Polycyclic Aromatic Hydrocarbons In The Tamar Estuary

Abstract

The high particulate association of PAH in aquatic systems hasoften been attributed to the hydrophobic nature of the compoundsleading to adsorption. Results presented i n this thesis stronglysuggest that a significant proportion of PAH in the Tamar areparticle-incorporated and unavailable for dynamic partition andphysical, chemical and biological fates.The generally uniform PAH composition identified throughout theestuary is highly indicative of a combustion or road and urban runoffsource. PAH distrubution in a dated Tamar Estuary sediment coreshowed an exponential decrease with depth and identified dramaticincreases in PAH flux during the last 20 years. This suggests anassociation with motor vehicles probably via road runoff. Nosignificant trends of change in PAH composition with depth wereapparent, indicating unifoinnlty of source and the unimportance ofPAH degradation mechanisms in the anoxic-sediment. Ibrylene displayedan anomalous distribution that could be attributed to its biogenicorigin.A survey of PAH distribution in the estuarine water columnidentified two areas exhibiting high concentrations. The first wasobserved at the turbidity maximum at the head of the estuary (byvirtue of particle-associated PAH) and the second as a result of anemission in the urban region during the, sampling period. A similardistribution was identified in the estuarine surface sediments whichare shown to act as a sink for both riverine and urban PAH.Suspended particulates in the water column, in general, containsimilar levels and compositionally reflect the higher molecularweight PAH (M>200) in the sediments. Ihis underlines theimportance of particulate transport and indicates that degradation ofthese PAH in the water column, is of minor significance, with sedimentincorporation as their primary fate. Lower MW PAH (MW<200)wereenriched in soluble forms in the water column. Microbialheterotrophic degradation and volatilisation are proposed as importantenvironmental fates of these low MW compounds.

Date of Award	1982
Original language	English
Awarding Institution	University of Plymouth