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1.
Tov Elperin Andrew Fominykh Boris Krasovitov 《Meteorology and Atmospheric Physics》2013,122(3-4):215-226
We suggest a one-dimensional model of precipitation scavenging of soluble gaseous pollutants by non-evaporating and evaporating droplets that is valid for arbitrary initial vertical distribution of soluble trace gases in the atmosphere. It is shown that for low gradients of soluble trace gases in the atmosphere, scavenging of gaseous pollutants is governed by a linear wave equation that describes propagation of a wave in one direction. The derived equation is solved by the method of characteristics. Scavenging coefficient and the rates of precipitation scavenging are calculated for wet removal of sulfur dioxide (SO2) and ammonia (NH3) using measured initial distributions of trace gases. It is shown that scavenging coefficient for arbitrary initial vertical distribution of soluble trace gases in the atmosphere is non-stationary and height-dependent. In case of exponential initial distribution of soluble trace gases in the atmosphere, scavenging coefficient for non-evaporating droplets in the region between the ground and the position of a scavenging front is a product of rainfall rate, solubility parameter, and the growth constant in the formula for the initial profile of a soluble trace gas in the atmosphere. This expression yields the same estimate of scavenging coefficient for sulfur dioxide scavenging by rain as field estimates presented in McMahon and Denison (1979). It is demonstrated that the smaller the slope of the concentration profile the higher the value of a scavenging coefficient. 相似文献
2.
结合MEIC大气污染物排放源清单,利用耦合了大气化学模式的中尺度气象数值模式WRF-Chem,对2016年5月6日广东地区一次深对流天气过程及其大气化学气体成分变化进行模拟,着重研究深对流系统对大气化学气体成分再分布的影响。结果表明:数值模拟较真实地再现了这次深对流天气过程中大气污染物的时空分布特征。通过计算,评估了这次对流降水对不同溶解度的大气污染气体的湿清除效率,发现湿清除过程对低溶解度大气污染气体CO、NO_2和O_3的湿清除效率几乎可以忽略不计,而对SO_2、H_2O_2和HNO_3的湿清除效率则分别达到50.8%、98.6%和38.2%。随着溶解度的增大,清除效率并不一定增大,这是因为大气物理和化学过程共同影响着气体污染物的清除效率。 相似文献
3.
一次重雾霾天气成因及湿清除特征分析 总被引：1，自引：1，他引：0
为了深入了解发生在武汉地区一次重雾霾天气过程的气象条件、污染源和污染物的湿清除特征,本文利用空气质量监测资料、地面观测资料和遥感火点监测资料和实测雨滴谱资料,详细分析了这次过程。结果表明:此次持续10 d的重雾霾天气过程发生在高压天气系统和静风条件下,辐射降温形成的稳定逆温边界层结构有利于污染气溶胶的积累和雾霾的形成和发展,尤其是来自南方持续不断的湿平流使雾霾天气得以长时间持续和发展,整个雾霾天气期间能见度均小于2 km,最低能见度不足50 m。2014年11月23~24日降水过程对此类污染物有明显的清除效果,清除率最高的是颗粒物污染,NO_2、SO_2和CO次之,最差的是O_3,通过与Scott(1982)按平均碰并系数E(E=0.65)得到的清除率和雨强的关系比较,武汉地区稳定性降水对气溶胶的平均碰并系数可取0.25~0.35。 相似文献
4.
The role of trace gases and aerosol particles in the control of sulfur and nitrogen levels in atmospheric precipitation is estimated on the basis of the enrichment factor in the precipitation of these elements relative to particulate matter in the air. By using air and precipitation chemistry data obtained at a Hungarian background air pollution station (K-puszta) it is found that the fraction of ammonium, nitrate and sulfate in precipitation, due to the removal of particulate matter is at least 59, 27 and 31%, respectively. The relationship between wet depositions and air concentrations of different species is determined statistically by applying daily data set. The regression equations obtained make the estimation of the sub-cloud scavenging ratios possible and they give some information on the magnitude of in-cloud scavenging processes. The results show that the in-cloud scavenging is a determining factor for precipitation sulfate, while it is relatively unimportant in the case of ammonium. The sub-cloud scavening of NO2 and SO2 is not too significant. However, for HNO3, and NH3 it is an effective process. The sub-cloud scavenging ratio of sulfur and nitrogen-containing particles varies around 0.25×106. 相似文献
5.
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
6.
7.
