A review of water pollution arising from agriculture and mining activities in Central Asia: Facts, causes and effects

Highlights: • Agriculture and mining activities are the two main causes of water pollution in Central Asia. • Water pollution with nitrogen and phosphorus as pollutants is mainly distributed in irrigated areas of the middle and lower Amu Darya and Syr Darya Rivers. • Water pollution with heavy metals and radionuclides as typical pollutants is mainly distributed in the "Asian Gold Belt". • Water pollution poses a great threat to human health and fragile dry-land ecosystems. Central Asia is one of many regions worldwide that face severe water shortages; nevertheless, water pollution in this region exacerbates the existing water stress and increases the risk of regional water conflicts. In this study, we perform an extensive literature review, and the data show that water pollution in Central Asia is closely linked to human activities. Within the Asian Gold Belt, water pollution is influenced mainly by mining, and the predominant pollutants are heavy metals and radionuclides. However, in the irrigated areas along the middle and lower reaches of inland rivers (e.g., the Amu Darya and Syr Darya), water pollution is strongly associated with agriculture. Hence, irrigated areas are characterized by high concentrations of ammonia, nitrogen, and phosphorus. In addition, the salinities of rivers and groundwater in the middle and lower reaches of inland rivers generally increase along the flow path due to high rates of evaporation. Soil salinization and frequent salt dust storms in the Aral Sea basin further increase the pollution of surface water bodies. Ultimately, the pollution of surface water and groundwater poses risks to human health and deteriorates the ecological environment. To prevent further water pollution, joint monitoring of the surface water and groundwater quantity and quality throughout Central Asia must be implemented immediately.