Sunday, February 25, 2007

Chemistry of Atmospheric Aerosols

In recent years, the role of atmospheric aerosols is being increasingly recognized both in climate system of Earth and in global biogeochemical cycle. Aerosols affect the radiative balance of the Earth directly by scattering or absorbing incoming shortwave radiation and indirectly by acting as cloud condensation nuclei, altering a temperature effect at the surface because of changes in cloud cover. In addition, aerosol particles are closely coupled to atmospheric chemistry as chemical reactions in the atmosphere are often accelerated on aerosol surfaces. Also, the chemistry of aerosols may alter their physical and optical properties such as size distribution (fine to coarse) due to interaction between acidic (sulpahte, nitrate) and alkaline (mineral dust) aerosols; single scattering albedo (because of coating of one type of aerosols over other); and surface properties (hydrophilic/hydrophobic), and thus, their direct and indirect effects on climate change. Long range transport and deposition of atmospheric aerosols facilitate the export of nutrients (such as nitrate, phosphate and iron) to and across the oceans which is major source of nutrients as well as limiting factor for primary productivity (or phytoplankton growth) in remote oceans. These phytoplanktons produce biogenic sulfate (via dimethylsulhide), which is the major source of sulfate aerosols over remote oceans.
Also, aerosols are integral part of air pollution and to diagnose and cure the diseases caused by aerosols, the knowledge of their chemical composition is essential. Thus, in order to better understand the effects of aerosols on climate and human health, their physical and chemical properties shall be studied together. For more insight, please see following references:
Andreae, M. O., and P. J. Crutzen (1997), Atmospheric aerosols: Biogeochemical sources and role in atmospheric chemistry, Science, 276, 1052– 1058.
Dentener, F. J., G. R. Carmichael, Y. Zhang, J. Lelieveld, and P. J. Crutzen (1996), Role of mineral aerosol as a reactive surface in the global troposphere, J. Geophys. Res., 101, 22,869–22,889.
Jordan, C. E., J. E. Dibb, B. E. Anderson, and H. E. Fuelberg (2003), Uptake of nitrate and sulfate on dust aerosols during TRACE-P, J. Geophys. Res., 108(D21), 8817, doi:10.1029/2002JD003101.
Rastogi, N., and M. M. Sarin (2006), Chemistry of aerosols over a semi-arid region: Evidence for acid neutralization by mineral dust, Geophys. Res. Lett., 33, L23815, doi:10.1029/2006GL027708.
Tabazadeh, A., M. Z. Jacobson, H. B. Singh, O. B. Toon, J. S. Lin, R. B. Chatfield, A. N. Thakur, T. W. Talbot, and J. E. Dibb (1998), Nitric acid scavenging by mineral and biomass burning aerosols, Geophys. Res. Lett., 25, 4185–4188.
Zhuang, H., C. K. Chan, M. Fang, and A. S. Wexler (1999), Formation of nitrate and non-sea-salt sulfate on coarse particles, Atmos. Environ., 33, 4223– 4233.

Wednesday, February 21, 2007

Absorption by aerosol - Comprehensive bibliography

Friends! I was looking for something important to write about aerosol and stumble upon this web-site.

Absorption references:
  • ...
  • Ganguly,D., Jayaraman,A., Gadhavi,H., Rajesh,T., Features in wavelength dependence of aerosol absorption observed over central India, Geophys.Res.Lett., Vol.32, L13821, doi:10.1029/2005GL023023, 2005.
  • Moorthy,K., Satheesh,S., Babu,S., Saha,A., Large latitudinal gradients and temporal heterogeneity in aerosol black carbon and its mass mixing ratio over southern and northern oceans observed during a trans-contiental cruise experiment, Geophys.Res.Lett., Vol.32, L14818, doi:10.1029/2005GL023267, 2005.
  • Wang,G., Bai,J., Kong,Q., Emilenko,A., Black carbon particles in the urban atmosphere in Beijing, Advances in Atmospheric Sciences, Vol.22, No.5, pp.640-646, 2005."
  • ...
Well well! you got it! I was doing ego search and found out this web-site. Nevertheless my first statement remains true. This web-page contains well organized and exhaustive list of references pertaining to aerosol absorption. Active researchers studying atmospheric aerosols can hardly afford not to bookmark it. And more importantly author of the page provides list in latex format. Cheers LaTeX users! Did I mentioned that web-page contains more than 400 references? If you don't know what efforts one requires to create such a long bibliography, get counseling from Jorge Cham here.

