[Study on the best sampling time and the time distribution of atmospheric bacterial particle]

The changes of atmospheric bacterial particle concentrations in three areas--Beijing, Tianjin and Shenyang, were investigated in different seasons and period of one day. The samplers used in this study were MF-45 and HTK-201 air microbial samplers. The results showed that the concentrations of atmospheric bacterial particle in Beijing and Tianjin are higher in spring than those in other seasons. They are 2053/m3 and 2556/m3 respectively in spring, 995/m3 and 1064/m3 respectively in summer. The concentrations of atmospheric bacterial particle in Shenyang is higher in autumn (10108/m3) and lower in winter (1294/m3). The changes of atmospheric bacterial particle concentrations have two peak values during a day. The two high peak values are at 6:00 to 7:00 and 18:00, while the two low values are at 11:00 to 13:00 and 1:00 to 2:00. We sampled the atmospheric bacterial particles at 4 different combinations of sampling time in the three cities. They were 12, 8, 6 and 4 times a day. The sampling time combination was analyzed by mathematical statistics according to the results. The best sampling time was decided by the statistics results and time distribution character of atmospheric bacterial particle concentration in different seasons and period of one day. The concentration of atmospheric bacterial particle should be detected in the middle month of the four seasons: January, April, July and October. Sampling time at 7:00, 10:00, 13:00, 16:00, 19:00, 22:00, 1:00 and 4:00 could be selected for 8 times sampling a day. The sampling time sequence should be at 5:00, 11:00, 17:00 and 23:00 for 4 times sampling a day. The four times sampling at daytime in spring and fall should be at 6:00, 9:00, 12:00 and 19:00; 5:00, 9:00, 13:00 and 17:00 in summer; 7:00, 10:00, 13:00 and 16:00 in winter.