Determination of volatile organic compounds around Aliaga by passive sampling methods

Volatile organic compounds (VOCs) are most important air pollutants because of their role in the tropospheric chemistry and their adverse effects on human health. In order to determine their ambient VOC concentrations in Aliağa urban and industrial region a grid system with 48 sampling points for weekly passive sampling were established. The five sampling campaign periods that were conducted on December, 19-26, 2005; March 21-28, 2006; June, 19-26, 2006; August 29 ? September 5, 2006 and February 9-16, 2007. Twenty-three VOCs were detected and quantified in these five periods, although 55 such compounds were measureable and quantifiable with the method used. In this thesis work, four of the VOCs, namely the benzene, toluene, ethylbenzene and xylene which are altogether called BTEX compounds held by the sample tubes were studied in depth. BTEX are the most important group of VOCs for their abundance, common sources and serious health effects.Styrene was the most abundant volatile organic compound, followed by 2-methylhexane and toluene with an average of 2.10 µg m-3, 1.65 µg m-3 and 1.44 µg m-3 at Aliaga region. The highest VOC concentrations were measured at petrochemical and refinery areas.The levels of BTEX were relatively higher in winter as compared to summer periods. The reason of having lower levels of BTEX might be the effects of higher chemical removal reaction rates by higher temperatures and sunlight.The average BTEX ratios were 2.5:5.3:1.0:1.5 for period 1, 2.7:4.9:1.0:2.2 for period 2, 2.0:6.7:1.0:2.5 for period 3, 2.5:8.3:1.0:3.6 for period 4 and 13.0:25.9:1.0:3.3 for period 5. Toluene to benzene (T/B) ratio was also studied to identify the possible sources of VOCs. T/B ratios were 2.1 for period 1, 1.8 for period 2, 3.4 for period 3, 3.3 for period 4 and 2.0 for period 5. In winter vehicular exhaust was the main source of VOCs, however in summer industrial activities also affect the air pollution as source of VOCs. According to T/B ratios, these compounds were more likely originating from the vehicles in traffic in winter, however, they might be more affected by industrial emissions in summer. Although a source detection study was not made in this study, correlations between different BTEX concentrations showed that their major source were the traffic emissions.Also benzene levels were evaluated for the cancer risk in Aliaga region. Benzene is a known carcinogen and continous exposure to 1 µg m-3 produces a lifetime risk ranging of 2.2 x 10-6 ? 7.8 x 10-6 for leukaemia. Usually, 5µg m-3 is considered a practical limit (ENDS, 1996). Average benzene concentrations were 0.66 for period 1; 1.22 for period 2; 0.27 for period 3; 0.13 for period 4 and 0.78 for period 5. Generally speaking , these average values indicate no significant cancer risk due to benzene in the area. However benzene levels were higher than 5µg m-3 at the petrochemical and refinery yards and there was the risk for people which must definitely be studied further.