Application of hydrochemical and multi-isotopic (87Sr/86Sr, δ13C-DIC, δ2H- H2O, δ 18O-H2O) tools to determine contamination sources and processes in the Guadalhorce River Basin, southern Spain

The integrated use of multi-isotopic (Sr-87/Sr-86, delta C-13-DIC, delta H-2-H2O, delta O-18-H2O) and hydrochemical data was applied in the highly anthropized Guadalhorce river basin, southern Spain, to improve the knowledge about water contamination sources and processes and to achieve improved water resource management. The results obtained highlight the importance of the use of isotopes as tracers of pollutants. DIC, delta H-2-H2O, delta O-18-H2O and delta C-13-DIC allowed differentiating two water recharge end members: direct rainwater, infiltrated into the upper and lower detritic aquifers of the sub-basins, and the Guadalhorce dam system, which act as a source in some groundwater and surface waters of the lower sub basin. Sr-87/Sr-86 data supported the existing conclusions in relation to pollution sources in the study area. The Triassic basement (evaporites) of the carbonate and detritic aquifers of the basin generally controls the natural 87Sr/86Sr composition in waters of the upper sub-basin. Only one groundwater sample reflects the influence of a human organic source (sewage) in its composition. On the other hand, mixing of human inorganic (fertilizers and detergents) strontium sources is required to explain the Sr-87/Sr-86 contents of the lower sub-basin waters. Discriminating the use of domestic detergents as another anthropogenic source of strontium and sulphate in waters is a novel finding in this research. The conclusions reached can be extrapolated to other anthropized basins.

Automated summary

The integrated use of multi-isotopic and hydrochemical data can improve the understanding of water contamination sources and achieve improved water resource management. Isotopes can serve as tracers of pollutants and differentiate different water recharge end members. The study also identified domestic detergents as an anthropogenic source of strontium and sulphate.