Properties of natural microlayers on Australian freshwater storages and their potential to interact with artificial monolayers
Pamela A. Pittaway A C and Tania R. van den Ancker BA Cooperative Research Centre for Irrigation Futures, National Centre for Engineeringin Agriculture, University of Southern Queensland, West Street, Toowoomba,Qld 4350, Australia.
B St Saviour’s College, Neil Street, Toowoomba, Qld 4350, Australia.
C Corresponding author. Email: pittaway@usq.edu.au
Marine and Freshwater Research 61(10) 1083-1091 https://doi.org/10.1071/MF09159
Submitted: 29 June 2009 Accepted: 14 April 2010 Published: 14 October 2010
Abstract
Microlayers are natural surface films derived from hydrophobic organic compounds that form on most lakes and streams. Holarctic brown-water lakes have been most commonly studied, with Australian research limited to marine microlayers. Artificial monolayers based on long-chain fatty alcohols have been applied to freshwater storages to reduce evaporative loss. As a water conservation strategy, monolayer technology was not widely adopted because of variable field performance. However, the role of natural microlayers in reducing monolayer performance has not previously been investigated. In the present study, microlayer and subsurface samples from six water storages in Queensland were characterised for water-quality indices, including biochemical oxygen demand, permanganate index and ultraviolet light absorbance. Microlayer enrichment in south-eastern Queensland is comparable to or higher than that in holarctic lakes. The results indicated that microlayer compounds have the potential to disrupt monolayers in at least the following three ways: as substrates for microbes capable of degrading monolayer compounds, as chromophores accelerating photodegradation, and as impurities disrupting the molecular packing required to reduce evaporative loss. The knowledge gained from studying natural microlayers can also be used to benchmark novel monolayer compounds, to minimise their environmental impact on freshwater ecosystems.
Additional keywords: BOD, permanganate index, UV-light absorbance.
Acknowledgements
This research was funded by the Cooperative Research Centre for Irrigation Futures (CRCIF), as part of the Evaporation Mitigation Project. The authors thank Kim Larsen (University of Southern Queensland) and John Mills (Toowoomba Regional Council Laboratory Services) for technical advice and support, and staff from the National Centre for Engineering in Agriculture, the Water Quality and Biology Laboratories of the University of Southern Queensland for their assistance and support. We also thank Geoff Barnes and Nigel Hancock from the CRCIF for discussions on this research, and for reviewing this manuscript.
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