S. Fuzzi M. C. Facchini D. Schell W. Wobrock P. Winkler B. G. Arends M. Kessel J. J. Möls S. Pahl T. Schneider A. Berner I. Solly C. Kruisz M. Kalina H. Fierlinger A. Hallberg P. Vitali L. Santoli G. Tigli 《Journal of Atmospheric Chemistry》1994,19(1-2):87-106
The chemistry of cloud multiphase systems was studied within the Kleiner Feldberg Cloud Experiment 1990. The clouds encountered during this experimental campaign could be divided into two categories according to the origin of air masses in which the clouds formed. From the chemical point of view, clouds passing the sampling site during the first period of the campaign (26 October-4 November) were characterized by lower pollutant loading and higher pH, as compared to clouds during the final period of the experimental campaign (10–13 November). The study of multiphase partitioning of the main chemical constituents of the cloud systems and of atmospheric acidity within the multiphase systems themselves (gas + interstitial aerosol + liquid droplets) are presented in this paper. A general lack of gaseous NH3 was found in these cloud systems, which caused a lack of buffer capacity toward acid addition. Evidence supports the hypothesis that the higher acidity of the cloud systems during this final period of the campaign was due to input of HNO3. Our measurements, however, could not determine whether the observed input was due to scavenging of gaseous HNO3 from the air feeding into the cloud, or to heterogeneous HNO3 formation via NO2 oxidation by O3 to NO3 and N2O5. Sulfate in cloud droplets mainly originated from aerosol SO
4
2–
scavenging, since S(IV) to S(VI) liquid phase conversion was inhibited due to both lack of H2O2 and low pH of cloud droplets, which made O3 and metal catalyzed S(IV) oxidation inefficient. 相似文献
8.
无锡梅雨期湿沉降综合分析 总被引：2，自引：0，他引：2
利用2008—2014年梅雨期间酸雨观测资料及2014年6月16—27日降水个例加密采样资料,结合大气污染物资料分析了近7 a无锡梅雨期酸雨特征,研究降水过程中空气污染物、p H值、电导率的变化及降水对污染物的清除作用。结果表明:无锡市梅雨期酸雨年平均p H值呈现逐年递增趋势。降水过程中,颗粒物质量浓度显著降低;气体浓度变化受其自身日变化及排放源影响大于雨水的清除作用;样品的p H值、K值每个过程变化并不一致,K值变化与颗粒物质量浓度变化大致保持一致。降水、风对颗粒物质量浓度影响大于对气体浓度的影响。长时间连续降水时,降水对颗粒污染物的清除存在极限。小时雨量在0~0.5 mm时,降水对颗粒物浓度做负清除,其值反而略有增加;小时雨量在0.6~5.0 mm时,降水对颗粒物质量浓度做正清除;小时雨量达到5.1 mm及以上时,对PM_(2.5)和PM_(2.5-10)做正清除,对PM_(10)做负清除。降水对SO_2有稀释清除作用;对NO_2的稀释作用取决于其开始浓度值;对CO、O_3的清除作用不显著。 相似文献
9.
The rainout-removal of SO2 and the acidification of precipitation from stratiform clouds are simulated using a one-dimensional, time-dependent model,
parameterized microphysically in which dissolution and dissociation of gaseous SO2 and H2O2, and oxidation reaction in aqueous phase are taken into account. The effects of dynamic factors, including updraft flow and
turbulent transport, and the concentration of gaseous SO2 and H2O2 being transported into the clouds on pH value of the precipitation, the conversion rateS(IV)-S(VI) and the wet deposition rate of SO2 are discussed.
This work was supported by fund from the National Scientific Foundation of China. 相似文献
10.
The concentrations of H+, nitrate (NO3
-), and sulfate (SO4
2-) in rainwater and their temporal changes were analyzed on the basis of continuous observation from 1 July 1991 to 30 June 1992 at a suburb of Nagoya, Japan. The yearly average for pH was 4.4. In general, an increasing pH with increase in precipitation amount was observed for rain events. Relatively high pH rainwater was sometimes observed at the beginning of rainfall, even though high concentrations of NO3
- and SO4
2- were involved. The high pH values were considered to be caused by the neutralization process with particulate matter containing cations. The yearly averaged ratio of equivalent concentration of nitrate to sulfate (N/S) in rainwater was 0.58. In the early stage of rain, the N/S value was usually more than 1.0 due to the difference of scavenging process between NO3
- and SO4
2-. High values of N/S ranging from 5 to 10 were found under the atmospheric conditions of calm winds and low humidity, during which it is possible that atmospheric particles float for a long time in the air before a rain event. The adsorption of NO3
- in the early stage of rainfall by particulate matter was suggested from the difference in scavenging processes of NO3
- and SO4
2-. A possible scavenging process, called limb cloud scavenging, is presented to explain the interaction of particles and nitrate ions at the early stage of rain. In limb cloud scavenging, the repeated migration of cloud particles or raindrops between the inside and outside of clouds increases the absorption of ions to a highly condensed level, thus increasing the N/S value of rainwater. The influence of global scale seasonal phenomena with large amounts of particulates, such as typhoons or Asian dust storms, was also studied. 相似文献
11.
