An assessment of the contamination and toxicity of marine sediments in theHoly Loch, Scotland

Following the closure of the United States Navy Submarine Base in 1992, vid eo surveys revealed that a considerable amount of debris, largely scrap met al, was present on the bed of the Holy Loch. A working group was set up to examine ways of 'cleaning-up' the loch, Consultants were employed by the UK Ministry of Defence to carry out an environmental survey of the Holy Loch, including an assessment of the consequences of lifting the debris from the loch bed. This survey revealed that a number of contaminants were present at high concentrations in the bed sediments. These contaminants included pe rsistent, toxic and bioaccumulable substances such as trace organic contami nants and trace metals. Concern was expressed that the debris removal opera tion may lead to the release of sediment-bound contaminants, which may in t urn exert toxic effects on local flora and fauna. Consequently, the Scottis h Environment Protection Agency carried out a survey to verify the levels o f persistent organic contaminants and trace metals in the sediments, to set these in contest on a UK scale, and to assess the toxicity of sediment/wat er mixtures, Contamination of Holy Loch sediments by polychlorinated biphen yls (PCBs) and by trace metals, especially copper and zinc, was confirmed a s severe but localized. Sediment bioassays indicated that acute mater colum n toxicity was unlikely to arise from the release of sediment-bound contami nants during the debris removal operation. Contaminant levels in mussels co llected before and after the initial phase of the debris removal operation showed little change, suggesting no impact on local flora and fauna, (C) 20 00 Elsevier Science Ltd. All rights reserved ed.