S20 Mercury research in developing countries

In the framework an IAEA Technical Cooperation Project “Use of Nuclear Techniques to Address the Management Problems of Coastal Zones in the Caribbean Region (RLA7012)” sediment cores from twelve coastal areas in the Caribbean were collected, analyzed for geochemical parameters, pollutants and dating using Pb-210 radiochronology models. In this work, we present the temporal behaviours of mercury in these ecosystems. An increase in mercury fluxes to the coastal zone is characteristic at all sites, mainly in densely populated areas (Port-au- Prince, Haiti) or near to discharges from chlor-alkaly plants (Cartagena bay-Colombia and Sagua Estuary-Cuba ). These results contribute to the sparse database for mercury in the Caribbean marine environment and represent the first report of pollution in marine sediments in some sampled areas.

The Three Gorges dam was huge project in the worldwide, and considerable attention has been focus on its impact on human beings. Mercury pollution brought by dam building has become an active field of research all over the world by scientists engaged in relevant subject. To elucidate the fate of total mercury (THg) and methylmercury (MMHg) in Three Gorges reservoir we have been studying the distribution in water of Hg in the area and its tributaries. Measurements of THg and MMHg have been made in the surface waters and at several depths within the water column of the reservoir system, we also collect water from paddy fields and a shrubbery, which submerged by water. Water quality parameters including T, DO, pH, and Eh were measured on site, and unfiltered methylmercury levels were measured using GC-CVAFS detection. In Three Gorges reservoir, Surface water THg concentrations has a high suspended sediment (SPM) load 5.5 mg/L, and for the Surface water, where THg is generally 26.46 ng/L or less. THg concentrations tend to increase in the down-layer. This increase coincides with a decrease in SPM. Measurement of THg and MMHg in the paddy field and shrubbery waters in the reservoir area demonstrate the increased concentration of Hg, and especially MMHg, under low oxygen conditions, and the most likely source is the release of these species from shrubs and sediments. THg concentrations can exceed 60.1 ng/L in the water of paddy field and MMHg concentrations approach 0.90 ng/L in the water of shrubbery. The THg concentrations in the water followed this trend: paddy field > shrubbery > river, and MMHg concentrations in the water indicated: shrubbery > paddy field > river.

Mercury pollution brought by The Three Gorges dam building has become an active field of research worldwide by scientists engaged in relevant subject. The present study evaluated the total mercury (THg) and methyl mercury (MMHg) concentrations and the MeHg to THg ratio (%MeHg) in water samples from different points of the area in September 2010 (high flux period) and January 2011 (low flux period). We collected water samples in different site of the reservoirs, including upstream, midstream, downstream and in the tributaries, as well as at several depths within the water column. Water quality parameters including T, DO, pH, and Eh were measured on site, and unfiltered methyl mercury levels were measured using GC-CVAFS detection. Long-term measurements show that THg in the unfiltered lake water varied spatially, with concentrations of THg in unfiltered water ranged from 10.17 to 67.20 ng/L，and were well correlated with suspended particulate matter (SPM). SPM strongly affects the migration and distribution of mercury. Concentrations of THg were typically highest in the summer, when precipitation, fluvial discharges, and SPM were greatest. The concentrations of water MMHg ranged from 0.034 to 0.767 ng/L. The %MeHg averaged as 0.5% in high flux period，and during the low flux averaged 0.4%. Concentrations of MMHg and THg were not significantly related to each other. COD and THg were also not correlated. The concentrations of THg，MMHg concentrations in high flux period were higher than low flux period. This was mainly due to changes in rainfall， suggesting the importance of exogenous mercury inputs.

Recent global emissions estimates have proposed South Africa as a major contributor to the atmospheric mercury inventory through coal burning and artisanal gold mining. These sources should leave a regional as well as a global signature. To examine these we present a comparison of the Limpopo and Olifantsi river watersheds in northern South Africa where coal burning is an important industry with the Fish-Tsitskamma river watershed where agriculture is the dominant economic activity in the region. Total mercury and methylmercury were measured in sediments, waters, and biota at 17 sites in the three watersheds. In all three regions, mercury levels in sediment were less than 34 ppb, suggesting no major local sources in the vicinity of the sites sampled. Nonetheless, higher sedimentary mercury concentrations were observed in the Limpopo and Olifants watersheds than in the Fish-Tsitskamma, and the statistical strength of this difference will be discussed in the presentation. Total mercury in filtered stream waters typically ranged from 1 -30 pM, with one exception being the Riet River where 80 – 100 pM was measured. Mercury levels in biota show a general trend of increasing concentration with trophic level and little variation between study sites. This study was conducted within the framework of collaboration between the South African Council for Scientific and Industrial Research (CSIR) and the University of Connecticut, which brought an additional benefit of fostering intercontinental communication.

