Heavy metal pollution caused by small-scale metal ore mining activities: A case study from a polymetallic mine in South China
Graphical abstract
Introduction
Heavy metals are natural constituents of the earth's crust, and some of them (e.g., Cu and Zn) are essential for normal metabolic functions in plants, animals, and humans (McLennan, 1999; Saracoglu et al., 2009). They are rarely accumulated to levels that would pose detrimental effect to the environment and ecosystem under natural conditions (Chibuike and Obiora, 2014; Moore and Ramamoorthy, 1984). However, with fast industrialization and urbanization, soil heavy metal pollution caused by anthropogenic activities, such as industrial production, traffic, wastewater irrigation, sludge or municipal compost, pesticides and fertilizers, has occurred widely in many developing countries (Adler Miserendino et al., 2013; Ahmad and Goni, 2010; Deb et al., 2008; He et al., 2017; Hu and Cheng, 2013; Hu et al., 2013; Lin et al., 2018). In the rural regions, mining activities are well documented as one of the most significant sources of soil heavy metal pollution (Dong et al., 2011; Li et al., 2014; Li et al., 2015; Navarro et al., 2008; Rodríguez et al., 2009; Schmitt et al., 2007; Xiao et al., 2017; Zhuang et al., 2009). China holds diverse mineral resources and there are thousands of large- or medium-scale metal mines and numerous small-scale metal mines distributed in various parts of the country (Hu et al., 2011; Li et al., 2014). Small-scale mines have relatively limited exploitable reserves and low annual production rates of ores, and the mining operations may not last long. According to a directive released by the Ministry of Land Resources in 2004, opencast mines of iron ore with production capacities <0.6 Mt/yr and lead‑zinc ore mines with production capacities below 0.3 Mt/yr are classified as small-scale mines in China. The mining industry has been, and continues to be an important pillar of the national economy (Shen and Gunson, 2006). Unfortunately, inappropriate exploitation and uncontrolled dumping of the mine tailings, particularly at the small-scale mines, could cause serious heavy metal pollution problems.
Mining activities could pollute the surrounding environment through a range of pathways, including physical disturbance of the landscape, spilling of mine tailings, emissions of dusts contain heavy metals into atmosphere, and generation of large quantity of acidic drainage that contains heavy metals (Cheng et al., 2009; Zhuang et al., 2009). Small-scale mining activities take place throughout the world, and they are particularly widespread in the developing countries in Africa, Asia, and South America, primarily due to poor government oversight and lack of environmental awareness (Bose-O'Reilly et al., 2010; Bose-O'Reilly et al., 2010; Bosso and Enzweiler, 2008; Charles et al., 2013; Fei et al., 2017; Hurtado et al., 2006). Small-scale mines, especially the illegal ones, can be extremely damaging to the environment and often have serious health and safety consequences for the inhabitants in surrounding communities, due to their poor practices in the mining and processing of the target minerals (Hentschel et al., 2008). In recent years, the environmental problems caused by small-scale mining activities have attracted growing attention worldwide (Adler Miserendino et al., 2013; Bosso and Enzweiler, 2008; Deb et al., 2008; Tarras-Wahlberg, 2002). It has been suggested that many of the worst heavy metal pollution problems in the world resulted from the poorly regulated small-scale operations (e.g., artisanal mining) (Harris and McCartor, 2011; Scholz, 2017; Xiao et al., 2017). Over the past decade, the pollution and ecological risk arising from large-scale mining operations have been relatively well documented in China (Zhao et al., 2012; Zhuang et al., 2013), while little attention has been paid to those associated with small-scale mining activities.
