Survey site
Configuration of the survey site is illustrated in Fig. 1.The size of the storage area is 13.5 x 3.1 x 2.5 m with a wall made up of thin corrugated iron. There is about 0.3 m opening between the wall and the roof. The storage house is built on a concrete floor surrounded by soil ground. According to the Electricity Generating Authority of Thailand (EGAT), small size capacitors
containing PCB oil were brought into the storage house in November 1989 and later brought out in April 1992.When the capacitors were brought out from the storage house, the wall was dismantled. The second batch of used capacitors were brought into the storage house in October 1992 and the wall was rebuilt. The total number of capacitors in the first and second batches was 891
and 1316, respectively.Sample collection Airborne PCBs were collected by using samplers consisting of a glass tube (27 mm i.d., 390 mm length) packed with six polyurethane foam (PUF) plugs (each31 mm diameter, 50 mm length, 20+ 1.6 kg/m3), a low volume air pump and a flow meter. Samples were collected bimonthly from August 1991 to November 1992.Methods for preparation of PUF plugs were followed to Ramesh etal. (1989).Just before starting every sampling, wind direction was measured at the survey site for 10 min by using a wind velocity meter. According to the dominant wind direction, samplers were then placed at windward 5 m from the storage, at leeward 5 m from the storage and at leeward 25 m from the storage in August 1991; by leeward
side of the storage and at leeward 5 m from another sampler during the period of capacitor-stocked in the storage (other than in August 1991); at the center of the storage and at leeward 5 m from another sampler during the period of capacitor-non-stocked (Fig. 2).