EGU General Assembly 2008
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  Information - AS3.18 Importance of aerosol water uptake and organic nitrogen compounds (co-listed in BG)

Event Information

Aerosol water can affect weather and climate through alterations of the Earth’s radiation budget. In turn, aerosol water is affected by air pollution and depends on thermodynamics. Anthropogenic emissions can be directly linked to visibility reduction, cloud formation and climate forcing, if aerosol water mass is explicitly accounted for. Under ambient conditions the equilibrium relative humidity (ERH) determines the saturation molality, solute and solvent activities and the aerosol water mass, since the water content is fixed by ERH for a given aerosol concentration and type. As a consequence, aerosol water drives the gas/liquid/solid aerosol partitioning, ambient aerosol size-distributions and directly links aerosol hygroscopic growth into fog, haze and cloud formation.


Up to date, most studies about fixed nitrogen in atmospheric gaseous and condensed phases have focused on inorganic species (nitrite, nitrate and ammonium), and relatively little is known about atmospheric organic nitrogen (AON) compounds. AON include organic nitrates (mainly peroxyacetyl nitrate (PAN) and related species) that are the oxidized end products of reactions of hydrocarbons with NOx (NO + NO2) in polluted air masses, marine and terrestrial sources of reduced (amino acid) N, and biological and particulate forms of organic N including bacteria, dust particles and pollen. AON has been measured in dry deposition, precipitation, cloud waters, fogwaters, and atmospheric particles. The ubiquity of these compounds suggests that they might play important roles for the effects of PM2.5 on visibility, climate, and human health and the biogeochemical cycling of N. Organic nitrates are estimated to constitute more than 50% of the total atmospheric NOy. PAN and related species were found to be taken up by plant stomata and cuticles, which has important implications for balancing global and regional N cycles. Experimental results suggest that current models underestimate deposition velocities of PAN by a factor of four to five.

Session focus: modeling, field, laboratory and satellite studies about aerosol water, hygroscopic growth and water uptake of atmospheric aerosols, and its link with weather and climate, in-situ measurements of organic N compounds (e.g., dry deposition, precipitation, cloud water, fog water and aerosols).

Preliminary List of Solicited Speakers
John Neil Cape
Centre for Ecology & Hydrology

Jeffrey L. Collett, Jr
Atmospheric Chemistry / Air Quality Program
Department of Atmospheric Science
Colorado State University


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