Identification of anthropogenic impact using nitrogen isotope as chemical markers. Case study: Three reservoirs with different eutrophication level in Córdoba (Argentina).

GRIBOFF, JULIETA; AMÉ, MARÍA VALERIA; WUNDERLIN, D.A; MONFERRÁN, MAGDALENA VICTORIA

Pretoria

Workshop; Africa Food Safety Workshop 2018; 2018

International Atomic Energy Agency, National Metrology Institute of South Africa

In this study we measure δ15N values in various organisms (from primary producers to upper consumers) to understand the influence of the different anthropogenic activities on the environment and the possibility to distinguish regions with different type of contamination, as well as areas of greater or lesser risk to food production, in particular aquaculture.Study site samplings were carried out during April 2014 and April 2017 in three reservoirs in Córdoba, Argentina: San Roque, Los Molinos and Río Tercero reservoirs. San Roque reservoir supplies drinking water to Córdoba, and is also intended for recreational uses. It is surrounded by cities and settlements which are not fully connected to public sewage system. Los Molinos reservoir provides water to the Southeast of the city of Córdoba and is used for recreational activities and irrigation. In the surrounding agriculture dominantly corn and sorghum is produced. Río Tercero is the largest artificial reservoir in the province of Córdoba and used for water supply and industrial activities, as providing cooling water for a nuclear power plant.We collected water, plankton, shrimp (Palaemonetes argentinus), and fish (Odontesthes bonariensis) from each reservoir. Stable isotope analysis was performed in an Isotope Ratio Mass Spectrometer, connected with an elemental analyzer (both Thermo Fisher Scientific). San Roque reservoir showed the highest δ15N values, for all the samples, indicating the most prominent influence of sewage on the lake ecology. Moreover, highest δ15N values in edible fish were observed during 2017 monitoring campaign with respect to 2015 one, warning about the deterioration of the reservoirs.Further research studies are being conducted to confirm this preliminary result, providing an interesting alternative to link sewage discharges with levels of stable isotopes in biota, including edible fish; thus, pointing out risk for people drinking water or eating fish from such impacted lakes.