scholarly journals The impact of a deep convection on sulfate transport and redistribution

2002 ◽  
Vol 2 (2) ◽  
pp. 385-430
Author(s):  
V. Spiridonov ◽  
M. Curic
Keyword(s):  
Chemical Reactions ◽  
Wet Deposition ◽  
Deep Convection ◽  
Aerosol Particles ◽  
Parameterization Scheme ◽  
Chemical Components ◽  
Total Sulfur ◽  
Henry's Law ◽  
Henry’S Law ◽  
The Impact

Abstract. A three-dimensional compressible cloud model was used to simulate the processes related to dynamics, microphysics and chemistry of continental non-polluted and continental polluted clouds. The chemical components are formulated in terms of continuity equations for different chemical species in the aqueous phase within the cloud. Their evolution in this model came from not only by the processes of advection and turbulence transport, but also the chemical reactions and microphysical transfers. The model includes a method of kinetic uptake limitations. Gases with low solubility H* < 103 mol dm-3 atm-1 are in Henry's law equilibrium with temperature dependence of Henry's law coefficients. Seven pollutant groups are currently included in the chemistry parameterization scheme: S(IV), S(VI), (H2O2), (O3), N(V), (NH3), (CO2). The present model contains explicit treatment of SO2 and O3, a kinetic method of gas uptake as well as an improved microphysical parameterization scheme. The primary objective of this model is to study the impact of the deep convection on the pollutant transport, redistribution and deposition. It is done through chemical reactions, oxidation, scavenging of aerosol particles and transfer via microphysical transitions among water categories. Two base run simulation parameters are used to initialize the model. The first model run is for the 6 July 1995 event, characterized by intensive convective cloud activity and a large amount of precipitation, manifested as a flashflood. The second one is related to transboundary dust transport and sulfate wet deposition. The chemical field initialization is based on the vertical distribution profiles of gases and aerosols for continental non-polluted and continental polluted background. The study has revealed the importance of considering interactions between dynamics, microphysics and cloud chemistry. Deep convection in the first analyzed case generates rapid upward and downward transport of pollutants. It stimulates the impact of scavenging processes and microphysical conversions, pollutant redistribution and wet deposition. We find good agreement between calculated and observed rainfall, pH, sulfate concentration and wet deposition, in the second simulated case. Aerosol particles partially dissolved in precipitation changed their qualitative and quantitative features, acidity and increment of all chemical components. A lot of sensitivity tests of the terms included in the chemistry parameterization scheme indicate that assumption of Henry's law equilibrium leads to a factor 2 to 3 underestimate of a soluble gas in cloud water and 3 to 5 in rainwater, respectively. Our calculations demonstrate that assumption of Henry's law leads to a factor of about 1.0 to 1.3 overestimation of the integrated sulfur mass removed by wet deposition. Analysis of the relative contribution of some parameters implies that 20% - 24% of total sulfur mass deposited belongs to both nucleation and impact scavenging. Liquid phase oxidation contributed 22% and 28% of the total sulfur mass deposited for continental non-polluted and continental polluted background, respectively. Neglecting liquid-ice phase chemical reactions leads to underestimation of the total sulfur mass deposited by about a factor of 1.0 to 1.2 for continental non-polluted and continental polluted distributions, relative to the base run.

scholarly journals Sensitivities of Summertime Mesoscale Circulations in the Coastal Carolinas to Modifications of the Kain–Fritsch Cumulus Parameterization

2017 ◽  
Vol 145 (11) ◽  
pp. 4381-4399 ◽  
Author(s):  
Aaron P. Sims ◽  
Kiran Alapaty ◽  
Sethu Raman
Keyword(s):  
Numerical Models ◽  
Deep Convection ◽  
Coastal Region ◽  
Turnover Time ◽  
Cumulus Parameterization ◽  
Parameterization Scheme ◽  
Subgrid Scale ◽  
Mesoscale Circulations ◽  
Near Surface ◽  
The Impact

