A SURVEY ON VARIATIONS OF BTEX AND OZONE FORMATION POTENTIAL IN YAZD CITY AND MAPPING WITH GIS

Today use of unleaded gasoline is increasing in the world which contains
abundant amount of aromatic organic carcinogenic compounds. This study aims to monitor the temporal
and spatial concentration of BTEX volatile organic compounds and ozone formation potential (OFP) in
the air of Yazd city.
Materials & Methods: This research was carried out at different hours of the morning and evening in
the early fall of 2015. Sampling and measurement of benzene - toluene was done according to1501
NIOSH guidelines using active sampling and GC-FID. GIS software was used for zoning.
Results: The mean concentration of BTEX in the early morning hours was 130 and 659 (μg / m3) and
late in the morning was 159 and 830 (μg / m3), respectively, which indicates an increase in emissions in
the last hour’s morning. Also, Toluene to benzene ratio (T / B) obtained 1.3 to 2.1 and 1.2 to 3, which
represents benzene and toluene emissions caused by traffic. T/B, xylene to benzene (X/B) and xylene to
ethyl benzene (X/EB) Ratio ranges were obtained 1.2 to 2.1, 1 to 4 and 2 to 6.
Conclusion: In this study, spatial analysis by GIS software showed the center and south parts of Yazd
more polluted than the north part. Also, spatial variations of BTEX and OFP concentrations were more,
but the temporal trend obtained less values and Spearman good correlation (0.01> P and 0.89 <r)
between BTEX values in the early hours of morning and evening confirmed trend of temporal and
spatial. Also the street traffic and exhaust emissions from cars and gas stations were identified as the
main cause of BTEX emissions