Reservoir stratification affects methylmercury levels in river water, plankton, and fish downstream from Balbina hydroelectric dam, Amazonas, Brazil.
Environ Sci Technol
; 48(2): 1032-40, 2014 Jan 21.
Article
em En
| MEDLINE
| ID: mdl-24397364
ABSTRACT
The river downstream from a dam can be more contaminated by mercury than the reservoir itself. However, it is not clear how far the contamination occurs downstream. We investigated the seasonal variation of methylmercury levels in the Balbina reservoir and how they correlated with the levels encountered downstream from the dam. Water, plankton, and fishes were collected upstream and at sites between 0.5 and 250 km downstream from the dam during four expeditions in 2011 and 2012. Variations in thermal stratification of the reservoir influenced the methylmercury levels in the reservoir and in the river downstream. Uniform depth distributions of methylmercury and oxygen encountered in the poorly stratified reservoir during the rainy season collections coincided with uniformly low methylmercury levels along the river downstream from the dam. During dry season collections, the reservoir was strongly stratified, and anoxic hypolimnion water with high methylmercury levels was exported downstream. Methylmercury levels declined gradually to 200 km downstream. In general, the methylmercury levels in plankton and fishes downstream from the dam were higher than those upstream. Higher methylmercury levels observed 200-250 km downstream from the dam during flooding season campaigns may reflect the greater inflow from tributaries and flooding of natural wetlands that occurred at this time.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Plâncton
/
Poluentes Químicos da Água
/
Monitoramento Ambiental
/
Rios
/
Peixes
/
Compostos de Metilmercúrio
Tipo de estudo:
Prognostic_studies
Limite:
Animals
País como assunto:
America do sul
/
Brasil
Idioma:
En
Ano de publicação:
2014
Tipo de documento:
Article