²²²RN ENRICHMENTS AND NUTRIENT CONCENTRATIONS IN THE COASTAL ZONE OF ARGENTINA?S PATAGONIA

TORRES, AMÉRICO IADRAN; DE ANDRADE, CARLOS; ATTISANO, KARINA; FALESCHINI, MAURICIO; DE PAIVA, MARIELE; DEPETRIS, PEDRO; ESTEVES, JOSÉ LUIS; NIENCHESKI, LUIS FELIPE

Bahía Blanca

Congreso; II Reunión Argentina de Geoquímica de la Superficie; 2012

IADO - CONICET/UNS

The natural enrichment of radioactive isotopes in coastal environments, such as 222Rn and 226-228Ra has been used to describe the submarine groundwater discharge (SGD) in various regions around the world. The coastal region of Patagonia is 3000 Km long, semi-arid conditions (precipitation <200mm/year) prevail and presents a semi-diurnal tide amplitude that can reach 12 m. The goal of this study was to evaluate the activity of 222Rn and nutrient concentrations in some coastal sites of Argentina?s Patagonia. Measurements were made in March 2011 on the groundwater and surface water from Puerto Deseado to San Matías gulf. In groundwater, the highest nitrate and phosphate concentrations were found in Puerto Deseado (129 µM and 2 µM, respectively) and the highest ammonium and silicate concentrations were found in Bustamante Bay (26 µM and 499 µM, respectively).In surface water the highest ammonium, nitrate, phosphate and silicate concentrations were obtained in Puerto Deseado (9 µM, 56 µM, 0.6 µM and 362 µM, respectively). Excess of 222Rn at the beach area, based on the total number of observed data for 226Ra and 222Rn, was 2 dpm·L-1. This value indicates an important advection of groundwater. Considering also that the coastal area is subjected to constant action of wind and waves that produce losses of Rn, this process may be very important. SGD is intense in southern Brazil, where the values of 222Rn are situated around 1 dpm·L-1, we assume that Patagonia?s coastal region cannot be excluded from the list of regions where the SGD contributes greatly to the biologic production. Further studies are being planned, involving other tracers such as radium isotopes and O18.