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Estimation of the ecological and human health risk of mercury in a mangrove area of the La Puntilla estuary, El Oro province, southern Ecuador

Abstract:

Present study focused on the evaluation of total mercury concentration and the estimation of ecological risk (Er), the ecological risk index (IR); and the toxic risk or hazard quotient (HQ) for human health in a mangrove area that borders the mouths of the Chaguana and Siete rivers, in La Puntilla estuary in the south of Ecuador. For the determination of the Er, RI, and HQ, we identified three indicators of mercury contamination: sediments, mangrove root, and soft tissue of the bivalve mollusk Anadara tuberculosa. In the mangrove area that borders the mouth of the Chaguana river, the mercury concentration fluctuated between 0,11-0,06 mg/kg in sediments, 0.06-0,01mg/kg in mangrove root, with a more consistence presence of A. tuberculosa, but one bivalve sample reported a level of 0,034 mg/kg of mercury. In contrast to the mangrove area adjacent to the mouth of the Siete river, whose concentrations ranged from 0,77-0,42 in sediments, and 0,15-0,12 in mangrove root, we found the highest mercury contamination, being imperceptible to the presence of A. tuberculosa. Results of the risk analysis indicated that, at the mouth of the Chaguana river, the Er and the RI index were placed in the “low” category. In contrast, at the mouth of the Siete river, the Er was “high,” and RI was “moderate.” Potential risk to human health was low, consistent with the value of HQ < 1 that considers the consumption of A. tuberculosa and dermal contact through sediments; however, the low presence of the bivalve at the mouth of the Siete river is of concern.