scholarly journals Atmospheric transport of persistent semi-volatile organic chemicals to the Arctic and cold condensation in the mid-troposphere – Part 2: 3-D modeling of episodic atmospheric transport

2010 ◽  
Vol 10 (15) ◽  
pp. 7315-7324 ◽  
Author(s):  
L. Zhang ◽  
J. Ma ◽  
C. Tian ◽  
Y. Li ◽  
H. Hung
Keyword(s):  
Atmospheric Circulation ◽  
Atmospheric Transport ◽  
The Arctic ◽  
Organic Chemicals ◽  
High Latitudes ◽  
Volatile Organic ◽  
Volatile Organic Chemicals ◽  
Cold Condensation ◽  
Condensation Effect ◽  
Modeling Study

Abstract. Two 3-dimensional global atmospheric transport models for persistent organic pollutants (POPs) have been employed to investigate the association between the large-scale atmospheric motions and poleward transports of persistent semi-volatile organic chemicals (SVOCs). We examine the modeled daily air concentration of α- and γ-hexachlorocyclohexane (HCH) over a period from 1997 through 1999 during which a number of episodic atmospheric transport events were detected in this modeling study. These events provide modeling evidence for improving the interpretation on the cold condensation effect and poleward atmospheric transport of SVOCs in the mid-troposphere. Two episodic transport events of γ-HCH (lindane) to the high Arctic (80–90° N), one from Asian and another from Eurasian sources, are reported in this paper. Both events suggest that the episodic atmospheric transports occurring in the mid-troposphere (e.g. from 3000 m to 5500 m height) are driven by atmospheric horizontal and vertical motions. The association of the transport events with atmospheric circulation is briefly discussed. Strong southerly winds, forced by the evolution of two semi-permanent high pressure systems over mid-high latitudes in the Northern Hemisphere, play an important role in the long-range transport (LRT) of HCHs to the high latitudes from its sources. Being consistent with the cold condensation effect and poleward atmospheric transport in a mean meridional atmospheric circulation simulated by a 2-D atmospheric transport model, as reported by the first part of this study, this modeling study indicates that cold condensation is likely occurring more intensively in the mid-troposphere where rapid declining air temperature results in condensed phase of the chemical over and near its source regions and where stronger winds convey the chemical more rapidly to the polar region during the episodic poleward atmospheric transport events.

scholarly journals Atmospheric transport of persistent semi-volatile organic chemicals to the Arctic and cold condensation at the mid-troposphere – Part 2: 3-D modeling of episodic atmospheric transport

2009 ◽  
Vol 9 (6) ◽  
pp. 26237-26264 ◽  
Author(s):  
◽  
◽  
◽  
Keyword(s):  
Atmospheric Circulation ◽  
Atmospheric Transport ◽  
The Arctic ◽  
Organic Chemicals ◽  
High Latitudes ◽  
Volatile Organic ◽  
Volatile Organic Chemicals ◽  
Cold Condensation ◽  
Condensation Effect ◽  
Modeling Study

Abstract. Two 3-dimensional global atmospheric transport models for persistent organic pollutants (POPs) have been employed to investigate the association between the large-scale atmospheric motions and poleward transports of persistent semi-volatile organic chemicals (SVOCs). We examine the modeled daily air concentration of α- and γ-hexachlorocyclohexane (HCH) over a period from 1997–1999 during which a number of episodic atmospheric transport events were detected in this modeling study. These events provide modeling evidence for improving the interpretation on the cold condensation effect and poleward atmospheric transport of SVOCs at the mid-troposphere. Two episodic transport events of γ-HCH (lindane) to the high Arctic (80–90° N), one from Asian and another from Eurasian sources, are reported in this paper. The both events suggest that the episodic atmospheric transports occurring at the mid-troposphere (e.g. from 3000–5500 m height) are driven by atmospheric horizontal and vertical motions. The association of the transport events with atmospheric circulation is briefly discussed. Strong southerly winds, forced by the evolution of two semi-permanent high pressure systems over mid-high latitudes in the Northern Hemisphere, play an important role in the long-range transport (LRT) of HCHs to the high latitudes from its sources. Being consistent with the cold condensation effect and poleward atmospheric transport in a mean meridional atmospheric circulation simulated by a 2-D atmospheric transport model, as reported by the first part of this study, this modeling study indicates that cold condensation is likely occurring more intensively at the mid-troposphere where rapid declining air temperature results in condensed phase of the chemical over and near its source regions and where stronger winds convey the chemical more rapidly to the polar region during the episodic poleward atmospheric transport events.

