Arsenic speciation and transport associated with the release of spent geothermal fluids in Mutnovsky field (Kamchatka, Russia)

Journal Article · Tue Sep 20 04:00:00 EDT 2011 · Chem. Geol.

DOI:https://doi.org/10.1016/j.chemgeo.2011.07.010· OSTI ID:1023689

Ilgen, Anastasia G; Rychagov, Sergey N; Trainor, Thomas P ^[1]

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1. Alaska Fairbanks

The use of geothermal fluids for the production of electricity poses a risk of contaminating surface waters when spent fluids are discharged into (near) surface environments. Arsenic (As) in particular is a common component in geothermal fluids and leads to a degradation of water quality when present in mobile and bioavailable forms. We have examined changes in arsenic speciation caused by quick transition from high temperature reducing conditions to surface conditions, retention mechanisms, and the extent of transport associated with the release of spent geothermal fluids at the Dachny geothermal fields (Mutnovsky geothermal region), Kamchatka, Russia -- a high temperature field used for electricity production. In the spent fluids, the arsenic concentration reaches 9 ppm, while in natural hot springs expressed in the vicinity of the field, the As concentration is typically below 10 ppb. The aqueous phase arsenic speciation was determined using Liquid Chromatography (LC) coupled to an Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The arsenic speciation in the bottom sediments (< 65 {mu}m fraction) of the local surface waters was analyzed using X-ray Absorption Spectroscopy (XAS). Arsenic in the geothermal source fluids is predominantly found as As(III), while a mixture of As(III)/As(V) is found in the water and sediment of the Falshivaia River downstream from the power plant. The extent of elevated arsenic concentrations in water is limited by adsorption to the bottom sediment and dilution, as determined using Cl{sup -} from the deep well fluids as a tracer. Analysis of the Extended X-ray Absorption Fine Structure (EXAFS) spectra shows that sediment phase arsenic is associated with both Al- and Fe-rich phases with a bi-dentate corner sharing local geometry. The geothermal waste fluids released in the surface water create a localized area of arsenic contamination. The extent of transport of dissolved As is limited to {approx}7 km downstream from the source, while As associated with bottom sediment travels {approx}3 km farther.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSFDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1023689
• Journal Information: Chem. Geol., Journal Name: Chem. Geol. Journal Issue: (3-4) ; 09, 2011 Vol. 288; ISSN CHGEAD; ISSN 0009-2541
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

15 GEOTHERMAL ENERGY
ABSORPTION SPECTROSCOPY
ADSORPTION
ALUMINIUM
ARSENIC
DILUTION
ENVIRONMENTAL TRANSPORT
FINE STRUCTURE
FLUIDS
GEOTHERMAL FIELDS
GEOTHERMAL FLUIDS
HOT SPRINGS
IRON
KAMCHATKA
LIQUID COLUMN CHROMATOGRAPHY
MASS SPECTROMETERS
POWER PLANTS
RETENTION
RIVERS
SEDIMENTS
SURFACE WATERS
TEMPERATURE DEPENDENCE
WASTES
WATER
WATER POLLUTION
WATER QUALITY
WELLS