Atmospheric mercury and trace elements in the region of Alta Floresta in the Amazon Basin

In the early 1980's the Amazon region in the North of Brazil was the scene of the most intense gold rush in the history of Brazil. Metallic mercury (Hg) in gold mining activities is used to amalgamate particulate gold. The other sources of Hg emissions in Amazonian are tailing deposits and biomass burning of tropical forests and savannas. Total Hg concentrations in the urban area of Alta Floresta ranged from 20 to 5800 ng/m³. Indoor total Hg concentration in gold shops ranged from 250 to 40600 ng/m³. Particulate Hg accounts for 5 to 20% of total Hg in Alta Floresta. Through Factor and cluster analysis it was obtained a pattern of relationships between total Hg, fine and coarse mode particulate Hg, Pt, Pb, Ag and several other trace elements associated with the amalgamation process. A clear correlation was also observed with the fine mode biomass burning aerosol and coarse mode soil dust.     

Mercury contamination in the Brazilian Amazon. Environmental and occupational aspects

Mercury (Hg) contamination of miners, riparian and Indian populations and fish in the Amazon region, due to gold extracting activities, has been studied. Samples of hair, urine, and blood of Indians and prospectors, and hair from riparian fish-eating population and fishes from Madeira river, respectively, were collected and analyzed by Cold Vapor, Atomic Absorption Spectrometry (CV-AAS) techniques. The results obtained showed that the aquatic food chains in the Amazonian ecosystems are contaminated by methylmercury (MeHg), exposing Indians, prospectors and riverines to thr risk of severe health hazard. The highest levels of contamination, based upon hair analysis, were found in riparian of the Madeira river, followed by Cuniã Lake population, Indians (Fresco river) and prospectors, in that order. Blood analysis showed 59% of the samples from Indians and 33% from prospectors with Hg contents above 10 ng mL^?1. Analysis of urine, on the other hand, showed 44% of Indians with Hg levels below the detection limit (d.l.), and 30% above 20 ng mL^?1, whereas 38% of the prospectors presented Hg concentrations over 20 ng mL^?1, and 20% below the d.l. These results prove that prospectors, who hardly ever eat fish but are badly exposed to inorganic Hg vapor, are ocupationally contaminated, while the rest of the populations under survey are exposed to environmental contamination by Hg, through polluted fish ingestion.     

Evolution of Mercury Contamination in Brazil

This paper reviews the history of Hg contamination in Brazil by characterizing and quantifying two major sources of Hg emissions to the environment: industrial sources and gold mining, industry was responsible for nearly 100% of total Hg emissions from the late 1940's to the early 1970's, when efficient control policies were enforced, leading to a decrease in emissions. Gold mining, on the other hand was nearly insignificant as a Hg source up to the late 1970's, but is presently responsible for over 80% of total emissions. Presently, over 210 t of Hg are released into the environment in Brazil annually. Nearly 170 t come from gold mining operations. 17 t come from chlor-alkali industry and 10 t come from all other industrial uses. Emissions to the atmosphere are the major pathway of Hg releases to the environment and reach over 160 t.yr-1 with approximately 136 t.yr-1 from gold mining.     

Assessment of Mercury Levels in Soils,Waters, Bottom Sediments and Fishes of Acre State in Brazilian Amazon

Mercury in the aquatic biota and geologic materials in areas without anthropogenic sources has been stimulating the discussion about the possibility of natural Hg occurrence in the Amazon region. In this study the dispersion of Hg in different geologic materials as well as its relationship with high Hg levels, detected in some species of carnivorous fish consumed in the Rio Branco city, is evaluated. Bottom and suspended sediments, river water and fishes were sampled in the Acre and Purus Rivers and in some of their tributaries. Total mercury as well as physical and chemical characterization of the waters were done. Hg on top soil and upper horizons samples were also determined to evaluate the potential Hg accumulation in these materials. In addition the dominant minerals were determined by X-ray Diffraction analysis. Furthermore, ten samples of fossilized material were analyzed. The Hg analysis were carried out by CVAAS. The Hg mean levels in the bottom and suspensed sediments were 0.042 and 0.060 μg g^-1, respectively. In the river water samples, the Hg levels were below the detection limit. The Hg mean values in the different soil samples were as follow: soil samples (0.077 μ g^-1), lower (50–60 cm depth) horizons samples (0.117 μ g^-1), ferruginous nodules within the clayey matrix (0.190 μ g^-1) and fossilized material (0.379 μ g^-1). In the fishes the Hg levels are high with mean of the 1.287 μ g^-1 in the carnivorous species. These levels indicate a possible bioaccumulation of Hg mostly in the carnivorous fishes. Although low concentrations of Hg were found in the river waters, it is assumed here that the bioavailable Hg can is original large from the ferruginousnodules and fossilized materials.     