There are numerous small-scale mines scattered in the remote mountainous areas of south China, including Hunan, Guangdong, Guangxi, and Jiangxi provinces, which are rich in nonferrous metal resources (Hu et al., 2016). With limited resource reserves, combined with the mountainous terrain, these small mines are unattractive to the large mining companies. Nonetheless, small developers, and often local farmers take the opportunity of exploiting them. The mineral deposits are typically extracted in primitive ways, and the minerals mined are usually sold to the large mining companies. In contrast to the large state-owned mines that follow standardized mining practices and observe environmental protection regulations, the small-scale mines are privately owned and often pay minimum attention to pollution control (Hilson, 2000; Hu et al., 2016). The wastes and wastewaters produced from the extraction, beneficiation, and processing of minerals are dumped and discharged out of convenience. Unfortunately, such small-scale mining activities, sometimes even illegal, have caught little attention because they are located in the sparsely populated remote regions and are not aware by the general public, even though the pollution caused by them can pose serious threats to the local environment and the health of local residents. Once the operations become uneconomical, the owners often abandon the mines without taking any conservation or protective measures. As a result, the abandoned mining sites could continue to serve as a source of pollution, even after active mining has long ceased.
This study was conducted to (1) evaluate the soil and water pollution caused by small-scale mining activities in China using a recently abandoned mine located in the remote mountainous region of Guangdong province as a case study, and (2) estimate the input fluxes of heavy metals from the abandoned mine to the farmlands in the surrounding areas, and thus demonstrate the significant need for proper containment of the mining tailings. The Yaoposhan polymetallic mining district, which encompasses multiple small-size opencast mining sites, is located in the remote mountainous part of northern Guangdong province in China (Fig. 1). The production scale of this mine was set at 0.05 Mt/yr of raw iron ore and 0.03 Mt/yr raw lead‑zinc ore, which merely meet the minimum thresholds for establishing a mining operation. Although the planned production period was 10 years, the actual production lasted no more than 5 years at the mining district. A cluster of mining sites (mostly abandoned) are scattered on the small hills with good vegetation coverage. Except for the mining and farming activities, and very limited vehicle traffic, surface soils in this area are not affected by other obvious anthropogenic sources. Thus, this area is ideal for examining the impact of small-scale mining activities on the surrounding environment. The total contents of heavy metals in the mine tailings, surface soils, and water samples collected in the area were analyzed in this study, and the chemical speciation of heavy metals in selected surface soil samples were also characterized. Sources of the heavy metals in the surface soils of the local farmlands was identified by Pearson's correlation matrix and multivariate statistical analysis, including principal component analysis (PCA) and cluster analysis (CA). Pollution indices were used to assess the overall pollution status of the surface soils, and the potential ecological risk posed by the heavy metals in the farmland soils was also evaluated. Finally, the mass fluxes of heavy metals released into the surface soils from the mining sites were estimated.
Section snippets
Study area and sample collection
Yaoposhan polymetallic mine (24°31′16″, 113°04′29″) is located in Shaoguan, close to the border between Guangdong and Hunan provinces of south China (Fig. 1). The primary minerals of this mine include limonite, pyrite, lead‑zinc ore, and some rare earth minerals. A cluster of opencast mining sites are situated on the top of the hills. Relatively large-scale exploitation activities started in 2012, while most of the production sites were abandoned in 2014. To date, primitive ore mining still
Heavy metal pollution of soil and water
Table 1 summarizes the mean contents of heavy metals in the mine tailings, the surface soils from the surrounding farmlands, the drainage and stream source water samples in the mining district, and the stream water samples, along with their pH ranges. As expected, the mine tailings contain a range of heavy metals at elevated levels: the mean contents of Cu, Zn, As, Cd, and Pb were up to 2.48 × 103, 2.87 × 103, 440, 26.6, and 3.17 × 103 mg/kg, respectively. The mine drainage samples were acidic
Conclusions
The dumped mine tailings and drainage of the tailings in the abandoned Yaoposhan polymetallic mine had high levels of heavy metals, while the farmland soils surrounding the mining district were seriously polluted by heavy metals. Pollution by Cu, Zn, As, and Cd was detected in nearly all the soil samples, while pollution by Pb occurred in approximately 80% of the soil samples. Results of Pearson correlation matrix, PCA, and CA indicate that Cr and Ni in the soils derived primarily from
Acknowledgement
This work was supported in parts by the National Key Research and Development Program of China (2016YFD0800302), the Natural Science Foundation of China (Grant Nos. 41725015, 41673089, and 41472324), and the Fundamental Research Funds for the Central Universities (Grant No. 2652015141).