scholarly journals Atmospheric transport of persistent semi-volatile organic chemicals to the Arctic and cold condensation in the mid-troposphere – Part 1: 2-D modeling in mean atmosphere

2010 ◽  
Vol 10 (15) ◽  
pp. 7303-7314 ◽  
Author(s):  
J. Ma
Keyword(s):  
Atmospheric Circulation ◽  
Aqueous Phase ◽  
Atmospheric Transport ◽  
Lower Atmosphere ◽  
The Arctic ◽  
Organic Chemicals ◽  
Volatile Organic ◽  
Volatile Organic Chemicals ◽  
Cold Condensation ◽  
Condensation Effect

Abstract. In the first part of this study for revisiting the cold condensation effect on global distribution of semi-volatile organic chemicals (SVOCs), the atmospheric transport of SVOCs to the Arctic in the mid-troposphere in a mean meridional atmospheric circulation over the Northern Hemisphere was simulated by a two-dimensional (2-D) atmospheric transport model. Results show that under the mean meridional atmospheric circulation the long-range atmospheric transport of SVOCs from warm latitudes to the Arctic occurs primarily in the mid-troposphere. Although major sources are in low and mid-latitude soils, the modeled air concentration of SVOCs in the mid-troposphere is of the same order as or higher than that near the surface, demonstrating that the mid-troposphere is an important pathway and reservoir of SVOCs. The cold condensation of the chemicals is also likely to take place in the mid-troposphere over a source region of SVOCs in warm low latitudes through interacting with clouds. We demonstrate that the temperature dependent vapour pressure and atmospheric degradation rate of SVOCs exhibit similarities between lower atmosphere over the Arctic and the mid-troposphere over a tropical region. Frequent occurrence of atmospheric ascending motion and convection over warm latitudes carry the chemicals to a higher altitude where some of these chemicals may partition onto solid or aqueous phase through interaction with atmospheric aerosols, cloud water droplets and ice particles, and become more persistent at lower temperatures. Stronger winds in the mid-troposphere then convey solid and aqueous phase chemicals to the Arctic where they sink by large-scale descending motion and wet deposition. Using calculated water droplet-air partitioning coefficient of several persistent organic semi-volatile chemicals under a mean air temperature profile from the equator to the North Pole we propose that clouds are likely important sorbing media for SVOCs and pathway of the cold condensation effect and poleward atmospheric transport. The role of deposition and atmospheric descending motion in the cold condensation effect over the Arctic is also discussed.

scholarly journals Atmospheric transport of persistent semi-volatile organic chemicals to the Arctic and cold condensation at the mid-troposphere – Part 1: 2-D modeling in mean atmosphere

2010 ◽  
Vol 10 (1) ◽  
pp. 453-489 ◽  
Author(s):  
J. Ma
Keyword(s):  
Transport Model ◽  
Atmospheric Transport ◽  
Lower Atmosphere ◽  
The Arctic ◽  
Tropical Region ◽  
Organic Chemicals ◽  
Volatile Organic ◽  
Volatile Organic Chemicals ◽  
Cold Condensation ◽  
Condensation Effect

