The Transport and Fate of Organic Contaminants in Estuarine and Coastal Systems

Timothy W. Fileman

MPhil – August 2000

Department of Environmental Sciences, University of Plymouth, Plymouth, U.K.

in collaboration with

Plymouth Marine Laboratory, Plymouth, Devon, U.K.

The results of this study represent an attempt to construct an inventory of contaminants of several environmentally important organic contaminant classes in seawater, suspended particles and sediments and to consider their sources, persistence, physicochemical properties and potential marine ecological impacts. A series of coastal and estuarine surveys was carried out in the River Humber and it's coastal region to determine transport mechanisms and fates of anthropogenic inputs to the Humber system and provide a quantitative understanding of the behaviour of the selected contaminants. Also non-priority contaminants have been identified which potentially contribute to ecotoxicological impacts.

All of the compounds investigated showed seasonal variations, although trends differed. Dissolved atrazine generally increased gradually from winter to summer before declining in autumn. For dissolved PAHs the highest dissolved concentrations were found in autumn while the lowest were in summer. Atrazine behaved conservatively in the estuary while a non-conservative behaviour was demonstrated for dissolved lindane, even though riverine inputs to the estuary from the Trent and Ouse are the major source for both compounds. The results show that position and type of inputs as well as the intrinsic physicochemical properties of these compounds are critical in regulating their behaviour in estuarine and coastal environments. The two coastal surveys show that although some compounds such as atrazine and lindane were detectable at all stations, their concentrations were generally in the low ng L-1 range. Concentrations followed the general path of the Humber Plume with only a minor influence from the Wash, confirming that the Humber catchment is the major source of input of these pollutants in the study area. Pyrene was detected at most locations while malathion concentrations were below the detection limit at all sites outside of the estuary. The results showed that the Humber system is a sink for all the organic contaminants studied, regardless of their origin, solubility, hydrophobicity or degradation potential. The Humber estuary removed between 13 and 100% of atrazine, lindane, PCB 77 and PCB 118, although the degree of removal is substantially more significant for the more hydrophobic compounds PCB 77 and PCB 118. Atrazine and lindane were removed by 28 and 13%, respectively. The total balance shows that 5 and 20% of river-transported fluoranthene and pyrene, respectively, are removed from the estuary.

The results reported address a wide range of environmental contaminants and biogeochemical processes and have contributed substantially to several papers which have been published in peer reviewed international journals. Pollutants studied originate from many different sources and have a spectrum of physico-chemical properties. This research has answered many questions relating to their estuarine and coastal behaviour, but also raises a whole series of new issues that will require research in the future.

2000 by T.W. Fileman. All Rights Reserved

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