Chapter Eight - Nutrients and organic carbons in lake waters of the Third Pole

Abstract

The Third Pole (TP), spanning across eight countries in Asia, stores the largest amount of freshwater trapped as ice and snow outside the polar regions; and is home to a vast number of freshwater lakes. Despite tremendous environmental, socioeconomic, and cultural importance, the TP lakes face several natural and anthropogenic threats. The impacts of threats may be further exacerbated by the impacts of climate change, which could compromise their water quality and the crucial ecosystem services of these water bodies. Therefore the aim of this chapter is to review the status of nutrients (e.g., nitrogen and phosphorus) in lake water, and the regional cycling of POPs and carbonaceous matters in some of the TP lakes. Eutrophication is a growing environmental concern in many TP lakes. In general, remotely located high-altitude lakes in the region are still oligotrophic, but showing increasing trends of nitrogen (N) and P (Phosphorus)concentrations in contrast to lowland and mid-hill lakes characterized by a high concentration of nutrient materials. Among persistent organic pollutants (POPs), β-hexachlorocyclohexane (HCH) is the most dominant compound in TP waters, but the overall concentration of POPs in TP lakes is lower than those in European alpine lakes. In contrast, dissolved organic carbon concentrations are higher in some TP lakes. Many of the lakes are susceptible to long-range transport of atmospheric pollutants which could compromise the integrity of these water bodies. Detailed studies encompassing more substantial spatial and temporal variations combining past reconstruction of the environmental history of these pollutants could provide a comprehensive status and likely impacts of these pollutants.