Trace organic compounds and photosensitizing activity in Salvadoran surface and tap water sources: A first look

Despite their potential risks to human health and the environment at ng/L to μg/L concentrations, there has been relatively little effort to measure trace organic compounds (TOrCs) in surface waters of Central America. The concentrations of eighteen TOrCs detected at eleven surface water sites in the Lempa River basin of El Salvador and four sources of drinking water for the cities of San Salvador, Antiguo Cuscatlán, Soyapango, and Santa Tecla are reported here. All samples were analyzed via liquid chromatography with tandem mass spectrometry (LC-MS/MS). Detected TOrCs in surface water included sixteen compounds. Maximum concentrations of 23 μg/L, 6 μg/L, and 2 μg/L were measured for sulfamethoxazole, sucralose, and bisphenol A, respectively. In tap water, a total of fourteen species were found, with peak concentrations of 17 μg/L for sulfamethoxazole, 640 ng/L for bisphenol A, and 224 ng/L for tris(chloropropyl) phosphate (TCPP). To assess potential mechanisms of TOrCs attenuation in surface waters, samples were irradiated with UVA light (315-400 nm) for 12 h in the presence of furfuryl alcohol (FFA) to establish singlet oxygen (¹O₂) formation. All the samples exhibited photosensitizing activity upon irradiation, resulting in ¹O₂ concentrations of the order of 10^-14 M. To our knowledge, this is the first study that reports the quantification of TOrCs presence and the possible natural attenuation routes in Salvadoran surface and tap water sources.