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Rates of emission from CCA-treated wood in the marine environment: measurement, modelling and requirements for further research
2001 - IRG/WP 01-50166-12
Accurate estimates of rates of emission of leachate from preservative treated wood are crucial for realistic predictions of the environmental impact of its use in maritime construction. Estimates are available for some commonly used preservatives, but these vary widely. Though variable, these measurements suggest that emission generally decreases exponentially with time. Part of the variation is due to differences in methodology employed. Physical and chemical characteristics of the seawater used (e.g. temperature, salinity, pH and oxygen content) affect emission rate. So too do the specifics of the treatment process especially the preservative formulation used, and pre- and post-treatment handling of the wood. The nature of the treated wood samples is also important, with misleadingly high estimates being obtained from samples with unrepresentatively high proportions of cross-cut surfaces. A suggested strategy for developing an informative and standardised methodology is discussed. To form useful models of impacts of leaching, emission rates need to be considered in conjunction with site-specific information regarding a) water exchange rates between the area where leaching occurs and the sea, and b) the extent of partitioning of leachate between the water column, biota and sediment. The risk of environmental impact may be reduced by modification to treatment procedures and by careful planning of installation.
S M Cragg, C J Brown, R A Albuquerque, R A Eaton
PCP in aquatic environments arising from historic contamination at wood processing and preservation sites
1995 - IRG/WP 95-50040-14
Three different studies are reported that assess the impacts of Pentachlorophenol (PCP) in aquatic environments arising from its historic use at sawmilling and wood preservation sites. These studies involved New Zealand wood processing facilities, and collectively they aimed to measure the transport of PCP from sawmill sites into the aquatic environment, determine the background environmental concentration of PCP in isolated lakes of New Zealand, and assess the relative contribution of PCP from different potential sources, such as sawmills, urban areas and agricultural catchments. The PCP concentrations in water, sediment and biota from a lake catchment, near a major wood processing site, indicated that low level contamination had occurred. PCP levels in lake sediments and freshwater mussels were elevated compared to New Zealand remote lake sites but similar to comparable locations reported in the international literature. Water concentrations of PCP in the lake were less than the most stringent international water quality guidelines for the protection of aquatic life. Water and sediment PCP concentrations in streams within the catchment, isolated from point sources, were less than the detection limit. The PCP concentration found in sediments ( £ 1.3 ng.g-1 DW) from the remote lakes, reflects a New Zealand background concentration. The source of PCP in remote lake sites is unknown, though it is unlikely to be directly from the sawmilling industry. Although the historic use of PCP by the sawmilling industry appears to have caused localised contamination near areas of high use, the current evidence suggests that it has not lead to widespread contamination of New Zealand aquatic environments.
J S Gifford, P N McFarlane, M C Judd, S M Anderson