Effects Of Land Cover Changes On Specific Air Pollutants Dispersion In The Pearl River Delta Region

With the rapid development of urbanization, many urban agglomerations orurban corridors are coming into being in some developed regions of China.Large-scale land cover changes in these regions have altered the energy equilibriumof surface environment and characteristics of wind structures and turbulent air, thenthe laws of dispersion, transform and accumulate of pollutions change accordingly.The Pearl River Delta region is a typical one which velocity of urbanization andland cover changes is the most rapid in China. Its special geographical location whichsurrounded by mountains to the east, west and north, serried urban agglomerationsand comparatively stable aerosphere are not favorable for the dispersion of airpollutions in this region. Therefore, based on two underlying surfaces at present andin the future, this study applies CALPUFF atmospheric dispersion model to simulatethe effects of land cover changes (especially the increase of areas of civil land use) onthe distribution and dispersion of specific air pollutants. The following are someresults of this study:â‘ Based on underlying surface at present, we modeled the dispersion of SO₂and SO₄^2- in the study region. The results showed that the change trend of modeledmonthly SO₂ concentration in the city zone of Guangzhou is similar with the real one.The CALPUFF modeling system is suitable for simulating characteristics ofatmospheric pollutants dispersion in the Pearl River Delta Region.â‘¡We compared modeling results of dispersion of SO₂ and SO₄^2- on the basis oftwo underling surfaces, then analyzed the effects of land cover changes oncharacteristics of pollutants dispersion. Land use changes (especially the increase ofareas of civil land use) showed that some apparent effects on boundary layer structuresuch as boosting up the average temperature inversion, decreasing wind velocities andincreasing the frequency of dominant wind directions, it is adverse for pollutants todisperse from sources, and the pollution degrees of these areas locating within 50km away from sources become aggravated. In winter, the increase amplitude of pollutiondegrees resulted from land use changes (especially the increase of areas of civil landuse) is larger than that in summer.â‘¢The effects of land cover changes on specific air pollutants dispersion weremodeled under two kinds of typical meteorological conditions. The effects of landcover changes on air pollutants dispersion are different under diverse meteorologicalconditions. With the changes of land cover, the pollutants concentrations becomehigher, and the probability to happen severe pollution incidents was strengthenedunder the heavily polluted meteorological conditions.