期刊
ENVIRONMENT INTERNATIONAL
卷 146, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.envint.2020.106284
关键词
Estuarine soils; Manganese contamination; Iron oxides; Redox processes; Toxicity
资金
- Fundacao de Amparo do Espirito Santo (FAPES/CNPq/CAPES Rio Doce) [77683544/2017]
- Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior CAPES [001]
- CNPq [301161/2017-8, 305996/2018-5, 409593/2018-4]
- Sao Paulo Research Foundation (FAPESP) [2018/04259-2, 2019/17413-2, 2019/02855-0, 2019/19987-6, 2018/08408-2]
- Xunta de Galicia-Conselleria de Educacion e Ordeancion Universitaria de Galicia (Consolidation of competitive groups of investigation) [GRC GI 1574]
- CRETUS strategic group [AGRUP2015/02]
- Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro [E-26/202.757/2019]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
- DOE Office of Biological and Environmental Research
- National Institutes of Health, National Institute of General Medical Sciences [P41GM103393]
- National Institute of Health T32 Training Grant [T32 ES018827]
- USDA NIFA Hatch Project [CA-RENS-5151-H]
- Fulbright Award - J. William Fulbright Commission
The study assessed manganese contamination in the Rio Doce estuary after the collapse of the world's largest mine tailings dam, finding a significant increase in dissolved manganese and decrease in total manganese content in soils over the following two years. The dynamic interaction between Fe and Mn in the impacted estuary poses a high risk to estuarine biota and human health, indicating a possible chronic contamination scenario.
Manganese (Mn) is an abundant element in terrestrial and coastal ecosystems and an essential micronutrient in the metabolic processes of plants and animals. Mn is generally not considered a potentially toxic element due to its low content in both soil and water. However, in coastal ecosystems, the Mn dynamic (commonly associated with the Fe cycle) is mostly controlled by redox processes. Here, we assessed the potential contamination of the Rio Doce estuary (SE Brazil) by Mn after the world's largest mine tailings dam collapse, potentially resulting in chronic exposure to local wildlife and humans. Estuarine soils, water, and fish were collected and analyzed seven days after the arrival of the tailings in 2015 and again two years after the dam collapse in 2017. Using a suite of solid-phase analyses including X-ray absorption spectroscopy and sequential extractions, our results indicated that a large quantity of Mn-II arrived in the estuary in 2015 bound to Fe oxyhydroxides. Over time, dissolved Mn and Fe were released from soils when Fe-III oxyhydroxides underwent reductive dissolution. Due to seasonal redox oscillations, both Fe and Mn were then re-oxidized to Fe-III, Mn-III, and Mn-IV and re-precipitated as poorly crystalline Fe oxyhydroxides and poorly crystalline Mn oxides. In 2017, redox conditions (Eh: -47 +/- 83 mV; pH: 6.7 +/- 0.5) favorable to both Fe and Mn reduction led to an increase (similar to 880%) of dissolved Mn (average for 2015: 66 +/- 130 mu g L-1; 2017: 582 +/- 626 mu g L-1) in water and a decrease (similar to 75%, 2015: 547 +/- 498 mg kg(-1); 2017: 135 +/- 80 mg kg(-1)) in the total Mn content in soils. The crystalline Fe oxyhydroxides content significantly decreased while the fraction of poorly ordered Fe oxides increased in the soils limiting the role of Fe in Mn retention. The high concentration of dissolved Mn found within the estuary two years after the arrival of mine tailings indicates a possible chronic contamination scenario, which is supported by the high levels of Mn in two species of fish living in the estuary. Our work suggests a high risk to estuarine biota and human health due to the rapid Fe and Mn biogeochemical dynamic within the impacted estuary.
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