Atmospheric Structure: Composition, Properties, and Distribution of Atmospheric Aerosols
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The document discusses the structure and composition of Earth's atmosphere. It can be summarized as follows: 1) Earth's atmosphere consists of several layers identified by temperature changes with height. It is composed primarily of nitrogen and oxygen, as well as variable amounts of water vapor, carbon dioxide, and other gases. 2) Atmospheric aerosols exist in different sizes ranging from ultrafine to accumulation to coarse modes, which are produced and removed through various natural and human-influenced processes over timescales from minutes to days. 3) The composition and concentrations of atmospheric constituents vary significantly by location from urban to rural to remote areas, and between soluble and insoluble particle types that impact climate and air quality.
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Atmospheric Structure: Composition, Properties, and Distribution of Atmospheric Aerosols
- 1. ATMOSPHERIC STRUCTURE IFFAT ARA Lecturer Dept. of Geomatics LMA, PSTU
- 2. DEFINITION
- 3. What is Atmosphere of the Earth? • The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity. • The atmosphere consists of a series of layers, one outside the other, and identified mainly by the way temperature changes with height within them.
- 4. COMPOSITION
- 5. Composition of Atmosphere Proportional volume of gases composing dry air. Nitrogen and oxygen obviously dominate.
- 8. Variable or Minor Gases • WaterVapor • Carbon dioxide • Hydrogen • Neon • Xenon • Krypton • Methane
- 9. Changes in the atmosphere’s CO2 dioxide
- 10. Variable Components Air includes many gases and particles that vary significantly from time to time and place to place. Important examples include: • water vapor • SPM or Aerosols Although usually present in small percentages, they can have significant effects on weather and climate.
- 11. AEROSOLS
- 12. Types
- 15. Production, growth, and removal of atmospheric aerosols
- 16. Production, growth, and removal of atmospheric aerosols • Gas molecules are typically in the 10-4-10-3 mm size range. Clustering of gas molecules( nucleation) produces ultrafine aerosols in the 10-3-10-2 mm size range. • These ultrafine aerosols grow rapidly to the 0.01-1 mm fine aerosol size range by condensation of gases and by coagulation (collisions between particles during their random motions). • Growth beyond 1 mm is much slower because the particles are by then too large to grow rapidly by condensation of gases, and because the slower random motion of large particles reduces the coagulation rate. • Aerosol particles originating from condensation of gases tend therefore to accumulate in the 0.01-1 mm size range, often called the accumulation mode (as opposed to the ultrafine mode or the coarse mode).
- 17. Importance
- 18. Sources
- 19. Sinks • Lifetime in the Atmosphere: About 5-7 days • Removal Mechanisms: • Sedimentation (Settling)- about 10-20% by mass • Scavenging by Precipitation- about 80-90% by mass • Consequence: Aerosol is very uniformly mixed
- 20. Composition
- 21. Concentrations Location Number concentration (cm –3 ) Mass concentration ( µg m –3 ) Urban 105 – 107 101 –104 Rural 103 – 104 101 – 102 Remote maritime 102 101 – 102 Polar 100 – 103 10–1 – 101 Source of data: Heitzenberg, 1994
- 25. Size Distribution Based on particle distributions, different groups of atmospheric particles can be separated.
- 26. Size Distribution According to Formation Process Nucleation Mode: Produced from natural gas-to particle condensation or during condensation of hot vapor in combustion process Accumulation Mode: Emitted from condensation of vapor or incomplete combustion Coarse Mode: Emitted during mechanical processes from both natural and anthropogenic sources (e.g. sea-salt particles from ocean surface, soil and mineral dust, biological materials)
- 27. Nucleation Mode
- 28. Nucleation Mode • Aerosol particles below 0.1 µm in diameter constitute the nucleation (or Aitken) mode. • The smallest range of these particles (with particle diameter is lower than 0.01 µm) sometimes called ultrafine mode. • These particles are produced by homogeneous and heterogeneous nucleation processes • Due to their rapid coagulation or random impaction onto surfaces, the lifetime of these small particles is very short (order of minutes to hours).
- 30. Accumulation Mode • Larger aerosol particles in the size range 0.1 to 1 µm in diameter can accumulate in the atmosphere because their removal mechanisms are least efficient. • Their lifetime in the atmosphere is 7–10 days and during this period they can transported to a long distance from their sources. • Particles belonging to this accumulation mode are formed mainly by coagulation of smaller particles or condensation of vapors onto existing particles, and during these mechanisms they growth into this size range. • Accumulation particles removed from the atmosphere mainly by wet deposition.