Mercury contamination in the Brazilian Amazon has been investigated since 80 decade and constitutes a environmental health problem for the public health policy. This study is part of the Mercury Environmental Health Impact Project, associated with the phase construction of Madeira Hydroelectric Reservoir. The anthropogenic disturbances in the Amazon region have impacted the quality of the environmental services in the last thirty years. In the past, gold mining also had a great contribution for the environmental Hg contamination. Nowadays, deforestation, biomass burning and the infra-structure projects, such as hydroelectric power contribute to increase the environmental Hg load and consequently the burden of disease due to Hg exposure in the riparian communities. In the Brazilian Amazon, deforestation, biomass burning that increase the particulate wet and dry deposition and erosion, drain soil sediments into waterways. This study addresses the nowadays impact of mercury exposure by fish consumption on several communities of the Madeira River in the Western Brazilian Amazon during the period of 2009 and 2010. About 1200 hair samples were collected to measure mercury in adults and children, and blood pressure and blood tests were also carried out. An interview questionnaire was undertaken with questions about socioeconomic and demographic characteristics, environmental and health perception, environmental exposure, personal and nutritional habits. Risk factors also were investigated, such as history of alcoholism, smoke, diabetes, high blood pressure. The results show that about 40% of the fish consumed are carnivorous and 30% of the riparian communities consume carnivorous fish daily, which Hg concentration ranged from 0.2 to 1.8 mg/kg (ww). The statistical analysis, simple and multiple logistic models are being carried out. The preliminary descriptive results show that about, 23% of the population have hypertension, 7.4% suffer from diabetes. The average Hg in hair for the whole group was 9.0 mg/kg ( IC 95% 8.4 – 9.9). There is a significant difference among male and female Hg concentration in hair ( p value =0.000). This fact was also observed between the age groups below and above 15 years. About 29% of the individuals investigated presented mercury concentration in hair above 6 mg/kg and 9.5% above 20 mg/kg. Few individuals are suspect to present effects associated with Hg exposure.

Fish consumption is considered an important source of contaminant exposure and farmed fish can be exposed to contaminants via feed supply. Total mercury concentrations (THg) were determined in the muscle, liver and feed of farmed Nile tilapia (juveniles and adults) from 4 different fish farms (net cage and pond systems), by a flow injection mercury system. Mercury concentrations observed in muscle and liver were lower (12.8 - 28.7 µg.kg^-1; ww.) pasting than the values recommended by Brazilian regulatory agency (ANVISA) for fish of 500 µgTHg.kg^-1 and fish farm NC1 showed the highest THg concentrations when compared to the other fish farms. There are reports of strong gold exploration around 1987 in this region, where more than 100 ferries worked in mining this metal. The low THg concentrations found in muscle of farmed tilapia in this study confirm the low tendency of these fish to accumulate Hg, since they are less exposed to this contaminant than wild tilapias. Other factors, such as higher growth rate and shorter life span when compared to wild fish can contribute to marked reductions in THg concentrations. Body lipid content can also influence contaminant concentrations accumulated in an organism. Lipid concentrations in the present study in fish muscle ranged from 0.7 to 4.3%, noting that lipid levels were higher in NC than in PS fish farms. Thus, higher THg concentrations in the muscle tissue with lower lipid concentrations (PS farms) were observed. The low THg concentrations found in the analysed fish feed (5.2 – 33.2 µg.kg^-1; ww.) can be also responsible for the low concentration in fish muscle. Therefore, continuous monitoring of contaminant concentrations in fish feed is necessary due to variations in the use of ingredients, which cause variations in the concentrations of undesirable substances in commercial feeds. In relation to tissue analysis, a statistically significant difference (P <0.05) between Hg accumulation in liver and muscle was observed, where the liver presented the highest concentrations. Regarding fish age difference, a statistically significant difference (P <0.05) was observed when comparing Hg accumulation between adults and juveniles, with larger fish having higher THg concentrations than smaller fish. Differences in bioaccumulation rates can be related to the different nutritional needs of fish in different life stages. Thus, fish age is an important factor, due to changes in food supplies, as well as the increased exposure time of the animals to Hg. Thanks go to CNPq/MAPA/SDA 577906/2008-9 for finantial support and scholarships conceded.