石羊河流域植被生态系统生态风险评价研究

区域生态风险评价涉及到多风险因子、多风险受体、多评价终点,强调不确定因素以及空间异质性的特点.以石羊河流域植被生态系统为例,以区域生态系统类型为着手点,计算不同生态系统类型的生态指数、脆弱度和生态损失度,根据不同种类和级别生态风险源的综合风险权重,利用ArcGIS 9.3软件进行叠加分析,形成不同的生态风险区.结果表明,石羊河流域植被生态风险空间差异性较为明显,其中1级风险区主要分布在石羊河流域上游,占全区面积的3.87％,以肃南和天祝2个县最为集中,植被类型多为有林地;2级生态风险区分布多与1级风险区相连,占全区面积的4.38％,植被类型多为灌木林;3级和低风险区主要分布在下游和中游地区,植被类型为草地和耕地.对石羊河开发利用时应当避免在1级和2级风险区进行大规模的土地开发利用,在3级和低风险区进行土地利用时应注意对土地进行保护利用.     

Remediation Actions by a Risk Assessment Approach: A Case Study of Mercury Contamination

The risk assessment procedure for identifying the remediation actions which may be adopted at a mercury contaminated site, when the plants are upgraded in the future, is proposed. The potentially active exposure/migration pathways in the future arrangement of the area will be due to Hg contaminated subsoil as a primary source (vapor inhalation and groundwater leaching) and to groundwater as a possible secondary source (transport to the point of compliance). The data of mercury concentration in the soil were acquired through environmental monitoring campaigns, and were processed to establish the three-dimensional distribution of contamination in subsoil, to locate sources and to define their geometrical and chemical characteristics. Speciation tests of mercury in the soil indicated that the most abundant species present were poorly leachable under the site-specific environmental conditions, confirming the coefficient distribution value obtained by the leaching tests. Analytical and numerical fate and transport modeling tools were used to locate digging zones in the contaminated subsoil, so as to reduce the possible groundwater contaminant loading and to avoid the down-gradient exceeding the concentration limit according to regulations. Remediation actions additional to civil works were required, which consists of soil digging within one contamination source, for about 22,200 m³ of soil. In order to evaluate the Hazard Index (HI) for human receptors due to Hg vapor inhalation, the air concentration of volatile mercury at the exposure point was estimated, based on direct measurements carried out at the site. Simulation gave HI values below 1 for all tested scenarios, suggesting that public health is protected without any additional actions to the already scheduled plant upgrading and digging for groundwater protection.     

Mercury Accumulation in Sediments of a Mangrove Ecosystem in SE Brazil

The Hg accumulation in sedimentary environments of a mangrove ecosystem in Sepetiba Bay, SE Brazil, was investigated. These environments include sediments of a mangrove forest, the main tidal creek that drains the forest, and the bare seaward-edge mud flat adjacent to forest and tidal creek. Maximum Hg concentration peaks in sediments from the mud flat (184 ng g^-1), tidal creek (98 ng g^-1), and mangrove forest (60 ng g^-1) correspond to enrichment factors of 6.1, 3.3, and 2.0 above the estimated average background level, respectively. Average inventories of Hg excess (background-corrected) concentrations were substantiallydifferent between environments, decreasing from mud flat sediments (5.2 mg m^-2) to creek sediments (3.3 mg m^-2)to mangrove forest sediments (0.9 mg m^-2). Mercury concentration profiles indicated a consistently higher accumulation of Hg in surface layers of mud flat and tidal creeksediments, whereas mangrove forest sediments showed a higher Hgaccumulation in root-rich subsurface layers, in agreement with an enrichment of Fe and organic matter contents. While Hg distribution in mud flat and tidal creek sediments appears to belargely affected by contamination, its distribution in mangrove forest substrate appears to be greatly affected by root-sedimentinteractions. Mercury levels in the study site were comparable tothose observed in coastal sediments under moderate Hg contamination at local and regional scales. Results indicate thatsedimentary environments surrounding the mangrove forest retain most of the anthropogenic Hg reaching the ecosystem. Since tidal waters have been previously demonstrated as the main source of metals to the site, it is suggested that the Hg retention in mudflat sediments precede and may avoid a higher Hg accumulation inlandward environments.     

