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Global patterns and environmental controls of perchlorate and nitrate co-occurrence in arid and semi-arid environments

Jackson, W. Andrew ; Böhlke, J.K. ; Andraski, Brian J. ; Fahlquist, Lynne ; Bexfield, Laura ; Eckardt, Frank D. ; Gates, John B. ; Davila, Alfonso F. ; McKay, Christopher P. ; Rao, Balaji ; Sevanthi, Ritesh ; Rajagopalan, Srinath ; Estrada, Nubia ; Sturchio, Neil ; Hatzinger, Paul B. ; Anderson, Todd A. ; Orris, Greta ; Betancourt, Julio ; Stonestrom, David ; Latorre, Claudio ; Li, Yanhe ; Harvey, Gregory J.

Geochimica et cosmochimica acta, 2015-09, Vol.164, p.502-522 [Periódico revisado por pares]

Elsevier Ltd

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Título:
Global patterns and environmental controls of perchlorate and nitrate co-occurrence in arid and semi-arid environments
Autor: Jackson, W. Andrew ; Böhlke, J.K. ; Andraski, Brian J. ; Fahlquist, Lynne ; Bexfield, Laura ; Eckardt, Frank D. ; Gates, John B. ; Davila, Alfonso F. ; McKay, Christopher P. ; Rao, Balaji ; Sevanthi, Ritesh ; Rajagopalan, Srinath ; Estrada, Nubia ; Sturchio, Neil ; Hatzinger, Paul B. ; Anderson, Todd A. ; Orris, Greta ; Betancourt, Julio ; Stonestrom, David ; Latorre, Claudio ; Li, Yanhe ; Harvey, Gregory J.
É parte de: Geochimica et cosmochimica acta, 2015-09, Vol.164, p.502-522
Descrição: Natural perchlorate (ClO4−) is of increasing interest due to its wide-spread occurrence on Earth and Mars, yet little information exists on the relative abundance of ClO4− compared to other major anions, its stability, or long-term variations in production that may impact the observed distributions. Our objectives were to evaluate the occurrence and fate of ClO4− in groundwater and soils/caliche in arid and semi-arid environments (southwestern United States, southern Africa, United Arab Emirates, China, Antarctica, and Chile) and the relationship of ClO4− to the more well-studied atmospherically deposited anions NO3− and Cl− as a means to understand the prevalent processes that affect the accumulation of these species over various time scales. ClO4− is globally distributed in soil and groundwater in arid and semi-arid regions on Earth at concentrations ranging from 10−1 to 106μg/kg. Generally, the ClO4− concentration in these regions increases with aridity index, but also depends on the duration of arid conditions. In many arid and semi-arid areas, NO3− and ClO4− co-occur at molar ratios (NO3−/ClO4−) that vary between ∼104 and 105. We hypothesize that atmospheric deposition ratios are largely preserved in hyper-arid areas that support little or no biological activity (e.g. plants or bacteria), but can be altered in areas with more active biological processes including N2 fixation, N mineralization, nitrification, denitrification, and microbial ClO4− reduction, as indicated in part by NO3− isotope data. In contrast, much larger ranges of Cl−/ClO4− and Cl−/NO3− ratios indicate Cl− varies independently from both ClO4− and NO3−. The general lack of correlation between Cl− and ClO4− or NO3− implies that Cl− is not a good indicator of co-deposition and should be used with care when interpreting oxyanion cycling in arid systems. The Atacama Desert appears to be unique compared to all other terrestrial locations having a NO3−/ClO4− molar ratio ∼103. The relative enrichment in ClO4− compared to Cl− or NO3− and unique isotopic composition of Atacama ClO4− may reflect either additional in-situ production mechanism(s) or higher relative atmospheric production rates in that specific region or in the geological past. Elevated concentrations of ClO4− reported on the surface of Mars, and its enrichment with respect to Cl− and NO3−, could reveal important clues regarding the climatic, hydrologic, and potentially biologic evolution of that planet. Given the highly conserved ratio of NO3−/ClO4− in non-biologically active areas on Earth, it may be possible to use alterations of this ratio as a biomarker on Mars and for interpreting major anion cycles and processes on both Mars and Earth, particularly with respect to the less-conserved NO3− pool terrestrially.
Editor: Elsevier Ltd
Idioma: Inglês

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Global patterns and environmental controls of perchlorate and nitrate co-occurrence in arid and semi-arid environments

Elsevier Ltd

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