- 31. Coarse Mode
- 32. Coarse Mode • The Coarse mode contains particles with diameter larger than 1.0 μm. • Due to their relatively large mass, they have short atmospheric lifetimes because of their rapid sedimentation.
- 35. Soluble Particles • In continental regions, about 80% of smaller particles are water- soluble. • However, some types of coarse particles are also water soluble, like sea salt particles over oceans. • Most water-soluble aerosol components are hygroscopic and they can absorb water. • If aerosol particles consisting of water-soluble material, the uptake of atmospheric water vapour can results an aqueous solution droplet. • During this process, the size of particle increases by hygroscopic growth, even when relative humidity is lower than 100%. • Highly soluble particles are for example ammonium sulphate, ammonium nitrate and sodium chloride.
- 36. Insoluble Particles • Several particles are poorly soluble or insoluble in water. • Insoluble aerosols for example particles derived from soil dust or volcanoes (e.g. metal oxides, silicates, clay minerals).
- 38. Spatial Distribution Pattern - 1
- 39. Spatial Distribution Pattern - 2
- 40. Example: Effect
- 41. Q & A ThankYou!
Editor's Notes
- পৃথিবীর বায়ুমণ্ডল বলতে পৃথিবীকে চারপাশে ঘিরে থাকা বিভিন্ন গ্যাস মিশ্রিত স্তরকে বুঝায়, যা পৃথিবী তার মধ্যাকর্ষণ শক্তি দ্বারা ধরে রাখে। একে আবহমণ্ডল-ও বলা হয়। এই বায়ুমন্ডল সূর্য থেকে আগত অতিবেগুনি রশ্মি শোষণ করে পৃথিবীতে জীবের অস্তিত্ব রক্ষা করে। এছাড়ও তাপ ধরে রাখার মাধ্যমে (গ্রীনহাউজ প্রতিক্রিয়া) ভূপৃষ্টকে উওপ্ত করে এবং দিনের তুলনায় রাতের তাপমাত্রা হ্রাস করে। শ্বাস-প্রশ্বাস ও সালোকসংশ্লেষণের জন্য ব্যবহৃত বায়ুমন্ডলীয় গ্যাসসমূহের প্রদত্ত প্রচলিত নাম বায়ু বা বাতাস।পরিমাণের দিক থেকে শুষ্ক বাতাসে ৭৮.০৯% নাইট্রোজেন,২০.৯৫% অক্সিজেন,[১] ০.৯৩% আর্গন,০.০৩৯% কার্বন ডাইঅক্সাইড এবং সামান্য পরিমাণে অন্যান্য গ্যাস থাকে।বাতাসে এছাড়াও পরিবর্তনশীল পরিমাণ জলীয় বাষ্প রয়েছে যার গড় প্রায় ১%।বাতাসের পরিমাণ ও বায়ুমন্ডলীয় চাপ বিভিন্ন স্তরে বিভিন্ন রকম হয়,স্থলজ উদ্ভিদ ও স্থলজ প্রাণীর বেঁচে থাকার জন্য উপযুক্ত বাতাস কেবল পৃথিবীর ট্রপোস্ফিয়ার এবং কৃত্রিম বায়ুমণ্ডলসমূহে পাওয়া যাবে।
- In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are ppm (parts-per-million, 10−6), ppb (parts-per-billion, 10−9), ppt (parts-per-trillion, 10−12) and ppq (parts-per-quadrillion, 10−15).
- The amount of water vapor in the air varies considerably , from practically none at all up to about 4 percent by volume. Why is such a small fraction of the atmosphere so significant? Certainly the fact that water vapor is the source of all clouds and precipitation would be enough to explain its importance. However, water vapor has other roles. Like carbon dioxide, it has the ability to absorb heat given off by Earth, as well as some solar energy. The movements of the atmosphere are sufficient to keep a large quantity of solid and liquid particles suspended within it. Although visible dust sometimes clouds the sky , these relatively large particles are too heavy to stay in the air for very long. Still, many particles are microscopic and remain suspended for considerable periods of time. They may originate from many sources, both natural and human made, and include sea salts from breaking waves, fine soil blown into the air , smoke and soot from fires, pollen and microorganisms lifted by the wind, ash and dust from volcanic eruptions, and more Collectively, these tiny solid and liquid particles are called aerosols.