基于GIS的伊通河流域农业非点源污染风险评估

针对伊通河流域农业活动带来的水体污染及水土流失等环境问题,在分析农业非点源污染影响因子的基础上,选择了土地利用类型、土壤孔隙度、年降水量及氮磷排放量等影响因子,建立了农业非点源污染风险评估指标体系,并应用GIS技术,通过工程图绘制和叠加分析,采用幂法计算各因子权值,确定了风险等级指数,最后划分了农业非点源污染风险分区。研究结果表明:在沿河地区和相对发达的城市周边地区,受水田耕作和畜牧饲养等因素影响,农业非点源污染风险较高;在较偏远地区与林区,农业非点源污染风险相对较低。     

Clay mineral composition of river sediments in the Amazon Basin

Clay minerals are important in evaluating the maturity of suspended sediments, weathering intensity and source area. However, there are processes that can change the mineral assemblage such as river transportation, deposition, remobilization and tributary inputs. In terms of water discharge and sediment yield, the Amazon is one of the largest rivers in the world. Most of the suspended sediments come from the Andes, crossing the lowlands before reaching the ocean. This study measures the spatial distribution of clay mineral assemblages over the entire Amazon basin. The results obtained show the main features of the Amazon River main stem and larger tributaries from their sources to their confluence. Clay mineral composition highlights the evolution of the Madeira and Marañón–Solimões River, which start in the Andes with high illite + chlorite content. Downstream, smectite contents increase. Moreover, all shield tributaries show high kaolinite content. The lower Amazon River is characterized by relative high smectite content, different from the Andean sources. The clay mineral results show that suspended sediments of the Amazon River have three main sources: 1) the Andes mountains; 2) the Amazon shields and 3) the Piedmont basins, especially the Pastaza alluvial megafan and the Fitzcarrald Arch basin. Lateral bank erosion plays also a significant role, by the introduction of more mature sediments into the river, enriched in smectite.     

Probabilistic Assessment of Regional Mercury Exposure

A methodology for the probabilistic assessment of regional exposure to mercury is presented. The methodology is based on a multimedia model of the atmospheric fate and transport of mercury over a continental scale, and the aquatic simulation of the transformation and bioaccumulation of mercury in lakes in the region of interest. A probabilistic approach allows one to take into account the spatial variability of environmental characteristics and the variability of dose-related variables (e.g., fish consumption, body weight) among individuals. The methodology is demonstrated for total mercury deposition in the Great Lakes region of the U.S.     

基于输出系数模型的南四湖流域非点源污染输出风险评估

[目的]探究非点源污染物N、P输出风险在不同子流域、坡度等级和县市区的分布特征,为南四湖流域不同风险区制定管理方案和控制对策提供科学依据。[方法]以数字高程模型(digital elevation model,DEM)为基础数据,运用ArcGIS软件,提取南四湖流域的DEM,制作坡度等级图,再运用水文分析功能,提取水系图、河流图、并划定子流域,结合2013年南四湖流域土地利用图,通过运用输出风险模型分析不同的土地利用类型和坡度下氮(N),磷(P)污染的空间变化。[结果]氮素的平均风险概率达到51.67%,磷素的平均风险概率达到9.14%,南四湖流域非点源污染输出风险湖东小于湖西;随坡度增大,高风险区面积减小,低风险区面积增加;就不同县市区而言,济宁市中区的N风险较小之外,其余县市区N风险均较大,P风险较小。[结论]N是流域最主要的非点源污染物,非点源污染输出风险大小与土地覆盖和坡度有密切关系。     

