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Author: Lydia Dolvin Publisher: ISBN: Category : Aerosols Languages : en Pages :
Book Description
Organic aerosols in the atmosphere have a large impact on global climate and human health. Understanding the lifetimes and fates of these organics in the atmosphere is imperative for optimizing climate models and characterizing their contributions to net atmospheric warming. The warming and cooling properties of aerosols are related to their abilities to absorb or scatter light. Brown carbon is a type of organic aerosol that is of particular interest due to its ability to absorb light in the visible range. These absorption and scattering properties can change, however, if the aerosols are subjected to photolytic or chemical aging. These aging processes are limiting factors on an aerosol’s atmospheric lifetime. In the atmosphere aerosols exist in the dry and aqueous phase. Aqueous aerosols may be found in cloud-water systems, where photolytic and chemical aging can still take place. The literature reports characterizations of different secondary organic aerosol (SOA) component lifetimes in these cloud-water systems, but often does not investigate these lifetimes in “dirty” systems where more than one type of SOA molecule exists. This overlooks the potential for interactions between aerosols of different compositions and ages. In this work, we investigate the photolytic lifetimes of 4-nitrophenol under atmospheric cloud-water conditions. We characterize these lifetimes both alone and in a mixed system with a-pinene SOA by analyzing the kinetics of 4-nitrophenol photolysis. The presence of SOA seems to have an important impact on the photolytic lifetimes of 4-nitrophenol, with fresh SOA accelerating the rate of photo-decay and aged SOA slowing it. We hypothesize that OH radicals produced as photo-products contribute to the photo-decay of this brown carbon when in a system with other organic SOA.
Author: Lydia Dolvin Publisher: ISBN: Category : Aerosols Languages : en Pages :
Book Description
Organic aerosols in the atmosphere have a large impact on global climate and human health. Understanding the lifetimes and fates of these organics in the atmosphere is imperative for optimizing climate models and characterizing their contributions to net atmospheric warming. The warming and cooling properties of aerosols are related to their abilities to absorb or scatter light. Brown carbon is a type of organic aerosol that is of particular interest due to its ability to absorb light in the visible range. These absorption and scattering properties can change, however, if the aerosols are subjected to photolytic or chemical aging. These aging processes are limiting factors on an aerosol’s atmospheric lifetime. In the atmosphere aerosols exist in the dry and aqueous phase. Aqueous aerosols may be found in cloud-water systems, where photolytic and chemical aging can still take place. The literature reports characterizations of different secondary organic aerosol (SOA) component lifetimes in these cloud-water systems, but often does not investigate these lifetimes in “dirty” systems where more than one type of SOA molecule exists. This overlooks the potential for interactions between aerosols of different compositions and ages. In this work, we investigate the photolytic lifetimes of 4-nitrophenol under atmospheric cloud-water conditions. We characterize these lifetimes both alone and in a mixed system with a-pinene SOA by analyzing the kinetics of 4-nitrophenol photolysis. The presence of SOA seems to have an important impact on the photolytic lifetimes of 4-nitrophenol, with fresh SOA accelerating the rate of photo-decay and aged SOA slowing it. We hypothesize that OH radicals produced as photo-products contribute to the photo-decay of this brown carbon when in a system with other organic SOA.
Author: Kendric Smith Publisher: Springer Science & Business Media ISBN: 1475716621 Category : Medical Languages : en Pages : 564
Book Description
The covalent attachment to deoxyribonucleic acid in vivo of a large number of different types of chemical compounds (both normal cellular constituents such as proteins and amino acids, and also exogenous compounds such as drugs, carcinogens, etc. ) have been shown to exert profound effects upon cells. Four research activi ties, formerly considered to be totally independent, relate to this problem of nucleic acid adducts--(1) normal covalent attachment of DNA to membranes, protein linkers in chromosomes, etc. ; (2) the roles of radiation and chemical enhancement of DNA adduct formation in cell killing and mutagenesis. (A related field is the use of known cross-linking reactions to gain information on structural associations in macromolecular complexes. ); (3) the relevance of DNA adducts to chemical and radiation carcinogenesis; (4) the rele vance of DNA adducts to the cross-linking theory of cellular aging. (1) There are numerous examples of normal linkages between DNA and protein, e. g. , DNA-membrane attachment sites, protein linkers in chromosomes, amino acids covalently linked to DNA as a function of growth conditions, and gene regulation by non-covalently bound proteins. A summary of data on natural adducts to DNA thus serves to introduce the subject of the radiation and chemical enhancement of DNA adduct formation. (2) In the past, radiation biology has been concerned mainly with trying to understand the radiation chemistry of purified DNA, and the biological effects and repair of these radiation-induced alterations when produced in cellular DNA.
Author: Publisher: ISBN: Category : Ecology Languages : en Pages : 1216
Book Description
This database encompasses all aspects of the impact of people and technology on the environment and the effectiveness of remedial policies and technologies, featuring more than 950 journals published in the U.S. and abroad. The database also covers conference papers and proceedings, special reports from international agencies, non-governmental organizations, universities, associations and private corporations. Other materials selectively indexed include significant monographs, government studies and newsletters.
Author: Lydia Dolvin
Author: Lydia Dolvin
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Author: Kendric Smith
Author: Paul Brent Hatzinger
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Author: Masayuki Nakagawa
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Author: U.S. Fish and Wildlife Service
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