Gold has been mined at San Antonio-El Triunfo, (Baja California Sur, Mexico) since the 18th century. This area has approximately 5,700 inhabitants living in the San Juan de Los Planes and El Carrizal hydrographic basins, close to more than 100 abandoned mining sites containing tailings contaminated with potentially toxic elements such as arsenic. To evaluate the arsenic exposure of humans living in the surrounding areas, urinary arsenic species, such as inorganic arsenic (iAs) and the metabolites mono-methylated (MMA) and di-methylated arsenic acids (DMA), were evaluated in 275 residents (18-84 years of age). Arsenic species in urine were analyzed by hydride generation-cryotrapping-atomic absorption spectrometry, which excludes the non-toxic forms of arsenic such as those found in seafood. Urinary samples contained a total arsenic concentration (sum of arsenical species) which ranged from 1.3 to 398.7 ng mL(-1), indicating 33% of the inhabitants exceeded the biological exposition index (BEI = 35 ng mL(-1)), the permissible limit for occupational exposure. The mean relative urinary arsenic species were 9, 11 and 80% for iAs, MMA and DMA, respectively, in the Los Planes basin, and 17, 10 and 73%, respectively, in the El Carrizal basin. These data indicated that environmental intervention is required to address potential health issues in this area.
Abstract. Antimony has properties similar to arsenic with some of its compounds toxic to humans. Therefore it is necessary to control the wastes accumulated by anthropogenic activities, such as mining, where it is in tailings to be released to the environment. According to the Environment Protection Agency, the maximum value in sediments is 11.2 mg Sb kg -1 and the Earth´s crust average is 0.2 mg Sb kg -1 . In this semiarid area, the drainage basin El Carrizal is impacted with wastes of an abandoned gold mine at the Mining District El Triunfo (MD -ET) which have tailings with 17,600 mg kg -1 of antimony. In the main dry river (arroyo), the Sb content is between 0.6 and 122 mg kg -1 . This element is transported from the source throughout the fluvial basin to discharge into the Pacific Ocean. In the arroyo mouth we collected one sedimentary core and the sediment from dunes (28.6 -45.7 and 6.43 -7.74 mg Sb kg -1 ). This research concluded the antimony is enriched in this semiarid system, with Normalized Enrichment Factors severely enriched mainly in arroyo sediments close to the MD-ET
The mining district of El Triunfo (ET-MD) has an estimated 800,000 t of mine wastes scattered in the environment, contaminating the sediment with potentially toxic elements such as As, Cd, Pb, and Zn. In order to estimate the toxicity of the sediment to the adjacent biota, the aims of our study are to calculate the mortality and inhibition through bioassays, using sediment, and test organisms such as Daphnia magna and Selenastrum capricornutum (Pseudokirchneriella subcapitata), respectively. The D. magna mortality was 31 ± 12% and the S. capricornutum growth inhibition was 53 ± 24%. The contamination of the sediment determines the high mortality of D. magna and the high inhibition of S. capricornutum in the system, indicating risk for the biota in the contaminated system.
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