Tracking sewage derived contamination in riverine settings by analysis of synthetic surfactants

Abstract

A study has been made of the presence and reactivity of the most commonly used surfactants, both anionic (linear alkylbenzene sulfonates, LAS, and alkyl ethoxysulfates, AES) and non-ionic (alcohol polyethoxylates, AEOs, and nonylphenol polyethoxylates, NPEOs), in water and surface sediments from the middle stretch of the Guadalete River in SW Spain (12 stations). Average values were between 0.1 and 3.7 mg kg À1 in sediment, and between 0.2 and 37 mg L À1 in water. The sorption of surfactants was dominated by hydrophobic mechanisms, so those homologues having longer alkyl chains (e.g. C 18 AEO) showed higher relative percentages and concentrations in sediments compared with water. Local and sharply higher concentrations of these compounds were observed at three sampling stations (7, 9 and 12), indicating the occurrence of wastewater discharges into the river. By analysing the distributions of different surfactant homologues and their metabolites we were able to distinguish between sewage contamination from sources discharging treated and untreated wastewaters. Upstream (stations 1-2), LAS concentrations were below 30 mg L À1 and the composition of their degradation intermediates (sulfophenyl carboxylic acids, SPCs) (160 mg L À1) was dominated by short-chain homologues (C 6 -C 9 SPCs), indicating that the degradation of this surfactant is at an advanced stage. The highest concentration (487 mg L À1) of SPCs was detected near the effluent outlet of a sewage treatment plant (STP) (station 12). Sampling stations (7 and 9) affected by untreated wastewater discharges were the only ones showing the presence of the most reactive and biodegradable SPC isomers and homologues (e.g. C 11 SPC). Here, LAS reached the highest concentration values measured (>2 mg L À1 ), and showed a homologue distribution closer to that of commercial mixtures than LAS found at the other stations.

Distribution of anionic and nonionic surfactants in a sewage-impacted Mediterranean coastal lagoon: Inputs and seasonal variations

“…Sewage effluents may contain surfactant concentrations up to 872 μg/L for LAS , and from 0.9 to 15.6 μg/L for NPEOs and AEOs (Loyo-Rosales et al, 2007;Morrall et al, 2006). A considerable number of studies have also reported the presence of LAS (Corada-Fernández et al, 2011;Ding et al, 1999;Eichhorn et al, 2002;González-Mazo et al, 1998;Lara-Martín et al, 2008;León et al, 2002;Marcomini et al, 2000) and NPEOs (Belmont et al, 2006;Corada-Fernández et al, 2011;Isobe and Takada, 2004;Jonkers et al, 2003Jonkers et al, , 2005Lara-Martín et al, 2008;Lee Ferguson et al, 2001;Maruyama et al, 2000;Petrovic et al, 2002;Zoller, 2006;Zoller and Hushan, 2000) in surface waters all around the world, with values between b50 and N1000 μg/L and between b0.1 and 100 μg/L, respectively. Data on the occurrence of AEOs are more limited in spite of their production volumes being comparable to those for LAS and NPEOs.…”

Analysis of Surfactants in Environmental Samples by Chromatographic Techniques

“…Any environmental compartment (surface waters, sediment, biota…) is susceptible of being contaminated by these compounds and/or their degradation metabolites [2,28]. As example, a considerable number of studies have reported the presence of LAS in surface waters [29][30][31] at levels typically ranging from less than 1 ng/L to several hundreds of µg/L respectively, depending on the distance from urban wastewater discharge sources and the type of wastewater treatment. Available studies about the presence, environmental behavior and distribution of non-ionic surfactants are mainly focused on NPEOs (nonylphenol polyethoxylates, which are the major fraction of APEOs).…”

“…Available data concerning to the presence of aliphatic anionic (AES) and nonionic (AEOs) surfactants, as well as cationic surfactants of any class, are rather limited. There are only a few papers about the occurrence of AEOs [36,40,43,44] and AES [19,31] in sediments, showing levels ranging from <0.1 to 23 mg/kg. Some authors have also measured concentrations between <0.1 and 72 µg/L for AES [19,31] and AEOs [36,40,43] in surface waters.…”

“…There are only a few papers about the occurrence of AEOs [36,40,43,44] and AES [19,31] in sediments, showing levels ranging from <0.1 to 23 mg/kg. Some authors have also measured concentrations between <0.1 and 72 µg/L for AES [19,31] and AEOs [36,40,43] in surface waters. QACs have been measured at levels ranging from less than 2 µg/L in surface waters [20] to more than 100 mg/kg in sediments [45,46].…”

“…Levels of surfactants in surface sediments are usually higher by several orders of magnitude than those measured in water due to their moderate to high sorption capacity. Thus, the presence of LAS [31,[38][39][40] and NPEOs [22,[41][42][43][44] has been widely detected in sediments, with levels ranging from less than 1 to more than 200 mg/kg and from less than 0.1 to 28.5 mg/kg respectively. Available data concerning to the presence of aliphatic anionic (AES) and nonionic (AEOs) surfactants, as well as cationic surfactants of any class, are rather limited.…”