Estimation of BSF
ASTM test method D4600-87 (ASTM, 2001) was used for measuringBSF in DPM. This gravimetric method is
recommended by National Institute of Occupational Safety and Health, USA, to represent the toxic organic
compounds in the particulates in filter samples. Thimbles were desiccated for 12 h before and after sampling
and initial and final weights were recorded. Thimbles were cut into small pieces using a metal scissors and
were placed in a reagent bottle followed by addition of 20 ml of benzene. These reagent bottles were kept
for 20 min in ultrasonic bath (Enertech, Mumbai) for extraction of soluble fraction. Later, the sample was decanted and filtered through 0.45 m filter paper (Whatman). The filtrate was collected into a 100 ml beaker. The procedure was repeated with another 10 ml of benzene in the same reagent bottle to extract remaining soluble fraction. Benzene in the filtrate was evaporated in oven at 40 1 C for 12–18 h. The difference in initial and final weights of the beaker was measured to estimate the total mass of benzene soluble fraction in the sample.