Use of trialkylamines as an indicator of urban sewage in sludges, coastal waters and sediments

Abstract

Coastal areas receive a variety of land-based organic inputs, both natural and synthetic. The identification of specific organic markers in different marine compartments may be used to trace the pathways of transport, the regions of concentration and the short-term effects of such inputs into the ocean. Particular attention is being devoted to the assessment of urban wastes at coastal areas because of the environmental implications of discharging large quantities of urban sewage waters or sludges into the sea. Here we report the widespread occurrence of trialkylamines (TAMs) in coastal areas, originating from such sewage discharges. The concentrations of these compounds—which have the formula R₁R₂NCH₃, where R₁ = CH₃ or C_nH_2n+1 and R₂= C_nH_2n+1 for n = 14–18—in Western Mediterranean and North Sea coastal sediments (Fig. 1) ranged from 0.1 to 35 μgg⁻¹ depending on the distance from and the pollutant budget of the urban sewage sources. We have identified TAMs as trace impurities in quaternary ammonium salts used as fabric softeners in household laundry detergents, for which reason they are found in urban sewage waters, primarily associated with the particulate phase. They correlate in the sedimentary record with other domestic surfactant markers, such as the long-chain alkylbenzenes (LABs). We propose, therefore, that TAMs may serve as conservative indicators of urban sewage contamination of coastal areas.