| 1. |
- Mendoza, Jose Alfredo, et al.
(författare)
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Aquifer interactions with a polluted mountain river of Nicaragua
- 2008
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Ingår i: Hydrological Processes. - : Wiley. - 1099-1085 .- 0885-6087. ; 22:13, s. 2264-2273
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between a stream and nearby shallow aquifers were investigated in a mountain basin being polluted by mercury released during mining in central Nicaragua. Hourly data series of water levels and temperatures were analysed using cross-correlation. Resistivity imaging was used to map the subsurface and to complement the hydrological data interpretation. The results show the complex hydrogeological conditions that characterize the region, with weathering and fractured rock as main contributors to groundwater transport. The resistivity images suggest the presence of two vertical dykes perpendicular to the stream, and zones rich in clay. The data series indicate a rapid response from the aquifers to recharge events, followed by immediate discharge on a yearly basis. Furthermore, alternating periods of stream infiltration and aquifer discharge were identified. This work demonstrates that surface water pollution is a threat to groundwater quality in the area.
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| 2. |
- Picado, Francisco, et al.
(författare)
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Ecological, Groundwater, and Human Health Risk Assessment in a Mining Region of Nicaragua
- 2010
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Ingår i: Risk Analysis: an official publication of the Society for Risk Analysis. - : Wiley. - 1539-6924. ; 30:6, s. 916-933
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Tidskriftsartikel (refereegranskat)abstract
- Macroinvertebrates and fish in the contaminated river are faced with a higher risk to suffer from exposure to Hg than humans eating contaminated fish and bacteria living in the groundwater. The river sediment is the most hazardous source for the macroinvertebrates, and macroinvertebrates make up the highest risk for fish. The distribution of body concentrations of Hg in fish in the mining areas of the basin may exceed the distribution of endpoint values with close to 100% probability. Similarly, the Hg concentration in cord blood of humans feeding on fish from the river was predicted to exceed the BMDLs(0.1) with about 10% probability. Most of the risk to the groundwater quality is confined to the vicinity of the gold refining plants and along the river, with a probability of about 20% to exceed the guideline value.
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| 3. |
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| 4. |
- Picado, Francisco, et al.
(författare)
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Temporal and spatial distribution of waterborne mercury in a gold miner's river
- 2012
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Ingår i: Journal of Environmental Monitoring. - : Royal Society of Chemistry (RSC). - 1464-0325 .- 1464-0333. ; 14:10, s. 2746-2754
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Tidskriftsartikel (refereegranskat)abstract
- We examined the spatial and temporal (hourly) variation of aqueous concentrations of mercury in a gold miner's river to determine factors that control transport, retention, and export of mercury. The mercury flux was estimated to account for episodic inputs of mercury through mining tailings, variations in flow rate, and the partitioning of mercury between dissolved and particulate phases. Water samples were collected upstream and downstream of two gold mining sites in the Artiguas river, Nicaragua. The samples were analyzed for dissolved and suspended mercury, total solids, dissolved organic carbon, and total iron in water. Water velocity was also measured at the sampling sites. We found that mercury was mainly transported in a suspended phase, with a temporal pattern of diurnal peaks corresponding to the amalgamation schedules at the mining plants. The concentrations decreased with distance from the mining sites, suggesting dilution by tributaries or sedimentation of particle-bound mercury. The lowest total mercury concentrations in the water were less than 0.1 mu g l(-1) and the highest concentration was 5.0 mu g l(-1). The mercury concentrations are below the present WHO guidelines of 6 mu g l(-1) but are considered to lead to a higher risk to aquatic bacteria and fish in the stream than to humans. The aqueous concentrations exceed the hazard endpoints for both groups by a probability of about 1%. Particulate mercury accounted for the largest variation of mercury fluxes, whereas dissolved mercury made up most of the long-range transport along the stream. The estimated total mass of mercury retained due to sedimentation of suspended solids was 2.7 kg per year, and the total mass exported downstream from the mining area was 1.6 kg per year. This study demonstrates the importance of the temporal and spatial resolution of observations in describing the occurrence and fate of mercury in a river affected by anthropogenic activities.
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| 5. |
- Picado, Francisco
(författare)
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Fluvial transport and risk of mercury in a gold mining area
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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