| Southeastern coastal area of China is characterized by hilly territory and full of towns. The structure of atmospheric boundary layer (ABL) over it has its own special distribution and changing law, which impacting the ability of atmosphere to disperse, dilute and scavenge air pollution. Bioaerosol particles, including viruses, bacterial, fungi, pollen, plant or animal debris, as well as their fragments and products, have significant impact on the atmosphere environment, human health and climate change. Other than polluting gases, they have particular decay process in air. Over coastal complex terrain, the diffusion characteristics and distribution patterns of bioaerosols concentrations show more complicated because of the implication of turbulence and meteorological process. Therefore, the study of pollution meteorological characteris-tics, the clearing ability of atmospheric and their effects on bioaerosols dispersion over this area has theoretical significance and practical application value. The re-search work around the pollution meteorological characteristics and bioaerosols dis-persion includes following aspects:First, the characteristics of meteorological, turbulence, sea-land breezes and thermal intern boundary layer (TIBL) were analyzed, based on the observational data of ABL derived from field experiments at Fujian coastal area during July-August2008, the regular meteorological data of2005-2007from meteorological observing stations in this area, and the simulation result of the Weather Research and Forecast-ing (WRF) model. A new tilt correction scheme was put forward to turbulence data pre-processing in complex terrain, which can efficiently eliminate the implication of instrument leveling deficiencies and sloping terrain to turbulence flux and wind statis-tics. It showed that: 1. Integral turbulence characteristics generally agree with M-O similarity theory. The fitting coefficients between non-dimensionalised standard deviations of wind component normalized by friction velocity and the stability parameter over southeast-ern coastal area are bigger than that of flat terrain, which reflecting the role of com-plex terrain on turbulence. Sea-land breezes have significant effect on turbulence characteristics in this area. Sea breezes increase the mechanical turbulence and land breezes decrease it. Energy and flux of turbulence are increased under Sea-land breezes weather. Spectra patterns of wind components and temperature, and the rela-tionship between spectral and stability are similar to that of flat terrain. The average sizes of horizontal and vertical eddy are56m and14m, respectively, suggesting the leading role of bigger eddy in energy transport. Under instability, the energy of cross eddies at low frequencies increased largely, as well as those of vertical eddies. In ζ<-0.4, the cross energy of turbulence are bigger than the longitudinal energy.2. The maximum heights of thermal intern boundary layers (TIBL) observed at two sites in Fujian coastal area are of800-1000m, usually occurring in14-17pm. Sea-land breezes only formed in the bay area. The height of sea breeze circle may ex-tend1500m in vertical direction and20-35km in inland. The observed maximum speed of sea breezes exceed10m/s with height of200-260m, occurring in14-16pm. The characteristics of sea-land breezes and TIBL are less significant at peninsula.3. The meteorological characteristics of southeastern coastal area are character-ized by large annual speed, abundant precipitation and dominant neutral conditions with80%occurrence frequency. The average annual speeds at costal area are usually4-6m/s, gradually decreasing from coastal to inland area. The average annual pre-cipitation are above1400mm. These conditions are good for the dispersion, dilution and scavenging of air pollution. However, the standard deviations of wind direction is small, only70°at coastal area. Ordered flow fields and small wind shear may cause the accumulation of air pollution in the same direction.Secondly, the concept of air resource was put forward to investigate the clearing ability of atmospheric. Based on the analysis of climate characteristics and various weather systems associated with high levels of air pollution occurring in southeastern coastal area, the key factors that affected the ability of atmosphere to disperse, dilute and scavenge air pollution significantly were selected from the meteorological fields and turbulence parameters. They acted as evaluating indicators of regional air re-source. Each of the factors were classified and then graded to determine the weighted coefficient. The total scores of air resource were estimated from the weighted sum of the respective factor scores. The levels of air resource were determined subsequently. Then spatial distribution of the overall scores and the levels of air resource were ob-tained. It showed that the air resource over the Strait was of the top grade (5) with the score18. The grades in the rest were of2to4with the scores14to18. In general, the air resource in coastal area was most abundant, in inland flat less and in mountainous area the least, showing an inhomogeneous pattern.Finally, the Regional Air Quality Model System (RegAQMS) was improved. The Offshore and Coastal Dispersion (OCD) was nested in a regional dispersion model. WRF model provide meteorological fields and the atmospheric boundary layer model calculate turbulence fields. Then the process of dry deposition, wet scavenging, tem-perature decay, humid decay, biological ageing, ultra-violet radiation decay of bioaerosols are integrated in RegAQMS to made it can simulate distribution patterns of bioaerosols concentrations. The implications of types of emission source on bioaerosols concerntrations were analyzed. Taking the case of foot-and-mouth virus, Sensitivity analysises of physical and biological process were conducted. Virus con-centrations were simulated and used to risk and infection assessments further.1. Types of emission source have a great influence on the distribution of bioaerosols. A higher source height results in a reduction of daily average surface concentration and hourly fumigation concentration. However, it caused the contami-nated area (≥0.01μg/m3) increases, the max fumigation concentration of point source occurs from4.5km to6.3km, and this accompanied with the lowest max fumigation concentration of areal source in the longest distance.2. Sensitivity analysises for the biological and physical processes of foot-and-mouth virus show that the average surface concentration of July and August respectively reduce61.9%,65.6%and the contaminated area respectively reduce 25.6%and50.1%if all biological and physical processes are take into account. Tem-perature decay is the principal process which affects virus concentration in summer, and biological ageing and deposition are big factors too. However, relative humidity does not have great influence on the concentration.3. Risk and infection assessments for terrestrial areal sources show that most of the research areas are low of safe region and few research areas are high level of risk re-gion. The risk regions of July and August are respectively61.6%and54.2%. Infec-tion region takes up less than1%of the whole research region. With a same magni-tude natural emission, bigger assessment areas are calculated for risk region and in-fection region than former research in this paper. Ordered flow fields from inshore bottom contour contributes to a small wind direction diurnal fluctuation and horizon-tal turbulent intensity, and these results in a higher spreading and infection risk. |
PDF Full Text Request