Determining the relative impacts of natural and anthropogenic contamination in the Tambo River Basin, Peru

Abstract

Peruvian Andean Watersheds are under pressure. Mining, agriculture, urbanization, and natural stressors such as climate chance and geothermal and volcanic activity are causing water quality to deteriorate. Although rapidly declining, little attention has been given to understanding the current state of these watersheds and literature is often limited to grey literature such as academic theses and governmental reports which are difficult to access. Without baseline information on water quality, it can be challenging to properly identify sources of contamination and effectively manage these aquatic ecosystems. In this context, the water quality of the Tambo River Basin was assessed. Located in Southern Peru, the Tambo River Basin is subject to pressures from a variety of stressors such as a metal mine at its headwaters, geothermal and volcanic activity, agriculture, and urbanization. Water chemistry samples, physicochemical water quality measurements and benthic macroinvertebrates were collected from 15 sites across the basin, representing the different sources of contamination from source to mouth. Signs of contamination were evident at sites impacted by the mines, where acidic pH was recorded along with high metal concentrations exceeding Peruvian Water Quality standards for both drinking water and the aquatic environment. Sites along geothermal sources of contamination showed high concentrations of arsenic exceeding Peruvian Water Quality standards for both drinking water and the aquatic environment. At the most downstream and urbanized sites, high concentrations of lead were recorded. To our knowledge this is the first study of benthic macroinvertebrates in the region, thus it provides baseline information on the benthic macroinvertebrate communities of the Tambo River Basin. Changes in abundance, taxa richness and EPT% were compared at sites with different sources of contamination. More pollution-tolerant taxa dominated the contaminated sites and pollution-sensitive taxa were present at sites that had better water quality. Overall, this study provided baseline information on the water quality of the Tambo River Basin and helped to identify sources of contamination entering the basin contributing to pressures on the water quality and the aquatic environment. The use of benthic macroinvertebrates helped supplement physicochemical and chemistry water quality data which provides information on the conservation and management of the aquatic environment. However, given the complexity of the altitudinal gradient of this basin, this type of study should be repeated during both the dry and rainy seasons to further build upon this database. Efforts should also be directed towards preserving the ecological integrity of high altitudinal wetlands (bofedales) as they possess contaminant filtering capacity.