Fluvial transport and risk of mercury in a gold mining area

Författare

Francisco Picado

Summary, in English

My thesis is part of an overall environmental program evaluating the environmental and human health stress in areas of Nicaragua affected by anthropogenic emission of metals and man-made organic substances. I examine the fluvial transport of mercury contextually associated with the extent of the contamination and the observed human and environmental stress in a gold mining area. Field measurements (Papers I, II, IV, and V), experimental assays (Paper III), and risk assessment (Paper VI) are used in the investigation on a basin scale. Even though the same processes and mechanisms apply for the accumulation and the movement of mercury in river and ground water systems, the local hydrogeological and climatic conditions together with the dynamic of mining activity make the fluvial transport and the accumulation of mercury site specific. Therefore, I consider that efforts to elucidate the transport and fate of mercury dependence on local environmental settings and its implication for humans are compulsory in assessing the impact of the poorly-controlled use of mercury in gold mining areas. Hence, to take actions for human and environmental protection.

At the basin scale, flowing water is thought to export and dissipate the pollution. Hence, rivers and streams in gold mining areas are used for mercury-enriched waste disposal. Notwithstanding, levels of mercury of environmental concern are observed in water and river sediments. Since mercury in sediments is a threat to streams organisms and exposes riverine human populations through the consumption of mercury-contaminated fish, the accumulation of mercury in the sediment phase has been of particular importance from the perspective of human health. Therefore, it is of great importance to elucidate the processes involved in the fluvial transport and phase partitioning of mercury in a river, and the interaction with the groundwater system in such sensitive areas. Even though environmental levels of mercury in gold mining watersheds are low, a risk evaluation is also needed, because mercury bio-concentrates and bioaccumulates in exposed receptors. The results of my studies may also help to promote the environmental control and to contribute to the development of water quality criteria that can be used for regulatory purposes in gold mining areas of a developing country.

The insights gained from the investigations carried out in the Sucio river basin call for an environmental and human health care and apply for an environmental monitoring. Together with other findings reported by other studies, the insights can be a core of useful information to implement alternatives in the abatement of the contamination in the river basin.

Avdelning/ar