Tracing contaminants of emerging concern in the Awash River basin, Ethiopia

Awash River basin, Central Ethiopia The study focuses on characterization of Emerging Organic Contaminants (EOCs) in the Awash River basin. Characterization of the EOCs was supplemented by chemical analysis of samples from river, boreholes, tap water, and surface water reservoirs. Analyses of environmental isotopes (δ 2 H, δ 18 O, and 222Rn) were used to investigate the exchange of contaminants between surface and groundwater supply sources. More than 100 EOCs are identified in all water supply sources. The EOCs are linked to agricultural applications, urban, and industrial sources. Based on the analysis of chemical and environmental tracers, the deep groundwater has greater protection from contamination than the river and the shallow groundwater. The heavy metal analysis prevails the same. The shallow aquifers are affected by urban, industrial, and agricultural pollutants. Attributed to the different contaminant sources, distinct variations in terms of compound types were observed at different locations. Water supply sources located upstream are dominated by urban and industrial contaminants while compounds from agricultural applications dominate the downstream sites. Artificial infrastructures serve as attenuation points for urban and industrial sourced compounds. Characterization of EOCs showed new contaminant loads in the water supply sources, which haven't been tested before, with potential impact on human and wider environmental health, and may necessitate a revision of the customary water quality test and monitoring practices. • EOCs characterized in water supply sources in upper Awash River sub-basin, Ethiopia. • Awash River and shallow groundwater systems are intimately interconnected. • Highly contaminated Awash River impacts and the shallow groundwater quality. • The deep groundwater system is less affected from the Awash River pollution. • Artificial infrastructures like Aba Samuel and Koka Lakes act as pollution attenuation points