Input and behaviour of linear alkylbenzenesulphonates (LAS) in a stratified estuary

Abstract

Input and distribution of linear alkylbenzenesulphonates (LAS) in the highly stratified Krka River estuary were studied during 1990–1991. Determinations of individual LAS homologues in wastewater and estuarine waters were performed using reversed-phase high-performance liquid chromatography (HPLC) with spectrofluorimetric detection. The investigated municipal wastewaters contained LAS homologues with alkyl-chain lengths from C 10 to C 13 at total concentrations in the range of 285–1041 μg l −1. Total LAS input via wastewaters into Šibenik Harbour, the most polluted part of the estuary, was estimated at 12.6 kg day −1. A relatively large fraction of total LAS, depending on the wastewater particle load, was found in particulate form (11–59%). Distributions of the individual homologues in dissolved and particulate fractions were rather different, the latter being significantly enriched in higher homologues (C 12, C 13). The LAS concentration in the estuary was quite low (0.2–23.9 μg l −1) which was caused chiefly by a strong and fast dilution process. However, characteristic vertical distribution of LAS in the estuarine water column indicated that the wastewater plume spreads almost exclusively in the upper (brackish) layer. The concentration maxima were observed in the surface microlayer and at the brackish water/seawater boundary.