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区域酸性沉降的数值研究:Ⅱ.个例模拟和试验 总被引:4,自引:0,他引:4
利用建立的区域酸性污染物沉降模式,配合中尺度模式MM4预报的气象场,以1991年6月12 ̄14日淮河流域的一次降雨过程作为实例,对我国东半部及其相邻地区的酸沉降进行了数值模拟和试验研究。结果表明,模式基本上能够模拟出区域酸性沉降的特征,具有良好的综合模拟性能和广阔的应用前景。 相似文献
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本文使用中国科学院常熟和鹰潭生态实验站和气象站的观测资料,应用区域酸沉降模式系统(RegADMS)和大叶阻力相似模型来研究华东地区不同下垫面条件上的大气硫沉降问题,定量估计了农田下垫面上大气硫化物的沉降通量。SO2和硫酸盐的干沉降速率使用大叶阻力相似模型来估计,使用与降水量有关的参数化方案来确定湿沉降系数。结果表明,常熟地区农田下垫面的大气硫沉降通量为19.0gm^-2 a^-1,其中干沉降占42%;而位于江西红壤地区的鹰潭站的大气硫沉降通量为10.4gm^-2a^-1,其中干沉降占83%。比较发现,两地硫干沉降通量绝对值相差不大,但其在总沉降通量中所占的份额有较大差异;常熟站的硫湿沉降通量比鹰潭站要大9.23gm^-2a^-1,该差异是由两地污染状况和气象条件的不同造成。华东地区的年硫沉降总量为1.88Mt(1Mt=10^6t),其中72.8%沉降在农田下垫面上。硫沉降中43%是干沉降,57%是湿沉降。 相似文献
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利用次网格技术模拟华东地区大气硫氮沉降 总被引:5,自引:1,他引:5
采用数值模拟方法,在区域酸性沉降模式系统中引入次网格处理技术。通过4种次网格方案模拟结果的相互比较,选择最优方案,然后利用最优次网格方案,选取华东地区为例,进一步模拟研究大气硫氮沉降的空间分布。结果表明,就干沉积速率而言,以细网格方案(水平分辨率25 km)为参照,采用次网格方案比粗网格方案(水平分辨率75 km)有明显改进,其中“次网格风速与摩擦速度之积为常数”为最优次网格方案。华东地区硫的年总沉降量是1.92 mt(1 mt=106ton),氮的年总沉降量是0.65mt。华东地区硫化物(SO2、硫酸盐SO42-)干沉降量占总沉降量的49%,氮化物(NO、NO2、硝酸盐NO3-)干沉降量占总沉降量的80%,可见干沉降在大气沉降中具有重要地位。华东地区总的大气硫、氮沉降量中,70%以上到达有植被覆盖的土壤生态系统,这将对农田、草地和森林的硫素和氮素平衡有重要影响。此外,华东部分地区的硫沉降已经超过了临界负荷,而氮沉降尚未出现超临界负荷的现象。 相似文献
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酸沉降会对生态环境造成危害。要控制和减少酸沉降,就要了解酸沉降的幅度和不确定性,而模式研究是获得这些因子的重要工具。用东亚酸沉降模式比较计划(MICS-AsiaⅡ)中7个模式模拟的2001年7月和12月东亚地区酸沉降数据及东亚酸沉降监测网络(EANET)的观测数据,通过相关分析发现多模式模拟的平均值可表现东亚地区酸沉降的分布特征。采用各个模式与模拟结果平均值的离散程度来表征这些模式在东亚地区的不确定性,简要分析了目前模式模拟东亚酸沉降的不确定及其产生原因,可为制定酸沉降的控制措施提供依据。 相似文献
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1998年 11月~ 1999年 10月间在中国科学院红壤站 (江西鹰潭 )农田小气候站进行了大气二氧化硫 (SO2 )、硫酸盐粒子 (SO2 -4)浓度采样和雨水样本收集 ,利用阻力模式和全年逐时气象资料计算 SO2 和 SO2 -4的干沉降速度 ,估算干沉降通量 ,利用降水资料和雨水中硫酸根离子浓度估计大气硫的湿沉降 ,从而定量研究大气硫沉降输入农田生态系统的通量 ,结果表明 :农田下垫面上 SO2 和 SO2 -4干沉降速度的年平均值分别是 0 .373± 0 .170 cm· s-1(月均值 0 .16 1~ 0 .5 45 cm·s-1)、0 .198± 0 .12 3cm· s-1(月均值 0 .15 2~ 0 .2 6 9cm· s-1)。农田下垫面硫年总沉降量为 10 .3g· m-2 ,其中干沉降占总沉降的 83.3%。硫的干沉降又以 SO2 的干沉降为主 ,占年干沉降总量的 92 .2 %。大气硫沉降输入占农田生态系统输入总量的 90 %以上 ,是农田生态系统获取硫素的一个重要途径 相似文献
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南京郊区大气氮化物浓度和氮沉降通量的研究 总被引:12,自引:0,他引:12
为研究南京郊区的大气氮化物污染状况,进而估算其大气氮沉降通量,2005年6月-2006年5月在南京大学浦口校区气象园进行了大气、气溶胶和雨水样本的收集,同步进行近地面气象观测.在实验室分析大气氮化物NOx、NH3和有机氮浓度、总悬浮颗粒物(TSP)中硝酸盐、亚硝酸盐、铵盐和有机氮的质量浓度、雨水中NO-3、NO-2、NH+4离子和有机氮的质量浓度,利用气象资料和大叶阻力相似模型计算大气氮化物的干沉降速度,进而定量估算大气氮沉降通量.研究结果表明:南京郊区大气中有机氮浓度水平较高,无机氮(氨态氮和硝态氮)浓度水平较低.大气氮沉降量较大,且湿沉降和有机沉降贡献率占主导地位,这取决于本地区的下垫面和污染状况,同时也与气象条件有密切关系. 相似文献
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A one-dimensional cloud model with size-resolved microphysics and size-resolved aqueous-phase chemistry, driven by prescribed
dynamics, has been used to study gas scavenging by weak precipitation developed from low-level, warm stratiform clouds. The
dependence of the gas removal rate on the physical and chemical properties of precipitation has been explored under controlled
initial conditions. It is found that the removal of four gaseous species (SO2, NH3, H2O2 and HNO3) strongly depends on the total droplet surface area, regardless the mean size of droplets. The removal rates also correlate
positively with the precipitation rate, especially for precipitation having a mean radius larger than 20 μm. The dependence
of the scavenging coefficients on the total droplet surface area is stronger than on the precipitation rate.
