Dynamics of Hg and MeHg in the Madeira River basin (Western Amazon) before and after impoundment of a run-of-river hydroelectric dam

Wanderley R Bastos; José G Dórea; Luiz D Lacerda; Ronaldo Almeida; Walkimar Aleixo Costa-Junior; Célia C Baía; Izidro F Sousa-Filho; Eduardo A Sousa; Iuri Aparecida S Oliveira; Cássio S Cabral; Angelo G Manzatto; Dario P Carvalho; Kaio Augusto N Ribeiro; Olaf Malm

doi:10.1016/j.envres.2020.109896

Dynamics of Hg and MeHg in the Madeira River basin (Western Amazon) before and after impoundment of a run-of-river hydroelectric dam

Environ Res. 2020 Oct:189:109896. doi: 10.1016/j.envres.2020.109896. Epub 2020 Jul 17.

Authors

Affiliations

¹ Laboratório de Biogeoquímica Ambiental WCP, Fundação Universidade Federal de Rondônia, Brazil. Electronic address: bastoswr@unir.br.
² Faculdade de Ciências da Saúde, Universidade de Brasília, Brazil.
³ Instituto de Ciências Do Mar, Universidade Federal Do Ceará, Brazil.
⁴ Laboratório de Biogeoquímica Ambiental WCP, Fundação Universidade Federal de Rondônia, Brazil; Departamento de Ciências Sociais e Ambientais, Fundação Universidade Federal de Rondônia, Brazil.
⁵ Laboratório de Biogeoquímica Ambiental WCP, Fundação Universidade Federal de Rondônia, Brazil.
⁶ Laboratório de Biogeoquímica Ambiental WCP, Fundação Universidade Federal de Rondônia, Brazil; Instituto de Biofísica Carlos Chagas Filho, Universidade Federal Do Rio de Janeiro, Brazil.
⁷ Instituto de Biofísica Carlos Chagas Filho, Universidade Federal Do Rio de Janeiro, Brazil; Santo Antônio Energia, Porto Velho, RO, Brazil.
⁸ Santo Antônio Energia, Porto Velho, RO, Brazil.
⁹ Instituto de Biofísica Carlos Chagas Filho, Universidade Federal Do Rio de Janeiro, Brazil.

PMID: 32979999
DOI: 10.1016/j.envres.2020.109896

Abstract

The impact of a hydroelectric run-of-river (RoR) dam construction on the dynamics of total mercury (THg) and methylmercury (MeHg) is of interest to the environment and health of human and wild life. We monitored (May 2010 to October 2018) THg and MeHg in the waters and in the suspended particulate matter (SPM) of the Madeira River and its tributaries (before and after dam construction) to evaluate changes upstream and downstream from the Santo Antonio Hydroelectric Dam (SAHD). We collected 2826 samples of water and SPM at sampling stations upstream (UPMD-01, UPMD-02 and UPMD-03) and downstream the Madeira River (DWMD-04, DWMD-05 and DWMD-06), and Tributaries upstream (Branco River, Jaci-Parana River, Jatuarana-I Igarapé, Contra River, Caripunas Igarapé, Ceara Igarapé, and Teotonio Igarapé) and downstream (Jatuarana-II Igarapé and Belmont Igarapé) from the SAHD and monitored water and the total load of SPM. SPM was significantly higher in the Madeira River (median: 178.63 mg.L^-1) than in upstream and downstream tributaries (median: 15.30 mg.L^-1); however, the THg and MeHg concentrations were significantly higher in the tributaries (median: 161.14 ng g^-1 and 9.03 ng g^-1, respectively) than in the mainstream Madeira River (median = 57.06 ng g^-1 and 1.63 ng g^-1, respectively). THg concentration in the water was significantly higher in the mainstream Madeira River (median = 6.51 ng.L^-1) than in the tributaries (median = 2.57 ng.L^-1). However, the percentage of methylation in the tributaries (median = 4.9%) was 4-times higher than in the Madeira River (median: 1.3%). The significantly higher MeHg percentages in the tributaries may indicate natural (hydro-bio-geochemical factors) still predominant in this changing landscape of the Western Amazon. So far, the data suggest that this RoR has not yet impacted the THg and MeHg concentrations.

Keywords: Amazon; Damming; Gold mining; Mercury; Methyl-mercury; Rivers.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Environmental Monitoring
Humans
Mercury* / analysis
Methylmercury Compounds*
Rivers
Water Pollutants, Chemical* / analysis

Substances

Methylmercury Compounds
Water Pollutants, Chemical
Mercury