A new Lagrangian—Eulerian coupling model system is developed to study regional air quality. The system consists of mesoscale
dynamical meteorological model (MM), Monte—Carlo model (MCM), parameterized model on planetary boundary layer (PBL) turbulent
statistics, dry and wet removal model, and Eulerian nonlinear chemical model (ENCM). The physical, chemical and biological
processes on air pollutants are considered comprehensively. 3—D distribution laws tor acidic gaseous pollutants (SO2 and NOx) emitted by Thai Mae Moh Power Plant and the secondary pollutants are studied in detail. The results simulated by the coupling
model system are in good agreement with observational concentration data.
The authors wish to express their thanks to Prof. Zeng Q. C. for his support to this research and to Dr. Han Z. W. and Zhang
M. G. for their help in programming and numerical calculation of IAP, Chinese Academy of Sciences. Thanks are also due to
NSTD and EGAT in Thailand for supporting this research. 相似文献
12.
Partition, not kinetics, ultimately determines the concentration of highly soluble gases in cloud droplets. Partition equations are formulated and applied to idealized air-mass thunderclouds and precipitating stratus. Contribution to aqueous concentrations from sub-cloud scavenging of highly soluble gases is estimated at between 10 and 20% under relatively unpolluted conditions. Data indicate that evaporation can produce enhancements in concentration of as much as a factor of 3. The calculations give large-scale mean coefficients of wet removal of highly soluble gases of about 2.8×10-6 s-1 (4-day residence time) for air-mass thunderclouds and precipitating stratus. Removal is so effective that the mean scale heights of these gases should be decreased to 2 km or less. The criterion of high solubility in this paper is that K
H (Henry's Law coefficient) > 105 mol l-1 atm-1. Gases that are effectively highly soluble include HCl, HNO3, H2SO4, H2O2, NH3 in acid droplets, SO2 in oxidizing droplets (and probably some light amines and sulfonic acids), but not SO2 in the absence of oxidants, nor HCHO. A variation of removal coefficient and scale height with solubility is presented. A comparison of atmospheric NH3 concentrations deduced from rain NH4
+ and measured directly gives reasonable agreement. 相似文献
13.
B. Oberholzer J. L. Collett Jr. J. Staehelin A. Waldvogel 《Journal of Atmospheric Chemistry》1992,14(1-4):61-71
An in-cloud scavenging case study of the major ions (NH4
+, SO4
2- and NO3
-) determining the cloudwater composition at a mountain site (1620 m.a.s.l.) is presented. A comparison between in-cloud measurements of the cloudwater composition, liquid water content, gas concentrations and aerosol concentrations and pre-cloud gas and aerosol concentrations yields the following results. Cloudwater concentrations resulted from scavenging of about half of the available NH3, aerosol NH4
+, aerosol NO3
-, and aerosol SO4
2-. Approximately a third of the SO2 was scavenged by the cloudwater and oxidized to SO4
2-. Cloud acidity during the first two hours of cloud interception (pH 3.24) was determined mostly by the scavenged gases (NH3, SO2, and HNO3); aerosol contributions to the acidity were found to be small. Observations of gas and aerosol concentrations at three elevations prior to several winter precipitation events indicated that NH3 concentrations are typically half (12–80 %) of the total (gas and aerosol) N (-III) concentrations. HNO3 typically is present at much lower concentrations (1–55 %) than aerosol NO3
-. Concentrations of SO2 are a substantial component of total sulfur, with concentrations averaging 60 % (14–76 %) of the total S (IV and VI). 相似文献
14.
