RIESGO ECOLÓGICO POTENCIAL POR ARSÉNICO EN LA DESEMBOCADURA DEL RÍO LOA, NORTE DE CHILE

Potential ecological risk by arsenic in the available fractions of the sediment in the river, lagoon, mixing zone and beaches bordering the mouth of the Loa River, north of Chile, was determined based on low and medium range effects. The distribution constant, geoaccumulation index and As enrichment factor were deduced. To estimate reactive As, three simple extraction procedures were compared. In order to obtain the risk assessment code, the first two stages of sequential Tessier extraction and bioavailability were applied according to the modified BCR schema. The salty and alkaline continental waters showed a reducing character, low OD, N/P and Cu, but high As (1.13-1.80 mg/l), diluted in the sea at 0.012 mg/L. The neutral continental sediments presented low organic matter (2-6%), acceptable levels of N/P, CaCO 3 (5.3-31%) and Cu, but elevated As (516-856 mg/kg). As reached levels of 20 mg/kg in marine sediments. According to the geoaccumulation index values, there was terrestrial but not marine pollution, although the enrichment factors confirm the presence of high potential risk at the river mouth. Simple extractions and the risk assessment code point to As as mobile and bioavailable. The level of As in the fluvial sediment associated with interchangeable, reducible and oxidizable fractions confirm potential risk for the ecosystem under alkaline and reducing conditions. On the other hand, in the coastal border As was found associated mainly with residual and interchangeable fractions, which reduces this potential risk.