Two mesoscale circulations, the Sandhills circulation and the sea breeze, influence the initiation of deep convection over the Sandhills and the coast in the Carolinas during the summer months. The interaction of these two circulations causes additional convection in this coastal region. Accurate representation of mesoscale convection is difficult as numerical models have problems with the prediction of the timing, amount, and location of precipitation. To address this issue, the authors have incorporated modifications to the Kain–Fritsch (KF) convective parameterization scheme and evaluated these mesoscale interactions using a high-resolution numerical model. The modifications include changes to the subgrid-scale cloud formulation, the convective turnover time scale, and the formulation of the updraft entrainment rates. The use of a grid-scaling adjustment parameter modulates the impact of the KF scheme as a function of the horizontal grid spacing used in a simulation. Results indicate that the impact of this modified cumulus parameterization scheme is more effective on domains with coarser grid sizes. Other results include a decrease in surface and near-surface temperatures in areas of deep convection (due to the inclusion of the effects of subgrid-scale clouds on the radiation), improvement in the timing of convection, and an increase in the strength of deep convection.

Henry's law constants for C2–C3 fluorinated alcohols and their wet deposition in the atmosphere

2003 ◽  
Vol 37 (34) ◽  
pp. 4817-4822 ◽  
Author(s):  
Liang Chen ◽  
Norimichi Takenaka ◽  
Hiroshi Bandow ◽  
Yasuaki Maeda
Keyword(s):  
Wet Deposition ◽  
Henry's Law ◽  
Henry’S Law ◽  
Fluorinated Alcohols ◽  
Henry’S Law Constants ◽  
Henry's Law Constants

scholarly journals Compilation of Henry's law constants, version 3.99

2014 ◽  
Vol 14 (21) ◽  
pp. 29615-30521 ◽  
Author(s):  
R. Sander
Keyword(s):  
Gas Phase ◽  
Environmental Chemistry ◽  
Aerosol Particles ◽  
Dilute Solution ◽  
Henry's Law ◽  
Cloud Droplets ◽  
Henry’S Law ◽  
Equilibrium Ratio ◽  
Henry’S Law Constants ◽  
Henry's Law Constants

Abstract. Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles. Therefore, it is necessary to understand the distribution between the phases. According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution. Henry's law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format. The compilation contains 14775 values of Henry's law constants for 3214 species, collected from 639 references. It is also available on the internet at http://www.henrys-law.org.

A three-dimensional numerical simulation of sulfate transport and redistribution

2003 ◽  
Vol 81 (9) ◽  
pp. 1067-1094 ◽  
Author(s):  
V Spiridonov ◽  
M Curic
Keyword(s):  
Liquid Phase ◽  
Wet Deposition ◽  
Cloud Model ◽  
Chemical Species ◽  
Liquid Phase Oxidation ◽  
Atmospheric Pollutants ◽  
Total Sulfur ◽  
Cloud Chemistry ◽  
Phase Oxidation ◽  
The Impact

We have utilized a relatively sophisticated dynamic cloud model combined with standard bulk-parameterized microphysics and simple sulfur chemistry to explore the impact of deep convection on modification and transport of a suite of pollutants. Two base run simulation parameters are used to initialize the cloud-chemistry model. The simulation of the 6 July 1995 case, with continental polluted field initialization, has revealed that a convective storm generates strong vertical transport of gases and particulate compounds from the planetary boundary layer (PBL) to the upper troposphere (UT), perturbation of aerosol physical and chemical properties, modification of pollutant concentration, and change of the spatial distributions of chemical species. The early formation of precipitation and enhanced scavenging contributed to a registration of approximately 2.5 times the concentration of sulfate in the precipitation near the surface than in the air found at this level. The Spring case numerical experiment on 3 April 2000 with a chemical background taken from Macedonia, provided insight into the potential influence of the long-range transport of atmospheric pollutants and ascertained quantitative–qualitative information about processes by which acidic species are incorporated into precipitation. The model-computed parameters are in good agreement with observation. The average equivalent cloud water pH and rainwater pH when the higher acid precipitation occurs are about 5.0 and 4.5, respectively. The results from a number of sensitivity tests of cloud chemistry of the physical processes for the continental nonpolluted and continental polluted environments, indicate that nucleation and impact scavenging of aerosols account for between 20%–24% of the total sulfur mass removed by wet deposition. Liquid-phase oxidation contributes about 20%–28% of the sulfur content in precipitation. It means that neglecting liquid-phase oxidation when considering the chemistry in these clouds may lead to underestimates of about 20%–28% in sulfate wet deposition. Neglect of the ice phase when considering the chemistry in continental nonpolluted and continental polluted clouds may lead to overestimates of about 112%–130% of the total sulfur mass removed by wet deposition. The assumption of Henry's law equilibrium for those types of clouds gives an overestimation of about 100%–120%, respectively. PACS Nos.: 51.10.+y, 92.60.Sz

