Linear alkylbenzene sulfonate pollution investigation along the Capibaribe River Estuarine System (Northeast Brazil)...

The Capibaribe Estuarine System (CES), in Recife-Brazil, is threatened by pollution from domestic effluents, including linear alkylbenzene sulfonate (LAS), a widely used and potentially toxic surfactant. This study uses an innovative in situ methodology: digital image-based (DIB) captured by smartphone, focused on environmental issues and analysis of LAS contamination in CES, assessing pollution sources and tidal influence. Triplicate water samples were collected over 4 consecutive weeks at 6 stations along the CES. The DIB method quantified LAS through color intensity by reaction with methylene blue. LAS concentrations ranged from 0.06 to 1.43 mg L^-1, exceeding the limits allowed by CONAMA (National Environmental Council from Brazil) and USEPA (United States Environmental Protection Agency) (0.2 mg L^-1). The highest concentrations were observed at the confluence of polluted rivers, and at stations close to the discharge of treated or irregularly discharged effluents, characterizing these locals as the main input sources of LAS for the CES. Higher concentrations were observed especially at ebb flow during spring tides, with lower contaminant dispersion, while areas with stronger marine influence had lower concentrations. The results showed critical levels of LAS in the CES, highlighting potential impacts on local biodiversity and human health, since several people use its water for various activities, including fishing. The DIB methodology has proven to be accurate, fast, cost-effective, and sustainable, making it a promising tool for environmental monitoring and/or improving effluent management.