The “Zero-order Model” revisited: Paul Schindler's influence on the development of trace metal scavenging models     

Santschi  Peter H.  Honeyman  Bruce D.  Quigley  Matthew S. 《Aquatic Sciences - Research Across Boundaries》1993,55(4):230-239

In 1975 Paul Schindler produced the first oceanic trace metal scavenging model to explicitly include the role of surface chemistry as a control on trace metal water column residence times. The eighteen years that have elapsed since the publication of Schindler's seminal paper have seen the development of a variety of oceanic scavenging models; yet, the fundamental insight of his Zero-order Model remains the benchmark. This paper describes the role of Paul Schindler's work on surface chemistry in providing a framework for the current generation of trace element scavenging models.  相似文献   

Characteristics, threats and opportunities of landfill scavenging: The case of Gaborone-Botswana     

Batsumi Rankokwane  Thando D. Gwebu 《GeoJournal》2006,65(3):151-163

In Gaborone, as in other large cities in the developing world, individuals try to make a living by engaging in novel occupations such as landfill scavenging. This paper reports on a research conducted in the Gaborone landfill, the largest in Botswana. The study content-analyzed available literature from other countries. It also relied mainly on direct field observations. The discussions on and answers to closed and interview schedules by stakeholders, affected- and- interested – persons, provided the information on the threats and opportunities related to the landfill site and its informal management activities. This on-going case study lends credence to the potential of scavenging in sustaining livelihoods among those who cannot secure employment in the formal urban market. Scavenging tends to be useful although it may hazardous to the informal entrepreneurs. Taking all the threats into consideration, the decommissioning and closure of the landfill seems inevitable, in spite of the apparent short-term livelihood opportunities it provides to the informal sector.  相似文献   

无锡梅雨期湿沉降综合分析   总被引：2，自引：0，他引：2  

苏艳  刘端阳  彭华青  周彬  赵兵 《气象科学》2016,36(4):547-555

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   

降水对江浙沪PM_(2.5)的清除效率研究     

范凡  陆尔  葛宝珠  王自发 《气象科学》2019,39(2):178-186

为了解不同程度的降水对江浙沪地区大气PM_(2.5)的清除作用,搜集了2014—2016年该地区41个城市的降水和PM_(2.5)观测数据,通过对比2 a非降水和全时段PM_(2.5)平均浓度的差异,发现前者显著高于后者,说明降水对该地区PM_(2.5)具有清除作用。利用降水前与降水期间PM_(2.5)的浓度差异作为降水对PM_(2.5)的清除率,降水后与降水期间的浓度差异作为雨后浓度回升的增加率,分别研究了目标区域不同时期、不同降雨量以及不同降雨时长对PM_(2.5)的清除效果。结果显示:(1)与江浙沪南部地区不同的是,北部地区降水清除率与降水前浓度存在正相关,降水后浓度的增加与当地的排放量呈正相关。(2)当降水量为30 mm或者降水时长为36 h时,清除率增幅减缓,说明降水对PM_(2.5)的清除效率存在着阈值。  相似文献   

Absorption and desorption of dichloromethane vapor by water drops in air. An experimental test of scavenging theory     

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   

Model studies of the impact of chemical inhomogeneity on SO2 oxidation in warm stratiform clouds     

Xing Lin  William L. Chameides 《Journal of Atmospheric Chemistry》1991,13(2):109-129

A one-dimensional, time-dependent model of the physics and chemistry of a warm stratiform cloud is used to study the possible impact of chemical inhomogeneity among cloud and raindrops on the oxidation of SO₂ in clouds. The effects of chemical inhomogeneity are examined using two contrasting models: In Model 1 a bulk-solution parameterization is adopted which effectively treats all cloud and raindrops as if they are chemically homogeneous; in Model 2 we allow the cloud and raindrops to have a dichotomous distribution. The dichotomous distribution in Model 2 is simulated by assuming that the two groups of cloud droplets nucleate from two chemically distinct populations of condensation nuclei; one being acidic and the other being alkaline. While the two models yield essentially identical results when the ambient levels of H₂O₂ are greater than the ambient levels of SO₂, the rate of conversion of SO₂ to sulfuric acid and the amount of sulfate removed in the precipitation can be significantly enhanced in Model 2 over that of Model 1 under conditions of oxidant limitation (i.e., H₂O₂ < SO₂). This enhancement is critically dependent upon the fraction of alkaline nuclei assumed to be present in Model 2 and arises from the rapid increase in the aqueous-phase reaction between O₃+S_IV at high pH. Our results suggest that cloud models which adopt a bulk-solution parameterization for cloud droplet chemistry, may underestimate the amount of in-cloud SO₂ oxidation under oxidant-limited conditions.  相似文献   

