 |
| Titel |
Classification scheme for acid rock drainage detection - the Hamersley Basin, Western Australia |
| VerfasserIn |
Grzegorz Skrzypek, Shawan Dogramaci, Laura McLean |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147133
|
| Publikation (Nr.) |
 EGU/EGU2017-11244.pdf |
|
|
|
|
|
| Zusammenfassung |
| In arid environment where precipitation and surface water are very limited, groundwater is
the most important freshwater resource. For this reasons it is intensively exploited and needs
to be managed wisely and protected from pollutants.
Acid rock drainage often constitutes a serious risk to groundwater quality, particularly in
catchments that are subject to mining, large scale groundwater injection or abstraction.
However, assessment of the potential acid rock drainage risk can be challenging, especially in
carbonate rich environment, where the decreasing pH that usually accompanies
pyrite oxidation, can be masked by the high pH-neutralisation capacity of carbonate
minerals.
In this study, we analysed 73 surface and groundwater samples from different water
bodies and aquifers located in the Hamersley Basin, Western Australia. Although
the majority of samples had a neutral pH, there was a large spatial variability in
the dissolved sulphate concentrations that ranged from 1 mg/L to 15,000 mg/L.
Waters with high dissolved sulphate concentration were found in areas with a high
percentage of sulphide minerals (e.g. pyrite) located within the aquifer matrix and were
characterised by low δ34SSO4 values (+1.2‰ to +4.6) consistent with signatures of
aquifer matrix pyritic rock samples (+1.9‰ to +4.4). It was also found that the SO4
concentrations and acidity levels were not only dependent on δ34SSO4 values and
existence of pyrite but also on the presence of carbonate minerals in the aquifer
matrix.
Based on the results from this study, a classification scheme has been developed
for identification of waters impacted by acid rock drainage that also encompasses
numerous concomitant geochemical processes that often occur in aqueous systems. The
classification uses five proxies: SO4, SO4/Cl, SI of calcite, δ34SSO4 and δ18OSO4 to
improve assessment of the contribution that oxidation of sulphide minerals has
to overall sulphate ion concentrations, regardless of acidity levels of the aqueous
system.
This classification scheme enables a more direct monitoring regime for early detection of
acid rock drainage processes and better groundwater quality management.
References
Dogramaci S., McLean L., Skrzypek G., 2017. Hydrochemical and stable isotope
indicators of pyrite oxidation in carbonate-rich environment; the Hamersley Basin, Western
Australia. Journal of Hydrology 545, 288-298. |
|
|
|
|
|
|