Artisanal gold mining with metallic mercury (Hg) amalgamation is a common practice in Africa, and is on the rise in Burkina Faso since 1990. However, there are no data on the potential impact of these activities on Hg contamination of aquatic systems in Burkina Faso. Total mercury (THg) and methylmercury (MeHg) concentrations were determined in water and 350 muscle tissues of fish samples from 13 reservoirs in Burkina Faso in order to provide a first assessment of environmental mercury contamination. Hg concentration ranged from 0.45 to 17.04 ng l^-1 and 0.02 to 0.071 ng l^-1 for THg and MeHg in water, respectively. Hg was mostly associated with particulate matter due to rainfall runoff. Fish THg levels ranged from 0.002 to 0.607 µg g^-1 (wet weight). Most of fish mercury concentrations were below the Health Canada guideline limit of 0.2 µg g^-1 (wet weight) to protect people at risk. Only one fish species (Bagrus bajad) had Hg level above the World Health Organization (WHO) international trade guideline limit of 0.5 µg g^-1 (wet weight). These results suggest that, in general, most fish species are not significantly contaminated by Hg, with the exception of Bagrus bajad. In order to assess risk and develop policy recommendations, future studies should also consider consumption patterns of different subpopulations.

As the building of reservoirs increases in China, water quality issues such as mercury (Hg) biogeochemical cycling in reservoirs has also become increasingly relevant. Sediments of Baihua Reservoir (BR) are contaminated with Hg from an organic chemical plant upstream of the reservoir. There is concern related to the mobilization and bioavailability of monomethylmercury (MMHg) from the BR sediments. In June 2009 and 2010, we investigated the production and distribution of MMHg in the sediment, water column, and biota in BR, along with ancillary variables such as dissolved organic carbon and sulfide. We found high levels of total Hg (THg, 664-7421 ng g^-1 dry weight) and MMHg (3-21 ng g^-1 dry weight) in the sediments but low THg in fish (mostly carps; 4-254 ng g^-1 wet weight) in BR. The average (±1 standard deviation) dissolved MMHg in the sediment porewater was approximately 0.55±0.64 ng L^-1, representing 8% of the THg level. In comparison, 9% of the THg in the overlying water was present as MMHg (0.33±0.06 ng L^-1). Our data show that the sediment of BR is potentially an important source of MMHg to the water column. However, the transfer of MMHg produced in the sediment to the water column and the subsequent bioavailability of MMHg to the fish in BR is strongly influenced by a few physiochemical processes in the water column such as the persistent stratification, eutrophication, decomposition of settling particles (i.e. scavenge and/or release of MMHg), and demethylation. We also calculated the whole-reservoir sediment-water flux of MMHg under different water column conditions (e.g. stratified vs. non-stratified) in order to estimate the production and mobility of MMHg in BR, which offers some useful information for the water quality management of BR and similar reservoirs.

Mercury is a global contaminant from natural and anthropogenic sources, present in the atmosphere as Hg⁰, Hg (II) or adsorbed to suspended particulate. Hg can impact on ecosystems located at great distance from the sources, through dry and wet deposition, because the atmospheric residence time is approximately of two years. Previous studies in northern Patagonian lakes have reported high Hg levels in different compartments of lacustrine ecosystems. The aim of this work is to assess the atmospheric contribution of Hg from a sedimentary sequence extracted from Lake Moreno West. The lake is situated in the center of the Nahuel Huapi National Park, Patagonia Argentina, which is considered a pristine area without industrial development, but high levels of total Hg had been reported in this lake. The atmospheric Hg fraction as inorganic mercury (Hg (II)) plus dissolved gaseous mercury (Hg⁰) and also those that is weakly bound to inorganic and organic dissolved complexes was determined following acid digestion procedure and Hg concentrations were analyzed by cold vapor atomic fluorescence spectrometry (CV-AFS). The accuracy and precision of the method were evaluated using estuarine-certified reference materials (IAEA-405). On the other hand, eight tephra layers were identified and geochemically characterized, allowing the correlation with other lacustrine sequences in the area. The stratigraphy of the sequence and tephrochronological framework allowed the dating of the sedimentary record, indicating that the sequence recovered from Lake Moreno West spans approximately 600-700 years. The fraction of Hg measured showed background levels lower than 0.018 µg.g^-1 dry wt. with three peaks reaching concentrations of 0.508 µg.g^-1dry wt. The oldest peak corresponds to the XIV-XV century, the intermediate to middle of the XVI century and the most recent peak, to the last 50-60.. From another point of view, Hg results pointed out that in the last hundred years the atmospheric contribution of Hg exceeded 60% of the total Hg present in the sediments. Even thought we can not discriminate inputs from local natural sources, these results reaffirm the contribution of the global impact of Hg

Amazonian riverside communities have the highest reported mercury (Hg) exposure in the world today. Hg input to the aquatic environment occurs mainly through slash-and-burn agricultural practices, gold mining activities and hydroelectric reservoirs. Fish, which bioaccumulates and biomagnifies Hg, is a very nutritious food for local populations and often the dietary mainstay. In this region, human Hg exposure has been associated with motor, visual, cardiovascular, cellular and immunological impairments in adult fish consumers. Recently, omega-3 fatty acids have been associated with beneficial effects on various visual and motor functions. In light of such results, researchers have the responsibility to share these findings with the communities involved in the research process and with communities that could also be affected by this problem, as well as with local authorities.