Methylmercury in hair samples from different riverine groups,Amazon, Brazil

The present study was aimed to evaluate comparatively the levels of methylmercury (MeHg) in human hair, collected from different groups of Amazonian populations exposed to contamined fish. The study was undertaken in fishing villages and gold mining areas, mainly in the Tapajós and Madeira river basins, two of the main tributaries of Amazon river. The study population included 125 hair samples, chosen from a collection of over one thousand samples collected in different periods. Hair analyses were conducted with a new efficient extraction technique and measured with ECD-gas chromatographer. This analytical method presented good accuracy and precision when compared with standard hair samples from IAEA. A highly significant correlation was found at the interlaboratory exercise between National Institute for Minamata Disease and our laboratory at Federal University of Rio de Janeiro. The results of the present study showed, through hair analysis, a relationship between environmental contamination by mercury and methylmercury and dietary habits of the Amazon population. The highest levels of MeHg in hair samples were found in riverine population from upper Tapajós river and in riverine population from some tributaries of Madeira river, followed by population of fishing villages from Madeira river. Majority of the women of child-bearing age presented high MeHg concentration in hair samples (10 mg.kg-1). On the other hand, Yanomami Indians presented MeHg concentration below the limit tolerable of 6 mg.kg-1.     

苏南某区污染耕地农产品镉汞状况调查及健康风险评价

于2019年和2020年在苏南某区污染耕地采集了302份水稻和97份蔬菜样本,评估了农作物可食部分镉(Cd)和汞(Hg)的健康风险.结果表明:水稻籽粒中Cd和Hg含量均高于蔬菜,水稻籽粒和蔬菜Cd含量分别为59.5和50.7μg/kg,超标率为4.6％ 和4.1％;水稻和蔬菜Hg含量分别为4.7和0.7μg/kg,其中...     

Selenium and aflatoxin levels in raw Brazil nuts from the Amazon basin

Whereas selenium (Se) is an important antioxidant in human metabolism to prevent cancer, aflatoxins are highly carcinogenic. Brazil nuts from Eastern and Western Amazon regions were evaluated to find any relationship between Se and aflatoxins levels. A total of 80 (in-shell and shelled) nuts samples were collected directly from different forest sites and analyzed for Se by atomic emission spectrometry and aflatoxins by liquid chromatography tandem mass spectrometry. The limit of quantitation (LOQ) for Se was 2.0 mg/kg, and LOQ for total aflatoxins was 0.390 microg/kg. Nut Se levels from the Eastern region were higher than the Western, in addition to the aflatoxins. The moisture content (mc) and water activity (aw) of the raw nuts from the two regions did not present a significant difference, for either in-shell or shelled. The mc was 24.5% (minimum of 20.1% and maximum of 30.4%) and 22.1% (minimum of 14.6% and maximum of 28.9%) and a w of 0.85 for both regions. Further studies need to be carried out to discover the role of Se on fungi growth stress and aflatoxin production mechanisms.     

共和盆地塔拉滩土壤侵蚀潜在危险度评价

以青藏高原东北部的共和盆地塔拉滩草原为研究对象,采用地球化学放射性同位素——137Cs侵蚀模型来进行土壤侵蚀量的估算;通过野外调查以及土壤资料获得土壤容重和有效土层厚度;在ArcGIS 9.3下,由土壤年均侵蚀量、土层厚度和土壤容重得到抗蚀年限图.根据土壤侵蚀的特点参照水利部标准对土壤侵蚀潜在危险度进行分级,研究表明:共和盆地塔拉滩的土壤侵蚀潜在危险度以轻险型为主,面积为1 692.98 km2,占塔拉滩总面积的61.64％,从土壤侵蚀潜在危险指数(SEPDI)来看,为2.42,属于轻度危险区域.     

