| On-line measurements of particle number size distribution were conducted during 2004-07-13～2004-08-23 by using TDMPS-APS system in Beijing; in between the size distributions of particle mass and chemical compositions were measured by using MOUDI cascade impactor under three kinds of weather conditions: ① high temperature and high relative humidity night, ② high temperature and high relative humidity day, and ③ clear days. The results indicate that particulate matter, especially fine particle pollution becomes severe under high temperature and high relative humidity conditions, which results in low visibility (2.5km); the average concentrations of PM1.8 and PM10 are 170.68μg/m3 and 249.35μg/m3, respectively, PM1.8 accounts for 68% of PM10; number concentration mainly concentrates in the range of 50～100nm, about 2×104～3×104cm-3; rain process has a great effect on scavenging particles, especially fine particles. After the rain process PM10 is 3 times lower and PM1.8 is 6 times lower than the values before the rain; in the following clear day, new particle formation is observed, the newly formed particles (3～20nm) grow to 50～100nm rapidly. After that, the pollutants start to accumulate and it becomes heavy polluted in few days. |
