Sources, enrichment, and redistribution of As, Cd, Cu, Li, Mo, and Sb in the Northern Atacama Region, Chile: Implications for arid watersheds affected by mining

Long-established and widespread mining activities in the Northern Atacama Region of Chile have historically impacted the environment. Most notably, the Potrerillos and El Salvador mines, until 1976, were responsible for dumping over 150 ∙ 106 tons of tailings into the El Salado River, discharging directly into the bay of Chañaral on the coast. Water resources in the Northern Atacama Region are scarce; the few include the El Salado River and the Pedernales, Maricunga, and Laguna Verde basins. This region also contains two highly sensitive national parks: the Pan de Azúcar on the coast and the Nevado de Tres Cruces in the Andes. Protecting available water resources in this inherently dry region is critical and environmental degradation that has occurred has not been reported in terms of the most important superficial pollutants. In order to specifically evaluate the metals and metalloids polluting superficial water and fluvial sediments, a 3 year-long survey was carried out in the basins of the Northern Atacama Region. Additionally, impacts of the El Salado River flood in March 2015 were evaluated. When compared to the average concentrations of dissolved elements in river water worldwide, the most enriched elements of the Northern Atacama Region are, in decreasing order: Li, As, Mo, ± Cd, Sb, and Cu. In the case of fluvial sediments, compared to the composition of the upper continental crust, samples are enriched in the following elements (in decreasing order): As, Cu, Mo, Li, ± Cd and Sb. In surface waters, dissolved As, Li, Mo and Cd are naturally enriched, concentrations of Cu and Sb are inferred to be related to mining activities. In fluvial sediments, concentrations of As, Li and Cd are of natural origin while Cu, Mo and Sb are related to the exploitation and mineral treatment of porphyry copper deposits. During the intense March 2015 flood event, contaminant elements were remobilized in the Andes Mountains and El Salado Alto Basin, and concentrations increased in the El Salado Bajo Basin predominantly due to the creation of a hydrologic connection between adjacent basins. Despite the presence of world-class porphyry Cu-Mo and iron oxide copper‑gold deposits in the region, some of which have been mined since the end of the 19th century, concentrations of dissolved Cu are lower than previously reported. This is likely related to circumneutral pH and the complexation of Cu as a cation in contrast to As and Mo which might be stable as HAsO42 − and MoO42 −, respectively, in solution over long distances

Quantifying nutrient fluxes with a new hyporheic passive flux meter (HPFM)

The hyporheic zone is a hotspot of biogeochemical turnover and nutrient removal in running waters. However, nutrient fluxes through the hyporheic zone are highly variable in time and locally heterogeneous. Resulting from the lack of adequate methodologies to obtain representative long-term measurements, our quantitative knowledge on transport and turnover in this important transition zone is still limited.<br><br>In groundwater systems passive flux meters, devices which simultaneously detect horizontal water and solute flow through a screen well in the subsurface, are valuable tools for measuring fluxes of target solutes and water through those ecosystems. Their functioning is based on accumulation of target substances on a sorbent and concurrent displacement of a resident tracer which is previously loaded on the sorbent.<br><br>Here we evaluate the applicability of this methodology for investigating water and nutrient fluxes in hyporheic zones. Based on laboratory experiments we developed hyporheic passive flux meters (HPFMs) with a length of 50 cm which were separated in 5–7 segments allowing for vertical resolution of horizontal nutrient and water transport. The HPFMs were tested in a 7 day field campaign including simultaneous measurements of oxygen and temperature profiles and manual sampling of pore water. The results highlighted the advantages of the novel method: with HPFMs, cumulative values for the average N and P flux during the complete deployment time could be captured. Thereby the two major deficits of existing methods are overcome: first, flux rates are measured within one device instead of being calculated from separate measurements of water flow and pore-water concentrations; second, time-integrated measurements are insensitive to short-term fluctuations and therefore deliver more representable values for overall hyporheic nutrient fluxes at the sampling site than snapshots from grab sampling. A remaining limitation to the HPFM is the potential susceptibility to biofilm growth on the resin, an issue which was not considered in previous passive flux meter applications. Potential techniques to inhibit biofouling are discussed based on the results of the presented work. Finally, we exemplarily demonstrate how HPFM measurements can be used to explore hyporheic nutrient dynamics, specifically nitrate uptake rates, based on the measurements from our field test. Being low in costs and labour effective, many flux meters can be installed in order to capture larger areas of river beds. This novel technique has therefore the potential to deliver quantitative data which are required to answer unsolved questions about transport and turnover of nutrients in hyporheic zones

Mercúrio total em cabelos: uma contribuição para se avaliar o nível de exposição em Poconé, Mato Grosso, Brasil Total mercury in hair: a contribution to the evaluation of mercury exposure levels in Poconé, Mato Grosso, Brazil

Ocorrem na Bacia do Rio Bento Gomes (MT), às margens do Pantanal Mato-grossense, cerca de sessenta garimpos de ouro, onde o mercúrio é utilizado de forma intensiva nos processos de produção, através da formação de amálgamas que facilitam a aglutinação de partículas finas. A queima do amálgama nem sempre é feita em sistemas fechados de recuperação, havendo, portanto, perda de vapor para a atmosfera. Este estudo traz resultados de análises de mercúrio total nos cabelos de quatro grupos de voluntários que vivem em Poconé (MT), e faz uma caracterização geral do ambiente no que se refere à presença do metal na água e no sedimento do Rio Bento Gomes. Um equipamento de detecção por fluorescência foi usado para a determinação das concentrações, e os resultados indicam que os valores são mais baixos do que os de outras populações de áreas de garimpo no Brasil. Indicam também que a via ocupacional parece ser a mais eficiente rota potencial de contaminação da população por mercúrio.<br>There are some 60 gold-mining sites in the Bento Gomes River basin (Mato Grosso), at the border of the Mato Grosso Pantanal (Swamp), where mercury is used to agglutinate fine gold particles through amalgamation. During burning of the amalgam to release the gold, mercury vapor is lost to the atmosphere, since closed systems for mercury recovery are not always used. This study shows the results of total mercury analysis in hair from four volunteer groups living in Poconé, Mato Grosso, and presents a general environmental description pertaining to the presence of mercury in water and sediments from the Bento Gomes River. Atomic fluorescence was used for measuring mercury concentrations. The results were lower than for other populations from gold-mining areas in Brazil