Origin of organohalogens found in Baltic Sea sediments

Abstract

Sediment samples from the Baltic Sea and fulvic acids (FAs) from one unpolluted lake and three major rivers in the Baltic Sea drainage area were analysed with respect to organically bound halogens. After ethylation of phenolic groups, oxidative degradation of high molecular weight organic matter and methylation of formed carboxylic acids, halogenated aromatic compounds were found in three of the four FA samples and all samples of organic matter leached with base from Baltic Sea sediments. The methyl esters of mono- and dichlorinated 4-ethoxybenzoic acid were the most abundant chlorinated degradation products in both the FA samples and the sediment samples from the Baltic Proper and the Gulf of Riga, whereas the methyl esters of chlorinated 4-ethoxy-3-methoxybenzoic acids were predominant in a sediment sample taken 2 km from a bleached-kraft mill. Brominated aromatic compounds were found in degraded organic matter from all marine samples but not in any of the samples of degraded freshwater FA. Gas Chromatographic analysis of the phenolic and cyclohexane-extractable fractions of compounds showed that chlorinated phenols, stearic acids and abietic acids were present in the sediment sample taken in the vicinity of the bleached-kraft mill but not detectable in the other sediments. The obtained results strongly indicate that the major part of the lignin-derived organically bound halogens found in the Baltic Proper and the Gulf of Riga sediments is of natural origin. However, the study neither confirmed nor rejected the hypothesis that relatively lipophilic organohalogens present in bleached-kraft mill effluents are being accumulated in the sediments of the central parts of the Baltic Sea.