Researchers working in the Tapajós Region of the Brazilian Amazon have been involved in Hg research since 1994, using an ecosystem approach to human health. Every phase of data collection has been followed by dissemination of results with the participant communities and individuals. A major benefit of this approach resulted from discussions with the villagers participating to community meetings, which allowed the scientists to identify new research questions and adapt and improve their research strategies.

When returning the results to participants, researchers face a number of challenges. First, there is a need to distinguish population vs. individual effects associated with Hg exposure. Second, researchers need to inform the population about their findings without alarming the people or saturating them with too abundant information. Third, viable solutions need to be discussed with the communities. These can be of short, medium or long term and should be in harmony with the local reality. Fourth, research teams need to adapt diffusion tools to the participants they are working with. Finally, results have to be disseminated at the right moment and to the right actors. In order to facilitate the results dissemination phase of research projects, scientists should be asked to plan this phase at the beginning of a new study, and funding agencies should facilitate the attribution of funds for these activities from the beginning of the research process.

The present study addresses the mercury scenarios exposure in schoolchildren in the Brazilian Amazon. This investigation compares the dose of mercury in children from 5 to 16 years living in different riverside communities with a group of schoolchildren from a extractives reserve, also in the Madeira basin that has a large amount of fish consumption. One of the groups lives in the direct influence region of the hydroelectric power construction with observed environmental impacts as a consequence of the new economic profile of this region. The schoolchildren from the extractives reserve live in an indirect influence area of the hydroelectric power. It is well known that reservoirs from hydroelectric powers trends to increase the environmental Hg concentration with health consequences for the exposed inhabitants.

This study involved a epidemiological survey using specific questionnaires applied in the communities where the schoolchildren live. The survey included the geographic information system techniques, social demographic and economic information data, social and nutritional habits taking into account the frequency and quantitative amount of fish consumed weekly, and also the different species consumed from Madeira river. Referred morbidity and neurological evaluation of the schoolchildren were carried out. Mercury monitoring in hair was performed in 700 hair samples from schoolchildren, blood pressure and blood tests were also carried out. The results obtained up to now show a great variability of the schoolchildren exposure to mercury, ranging from 0.03 µg/kg/d to 2.2µg/kg/d. The low dose exposure found was due to the frequency, type the fish consumed, gender and age of schoolchildren. The Hg average concentration in hair for schoolchildren between 6 and 16 years old living in the Madeira riverside was 7,6 mg/kg. About 30% of the schoolchildren presented Hg in hair above 6 mg/kg. Preliminary results of the average concentration of Hg in hair do not show statistical significant difference between schoolchildren from the extractives reserve and those from the riverside.

In Bolivia, metal mining activities since historical times have been one of the most important sources of environmental pollution. In the National Area of Apolobamba Integrated Management (ANMIN of Apolobamba) in La Paz province, there are many high artisanal and small-scale gold mines (ASGM). Virgen del Rosario and Rayo Rojo are representatives philonian mining cooperatives in where mining activity is mainly gold extraction, its water effluents go to the Amazonian basin. In this mining district the productivity of metal extraction is very low but the processes can result highly polluting due to the high amount of mercury used. Suches mining cooperative belongs to alluvial mining in where the gold is exploited of fluvioglaciar alluvial valley and its water fluxes go to the Titicaca Lake through the Suches River; in this case the use of mercury is only limited to the amalgamation of fine gold. The aim of this work was to evaluate the mercury pollution caused by gold mining activities comparing two types of gold extractions. In each mining cooperative two representative zones were distinguished and sampled. Zone near the mining operation site was considered as affected by mineral extraction processes, while far away zones could be the non affected areas. In each zone, 3 plots were established; in each plot, 3 soil sampling points were selected in a random manner and analysed separately. In each sampling point, two samples were taken, one at the surface (0–5 cm), and the other between 5 and 15 cm. In addition, surface soils from mercury burn areas were also taken. Total and DTPA mercury were determined. In the philonian mining cooperatives stands out the high mercury values in soils of zone near the mining activities (2.1 mg kg^-1, 1.2 mg kg^-1, 1.9 mg kg^-1); however, the most polluted soils are mercury burn areas with high levels of mercury (between 0.5 and 106.9 mg Hg kg^-1). In Suches, the Hg results in the near and far zones to mining operations are similar, in both cases the results are below 1.0 mg kg^-1. Due to its high toxicity, the contamination by mercury creates the most critical environmental problems. This metal could be incorporated in the trophic chain, through the flora and the fauna, in their bio-available forms. Inhabitants of this area consume foodcrops, fish from lakes and rivers and use the waters for the livestock, and irrigation.