Natural input of arsenic into a coral-reef ecosystem by hydrothermal fluids and its removal by Fe(III) oxyhydroxides
- Univ. of Ottawa, Ontario (Canada). Ottawa-Carleton Geoscience Centre
The coral reef that circles Ambitle Island, Papua New Guinea, is exposed to the discharge of a hot, mineralized hydrothermal fluid. The hydrothermal fluids have a pH of {approximately}6 and are slightly reducing and rich in As. Seven individual vents discharge an estimated 1500 g of As per day into an area of approximately 50 x 100 m that has an average depth of 6 m. Despite the amount of As released into the bay, corals, clams, and fish do not show a response to the elevated values. The authors analyzed hydrothermal precipitates for their chemical and mineralogical composition in order to determine As sinks. Two mechanisms efficiently control and buffer the As concentration: (1) dilution by seawater and (2) incorporation in and adsorption on Fe(III) oxyhydroxides that precipitate when the hydrothermal fluids mix with ambient seawater. Fe(III) oxyhydroxides contain up to 76,000 ppm As, by an order of magnitude the highest As values found in a natural marine environment. Following adsorption, As is successfully retained in the Fe(III) oxyhydroxide deposits because oxidizing conditions prevail and high As activity allows for the formation of discrete As minerals, such as claudetite, arsenic oxide, and scorodite.
- OSTI ID:
- 354339
- Journal Information:
- Environmental Science and Technology, Vol. 33, Issue 9; Other Information: PBD: 1 May 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Iron transformation pathways and redox micro-environments in seafloor sulfide-mineral deposits: Spatially resolved Fe XAS and δ57/54Fe observations
Geochemistry and crystallochemistry of oceanic hydrothermal manganese oxyhydroxides showing Mn-Cu association