Study On Distribution Of Bioaerosol In Fall And Winter In Qingdao Coastal Region

Bioaerosol is a significant subgroup of atmospheric aerosols and it has important impact on the human health and air quality. Bioaerosol also has effects on the global climate and atmospheric process. Statistical characteristics of bioaerosol in Qingdao coastal region are important for better understanding characteristics of bioaerosol over the Yellow Sea and its impact on human health and atmospheric environment. Bioaerosol samples were collected by using a six-stage Andersen sampler in morning(8:00~9:00), at noon(12:00~13:00) and in afternoon(16:00~17:00) from September 2007 to February 2008 in Qingdao coastal region. The concentrations of terrestrial/marine bacteria/fungi in particles with different sizes were obtained. The concentration and size distribution characteristics of terrestrial and marine microorganisms were discussed. And the impacts of meteorological factors on microbial distribution were also discussed.Results showed that average concentrations of terrestrial/marine bacteria/fungi presented obvious diurnal, monthly and seasonal variations. The microbe had a highest concentration in morning and a lowest value at noon except marine fungi which had highest concentration in afternoon. Average concentrations of terrestrial bacteria, marine bacteria, terrestrial fungi and marine fungi varied widely, ranging from 116.8 to 607.7CFU/m3, 111.9 to 461.7CFU/m3, 124.9 to 647.0CFU/m3 and 231.4 to 1959.2CFU/m3 respectively. The highest concentrations of terrestrial/marine bacteria/fungi appeared in September 2007. There were the minimum values of bacteria in December 2007 and those of terrestrial and marine fungi in November 2007 and February 2008 respectively. The monthly variation of total microorganisms, bacteria and fungi presented double peaks distribution. The highest concentrations of total microorganisms, bacteria and fungi appeared in September 2007 and the minimum value appeared in February 2008 except for the minimum of total bacteria in December 2007. The concentration of different kinds of microorganisms in fall was much higher than in winter, and marine microbial concentration decreased greatly in winter compared with terrestrial microbe.Average concentration of terrestrial bacteria was higher than that of marine bacteria, while average concentration of terrestrial fungi was lower than that of marine fungi. Number of total marine microorganisms was higher than that of total terrestrial microorganisms. The contribution of terrestrial bacteria to the total bacteria was relatively stable, being slightly lower in winter. The contribution of terrestrial to the total bacteria fungi was 23.9% in fall and it increased to 45.3% in winter. The contribution of terrestrial bacteria to terrestrial microorganisms in fall was different from that in winter, being slightly higher than fungi in fall and lower in winter. For marine microorganisms, the contribution of bacteria was much lower than that of fungi, and there was little difference in fall and winter.The size distribution of bacteria and fungi showed no seasonal variation in fall and winter. The size distribution of airborne fungi presented skewness distribution. The terrestrial and marine bacteria are mainly existed in coarse particles larger than 2.1μm, accounting for more than 80.0% of total bacteria. The distribution pattern of airborne fungi presented log-normal distribution, mainly existing in the particles of 1.1~4.7μm. The count median diameter(CMD) of terrestrial and marine bacteria was higher than fungi and had a wide range, being 4.68~6.49μm and 4.40~6.33μm respectively. The CMD of terrestrial and marine fungi was 2.42~3.68μm and 2.58~3.22μm.The impact of meteorological factors such as temperature, relative humidity(RH) and wind velocity on airborne microbial concentration had been studied through multiple linear regression model. The results indicated that the model can explain about 5.1 percent of variation in terrestrial bacterial concentration in terms of temperature, 8.2 percent of variation in terrestrial fungal concentration in terms of RH, 22.0 percent of variation in terrestrial and marine fungal concentration in terms of temperature and RH, no significant correlation between marine bacterial concentration and three meteorological factors in Qingdao coastal region.The average concentration of terrestrial/marine bacteria/fungi in typical sunny weather was higher than in foggy weather in Qingdao coastal region except fungi in September 2007 when the temperature was higher and the fog was relative thin. The terrestrial and marine microbial concentrations increased with increasing wind velocity when the wind was north and northwest. The north and northwest wind had no obvious influence on proportion of terrestrial or marine microorganisms.At the beginning and during the process of the gale and temperature drop case, concentrations of various kinds of microbe increased. During the process of temperature dropping in December 29, 2007, the concentration of terrestrial bacteria, terrestrial and marine fungi was highest in morning and lowest in afternoon except marine bacteria concentration lowest at noon. During the whole process of temperature dropping, the proportion of bacteria size in six phases changed complicatedly.