The influence of aerosol particle composition on cloud droplet formation     

A. Hallberg  J. A. Ogren  K. J. Noone  K. Okada  J. Heintzenberg  I. B. Svenningsson 《Journal of Atmospheric Chemistry》1994,19(1-2):153-171

A difference in partitioning between cloud droplets and interstitial air for two chemical species (elemental carbon and sulphur) with different expected behaviour in nucleation scavenging was observed in clouds at Mt. Kleiner Feldberg (825 m asl), near Frankfurt, Germany. The fraction of sulphur incorporated in cloud droplets was always higher than the fraction of elemental carbon. This difference in partitioning has also been observed in fog but under different pollution conditions in the Po Valley, Italy. Both these studies were based on bulk samples. In the present study at Kleiner Feldberg, impactor samples of the particles in the interstitial air and the cloud droplet residuals were taken and a single particle analysis was done on the samples. It was found that, for a given particle size, the majority of particles forming cloud droplets were soluble and that insoluble particles preferentially remained in the interstitial air.  相似文献   

论雾与污染的关系   总被引：7，自引：1，他引：7  

周斌斌 《气象》1994,20(9):19-24

简述了近年来雾的研究进展，并从雾的酸化、雾层内污染物的扩散、雾层对污染物的清除、污染物对雾形成与发展的影响等方面讨论了雾与大气污染的关系。  相似文献   

区域酸性沉降的数值研究 I. 模式   总被引：17，自引：3，他引：17  

王体健  李宗恺  南方 《大气科学》1996,20(5):606-614

建立了一个三维时变的欧拉型区域酸性污染物沉降模式，模式包括源排放、平流输送、湍流扩散、干沉积、气相化学、液相化学及湿清除等六大部分。考虑到计算条件的承受能力和应用性的要求，在把握酸沉降形成的关键过程的前提下，合理地简化设计模式。相对于国内已有的工作，本模式在干沉积、气相化学、液相化学和湿清除等方面均有所改进。  相似文献   

A numerical model of the partitioning of trace chemical solutes during drop freezing     

A. L. Stuart  M. Z. Jacobson 《Journal of Atmospheric Chemistry》2006,53(1):13-42

Partitioning of volatile chemicals among the gas, liquid, and solid phases during freezing of liquid water in clouds can impact trace chemical distributions in the troposphere and in precipitation. We describe here a numerical model of this partitioning during the freezing of a supercooled liquid drop. Our model includes the time-dependent calculation of the coupled processes of crystallization kinetics, heat transport, and solute mass transport, for a freezing hydrometeor particle. We demonstrate the model for tracer partitioning during the freezing of a 1000 μm radius drop on a 100 μm ice substrate, under a few ambient condition scenarios. The model effectively simulates particle freezing and solute transport, yielding results that are qualitatively and quantitatively consistent with previous experimental and theoretical work. Results suggest that the ice shell formation time is governed by heat loss to air and not by dendrite propagation, and that the location of ice nucleation is not important to freezing times or the effective partitioning of chemical solutes. Even for the case of nucleation at the center of the drop, we found that dendrites propagated rapidly to form surface ice. Freezing then proceeded from the outside in. Results also indicate that the solid-liquid interfacial surface area is not important to freezing times or the effective partitioning of chemical solutes, and that the rate aspects of trapping are more important than equilibrium solid-liquid partitioning to the effective partitioning resulting from freezing.  相似文献