一种污染物的区域干沉积速度分布的计算方法

A METHOD FOR COMPUTING REGIONAL DRY DEPOSITION VELOCITY DISTRIBUTION OF POLLUTANTS

建立了一个模拟污染物的区域干沉积速度分布的数学模式，利用它计算了江苏省及周围地区ＳＯ２、硫酸盐、ＨＮＯ３（气）和硝酸盐四种污染物的干沉积速度分布，并通过数值试验研究了干沉积速度的时空变化特征。与国内外的此外场观测资料的比较表明，本模式能够实现对不同条件下污染物干沉积的模拟．

Dry deposition plays an important role in the removal of pollutants fromatmosphere. Many long-range transport / deposition models parameterize dry depositionof trace gases and particles in terms of deposition velocity (Vd) and assume it remains constant in either time or space. This assumption will severely limit a model's ability to predictdeposition flux, since measurements show that deposition veolcity has considerable variability in time and space. But Vd data is to limited to fit the transport/ deposition model. Tosolve the problem, a mathematic model for calculating regional dry deposition velocity distribution of contaminant is constructed in this paper. The model combines detailed landusedata with meteorological data from routine observation and uses a ground energy balancemethod to get the surface layer turbulance characteristics parameters, so it is objective,economic and practical. Using this model, the deposition velocities of SO2, sulfate, HNO3(gas)and nitrate in Jiangsu Province and its surrounding area are calculated. The domain averag.ed mid-day deposition velocities at a reference height of 20m of the four specials are0.59cm/ s, 0.18cm / s, 1 .30cm/ s, 0.30cm/ s respectively. At night, the deposition velocihes are 42%, 22%, 37% and 20% of the corresponding day time values for SO2, sulfate,HNO3(gas) and nitrate. The characteristics of the spatial-temporal variation of dry deposition velocity are studied by numerical experiments. In general. Vd value is greater on landthan on water and has a maximum at 13:00 to 15:00 during the day. Deposition velocitiesare found to strongly depend on surface, local meteorological conditions and depositionspecials. Comparisons with the observed data from national and international field experiments show that the model can simulate dry depostion process of various pollutants underdifferent conditions well.