Arsenic and Trace Metals in Water and Sediment of the Velhas River, Southeastern Iron Quadrangle Region, Minas Gerais, Brazil (original) (raw)
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Environmental Monitoring and Assessment, 2011
The Iron Quadrangle has been one of the most important gold production regions in Brazil since the end of the seventeenth century. There, arsenic occurs in close association with sulfide-rich auriferous rocks. The most abundant sulfide minerals are pyrite and arsenopyrite, yet trace metal sulfides occur in subordinate phases as well. Historical mining activities have been responsible for the release of As and trace metals to both aquatic and terrestrial environments close to mining sites in the region. Therefore, this study was aimed to evaluate the distribution and mobility of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn in streams in the southeast portion of the Iron Quadrangle between the municipalities of Ouro Preto and Mariana, the oldest Brazilian Au mining province. Total concentrations of some trace metals and arsenic in water were determined. The four-stage sequential extraction procedure proposed by the commission of the European Communities Bureau of Reference (BCR) was used to investigate the distribution of these elements in stream sediments. Arsenic concentration in water was >10 μg L −1 (maximum limit permitted by Brazilian environmental regulations for water destined for human consumption) at all sampling sites, varying between 36.7 and 68.3 μg L −1 . Sequential extraction in sediments showed high concentrations of As and trace metals associated with easily mobilized fractions.
ARSENIC IN WATER AND SEDIMENT IN THE IRON QUADRANGLE, STATE OF MINAS GERAIS, BRAZIL
Since the end of 17th century, the Iron Quadrangle in the State of Minas Gerais has been known as one of the most famous gold producing regions in Brazil. Gold was initially produced from alluvial placers and oxidation zones and, finally from primary ores in modern times. Total gold production must have exceeded 1300 t in all history. Only in the very famous Morro Velho mine around 600-t gold has been produced since 1834. The gold ore is rich in arsenic with the As/Au ratios ranging from 300 to 3000 among the several deposits deposits. The arsenic in rocks and ores (pyrite, pyrrhotite and arsenopyrite) undergo oxidation during the weathering processes and part of the arsenic is naturally liberated into the environment. Since the tailings produced in the past were discharged directly into drainage until 1980, the amount of arsenic that entered the drainage systems must have exceeded 390000 t in the whole region. In the Iron Quadrangle region, the highest arsenic concentrations in wat...
Rem: Revista Escola de Minas, 2015
A regional study on the arsenic concentration in surface waters and stream sediments, with a density of one sample every 13 km2, was carried out for the first time in the Quadrilátero Ferrífero (Brazil). The region was divided into 3rd order catchment basins, in which 512 areas were sampled. The arsenic concentration was determined in waters and stream sediments after partial digestion with the aid of ICP-OES. The arsenic values found in surface waters ranged from 57.70 to 414 µg.L-1, while for stream sediments, arsenic concentrations ranged from 0.63 to 1691 mg.kg-1, and from the 512 sampling points, 135 (26%) had arsenic concentrations above the limit of detection, which was 0.63 mg.kg-1. It was also found that 106 3rd order catchment basins had values above the third quartile, (5.09 mg.kg-1). The results show that high concentrations of this element are strongly related to the presence of Nova Lima rocks that contain minerals rich in arsenic. However, the anthropogenic influence ...
Ouro Preto county is southeast of Qua-drilatero Ferrifero in the state of Minas Gerais, one of the most known Brazilian mining regions, producing gold, topaz gems and several kinds of iron and manganese ores. However, these activities are the main forms of environmental degradation, affecting the surface and groundwater which is used for public supply and are the source of heavy metal contamination, including mercury and arsenic. The mining and predatory prospecting activity (garim-pos) has been carried out in Minas Gerais since the seventeenth century. At that time, hundreds of placer gold deposits were discovered on the streams in the region of Ouro Preto and Mariana, causing the first big gold rush in Brazilian history. This work presents public supply water quality data from a seasonal cycle, from September 1999 (winter) to February 2000 (summer). Chemical and physical-chemical parameters were assessed with the content of heavy metals. Leaching tests with rock samples to assess contribution to the metal content of water were carried out. Elements in the rocks have been determined and water analysis allowed the hydrog-eochemical classification of water. Leaching tests demonstrate the oxidizing conditions under which the As (and the other elements) is being mobilised to the hydrological system. As and Fe are elements dispersed in the drainage of the regions. This is due to the high amounts of sulfide and to the iron formations of the region.
