings and possible loose packing areas in the waste rock is examined. Although large displacements may develop due to the soft tailings foundation, the results show that the waste rock dump satisfies the safety requirements under both present and designed conditions.

Spatial distribution and ecological risk of heavy metals and their source apportionment in soils from a typical mining area, Inner Mongolia, China

Determining the distributions and sources of heavy metals in soils and assessing ecological risks are fundamental tasks in the control and management of pollution in mining areas.In this study,we selected 244 sampling sites around a typical lead(Pb)and zinc(Zn)mining area in eastern Inner Mongolia Autonomous Region of China and measured the content of six heavy metals,including cuprum(Cu),Zn,Pb,arsenic(As),cadmium(Cd),and chromium(Cr).The ecological risk of heavy metals was comprehensively evaluated using the Geo-accumulation index,Nemerow general pollution index,and potential ecological risk index.The heavy metals were traced using correlation analysis and principal component analysis.The results showed that the highest content of heavy metals was found in 0–5 cm soil layer in the study area.The average content of Zn,As,Pb,Cu,Cr,and Cd was 670,424,235,162,94,and 4 mg/kg,respectively,all exceeding the risk screening value of agricultural soil in China.The areas with high content of soil heavy metals were mainly distributed near the tailings pond.The study area was affected by a combination of multiple heavy metals,with Cd and As reaching severe pollution levels.The three pathways of exposure for carcinogenic and noncarcinogenic risks were ranked as inhalation>oral ingestion>dermal absorption.The heavy metals in the study area posed certain hazards to human health.Specifically,oral ingestion of these heavy metals carried carcinogenic risks for both children and adults,as well as noncarcinogenic risks for children.There were differences in the sources of different heavy metals.The tailings pond had a large impact on the accumulation of Cd,Zn,and Pb.The source of Cr was the soil parent material,the source of As was mainly the soil matrix,and the source of Cu was mainly the nearby Cu ore.The purpose of this study is to more accurately understand the extent,scope,and source of heavy metals pollution near a typical mining area,providing effective help to solve the problem of heavy metals pollution.

Land-Cover Change Monitoring in Obuasi, Ghana： An Integration of Earth Observation, Geoinformation Systems and Stochastic Modelling

For over twenty years, Obuasi Municipality, Ghana, has experienced land-cover change arising from gold mining and urbanisation. This project quantified the land-cover changes that have taken place and projected likely future land-cover. An integration of EO （earth observation）, GIS （geographical information science） and Stochastic Modelling was examined. Post-classification Change Detection employed Landsat TM or ETM＋ images in 1986, 2002 and 2008. Subsequently, Markov Chain Analysis projected the land-cover distribution for 2020. Seven broad land-use and land-cover classes were identified and mapped, namely： built-up areas, mine sites tailing ponds barren land forestland farmland and rangeland. The results obtained for the 2008 to 2020 projection revealed a continuous expansion of built-up areas （1.63%）, mine sites （0.89%） and farmland （3.4%）, and a reduction of forestland （4.17%） and rangeland （2.59%）. Despite the advent of very high resolution satellite imagery, this use of EO and GIS technology focussed on low-cost and lower resolution satellite imagery, coupled with Markov Modelling and was found to be beneficial in describing and analysing land-cover change processes in the study area, and was hence potentially useful for strategic planning purposes.

Abiotic and biotic constituents of oil sands process-affected waters

The oil sands in Northern Alberta are the largest oil sands in the world,providing an important economic resource for the Canadian energy industry.The extraction of petroleum in the oil sands begins with the addition of hot water to the bituminous sediment,generating oil sands process-affected water(OSPW),which is acutely toxic to organisms.Trillions of litres of OSPW are stored on oil sands mining leased sites in man-made reservoirs called tailings ponds.As the volume of OSPW increases,concerns arise regarding the reclamation and eventual release of this water back into the environment.OSPW is composed of a complex and heterogeneous mix of components that vary based on factors such as company extraction techniques,age of the water,location,and bitumen ore quality.Therefore,the effective remediation of OSPW requires the consideration of abiotic and biotic constituents within it to understand short and long term effects of treatments used.This review summarizes selected chemicals and organisms in these waters and their interactions to provide a holistic perspective on the physiochemical and microbial dynamics underpinning OSPW.

Using immune cell-based bioactivity assays to compare the inflammatory activities of oil sands process-affected waters from a pilot scale demonstration pit lake

In this study,we provide evidence that oil sands process-affected waters(OSPW)contain factors that activate the antimicrobial and proinflammatory responses of immune cells.Specifically,using the murine macrophage RAW 264.7 cell line,we establish the bioactivity of two different OSPW samples and their isolated fractions.Here,we directly compared the bioactivity of two pilot scale demonstration pit lake(DPL)water samples,which included expressed water from treated tailings(termed the before water capping sample;BWC)as well as an after water capping(AWC)sample consisting of a mixture of expressed water,precipitation,upland runoff,coagulated OSPW and added freshwater.Significant inflammatory(i.e.macrophage activating)bioactivity was associated with the AWC sample and its organic fraction(OF),whereas the BWC sample had reduced bioactivity that was primarily associated with its inorganic fraction(IF).Overall,these results indicate that at non-toxic exposure doses,the RAW 264.7 cell line serves as an acute,sensitive and reliable biosensor for the screening of inflammatory constituents within and among discrete OSPW samples.