POLYCYCLIC AROMATIC HYDROCARBON (PAH) DEPOSITION TO AND PROCESSING INA SMALL RURAL LAKE, CUMBRIA UK

PAH concentrations were determined in a dated sediment core collected from Esthwaite Water (EW), a seasonally anoxic lake in the English Lak e District. The most dramatic variations are associated with increased PAH fluxes from similar to 1900 and a sub-surface maximum (similar to 29 mg m(-2) year(-1)) in the late 1960s to early 1970s, followed by a fivefold decrease in fluxes to the sediment-water interface. This tre nd is believed to reflect enhanced fossil fuel burning, followed by ge neral improvements in combustion technologies, shifts in the fuels use d for domestic space heating and the implementation of various emissio n controls on releases from certain known PAH sources. When the relati ve contributions from individual compounds to the Sigma PAH were plott ed as vertical profiles, coherent time trends emerged. Perylene domina ted the pre-1900 sedimentary PAH composition, contributing > 75% to th e Sigma PAH mixture. The perylene profile provides good evidence for b oth natural and anthropogenic sources to EW. The ratios of annual sedi ment trap fluxes to surficial sediment accumulation rates are substant ially greater than one for the low molecular weight compounds, suggest ing release at or near the sediment water interface and subsequent rec ycling of these compounds. Recycling was found to increase with increa sing solubility and decreasing log K-ow. (C) 1998 Elsevier Science B.V .