Using Urban Streams as Drinking Water: The Potential Risk in Respect to Polycyclic Aromatic Hydrocarbons (PAHs) Content in Sediments

Abstract

Several polycyclic aromatic hydrocarbons are considered carcinogenic and mutagenic. 16 of these compounds are listed as priority control pollutants by the USEPA. The present study aimed at the evaluation of the presence of PAHs in sediments of an urban stream by GC-MS. The study area was located in Indaiatuba-São Paulo-Brazil, and supplies to approximately 40,000 people of a region with limited availability of water. Therefore, this water body flowing in the urban region represents a case study of the potential risk in using this water for drinking. The results show that, in general, the sampling site near the intake of the water treatment plant for human consumption had the highest concentration of total PAHs (247.7μg kg−1). This is the site that presents more contact with urban pollution and surface runoff from the streets. The PAHs composition pattern by ring number presented a higher proportion of hydrocarbons of 4- and 5-rings, and showed a tendency, in the majority of the samples, of predominance of the high-molecular-weight PAHs, except for samples collected on June 2011 that had a high concentration of naphthalene (a 2-ring PAH). The application of a principal component analysis helped to identify the sources of hydrocarbons as pyrogenic (PC1) and petrogenic origin (PC2). Through this statistical tool it is postulated that, in some periods, the stream was exposed to point and non-point sources of contamination, showing that this type of water supply option has a high degree of vulnerability mainly during the first rain after of a long dry period, and its consumption can cause long-term problems.