The web-page is maintained by Sandra Mogo. I guess this is a woman's name. If I am wrong I apologize in advance. Her PhD thesis is about optical methods for the measurement of absorption by atmospheric aerosols. She has participated in many GOA campaigns e.g. GOA Aerosol Arctic Campaigns, GOA Winter Aerosol Arctic Campaing, GOA LIDAR and Arctic Aerosol campaign, etc. First I thought this may be because of her Portuguese background. But then I thought when did in India these many aerosol campaigns launched from Goa. And if so how I missed all of them. I searched the whole world to find out this abbreviation, of cause that means I used Yahoo and Google both instead of only Google to search. But I couldn't find answer. At last on her page I found a logo that told GOA is GRUPO DE ÓPTICA ATMOSFÉRICA. Her home-page can be reached here in case you want to send a thank you e-mail, however better way to thank her would be include her articles in your bibliography which are not mentioned in her list of 400+.

Wednesday, February 14, 2007

Aerosols, Air Pollution and Health

Atmospheric aerosols or particulate matter (PM) are one of the most important components of the earth-atmosphere system and play important role in climate and weather related processes. Apart from climate, aerosols also have an impact on entire living biota on planet earth. Impact of air pollution on human health is of most concern in current time. Air pollution has both short-term and long-term effects. Short terms impacts includes, respiratory infections, irritation to the eyes, nose and throat, headaches, nausea, and allergic reactions. Short-term air pollution can intensify the medical conditions of individuals with asthma and emphysema. In 1952 London experienced one of the worst smog disasters, which killed more than four thousand people in few days due to very high concentration of particulate matter in the air. Long-term effects include lung cancer, heart disease, chronic respiratory disease, and even damage to the brain, nerves, liver, or kidneys. Continual contact to air pollution affects the lungs of growing children and may worsen or complicate medical conditions in the elderly. The World Health Organization estimates that 4.6 million people die each year from causes directly attributable to air pollution. Worldwide more deaths per year are linked to air pollution than to automobile accidents. Some examples from all around the world; approximately 310,000 Europeans die from air pollution annually, The Tata Energy Research Institute in India estimated 18, 600 premature deaths per year associated with poor air quality in the Delhi region, Increased PM was associated with 2400 deaths per year in Australia with an associated health cost of $17.2 billion and Sydney experiences around 400 premature mortalities each year due to increased levels of pollution and asthma is also common in this area. Similar mortality deaths are associated with air pollution in other parts of the world. Using statistical data collected in twenty big cities of the United States show that the daily mortality within a metropolitan area is associated with concurrent or lagged daily fluctuations in ambient PM concentrations. Apart from impact on human health, poor air quality also affects the health of animals and plants. Poor air quality conditions are also associated with damaging buildings and monuments around the world. Indirectly air pollution significantly affects the economy by increasing medical expenditures and preservation of the surrounding environment.

Saturday, February 10, 2007

Atmospheric Aerosols: What Are They, and Why Are They So Important

Atmospheric Aerosols: What Are They, and Why Are They So Important

More often than not, we (researchers in atmospheric aerosol field) have to answer questions from laymen about atmospheric aerosols such as what are they made up, how are they produced and removed, what is their importance in atmospheric research, etc. If you have ever faced difficulty answering these questions above web-site is for you. Explanations are very simple with nice pictures and without any technical jargon.