SOURCES AND FATES OF ORGANIC CONTAMINANTS
Report No FR/D0001
There is a general lack of information on the occurrence of organic contaminants in UK estuaries, and coastal waters. The Mersey estuary is widely regarded as one of the most polluted estuaries in Europe but information on the specific organic contaminants involved is sparse. Investigations were therefore carried out on the sources, distribution and behaviour of organic contaminants in the Mersey estuary. Such studies are essential to provide basic data on the range and concentration of contaminants in estuaries and also to assist in environmental fate predictions. Concerns over the possible uptake and bioconcentration of organic residues by fish and other marine life confirms the need for more information on organic contaminants in estuaries and coastal waters.
III RESUME OF CONTENTS
The rationale behind the estuarine and freshwater input water sampling strategy is described and the reasons for the selection of specific organic contaminants for study are presented. Concentration data for organic contaminants in freshwater inputs and the Mersey estuary are presented for a series of surveys conducted between May 1987 and November 1989. The spatial distribution of organic contaminants and their partitioning between 'dissolved' and 'particulate' phases has been investigated in both fresh and saline waters, and data are interpreted in terms of the physicochemical properties of specific contaminants.
Estimates have been made of the precision of analytical data for highly turbid and variable ionic strength water samples. Joint intercomparison exercises have been carried out with ICI and the NRA (NW division) to ascertain the comparability of survey data from different laboratories for compounds of recognised importance (eg volatile organohalogen compounds). In addition, estimates of contaminant inputs to the estuary have been made using freshwater flow data, and the observed patterns of specific contaminant concentrations in the Mersey estuary interpreted in terms of salinity mixing curves. Simple estuarine flux calculations have been employed to provide additional information on contaminant fates and the limitations of such procedures are described.
This study has provided detailed information on the range and concentrations of organic contaminants in the major freshwater inputs to the Mersey estuary. Information on the fate of these contaminants in the estuary has also been obtained. Data on a range of specific contaminants in freshwater inputs and the estuary has been supplemented by carrying out broad spectrum screening using GCMS techniques. The major conclusions from the study are as follows:
This study has provided new information on the diversity, concentration and distribution of organic contaminants in a major UK estuary.
The data from this study has provided an important database for the Mersey estuary and should serve as the basis for future monitoring programmes, particularly in view of the pollution abatement schemes currently being introduced. This investigation has highlighted several areas in need of further study. Analysis of fish caught in the estuary indicates that there is evidence for the bioaccumulation of organochlorine contaminants. However, no evidence for any significant inputs of these contaminants was obtained from analysis of water column samples. It is possible that historically contaminated sediments contribute to the contaminant load through resuspension mechanisms. A programme of analysing sediments from a range of locations in the estuary is recommended. It was not possible, as part of this study, to carry out an investigation of the food species of fish caught in the estuary. It is recommended that this work is undertaken, with subsequent analysis of food species for organo-chlorine contaminants to determine whether there is any evidence of a food chain link.
The partitioning behaviour of organic contaminants in the estuary has been investigated, and the importance of the 'third' or 'colloidal' phase in influencing contaminant partitioning has been recognised, but requires further investigation.
A large number of contaminants were detected in the GCMS analysis of both freshwater and estuarine samples. A large number of these were unable to be identified. The application of additional GCMS techniques such as positive and negative chemical ionisation or liquid chromatography mass spectrometry may assist in the identification of some of these contaminants.
Copies of the Report are available from FWR, price £15.00 less 20% to FWR Members