Abstract. In the first part of this study for revisiting the cold condensation effect on global distribution of semi-volatile organic chemicals (SVOCs), the atmospheric transport of SVOCs to the Arctic at the mid-troposphere in a mean meridional atmospheric circulation over Northern Hemisphere was simulated by a two-dimensional atmospheric transport model. Results show that under the mean meridional atmosphere the long-range atmospheric transport of SVOCs from warm latitudes to the Arctic occurs primarily at the mid-troposphere. Accordingly, the cold condensation of the chemicals is likely also to take place at the mid-troposphere over a source region of the chemicals in warm low latitudes. We demonstrate that the temperature dependent vapour pressure and atmospheric degradation rate of SVOCs exhibit similarities between lower atmosphere over the Arctic and the mid-troposphere over a tropical region. Frequent occurrence of atmospheric ascending motion and convection over warm latitudes carry the chemicals to a higher altitude where some of these chemicals may condense/partition to particle or aqueous phase through the interaction with atmospheric aerosols, cloud water droplets and ice particles, and become more persistence in the lower temperatures. Stronger winds at the mid-troposphere then convey the condensed chemicals to the Arctic where they are brought down to the surface by large-scale descending motion and wet deposition. Using calculated water droplet-air partitioning coefficient of several persistent organic semi-volatile chemicals under a mean air temperature profile from the equator to the North Pole we propose that clouds are likely important sorbing media for SVOCs and pathway of the cold condensation effect and poleward atmospheric transport. The role of deposition and atmospheric descending motion in the cold condensation effect over the Arctic was also discussed.

Dermal absorption of neat and aqueous volatile organic chemicals in the fischer 344 rat

1991 ◽  
Vol 55 (1) ◽  
pp. 51-63 ◽  
Author(s):  
D.L. Morgan ◽  
S.W. Cooper ◽  
D.L. Carlock ◽  
J.J. Sykora ◽  
B. Sutton ◽  
...  
Keyword(s):  
Dermal Absorption ◽  
Organic Chemicals ◽  
Fischer 344 ◽  
Fischer 344 Rat ◽  
Volatile Organic ◽  
Volatile Organic Chemicals

scholarly journals Neem and the Environment

2018 ◽  
Vol 4 (01) ◽  
pp. 01-09
Author(s):  
Rajendra Prasad ◽  
Samendra Prasad
Keyword(s):  
Nitrous Oxide ◽  
Azadirachta Indica ◽  
C Sequestration ◽  
Agricultural Fields ◽  
Organic Chemicals ◽  
N2o Production ◽  
Fertilizer Nitrogen ◽  
Volatile Organic ◽  
Volatile Organic Chemicals ◽  
Surface And Groundwater

Neem ( Juss) can play a key role in C-sequestration, Azadirachta indica reducing nitrous oxide (N2O) production from the agricultural fields, checking desertification and reducing nitrate eutrophication of surface and groundwater due to fertilizer nitrogen. Neem is a shady tree and reduces temperature of the micro environment under it. Neem also contains a large number of volatile organic chemicals (VOCs) that may purify the air around the tree; this is in addition to production of oxygen during the day as most trees and plants do.

scholarly journals Quantitation by Portable Gas Chromatography: Mass Spectrometry of VOCs Associated with Vapor Intrusion

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Justin D. Fair ◽  
William F. Bailey ◽  
Robert A. Felty ◽  
Amy E. Gifford ◽  
Benjamin Shultes ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Analytical Method ◽  
Gas Chromatography Mass Spectrometry ◽  
Organic Chemicals ◽  
Vapor Intrusion ◽  
Reliable Technique ◽  
Precise Identification ◽  
Volatile Organic ◽  
Volatile Organic Chemicals

Development of a robust reliable technique that permits for the rapid quantitation of volatile organic chemicals is an important first step to remediation associated with vapor intrusion. This paper describes the development of an analytical method that allows for the rapid and precise identification and quantitation of halogenated and nonhalogenated contaminants commonly found within the ppbv level at sites where vapor intrusion is a concern.

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