da Penha Rhodes Valdilene, de Lena Jorge Carvalho, Santolin Camila Vidal Alves, da Silva Pinto Thais, Mendes Louise Aparecida, Windmöller Cláudia Carvalhinho
Departamento de Geologia, Escola de Minas, Campus Morro do Cruzeiro, Universidade Federal de Ouro Preto, Ouro Preto, MG, 35400-000, Brazil.
Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Belo Horizonte, MG, 31270-901, Brazil.
Environ Monit Assess. 2017 Dec 28;190(1):49. doi: 10.1007/s10661-017-6394-4.
The Iron Quadrangle in SE Brazil was, in the eighteenth century, one of the most important Au producing regions of Brazil. In this region, gold is produced, even today, by artisanal methods that use Hg to increase the extraction efficiency with no control of Hg release to water systems and the atmosphere. In this context, the Gualaxo do Norte River is of particular interest; its springs are located in the Doce River basin, an important Brazilian basin that supplies water for 3.5 million people. The main goal of this work was to quantify and speciate the Hg in the sediments of the Gualaxo do Norte River using a direct mercury analyzer and gas chromatography-pyrolysis-atomic fluorescence detection system. Statistical analyses consisted of principal component analysis, aiming to assess interactions among elements and species and to group the variables in factors affecting the properties of sediment. The results show that total Hg (THg) and methylmercury (CHHg) concentrations in samples ranged from 209 to 1207 μg kg and from 0.07 to 1.00 μg kg, respectively (methylation percentages from 0.01 to 0.27%). Thermal desorption analysis showed that mercury is mainly present in the oxidized form, and correlation analyses pointed to a relationship between THg and MnO, indicating that manganese can oxidize and/or adsorb Hg. Together, MO and CHHg are important parameters in the third principal component, indicating the influence of OM on the methylation process. This first investigation on Hg methylation in this small-scale gold mining area points to the possibility of Hg bioaccumulation and to the need of better understanding the biogeochemical cycle of Hg in this area. Samples were collected in 2012, prior to the 2015 Fundão Dam disaster. The results are also a record of the characteristics of the sediment prior to that event.
巴西东南部的铁四角地区在18世纪是巴西最重要的金产区之一。在该地区，即使在今天，仍采用手工方法淘金，使用汞来提高提取效率，却未对汞排放到水体和大气进行控制。在此背景下，北瓜拉肖河尤为引人关注；其源头位于多西河盆地，这是巴西一个重要的流域，为350万人供水。这项工作的主要目标是使用直接测汞仪和气相色谱 - 热解 - 原子荧光检测系统，对北瓜拉肖河沉积物中的汞进行定量和形态分析。统计分析包括主成分分析，旨在评估元素和物种之间的相互作用，并将变量分组为影响沉积物性质的因素。结果表明，样品中的总汞（THg）和甲基汞（CHHg）浓度分别在209至1207μg/kg和0.07至1.00μg/kg之间（甲基化率为0.01至0.27%）。热脱附分析表明，汞主要以氧化态存在，相关性分析表明THg与MnO之间存在关系，这表明锰可以氧化和/或吸附汞。此外，MO和CHHg是第三主成分中的重要参数，表明有机质对甲基化过程的影响。这项对该小规模金矿开采区汞甲基化的首次调查指出了汞生物累积的可能性，以及更好地了解该地区汞生物地球化学循环的必要性。样品于2012年采集，早于2015年丰当大坝灾难。这些结果也是该事件之前沉积物特征的记录。
