PETROLEUM-DERIVED DISSOLVED ORGANIC-COMPOUNDS CONCENTRATED FROM INSHORE WATERS IN BERMUDA

In conjunction with the IOC/GEEP Workshop of September 1988, lipophilic dissolved organic material was concentrated from Bermuda inshore waters by liquid-solid adsorption on Amberlite XAD-2. Water samplers were moored at depths of 1-2 m on the reef platform and in inland seawater basins (Hamilton Harbour, Castle Harbour). Sample volumes were 221-4351. The adsorbed material was eluted from the resin with refluxing aqueous acetone in a specially designed apparatus. Fractions containing aliphatic and aromatic hydrocarbons were obtained by liquid chromatography on silica gel. Single compounds were identified and quantified by capillary GC/MS. Alkylated PAH with minor contributions of unsubstituted parent compounds were detected in the basins, strongly suggesting a fossil fuel origin. Concentrations diminishing steeply over a short distance between contaminated harbour water and a control station suggest a source of limited spatial extension for unsubstituted PAH. An even steeper concentration gradient of alkyl substituted PAH may indicate their more rapid environmental alteration. Thus, predominance of unsubstituted over substituted PAH in environmental samples could have two causes: a significant contribution of pyrolysis products or easier conversion/degradability of substituted PAH. Photochemically generated hydroxyl and carbonyl derivatives of alkylbenzenes were also measured. Concentrations of hydroxyl derivatives exceeded those of carbonyl derivatives in harbour water with a high load of dissolved organic material, as indicated by total lipid weight and UV fluorescence measurements. In waters with lower organic carbon load, concentrations of carbonyl derivatives were essentially similar but concentrations of hydroxyl derivatives dropped below the detection limit. We propose that the total concentration of dissolved organic material in the water influences the degree of oxidation and thus the composition of products formed. Combined concentrations of specific photo-oxidation products such as alkylacetophenones, alkylbenzaldehydes, quinones, alkylbenzyl alcohols, alkylphenylethanols were up to more than seven times higher than those of the parent hydrocarbons, indicating rapid conversion rates in this subtropical environment. These results support the need for further assessment of the relative toxicities of the reaction products in addition to those of the parent hydrocarbon contaminants in marine ecosystems. © 1990.