Mercury contamination in hair of riverine populations of Apiacás Reserve in the Brazilian Amazon

Total and inorganic Hg in 55 samples of hair from riverines, mainly descended from Munduruku and Apiaká Indians, living along the rivers Teles Pires and Juruena have been determined. The sampled population represents 18% of the inhabitants of the region and they eat fish 6 or 7 days a week. Cold-vapor AAS and alkaline digestion with CdCl2/SnCl2 as reducing agent were employed to estimate total Hg in hair samples. A LDC Analytical, Mod. 1255, Mercury monitor was used for Hg determination. The mean value of total Hg was 34.2µg g-1, with an average of 87.2% of organic Hg Ninety-three per cent of the sampled population present levels of Hg above 10µg g-1, and 18% over 50µg g-1. A relationship between the mean value of Hg and age of the sampled population is presented. All women at child-bearing age present concentrations of Hg above 10µg g-1. Fifty-four per cent of them had levels over 30µg g-1, with a mean of 41.2µg g-1. For the children under ten years of age, 14% show Hg concentration above 50µg g-1. Comparison of these results with those obtained in 10 other Amazon surveys (n=1672) is shown. The results of the concentration of mercury in fish, mainly piscivorous (n=967) from Amazonian and Wetland (pantanal matogrossense) are also presented, with a mean of 726 ng mg-1. There appears to be a relationship between level of Hg in human and their food ingestion habits.     

Human and Environmental Contamination by Mercury from Industrial Uses in Brazil

The amount of Hg used for industrial purposes in Brazil has been estimated as 105 t.yr-1, of which, 50% is released into the environment. As the industries that use this Hg are located in the neighborood of highly populated areas, the number of people exposed to the risk of contamination is high. Severe cases of chronically poisoned workers have been reported, most of them presenting neuropsychological disorders. Contamination of air, soil, and water resources are also observed. Analysis of sediments, water and biota of Guanabara Bay, Rio de Janeiro, show contamination of all segments by Hg originating mainly from a chlor-alkali plant located nearby. Higher concentrations of Hg were found in the sediments (0.7 to 20 mg.kg-1) where it is associated with organic matter usually under anoxic conditions. Mercury can became bioavailable by organification or by changes in the actual environmental conditions and is thus an important source of environmental contamination of people who consume its biota.     

黄河故道流域土壤盐渍化多维空间特征及其风险评价

掌握土壤盐渍化多维空间分布特征，分析盐渍化风险影响因素，实行风险区域分区管控，提升盐碱土利用效率。以山东省东营市河口区黄河故道流域为研究区，采用经典统计学方法对土壤盐渍化状况进行描述性统计，基于GIS插值对研究区盐渍化的二维空间分布格局进行分析，运用GMS三维反距离权重插值可视化分析盐分三维空间分布及其变化趋势，构建土壤盐渍化风险评价模型定量分析其风险程度。结果表明：研究区土壤含盐量均值为5.84 g·kg-1，整体属于重度盐渍化，pH均值为7.82，呈弱碱性；二维空间上，土壤含盐量高值区域（≥6 g·kg-1）主要分布于研究区北部，整体呈现从沿海向内陆降低的趋势，土壤盐分与pH分布趋势整体呈负相关；三维空间上，土壤盐分剖面分布特征整体以均质型为主，局部存在表聚、两端集聚，呈表聚型、均质型、两端集聚型三种类型共存的复杂特征；盐渍化风险程度分为4级，极高风险区域主要分布于研究区中北部、东北部；高风险区域主要分布在研究区中部及东北部区域，中风险区域主要分布在研究区西部、东南部，低风险区域主要分布于研究区西南部。 应预防极高风险区、控制高风险区、改良中低风险区，以最大程度减轻盐渍化风险危害。     

Trophic Structure and Bioaccumulation of Mercury in Fish of Three Natural Lakes of the Brazilian Amazon

The bioaccumulation of mercury by fish was studied in three natural lakes lining the Tapajós River, Brazilian Amazon. The Hg content variations are also reported between the rainy and the rising water seasons. Position of fish in the food chain and the source of carbon at the base of the food chain were determined using nitrogen and carbon stable isotopes ratios respectively. During the two seasons, the effect of the Hg biomagnification between the non-piscivorous and piscivorous fish of the three lakes is observed. The correlation between the mercury concentrations and the nitrogen isotopic ratios suggests that the fish mercury content variability is connected with the trophic position and size. Aside from classic observations on mercury biomagnification by certain species of fish (i.e. contents increase with size or trophic status), novel results were revealed as well, such as some species decrease of mercury contents with size of fish. Aquatic organisms in the Amazon are adapted to the complexity of trophic webs coupled with changes in environmental variables, depending on the location and/or the season, which results in a wide range of mercurial contamination among the Tapajós ichthyofauna.