<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> Benzene and toluene profiles in ambient air of Delhi as determined by active sampling and GC analysis </smarttagtype></smarttagtype>

Abstract

<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> Present study aims to standardise methodology for the measurement of benzene and toluene using active sampling onto sorbent tubes and to investigate their existing profile in the urban environment of Delhi, India. Samples were collected by active sampling onto preconditioned stainless steel standard adsorbent tubes packed with Tenax TA adsorbent using a portable constant low flow volume sampler. Sampling flow rate ranged 20-25 ml min^-1 and sampling duration 1.30-2.30 h. Samples were analysed by thermal desorption followed by gas chromatography coupled with automated thermal desorber. The desorption system was provided with a cryogenic trap filled with Tenax TA adsorbent. External calibration was performed using five concentration levels of standards solutions in carbon disulfide (CS₂). Linear fit in all cases were found good with R² > 0.99. Benzene concentration ranged 33.69-174.62 µg m^-3 whereas toluene ranged 45.18-228.83µg m^-3 in the vicinity of petrol pump along with heavy traffic roadside at Preet Vihar location. Average benzene and toluene concentration of ambient air at ITO (near a busy traffic intersection) ranged 13.03-33.06 µg m^-3 and 19.71-57.64 µg m^-3 respectively. While at East Arjun Nagar (a residential cum institutional area), levels were 17.69 µg m^-3 and 22.81 µg m^-3 for benzene and toluene, respectively. Present study indicated that the concentration of benzene at all the sites was higher than the limit values prescribed in the UK (16 µg m^-3, running annual average) and European Commission (5 µg m^-3, annual average). Average toluene and benzene ratio ranged between 1.29 µg m^-3 in residential cum institutional area to 1.74 µg m^-3 at busy traffic intersection. </smarttagtype></smarttagtype></smarttagtype>