The removal rates of SO2, NH3 and H2O2 by precipitation strongly depend on the others' initial concentrations. When NH3 (or H2O2) concentration is much lower than that of SO2, the removal rate of SO2 is then controlled by the concentration of H2O2 (or NH3). The removal of NH3 (or H2O2) also directly depends on the concentration of SO2. NH3 and H2O2 can also indirectly affect each other's removal rate through interaction with SO2. The scavenging coefficient of SO2 increases with the concentration ratio of NH3 to SO2 if the ratio is larger than 0.5, while the scavenging coefficient of NH3 increases with the concentration ratio of SO2 to NH3 when the ratio is smaller than 1. The scavenging coefficient of H2O2 generally increases with the concentration ratio of SO2 to H2O2. Although the Henry's law equilibrium approach seems to be able to simulate gas scavenging by cloud droplets, it causes large
errors when used for simulating the scavenging of soluble gas species by droplets of precipitating sizes. 相似文献
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Total sulfur deposition was determined above a Norway spruce forest, in Hungary. Two methods were applied, on one hand dry + wet deposition measurements and on the other, throughfall and stemflow deposition estimations have been carried out. Results show: total depositions are 3.3 and 3.2 g S m–2 yr–1 determined by dry + wet and throughfall deposition methods, respectively. The share of the dry deposition in the total S-load is 73%. The agreement between the results of the two different methods is good and suggests the needlessness of complicated dry + wet flux measurements, i.e. the total and dry deposition of sulfur compounds to forests can be determined by simple throughfall and wet deposition measurements. 相似文献
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J. N. Mphepya C. Galy-Lacaux J. P. Lacaux G. Held J. J. Pienaar 《Journal of Atmospheric Chemistry》2006,53(2):169-183
The chemical composition, as well as the sources contributing to rainwater chemistry have been determined at Skukuza, in the Kruger National Park, South Africa. Major inorganic and organic ions were determined in 93 rainwater samples collected using an automated wet-only sampler from July 1999 to June 2002. The results indicate that the rain is acidic and the averaged precipitation pH was 4.72. This acidity results from a mixture of mineral acids (82%, of which 50% is H2SO4) and organic acids (18%). Most of the H2SO4 component can be attributed to the emissions of sulphur dioxide from the industrial region on the Highveld. The wet deposition of S and N is 5.9 kgS⋅ha−1⋅yr−1 and 2.8 kgN⋅ha−1⋅yr−1, respectively. The N deposition was mainly in the form of NH4
+. Terrigenous, sea salt component, nitrogenous and anthropogenic pollutants have been identified as potential sources of chemical components in rainwater. The results are compared to observations from other African regions. 相似文献
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适用于大中尺度污染物输送模式的粒子干沉降参数化方案 总被引:2,自引:1,他引:2
用“二层”模式给出一个适用于污染物输送模式的粒子干沉降参数化方案,它比较详细地考虑了近地面层的气象条件,地表特性和气溶胶粒子的物理、化学特性等。从计算值与观测值的比较来看,计算值的离散范围能涵盖所有的观测结果,因而从总体上看此参数化方案是合理的,能够描述粒子总污染物干沉降的主要物理过程及机制。
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S. Lopez J. H. Topalian S. K. Mitra D. C. Montague 《Journal of Atmospheric Chemistry》1989,8(2):175-188
An experimental study of the scavenging of dichloromethane vapor by water drops falling at terminal velocity, has been carried out in the UCLA precipitation shaft, in order to test the predictions of theoretical washout models. Whereas good agreement between theory and experiment was found for drops of radius 0.332 mm, computed gas uptake rates for 1.253 and 2.21 mm radius drops were much slower than those measured, just as reported previously for the washout of both sulfur dioxide and acetaldehyde. An analysis shows that theory can be reconciled with all of the experimental data by replacing the compound specific aqueous phase Fickian molecular diffusion coefficient used in the theory, by an effective diffusivity, having a constant value, (3×10-4 cm2 s-1), independent of the physical and chemical nature of the absorbed species, for all drops of equivalent radii greater than 0.9 mm. 相似文献