Tidal influence on BTEX biodegradation in sandy coastal aquifers

Robinson, C., Brovelli, A., Barry, D. A. and Li, L. (2009) Tidal influence on BTEX biodegradation in sandy coastal aquifers. Advances in Water Resources, 32 1: 16-28. doi:10.1016/j.advwatres.2008.09.008


Author Robinson, C.
Brovelli, A.
Barry, D. A.
Li, L.
Title Tidal influence on BTEX biodegradation in sandy coastal aquifers
Journal name Advances in Water Resources   Check publisher's open access policy
ISSN 0309-1708
1872-9657
Publication date 2009-01-01
Year available 2008
Sub-type Article (original research)
DOI 10.1016/j.advwatres.2008.09.008
Volume 32
Issue 1
Start page 16
End page 28
Total pages 13
Editor Casey T Miller
D At Barry
W F Krajewski
Place of publication Oxford, U.K.
Publisher Elsevier Sci
Language eng
Subject C1
960503 Ecosystem Assessment and Management of Coastal and Estuarine Environments
090702 Environmental Engineering Modelling
Abstract A numerical study was conducted to investigate the influence of tides on the fate of terrestrially derived BTEX discharging through an unconfined aquifer to coastal waters. Previous studies have revealed that tide-induced seawater circulations create an active salt-freshwater mixing zone in the near-shore aquifer and alter the specific subsurface pathway for contaminants discharging to the coastal environment. Here the coupled density-dependent flow and multi-species reactive transport code PHWAT was used to examine the impact of these tidal effects on the aerobic biodegradation of BTEX released in a coastal aquifer and its subsequent loading to coastal waters. Simulations indicated that tides significantly enhance BTEX attenuation in the near-shore aquifer. They also reduce the rate of chemical transfer from the aquifer to the ocean and exit concentrations at the beach face. For the base case consisting of toluene transport and biodegradation, 79% of toluene initially released in the aquifer was attenuated prior to discharge with tides present, compared to only 1.8% for the non-tidal case. The magnitude of tidal forcing relative to the fresh groundwater flow rate was shown to influence significantly the extent of biodegradation as it controls the intensity of salt-freshwater mixing, period of exposure of the contaminant to the mixing zone and rate of oxygen delivery to the aquifer. The oxygen available for biodegradation also depends on the rate at which oxygen is consumed by natural processes such as organic matter decomposition. While simulations conducted with heterogeneous conductivity fields highlighted the uncertainties associated with predicting contaminant loadings, the study revealed overall that BTEX may undergo significant attenuation in tidally influenced aquifers prior to discharge.
Keyword Aquifer-ocean exchange
Subterranean estuary
Submarine groundwater discharge
Coastal water pollution
Q-Index Code C1
Q-Index Status Provisional Code

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Civil Engineering Publications
 
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Created: Thu, 03 Sep 2009, 19:01:17 EST by Mr Andrew Martlew on behalf of School of Civil Engineering