References (58)
- et al.
Challenges to measuring, monitoring, and addressing the cumulative impacts of artisanal and small-scale gold mining in Ecuador
Res. Policy
(2013) - et al.
Acid leaching of heavy metals from contaminated soil collected from Jeddah, Saudi Arabia: kinetic and thermodynamics studies
Int. Soil. Water Conserv. Res.
(2015) - et al.
Health assessment of artisanal gold miners in Indonesia
Sci. Total Environ.
(2010) - et al.
Health assessment of artisanal gold miners in Tanzania
Sci.Total Environ.
(2010) - et al.
Geochemical processes controlling fate and transport of arsenic in acid mine drainage (AMD) and natural systems
J. Hazard. Mater.
(2009) An ecological risk index for aquatic pollution control — a sedimentological approach
Water Res.
(1980)Barriers to implementing cleaner technologies and cleaner production (CP) practices in the mining industry: a case study of the Americas
Miner. Eng.
(2000)- et al.
A method for apportionment of natural and anthropogenic contributions to heavy metal loadings in the surface soils across large-scale regions
Environ. Pollut.
(2016) - et al.
The challenges and solutions for cadmium-contaminated rice in China: a critical review
Environ. Int.
(2016) - et al.
Contamination and health risks of soil heavy metals around a lead/zinc smelter in southwestern China
Ecotoxicol. Environ. Saf.
(2015)
A review of soil heavy metal pollution from mines in China: pollution and health risk assessment
Sci. Total Environ.
Linkage between human population and trace elements in soils of the Pearl River Delta: implications for source identification and risk assessment
Sci. Total Environ.
Abandoned mine sites as a source of contamination by heavy metals: a case study in a semi-arid zone
J. Geochem. Explor.
A modification of the BCR sequential extraction procedure to investigate the potential mobility of copper and zinc in shrimp aquaculture sludge
Microchem. J.
Contents and relationship of elements in human hair for a non-industrialised population in Poland
Sci. Total Environ.
Heavy metal distribution and chemical speciation in tailings and soils around a Pb–Zn mine in Spain
J. Environ. Manag.
Evaluation of trace element contents of dried apricot samples from Turkey
J. Hazard. Mater.
Accumulation of metals in fish from lead–zinc mining areas of southeastern Missouri, USA
Ecotoxicol. Environ. Saf.
Geochemical fractions of chromium, copper, and zinc and their vertical distribution in floodplain soil profiles along the Central Elbe River, Germany
Geoderma
The role of artisanal and small-scale mining in China's economy
J. Clean. Prod.
Environmental management of small-scale and artisanal mining: the Portovelo-Zaruma goldmining area, southern Ecuador
J. Environ. Manag.
Soil heavy metal contamination and health risks associated with artisanal gold mining in Tongguan, Shaanxi, China
Ecotoxicol. Environ. Saf.
Cadmium and manganese distributions in the Hudson River estuary: interannual and seasonal variability
Earth Planet. Sci. Lett.
Human health risk from soil heavy metal contamination under different land uses near Dabaoshan Mine, Southern China
Sci. Total Environ.
Soil heavy metal pollution around the Dabaoshan mine, Guangdong Province, China
Pedosphere
Heavy metal contamination in soil and soybean near the Dabaoshan mine, South China
Pedosphere
Health risk from heavy metals via consumption of food crops in the vicinity of Dabaoshan mine, South China
Sci. Total Environ.
Heavy metal contamination in water, soil, and vegetables of the industrial areas in Dhaka, Bangladesh
Environ. Monit. Assess.
Fractionation and mobility of cadmium and lead in soils of Amol area in Iran, using the modified BCR sequential extraction method
Chem. Speciat. Bioavailab.
Cited by (237)
Waste biomass derived chitosan-natural clay based bionanocomposites fabrication and their potential application on wastewater purification by continuous adsorption: A critical review
2024, South African Journal of Chemical Engineering