MICROORGANIC COMPOUNDS ASSOCIATED WITH SEDIMENTS IN THE HUMBER RIVERS

The study investigates pollution by micro-organic contaminants in rive rine systems in NE England with the following four key objectives: (1) to establish the range and concentrations of micro-organic compounds in relation to land use; (2) investigate how the type and concentratio ns of micro-organics can vary seasonally; (3) compare bed-sediment and suspended-sediment concentrations, and to (4) assess the use of 'whol e-water' samples as indicators of environmental water quality in parti cular with respect to the ecotoxicological impact of contaminant-laden sediments within fluvial, systems. Waters, bed-and suspended sediment s were collected from six freshwater tributaries of the Humber river a t quarterly intervals during the period July 1995-1996. A wide range o f micro-organic contaminants were analyzed by GC/MS and GC/NPD, chosen on the basis of information provided through the UK Land Ocean Intera ction Study (LOIS) core monitoring and additional data regarding water quality and land-use within the catchment. Thirty compounds were targ eted including a range of pesticide groups, e.g. triazines, oganophosp horus and synthetic pyrethroids, in addition to other compounds of con cern including polyaromatic hydrocarbons, e.g. fluoranthene and pyrene , and a surfactant residue, nonylphenol. The results show the presence of a wide range of micro-organic contaminants associated with river s ediments. The high concentration of compounds associated with both bed and suspended sediments appears unrelated to the concentrations measu red in the dissolved phase. Greater concentrations of contaminants are found associated with the industrial southern rivers, Aire, Calder an d Don. However, considerable temporal variation in the concentrations associated with sediment has been shown. It is suggested that these va riations reflect a number of factors such as differences in land-use a nd the effect of the seasonal application of contaminants in addition to differences in the sediment characteristics and hence the potential of the sediment to remove or release a contaminant. It is shown that river sediments can act as a 'sink' and potential secondary source of micro-organic contaminants within fluvial systems. The implication of such an association is also shown to be significant in terms of the ec otoxicological impact of micro-organic contaminants. This is demonstra ted for cis-and trans-permethrin for which the calculated porewater co ncentrations in some rivers are sufficient to cause adverse effects on benthic fauna. (C) 1998 Elsevier Science B.V.