Sulfur dioxide in rain clouds: Gas-liquid scavenging efficiencies and wet deposition rates in the presence of formaldehyde 总被引：1，自引：0，他引：1
Peter Warneck 《Journal of Atmospheric Chemistry》1989,8(2):99-117
The interaction of formaldehyde with SO2 dissolved in the aqueous phase of clouds leads to the formation of hydroxymethane sulfonate. The impact of this process upon the gas-liquid equilibrium distribution of SO2 in rain clouds and the ensuing wet SO2 precipitation rate is explored. Model vertical SO2 distributions are derived from observational data for three atmospheric regions: continental polluted, continental remote, and marine. The wet deposition rate for SO2 in the polluted atmosphere increases by about a factor of two in the presence of formaldehyde compared with its absence. The effect is much stronger in the remote atmosphere leading to a potentially significant enhancement of wet SO2 deposition. In the marine atmosphere, wet deposition of SO2 may contribute as much as 35% to the total removal rate for SO2 by all processes including dry deposition and chemical conversion to sulfate. 相似文献
15.
Tov Elperin Andrew Fominykh Boris Krasovitov 《Meteorology and Atmospheric Physics》2014,125(3-4):197-211
We suggest a non-isothermal one-dimensional model of precipitation scavenging of highly soluble gaseous pollutants in inhomogeneous atmosphere. When gradients of soluble trace gases’ concentrations and temperature in the atmosphere are small, scavenging of gaseous pollutants is governed by two linear wave equations that describe propagation of a scavenging and temperature waves in one direction. If wash-down front velocity is much larger than the velocity of the temperature front, scavenging is determined by propagating scavenging front in the atmosphere with inhomogeneous temperature distribution. We solved the derived equation by the method of characteristics and determined scavenging coefficient and the rates of precipitation scavenging for wet removal of sulfur dioxide using measured initial distributions of trace gases and temperature in the atmosphere. It is shown that in the case of exponential initial distribution of soluble trace gases and linear temperature distribution in the atmosphere, scavenging coefficient in the region between the ground and the position of a scavenging front is proportional to rainfall rate, solubility parameter in the under-cloud region, adjacent to a bottom of a cloud and to the growth constant in the formula for the initial profile of a soluble trace gas in the atmosphere. The derived formula yields the same value of scavenging coefficient for sulfur dioxide scavenging by rain as field estimates presented by McMahon and Denison (Atmos Environ 13:571–585, 1979). It is demonstrated that in the case when the altitude variation of temperature in the atmosphere is determined by the environmental lapse rate, scavenging coefficient increases with height in the region between the scavenging front and the ground. In the case when altitude temperature variation in the atmosphere is determined by temperature inversion, scavenging coefficient decreases with height in a region between the scavenging front and the ground. Theoretical predictions of the value of the scavenging coefficient for sulfur dioxide washout by rain and of the dependence of the magnitude of the scavenging coefficient on rain intensity are in good agreements with the atmospheric measurements of Martin (Atmos Environ 18:1955–1961, 1984). 相似文献
16.
Pedro Jiménez-Guerrero Juan J. Gómez-Navarro Rocío Baró Raquel Lorente Nuno Ratola Juan P. Montávez 《Climatic change》2013,121(4):661-671
Climate change alone influences future levels of tropospheric ozone and their precursors through modifications of gas-phase chemistry, transport, removal, and natural emissions. The goal of this study is to determine at what extent the modes of variability of gas-phase pollutants respond to different climate change scenarios over Europe. The methodology includes the use of the regional modeling system MM5 (regional climate model version)-CHIMERE for a target domain covering Europe. Two full-transient simulations covering from 1991–2050 under the SRES A2 and B2 scenarios driven by ECHO-G global circulation model have been compared. The results indicate that the spatial patterns of variability for tropospheric ozone are similar for both scenarios, but the magnitude of the change signal significantly differs for A2 and B2. The 1991–2050 simulations share common characteristics for their chemical behavior. As observed from the NO2 and α-pinene modes of variability, our simulations suggest that the enhanced ozone chemical activity is driven by a number of parameters, such as the warming-induced increase in biogenic emissions and, to a lesser extent, by the variation in nitrogen dioxide levels. For gas-phase pollutants, the general increasing trend for ozone found under A2 and B2 forcing is due to a multiplicity of climate factors, such as increased temperature, decreased wet removal associated with an overall decrease of precipitation in southern Europe, increased photolysis of primary and secondary pollutants as a consequence of lower cloudiness and increased biogenic emissions fueled by higher temperatures. 相似文献
17.