The impact of atmospheric wet deposition on roof runoff quality in an urbanized area

2015 ◽  
Vol 46 (6) ◽  
pp. 880-892 ◽  
Author(s):  
Hua-Peng Qin ◽  
Qiao-Ling Tang ◽  
Li-Yu Wang ◽  
Guangtao Fu
Keyword(s):  
Organic Acids ◽  
Wet Deposition ◽  
Rainwater Harvesting ◽  
Urban Site ◽  
Chemical Components ◽  
Roof Runoff ◽  
Alkaline Dust ◽  
Rooftop Rainwater Harvesting ◽  
The Impact ◽  
Fast Increase

Understanding the sources of chemical components in roof runoff can help to prevent water quality problems in rooftop rainwater harvesting. To identify the contribution of wet deposition to the mass of components in roof runoff, the samples from air, rainwater, dust buildup and roof runoff were collected from an urban site in Shenzhen of China in 2011–2012. The results indicate that: (1) wet deposition has a dominant contribution to the mass of total organic carbon (TOC), NH4+, NO3–, Cl– and organic acids in the roof runoff, while the mass of NH4+, acetic acid and formic acid in the roof runoff may be greatly reduced by the neutralization between the components with alkaline dust buildup on the rooftop; and (2) wet deposition partially contributes to the mass of Na+, K+, Mg2+, Ca2+, F– and SO42– in the roof runoff, while other factors like dust buildup on the rooftop and chemical reactions also have a non-negligible impact. Furthermore, TOC, NH4+, NO3– and organic acids in the wet deposition are mainly influenced by the atmospheric pollution due to fast increase in fossil fuel consumption (e.g. vehicle emissions). Therefore, the effects of wet deposition should be carefully considered for rooftop rainwater harvesting in urbanized areas.

scholarly journals Effect of dry or wet substrate deposition on the organic volume fraction of core–shell aerosol particles

2019 ◽  
Vol 12 (3) ◽  
pp. 2033-2042 ◽  
Author(s):  
Hansol D. Lee ◽  
Chathuri P. Kaluarachchi ◽  
Elias S. Hasenecz ◽  
Jonic Z. Zhu ◽  
Eduard Popa ◽  
...  
Keyword(s):  
Single Particle ◽  
Wet Deposition ◽  
Particle Deposition ◽  
Volume Fraction ◽  
Aerosol Particles ◽  
Model Systems ◽  
Core Shell ◽  
Solid Core ◽  
Mixing States ◽  
The Impact

Abstract. Understanding the impact of sea spray aerosol (SSA) on the climate and atmosphere requires quantitative knowledge of their chemical composition and mixing states. Furthermore, single-particle measurements are needed to accurately represent large particle-to-particle variability. To quantify the mixing state, the organic volume fraction (OVF), defined as the relative organic volume with respect to the total particle volume, is measured after generating and collecting aerosol particles, often using deposition impactors. In this process, the aerosol streams are either dried or kept wet prior to impacting on solid substrates. However, the atmospheric community has yet to establish how dry versus wet aerosol deposition influences the impacted particle morphologies and mixing states. Here, we apply complementary offline single-particle atomic force microscopy (AFM) and bulk ensemble high-performance liquid chromatography (HPLC) techniques to assess the effects of dry and wet deposition modes on the substrate-deposited aerosol particles' mixing states. Glucose and NaCl binary mixtures that form core–shell particle morphologies were studied as model systems, and the mixing states were quantified by measuring the OVF of individual particles using AFM and compared to the ensemble measured by HPLC. Dry-deposited single-particle OVF data positively deviated from the bulk HPLC data by up to 60 %, which was attributed to significant spreading of the NaCl core upon impaction with the solid substrate. This led to underestimation of the core volume. This problem was circumvented by (a) performing wet deposition and thus bypassing the effects of the solid core spreading upon impaction and (b) performing a hydration–dehydration cycle on dry-deposited particles to restructure the deformed NaCl core. Both approaches produced single-particle OVF values that converge well with the bulk and expected OVF values, validating the methodology. These findings illustrate the importance of awareness in how conventional particle deposition methods may significantly alter the impacted particle morphologies and their mixing states.