- Aerosols are tiny particles that are capable of suspending in the atmosphere. Most come from natural means such as dust storms, volcanoes, fires, or even vegetation and sea spray (sea salt released into the atmosphere). Human activity also contributes aerosol pollution through the alteration of natural surface cover, industrial pollutants, and the burning of fossil fuels. Aerosols are minute particles suspended in the atmosphere. When these particles are sufficiently large, we notice their presence as they scatter and absorb sunlight. Their scattering of sunlight can reduce visibility (haze) and redden sunrises and sunsets. There are natural aerosols and aerosol pollutants. Combined, the total amount, and type, of aerosols affect the amount of atmospheric forcing imposed inside the climate system. This is because some aerosols help reflect sunlight back out into space. This reduces the amount of solar energy reaching the earth's surface. To calculate total warming and cooling potentials, the total effect of aerosols and greenhouse gases (GHG's) needs to be calculated.
- ডাইমিথাইল সালফাইড Clod condensation nuclei Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles typically 0.2 µm, or 1/100th the size of a cloud droplet [1] on which water vapour condenses. A procedure in which blood is drawn and separated into its components by dialysis; some are retained and the rest are returned to the donor by transfusion
- ডাইমিথাইল সালফাইড Clod condensation nuclei
- Atmospheric aerosols originate from the condensation of gases and from the action of the wind on the Earth's surface. Fine aerosol particles (less than 1 mm in radius) originate almost exclusively from condensation of precursor gases. A typical chemical composition for fine aerosol in the lower troposphere is shown in Figure. A key precursor gas is sulfuric acid (H2SO4), which is produced in the atmosphere by oxidation of sulfur dioxide (SO2) emitted from fossil fuel combustion, volcanoes, and other sources. H2SO4 has a low vapor pressure over H2SO4-H2O solutions and condenses under all atmospheric conditions to form aqueous sulfate particles. The composition of these sulfate particles can then be modified by condensation of other gases with low vapor pressure including NH3, HNO3, and organic compounds. Organic carbon represents a major fraction of the fine aerosol ( Figure 8-1 ) and is contributed mainly by condensation of large hydrocarbons of biogenic and anthropogenic origin. Another important component of the fine aerosol is soot produced by condensation of gases during combustion. Soot as commonly defined includes both elemental carbon and black organic aggregates.
- These particles are too small to sediment at a significant rate, and are removed from the atmosphere mainly by scavenging by cloud droplets and subsequent rainout (or direct scavenging by raindrops). Coarse particles emitted by wind action are similarly removed by rainout. In addition they sediment at a significant rate, providing another pathway for removal. The sedimentation velocity of a 10 mm radius particle at sea level is 1.2 cm s-1, as compared to 0.014 cm s-1 for a 0.1 mm particle.
- Typical chemical composition of aerosols can vary at different locations, times, weather conditions and particle size fractions. The carbonaceous fraction of the aerosols consists of both elemental carbon (EC) or black carbon (BC) and organic carbon (OC). The ratio of elemental to total carbon (EC+OC) is strongly depends on the sources. The main sources of elemental carbon particles are biomass and fossil fuel burning. Particles containing organic carbon can emitted directly to the atmosphere also from biomass burning or combustion processes and by secondary organic aerosol (SOA) formation during the atmospheric oxidation of biogenic or anthropogenic volatile organic compounds (VOC).
- Data correspond to mass fraction in % of the total fine particle mass concentration.
- Aerosol particles in the atmosphere have widely variable shapes. Their dimensions are usually characterized by a particle diameter, which span over four orders of magnitude, from a few nanometers to around 100 μm. Particle size is one of the most important parameters to describe the behaviour of aerosols, affecting both their lifetime, physical and chemical properties. Distribution of aerosol particles is generally defined by their number, surface or volume
- nucleation (Aitken) mode (particle diameter < 0.1 µm), accumulation mode (particle diameter: 0.1 µm > d > 1 µm) coarse mode (particle diameter d > 1 µm).
- Coagulation: The process of forming semisolid lumps in a liquid
- atmospheric particles can also be categorized by their water solubility, that is, how well they dissolve in water.
- This portrait of global aerosols was produced by a GEOS-5 simulation at a 10-kilometer resolution. Dust (red) is lifted from the surface, sea salt (blue) swirls inside cyclones, smoke (green) rises from fires, and sulfate particles (white) stream from volcanoes and fossil fuel emissions.
- This portrait of global aerosols was produced by a GEOS-5 simulation at a 10-kilometer resolution. Dust (red) is lifted from the surface, sea salt (blue) swirls inside cyclones, smoke (green) rises from fires, and sulfate particles (white) stream from volcanoes and fossil fuel emissions.
- Aerosols are