Saline lakes as barriers against pollution: the case of Pétrola Lake

Nicolás Vicente Parra

Saline lakes are diverse ecosystems mostly located in arid and semi-arid regions associated with endorheic basins. These lakes are vulnerable to numerous environmental impacts closely related to human activities, including pollution. The low precipitation and high evaporation rates typical of arid regions lead to the accumulation and biomagnification of pollutants. Pollution is frequently associated to inputs from agricultural wastewaters, resulting in an increase in nutrients and subsequent eutrophication of the ecosystem. Aquatic interfaces are critical sites for nutrient turnover and biodiversity. Here, microbially mediated redox processes exert an important control on water quality. 

Pétrola Lake, in Castilla-La Mancha region (central Spain), is a good example of a saline lake heavily disturbed by agricultural activities and urban wastewater discharges. Such practices led to the declaration of this wetland as vulnerable to nitrate pollution in 1998. In this regard, Pétrola lake-aquifer system has an important potential for removing pollutants, including nitrate. Its attenuation potential is not only associated to the sediment-water interface, but also to the freshwater-saltwater interface, where the density driven flow associated to saline lakes plays a key role. In order to unravel these mechanisms, a multidisciplinary approach involving hydrochemical, multi-isotopic, geophysical, and molecular techniques was addressed. These findings have significant implications for the understanding of how saline lakes act as reactive zones pollution.