Both aerosol and rainwater samples were collected and analyzed for ionic species at a coastal site in Southeast Asia over
a period of 9 months (January–September 2006) covering different monsoons. In general, the occurrence and distribution of
ionic species showed a distinct seasonal variation in response to changes in air mass origins. Real-time physical characterization
of aerosol particles during rain events showed changes in particle number distributions which were used to assess particle
removal processes associated with precipitation, or scavenging. The mean scavenging coefficients for particles in the range
10–500 nm and 500–10 μm were 7.0 × 10−5 ± 2.8 × 10−5 s−1 and 1.9 × 10−4 ± 1.6 × 10−5 s−1, respectively. A critical analysis of the scavenging coefficients obtained from this study suggested that the wet removal
of aerosol particles was greatly influenced by rain intensity, and was particle size-dependent as well. The scavenging ratios,
another parameter used to characterize particle removal processes by precipitation, for NH4
+, Cl−, SO4
2−, and NO3
− were found to be higher than those of Na+, K+, and Ca2+ of oceanic and crustal origins. This enrichment implied that gaseous species NH3, HCl, and HNO3 could also be washed out readily. These additional sources of ions in precipitation presumably counter-balanced the dilution
effect caused by high total precipitation volume in the marine and tropical area. 相似文献
18.
Abhijit Chatterjee Achutan Jayaraman T. Narayana Rao Sibaji Raha 《Journal of Atmospheric Chemistry》2010,66(1-2):27-40
The temporal variation in concentrations of major water soluble ionic species has been studied from several rain events occurred over Gadanki (13.5 °N, 79.2 °E), located in tropical semi arid region in southern India. The contribution from rain-out (in cloud) and wash-out (below cloud) processes to the total removal of ionic species by rain events is also estimated using the pattern of variations of ionic species within an individual event. A number of rain samples were collected from each rain event during June–November in 2006, 2007 and 2008. On average, nearly 20% of the total NH 4 + and non-sea SO 4 2? is removed by in-cloud scavenging, suggesting that their removal by “below cloud” washout is relatively dominant. In contrast Na+, Ca2+, Mg2+, NO 3 ? and sea-SO 4 2? are mainly removed by below-cloud scavenging or wash-out process. A significant variation in the acidity was observed within rain events with successive precipitation showing higher acidity at the final stage of the precipitation due to partial neutralization of non-sea SO 4 2? . Overall, greater influence of both terrestrial and anthropogenic sources is recorded in the rain events compared to that from marine sources. 相似文献
19.
为更科学地量化大气对污染物的清除能力,使用WRF-NAQPMS模式对2017年12月进行模拟,对比分析影响大气清除能力的主要关键物理因子,修正A值法和大气自净容量算法的差异,进一步计算大气自净容量余量及各关键物理化学过程的贡献量。结果表明,边界层高度、风廓线、湿清除系数等3个关键物理参数较混合层高度、10 m高度风速、雨洗强度等更适用于量化清除过程;修正A值法和大气自净容量算法虽均能表征大气清除能力的强弱,但前者受目标城市面积影响较大,结果远高于大气自净容量算法;大气自净容量余量与细颗粒物（PM2.5）浓度变化趋势呈负相关,污染越重,大气自净容量亏空越多,其中平流扩散对大气自净容量贡献最大,化学转化过程次之,湿沉降等过程也不可忽视。 相似文献
20.
Guillaume Bertrand Hélène Celle-Jeanton Paolo Laj Jérôme Rangognio Gilles Chazot 《Journal of Atmospheric Chemistry》2008,60(3):253-271
The present study investigates the chemical composition of wet atmospheric precipitation samples on a daily and an intra-event
timescales in Opme, an experimental meteorological station located near Clermont-Ferrand, France. The samples have been collected
from November 2005 to October 2007. A total of 217 rainwater samples, integrated for 24 h, were collected and analyzed for
pH, conductivity, Na+, K+, Mg2+, NH4+, Ca2+, Cl−, NO3− , SO42− , PO43− and HCO3−. The composition of the rainwater collected appeared to be controlled by the following potential sources: neutralisation
process (association among calcium, ammonium with nitrate and sulphate), marine and terrestrial sources. In order to determine
the role of long-range transport, the integrated events were classified according to four origins of air-masses: (1) West,
(2) North and East, (3) South including Iberian and Italian Peninsulae and (4) local. This analysis allows identifying the
source areas of the different association of elements defined. Although calcium is always dominant, total content of rainfall
is variable and neutralisation process can be more or less efficient and specific. Rainout (long-range transport) and washout
(below-cloud scavenging) were investigated through intra-event measurements of chemical species. Four rain-events have been
selected according to the four classes of origins of air-masses. It appears that the first fractions are responsible for an
important part of the chemical content of the whole event. Terrestrial species, locally emitted, induce the neutralisation
process of acid species. Local meteorological conditions, such as wind’s speed and direction, play an important role as they
could provoke recharges of the below cloud air column during the event. 相似文献