Modeling Atmospheric Chemistry: Interactions between Gas-Phase Species and Liquid Cloud/Aerosol Particles

For detailed modeling of atmospheric chemistry it is necessary to consider aqueous-phase reactions in cloud droplets and deliquesced aerosol particles. Often, the gas-phase concentration is in equilibrium with the aqueous phase. Then Henrys law can be used to describe the distribution between the phases provided that the Henrys law coefficient is known. In some cases, thermodynamic equilibrium will not be reached and it is necessary to use kinetic expressions of the rates involved. These rates depend on diffusion constants, accommodation coefficients, Henrys law coefficients, particle size distributions, and several other parameters. This review describes how these processes can be treated in computer modeling and how the necessary data can be obtained. Even though it is written primarily for use in modeling atmospheric chemistry, some parts will also be useful for waste water and pesticide control and in other areas where the distribution of chemicals between the aqueous and the gas phase is important.     

Dispersive Particle Transport: Identification of Macroscale Behavior in Heterogeneous Stratified Subsurface Flows

Dispersive mass transport processes in naturally heterogeneous geological formations (porous media) are investigated based on a particle approach to mass transport and on its numerical implementation using LPT3D, a Lagrangian Particle Tracking 3D code. We are currently using this approach for studying microscale and macroscale space–time behavior (advection, diffusion, dispersion) of tracer plumes, solutes, or miscible fluids, in 1,2,3-dimensional heterogeneous and anisotropic subsurface formations (aquifers, petroleum reservoirs). Our analyses are based on a general advection-diffusion model and numerical scheme where concentrations and fluxes are discretized in terms of particles. The advection-diffusion theory is presented in a probabilistic framework, and in particular, a numerical analysis is developed for the case of advective transport and rotational flows (numerical stability of the explicit Euler scheme). The remainder of the paper is devoted to the behavior of concentration, mass flux density, and statistical moments of the transported tracer plume in the case of heterogeneous steady flow fields, where macroscale dispersion occurs due to geologic heterogeneity and stratification. We focus on the case of perfectly stratified or multilayered media, obtained by generating many horizontal layers with a purely random transverse distribution of permeability and horizontal velocity. In this case, we calculate explicitly the exact mass concentration field C(x, t), mass flux density field f(x, t), and moments. This includes spatial moments and dispersion variance ² _x (t) on a finite domain L, and temporal moments on a finite time scale T, e.g., the mass variance of arrival times ² _T (x). The moments are related to flux concentrations in a way that takes explicitly into account finite space–time scales of analysis (time-dependent tracer mass; spatially variable flow through mass). The multilayered model problem is then used in numerical experiments for testing different ways of recovering information on tracer plume migration, dispersion, concentration and flux fields. Our analyses rely on a probabilistic interpretation that emerges naturally from the particle approach; it is based on spatial moments (particle positions), temporal moments (mass weighted arrival times), and probability densities (both concentrations and fluxes). Finally, as an alternative to direct estimations of the flux and concentration fields, we formulate and study the Moment Inverse Problem. Solving the MIP yields an indirect method for estimating the space–time distribution of flux concentrations based on observed or estimated moments of the plume. The moments may be estimated from field measurements, or numerically computed by particle tracking as we do here.     

湘黔地区“卡林型”金矿中金的赋存形式

对矿石的化学物相分析结果表明，湖南─贵州─带“卡林型”金矿原生矿石中的金主要呈微粒状单质金被包裹于硫化物及以绢云母为主的粘土矿物中，反映了金的矿化作用与黄铁矿化和绢云母化等是同时发生的。不同的“卡林型”金矿床之间，由于形成的物理化学条件的差异，其主要载金矿物的种类也不相同。表生氧化带中，载金矿物硫化物和绢云母发生了氧化和分解作用，使矿石中的大部分金转化为游离态形式存在，提高了矿石的可选性。     

PRELIMINARY STUDY OF VARIATION OF SO_2 AND AEROSOL PARTICLE BACKGROUND CONCENTRATIONS IN THE EASTERN CHINA

The average concentrations of sulphur dioxide,sulfate aerosol and TSP were about 8—10 ppb,15.08 μg m~(-3),and241.40 μg m~(-3) respectively,which were measured at the Lin'an regional background station during August—November,1991.The higher concentrations of SO_2 and SO_4~(2-) maybe acidify the rainfall.It has a great influence uponthe human health and ecosystem.The simulated results indicate that the distributions of SO_2 and SO_4~(2-) were deter-mined by local emission sources.Average aerosol particle number density was 2.0×10~4 cm~(-3).It shows that social devel-opment and human activities strongly affect the atmospheric background level.     

The role of organic material in atmospheric aerosols

An estimated budget of organic substances in the atmosphere is compiled to whow the importance of organics in the aerosol. The distribution of organic compounds in background aerosols is estimated and it will be shown that the Aitken particles probably consist of roughly one quarter of organic substances. This is important for the dynamics of the aerosol and calculations are presented to estimate the aerosol production distribution for gas-to-particle conversion processes.     

The importance of grain size and shape in controlling the dispersion of the Vedde cryptotephra

Volcanic ash is dispersed in the atmosphere according to meteorology and particle properties, including size and shape. However, the multiple definitions of size and shape for non-spherical particles affect our ability to use physical particle properties to understand tephra transport. Moreover, although particles are often excluded from operational ash dispersion model setups, ash in tephra deposits 1000 km from source can exceed . Here we measure the shape and size of samples of Vedde ash from Iceland, an exceptionally widespread tephra layer in Europe, collected in Iceland and Norway. Using X-ray computed tomography and optical microscopy, we show that distal ash is more anisotropic than proximate ash, suggesting that shape exerts an important control on tephra dispersion. Shape also impacts particle size measurements. Particle long axis, a parameter often reported by tephrochronologists, is on average greater than geometric size, used by dispersion modellers. By using geometric size and quantifying shape, we can explain the transport of Vedde ash particles more than 1200 km from source. We define a set of best practices for measuring the size and shape of cryptotephra shards and discuss the benefits and limitations of using physical particle properties to understand cryptotephra transport.     

How are storm time injections different from nonstorm time injections?

One of the key elements of storms and substorms is the injection of energetic particles into the region of near geosynchronous orbit, that is, the sudden flux enhancement in the energy range of tens to hundreds of keV. This paper reports the observational results on how such injection features during storm times are different from those of nonstorm times. We particularly focus on the difference between proton injections and electron injections. Based on a number of storm time injection events that meet our strict selection criteria, we find a notable difference between proton injections and electron injections in the energy-spectral dependence of the flux enhancement averaged over the first 30 min after the injection onset: The average flux enhancement of many protons injections tends to be bigger at higher energy channels than at lower energy channels, but electron injections exhibit the opposite tendency for the energy-spectral dependence of flux enhancement, i.e., average flux enhancement decreasing with increasing energy. We show that this feature is almost unique only for the injection events during the storm main and early recovery phase. It is suggested that any successful scenario intended to model storm time injections should be able to explain this difference between proton injections and electron injections.