scholarly journals Dry versus wet? Implications on aerosol impaction and organic volume fraction

2018 ◽  
Author(s):  
Hansol D. Lee ◽  
Chathuri P. Kaluarachchi ◽  
Elias S. Hasenecz ◽  
Zhehao Zhu ◽  
Eduard Popa ◽  
...  
Keyword(s):  
Single Particle ◽  
Wet Deposition ◽  
Particle Deposition ◽  
Volume Fraction ◽  
Aerosol Particles ◽  
Model Systems ◽  
Solid Core ◽  
Particle Volume ◽  
Mixing States ◽  
The Impact

Abstract. Understanding the impact of sea spray aerosols (SSA) on the climate and atmosphere requires quantitative knowledge of their chemical composition and mixing states. Furthermore, single particle measurements are needed to accurately represent large particle-to-particle variability. To quantify the mixing state, organic volume fraction (OVF), defined as the relative organic volume with respect to the total particle volume, is measured after generating and collecting aerosol particles, often using deposition impactors. In this process, the aerosol streams are either dried or kept wet prior to impacting on solid substrates. However, the atmospheric community has yet to establish how dry versus wet aerosol deposition influences the impacted particle morphologies and mixing states. Here, we apply complementary offline single particle atomic force microscopy (AFM) and bulk ensemble high performance liquid chromatography (HPLC) techniques to assess the effects of dry and wet deposition modes on the substrate-deposited aerosol particles' mixing states. Glucose and NaCl binary mixtures that form core-shell particle morphologies were studied as model systems, and the mixing states were quantified by measuring the OVF of individual particles using AFM and compared to the ensemble measured by HPLC. Dry deposited single particle OVF data positively deviated from the bulk HPLC data by up to 60 %. The positive deviation was attributed to significant spreading of the NaCl core upon impaction with the solid substrate, which is not readily evident in AFM imaging and leads to underestimation of the core volume. NaCl core spreading under impaction was confirmed by imaging dry deposited NaCl particles. This problem was circumvented by (a) performing wet deposition and thus bypassing the effects of the solid core spreading upon impaction and (b) performing a hydration-dehydration cycle on dry deposited particles to restructure the deformed NaCl core. Both approaches produced single particle OVF values that converge well with the bulk and expected OVF values, validating the methodology. These findings illustrate the importance of awareness in how conventional particle deposition methods may significantly alter the impacted particle morphologies and their mixing states. Our work can help improve quantification and predictions of chemical mixing states of atmospherically-relevant aerosols.

Biotransformation of Coumarins by Filamentous Fungi: An Alternative Way for Achievement of Bioactive Analogs

2019 ◽  
Vol 16 (6) ◽  
pp. 568-577 ◽  
Author(s):  
Jainara Santos do Nascimento ◽  
João Carlos Silva Conceição ◽  
Eliane de Oliveira Silva
Keyword(s):  
Filamentous Fungi ◽  
Chemical Reactions ◽  
Biological Activities ◽  
Chemical Transformations ◽  
Chemical Structures ◽  
Pattern Structures ◽  
Pharmacological Interest ◽  
Aspergillus Sp ◽  
The Impact ◽  
Related Compounds

Coumarins are natural 1,2-benzopyrones, present in remarkable amounts as secondary metabolites in edible and medicinal plants. The low yield in the coumarins isolation from natural sources, along with the difficulties faced by the total synthesis, make them attractive for biotechnological studies. The current literature contains several reports on the biotransformation of coumarins by fungi, which can generate chemical analogs with high selectivity, using mild and eco-friendly conditions. Prompted by the enormous pharmacological interest in the coumarin-related compounds, their alimentary and chemical applications, this review covers the biotransformation of coumarins by filamentous fungi. The chemical structures of the analogs were presented and compared with those from the pattern structures. The main chemical reactions catalyzed the insertion of functional groups, and the impact on the biological activities caused by the chemical transformations were discussed. Several chemical reactions can be catalyzed by filamentous fungi in the coumarin scores, mainly lactone ring opening, C3-C4 reduction and hydroxylation. Chunninghamella sp. and Aspergillus sp. are the most common fungi used in these transformations. Concerning the substrates, the biotransformation of pyranocoumarins is a rarer process. Sometimes, the bioactivities were improved by the chemical modifications and coincidences with the mammalian metabolism were pointed out.

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