Environmental Geology, 2003
The Iron Quadrangle has been the scenery of the most important gold production in Brazil. It is estimated that during the three centuries of gold mining in the Iron Quadrangle, at least 390,000 t of arsenic was discharged into the drainage system. This study presents geochemical data for the three river basins in the region, with focus on surface water and stream sediment monitoring. Samples of primary and oxidized sulfide ores as well as of tailings and groundwater from the major gold mines were also studied. The highest As concentrations in water and stream sediments occur in the vicinity of mining areas. In surface water, up to 300 lg As/l were found whereas the As contents in stream sediments were in the range of 20 to 4,000 mg/kg. The As 3+ /As 5+ concentration ratios obtained for some water samples range from 1.10 )1 to 4.10 )2 . The As mobility associated with ore-deposit weathering could be traced in some closed gold mines by observation of insitu pyrite and arsenopyrite oxida-tion, precipitation of scorodite and gippsite, As adsorption onto goethite, and final liberation of As into underground and surface waters. This process is likely to produce large volumes of mine effluents containing total As and trivalent As up to 1,960 and 60 lg/l, respectively. River sediments and tailings pile samples were submitted to a leaching procedure showing maximal arsenic release from 1 to 4% of the original total As in the samples. There are potential risks for As hazards in some areas induced by, for instance, the dispersion of old tailings by flooding, occupation of poisoned soils for settlements, and occasional consumption of contaminated surface and groundwater.
Exposure and Health
The “Quadrilátero Ferrífero” (Iron Quadrangle) is a mineral-rich province in Brazil, where arsenic anomalies are associated with gold mining and tailings dam failures. Urine samples were randomly collected from residents of Belo Horizonte (BH) city (N = 506 total/138 speciation) and the metropolitan area (N = 35 total/10 speciation), with stratifications in age, female-male and geopolitical regions. Creatinine, acid-digested total arsenic (TAs), and five inorganic and organic arsenic species were measured: arsenobetaine (AsB); arsenous (AsIII) and arsenic (AsV) acids and their dissociation products; monomethylarsonic acid (MMA); and dimethylarsinic acid DMA). Overall, the TAs GM (μg/g creat) of all stratification groups indicated no statistical difference. The TAs geometric mean (GM) of BH was 9.68 [9.17–10.2] μg/g creat, being AsB (43.8%) and DMA (20.7%) the major components. The toxic arsenic (ToxAs) fraction (i.e., AsIII + AsV + MMA + DMA) was 5.23 [4.45–6.15] μg/L. These TAs and...
Human and environmental contamination in the Iron Quadrangle, Brazil
Applied Geochemistry, 2000
Arsenic (As) exposure is a potential health risk to local populations around Au mining areas in southeastern Brazil. In April 1998, 126 schoolchildren, aged 9.8 2 1.12 years in the Minas Gerais mining districts of Nova Lima and Santa Barbara, had their spontaneous urine sampled. Toxicologically low Cd (0.04±0.35 mg L À1 , mean 0.13 mg L À1 ), partly elevated Hg (0.1±16.5 mg L À1 , mean 1.1 mg L À1 ), and generally elevated to high As concentrations (2.2± 106 mg L À1 , mean 25.7 mg L À1 ) were found. Twenty per cent of the total sample population showed elevated As concentrations where adverse health eects cannot be excluded on a long-term basis.
Long-term environmental impact of arsenic-dispersion in Minas Gerais, Brazil
2007
To answer the question whether up to 250 years of continual gold mining, and related industrial activities in parts of the Iron (Fe) Quadrangle, Brazil, have lead to As-pollution problems, a comprehensive research project was launched in 1998. Within this project, air, soil, surface and groundwater, suspended particulates, and fresh unconsolidated sediments were sampled and investigated together with home-grown vegetables, home dust, human urine and hair, and private water supplies. All sampling, sample processing, and analytical work have been done by the same people using the same methods applying strict quality control measures.Elevated to very high soil As-concentrations (50–1000mg As/kg) in living quarters, and extremely high (percentage range) As-values on derelict industrial sites, including old tailings surfaces, characterize the areas. Soil dust, As-enriched vegetables, and partly As-contaminated water from private wells and unauthorized surface sources explained the partia...
Environmental science and pollution research international, 2018
Arsenic (As) is a dangerous and carcinogenic element and drinking water is its main pathway of human exposure. Gold mines are widely recognized as important sources of As pollution. This work proposes the assessment of As distribution along watersheds surrounding "Morro do Ouro" gold mine (Paracatu, southeastern Brazil). A balance approach between filtered As fluxes (As < 0.45 μm) and suspended particulate material (AsSPM) in different river segments was applied. Ultrafiltration procedure was used to categorize As into the following classes: particulate > 0.1 μm, colloidal < 0.1 μm to > 10 kDa, dissolved < 10 kDa to > 1 kDa, and truly dissolved < 1 kDa. By applying this approach, arsenic contributions from mining facilities were quantified in order to identify critical fluvial segments and support decision makers in actions of remediation. The mass balance indicated the occurrence of a decreasing gradient from upstream to downstream: (i) of the As conc...