The characteristics of BTEX concentration in various types of environment in the Baltic Sea Region, Lithuania

Benzene, toluene, ethylbenzene and xylene (BTEX) form an important group of volatile organic compounds (VOCs) affecting troposphere and posing risk to human health. The article examines the Mažeikiai area in the northern part of Lithuania where one of the largest Central European companies and the only oil refinery in the Baltic region (200,000 barrels/day) are close to the Baltic Sea. The research carried out mainly focuses on the following objectives: quantitative assessment of the amounts of BTEX occurring in the impact zone of the oil refinery and transport; estimation of background BTEX concentrations in the region; establishing the main sources of BTEX in the region researched and evaluation of impact of meteorological parameters on BTEX concentrations in different seasons. The passive measurement method was used for analysing VOCs (benzene (C₆H₆), toluene (C₇H₈), ethylbenzene (C₈H₁₀) and ortho-, meta- para-xylene (C₈H₁₀)). The research was carried out in 2010-2012. Its results showed that the average annual concentration of benzene was below the threshold value of 5 μg/m³. Within the measurement period, the average concentration of benzene fluctuated from 1.2 to 2.4 μg/m³, that of toluene varied from 1.3 to 3.5 μg/m³, that of ethylbenzene varied from 0.3 to 0.7 μg/m³ and that of xylene (calculated as para-, meta- and ortho-xylene) varied from 1.0 to 2.4 μg/m³. Compared to the established BTEX concentration, the actual background BTEX concentration in the urban area is two times higher. The seasonal analysis suggests that the highest values of benzene concentration are observed in the winter season.