[Size distribution characteristics of particulate mercury on haze and non-haze days].

ABSTRACT

With the rapid economic development, China suffers from the severe haze and atmospheric mercury pollution. Particulate mercury transport has an important significance in its global cycle. In order to investigate the distribution characteristics of particulate mercury, 12 degrees Nano-moudi (6.2-9.9 µm, 3.1-6.2 µm, 1.8-3.1 µm, 1.0-1.8 µm, 0.56-1.0 µm, 0.32-0.56 µm, 0.18- 0.32 µm, 0.10-0.18 µm, 0.056-0.10 µm, 0.032-0.056 µm, 0.018-0.032 µm, 0.010-0.018 µm) impactor was used to measure the size distributions of atmospheric particulate mercury on both haze and non-haze days in Shanghai. The results indicated that particulate mercury levels were positively correlated with those of the particles. The average concentration of particulate mercury (0.31 ng x m (-3)) on haze days was 2-3 times than that on non-haze days (0.11 ng x m(-3)). The mass size distributions of aerosols and particulate mercury showed bimodal distributions. The peak shifted from 0.56-1.0 µm and 3.1-6.2 µm on haze days to 0.32-0.56 µm and 3.1-6.2 µm on non-haze days. The particles with aerodynamic diameter smaller than 1 µm which could stay for a long time and transport for a long distance, had higher particulate mercury concentrations. The average contribution of particulate mercury to total PM aerosol were higher on haze days (0.029 ng x µg(-1)) than on non-haze days (0.015 ng x µg(-1)), indicating that secondary particles typically grew faster than mercury during the haze pollution events. The particulate mercury concentration in accumulation mode was 2.06 ng x m(-3) on haze days, while it was 0.55 ng x m(-3) on non-haze days. The large increase of the accumulation mode particles was a main reason for the formation of haze. Emissions from the coal burning as well as road surface dust and dust from long-range transport accounted for the serious pollution on haze days.