Validation of basaltic glass adsorption capabilities from geothermal arsenic in a basaltic aquifer: A case study from Bjarnarflag power Station, Iceland

Arsenic is a carcinogen known for its acute toxicity to organisms. Geothermal waters are commonly high in arsenic, as shown at the Bjarnarflag Power Plant, Iceland (∼224 μg/kg of solvent). Development of geothermal energy requires adequate disposal of arsenic-rich waters into groundwater/geothermal...

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Bibliographic Details
Published in:Geoscience Frontiers
Main Authors: Weaver, KC, Hoque, MA, Amin, SM, Markússon, SH, Butler, AP
Format: Article in Journal/Newspaper
Language:unknown
Published: Elsevier 2019
Subjects:
Science & Technology
Physical Sciences
Geosciences
Multidisciplinary
Geology
Geothermal
Groundwater
Hydrogeochemistry
Arsenic
Modelling
GROUNDWATER-FLOW SYSTEMS
LAKE MYVATN
BEHAVIOR
WATER
0402 Geochemistry
0403 Geology
0404 Geophysics
Mývatn
Bjarnarflag
Iceland
Online Access:http://hdl.handle.net/10044/1/69366
https://doi.org/10.1016/j.gsf.2019.01.001
Description
Summary:Arsenic is a carcinogen known for its acute toxicity to organisms. Geothermal waters are commonly high in arsenic, as shown at the Bjarnarflag Power Plant, Iceland (∼224 μg/kg of solvent). Development of geothermal energy requires adequate disposal of arsenic-rich waters into groundwater/geothermal systems. The outcome of arsenic transport models that assess the effect of geothermal effluent on the environment and ecosystems may be influenced by the sensitivity of hydraulic parameters. However, previous such studies in Iceland do not consider the sensitivity of hydraulic parameters and thereby the interpretations remain unreliable. Here we used the Lake Mývatn basaltic aquifer system as a case study to identify the sensitive hydraulic parameters and assess their role in arsenic transport. We develop a one-dimensional reactive transport model (PHREEQC ver. 2.), using geochemical data from Bjarnarflag, Iceland. In our model, arsenite (H 3 AsO 3 ) was predicted to be the dominant species of inorganic arsenic in both groundwater and geothermal water. Dilution reduced arsenic concentration below ∼5 μg/kg. Adsorption reduced the residual contamination below ∼0.4 μg/kg at 250 m along transect. Based on our modelling, we found volumetric input to be the most sensitive parameter in the model. In addition, the adsorption strength of basaltic glass was such that the physical hydrogeological parameters, namely: groundwater velocity and longitudinal dispersivity had little influence on the concentration profile.

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