Assessment of PAHs and alkanes in sediments and water of theMonjolinho river watershed (Sāo Carlos, SP-Brazil)

Almas TAJ Awan, Leidy Camacho, Murilo Paix, Antonio Mozeto, Pedro Fadini

Thursday 2 july 2015

9:30 - 9:45h at Asia (level 0)

Themes: (T) Hydro-environment, (ST) Impacts of pollutants on the water environment

Parallel session: 10G. Environment - Impact

The main organic sources of contaminants in aquatic ecosystems are the polycyclic aromatic hydrocarbons (PAHs), and aliphatic hydrocarbons. PAHs are carcinogenic and mutagenic and have been identified as important emerging contaminants. Impacts of PAHs, together with n-alkanes (the aliphatic hydrocarbons) on the water bodies of urban areas become worse. The Monjolinho River is an urban tropical stream in central region of São Paulo State that receives both treated and untreated effluents. Our investigation was based on monitoring studies of the PAHs and n-alkanes in the sediment and water of Monjolinho River and to evaluate their possible sources that cause potential impacts on sediment–water quality. Several distribution or diagnostic indexes were also calculated to deduce the nature of potential sources of these hydrocarbons (biogenic, pyrogenic, and petrogenic). Results from our study showed n-Alkanes were predominant in the range of C17- C36. The predominant PAHs were of high molecular weight specially benzo(a)pyrene, indeno(1,2,3-cd) pyrene, dibenzo(a,h)anthracene and benzo(g,h,i)perylene compared with the concentrations of low molecular weight PAHs that indicated the importance of pyrogenic sources. Application of various diagnostic indexes for the data analyses revealed the significant presence of pyrogenic sources of hydrocarbons in sediments originating mainly from incomplete combustion of fossil fuels. However, the importance of petrogenic sources was confirmed by the high intensities of the CPI (carbon preference index). The biogenic contribution to the water body can be diagnosed by the relatively high total concentrations of n-alkanes in samples. The TEL and PEL violations were observed in very few samples. It suggests that toxicity to the benthic community may be a concern due to PAHs. Studies related to other contaminants (such as metals, nutrients, pharmaceuticals etc.) are important to be considered for exposing the vulnerability of the river and thinking about using it as a source of consumption. KEYWORDS: n-Alkanes and Isoprenoids, PAHs, Distribution indexes, Sediments, Water quality.