Beta

Slashdot: News for Nerds

×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

This is required

ankhank (756164) writes | more than 9 years ago

User Journal

PERSISTENT TRANS-PACIFIC TRANSPORT CAUSES ASIAN AEROSOLS TO DOMINATE THE "BACKGROUND" AEROSOL OVER NORTH AMERICA.

Print: Print this page
PERSISTENT TRANS-PACIFIC TRANSPORT CAUSES ASIAN AEROSOLS TO DOMINATE THE "BACKGROUND" AEROSOL OVER NORTH AMERICA.
R. VanCuren(1); S. Cliff (2); K. Perry(3);

PERSISTENT TRANS-PACIFIC TRANSPORT CAUSES ASIAN AEROSOLS TO DOMINATE THE "BACKGROUND" AEROSOL OVER NORTH AMERICA.

Print: Print this page
PERSISTENT TRANS-PACIFIC TRANSPORT CAUSES ASIAN AEROSOLS TO DOMINATE THE "BACKGROUND" AEROSOL OVER NORTH AMERICA.
R. VanCuren(1); S. Cliff (2); K. Perry(3);

(1)California Air Resources Board, Research Division, 1001 I St. Box 2815 Sacramento, CA 95812, United States
(2)University of California, Applied Science, 1 Shields Ave. Davis, CA 95616, United States
(3)University of Utah, Meteorology, University of Utah WILLIAM BROWNING 135 S 1460 EAST RM 819 Salt Lake City, Utah 84112, United States
(rvancure@arb.ca.gov)

Six weeks of continuous size- and time- resolved aerosol sampling conducted for the Intercontinental Transport and Chemical Transformation 2002 Study (ITCT-2K2) and analyses of a decade of twice-weekly aerosol sampling by a network that spans North America combine to show that Asian aerosols are a dominant component of the "background" over extra-tropical North America. Integrating the ITCT-2K2 findings with the long term record shows that: 1) Asian aerosols are only infrequently observed at sea level while unmodified marine aerosols are very rare at elevated near-coastal sites; 2) aerosols collected at elevated sites in western North America are persistently of Asian continental origin, with concentrations strongly modulated by synoptic meteorology; 3) Asian aerosols are regularly present at remote sites across North America, often overwhelming local aerosol sources. We conclude that, except during winter cyclonic storms, lower free troposphere aerosol concentrations are modulated by synoptic meteorology, but the source material remains predominantly continental. These data refute an episodic characterization of transPacific transport and show that the aerosols in the lower free troposphere over the northeastern Pacific Ocean and western North America are dominated by continental outflow from Asia, with little or no marine influence and only weak North American contributions. These findings have important implications for projecting trends in North American air quality and for understanding the role of anthropogenic aerosols in modulating the radiant energy balance over North America.

-------
Print: Print this page
CONSEQUENCES OF THE ANTHROPOGENIC ACTIVITIES ON THE RAINWATER CHEMISTRY IN THE TROPICS
L.B.L.S. Lara(1); P. Artaxo(2); L.A. Martinelli(1); E.A. Holland(3); T. Pauliquevis(2); P.B. Camargo(1); V.P. Silveira(1);

(1)USP, CENA, Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Av: Centenário 303, 13416-000, SP, Brazil, Brazil
(2)USP, IF, Instituto de Física, Universidade de São Paulo, Rua do Matão, Travessa R, 187, CEP 05508-900, São Paulo, S.P., Brazil, Brazil
(3)NCAR, ACD, Atmospheric Chemistry Division, National Center for Atmospheric Research, PO Box 3000, Boulder, CO, USA 80307 , United States
(luciene@cena.usp.br)

The atmospheric deposition of chemical species within the Earth's ecosystems not only provides a natural sink but also acts as a source of nutrients and plays an essential role in controlling the biogeochemical cycles of carbon and nitrogen. In the tropics, the intense land-use changes followed by rapid urbanization, associated with a large industrial expansion are possibly altering the atmospheric chemistry. Indeed, the acidification of precipitation and subsequent high N deposition rates has been taken place in disturbed regions in Brazil. In order to investigate the relationship between land cover and atmospheric chemistry we collected rainwater samples in different sites in Southern Brazil and in Amazon Basin. Land cover and land-use changes are probably responsible for the spatial variability found in precipitation chemistry. As a consequence of the anthropogenic activities significant rainfall acidity was detected (VWM pH = 4.5). The origin of the free acidity in rainwater is different in each site and come out to be linked to the land cover. Organic acids appear to control the acidity in remote areas while in other sites inorganic acidity has been detected. In addition, nitrogen deposition was significantly higher in the disturbed sites and DOC (Dissolved organic carbon) deposition was significantly lower in these sites. According to the Factor and Cluster Analyses, the composition of rainwater in the disturbed sites appears to be controlled mostly by two sources: biomass burning and industrial emissions, and in the remote areas by biogenic emissions and marine influence. If the anthropogenic activities continues to accelerate at the present rate, in a few years, significant regional biogeochemical cycles changes can be expected and, also alterations in the regional climate with possible global impacts.

-----
Print: Print this page
Chemical-looping combustion for the production of clean energy from methane and an oxygen carrier reaction
Sebastien Roux(1);

(1)UMR CNRS 6067 GPI UTC, Centre de Recherche de Royallieu COMPIEGNE 60200, France
(sebastien.roux@utc.fr)

Increasing amounts of CO2 released to the atmosphere can promote the natural greenhouse effect, and so affect the global climate. The use of chemical-looping combustion could be an option for reducing emissions of this greenhouse effect gas in atmosphere by using fossil fuels, as energy source, by separating and disposing CO2 from flue gas. In this process, metal oxide is used to transfer oxygen to fuel for its combustion and thus, the flue gas issued from the combustion is composed exclusively of CO2 and H2O, which could be separated without any energy lost, by condensation of water. The metal obtained from the combustion is regenerated in a second reactor using air, and recycled. In chemical-looping combustion, it is important that the metal oxide, which is used as an oxygen carrier, has a sufficient reduction and oxidation rate and should be enough strength to limit particle breakage ; it is also an advantage if the metal oxide is cheap and environmentally sound. In this study, a number of different metals and their corresponding oxides were tested and their feasibility was investigated. The kinetics study of oxidation and reduction of respectively the metals, using atmospheric air and metals oxide, using methane was realised in a fixed bed reactor. The performance of each reagent was evaluated and their reactivity was compared. The parameters obtained are closely related and could be used to design a chemical-looping combustion system based on two interconnected reactors.

--------

Print: Print this page
APPORTIONMENT OF SOURCES OF ATMOSPHERIC AEROSOL IN THE EASTERN US
A.V. Polissar(1);

(1)New Jersey Department of Environmental Protection, Division of Science, Research and Technology, PO BOX 409, Trenton, NJ 08625-0409, United States
(alexander.polissar@dep.state.nj.us)

Analysis of aerosol chemical composition data from several National Park Serving sampling locations in the Eastern US was performed. The data has been analyzed by an advanced factor analysis method, three-way positive matrix factorization (PMF3), by pooling several data sets into one large three-way array. A variety of sources of aerosol have been identified. They were related to soil particles, sea salt, long range transported sulfate particles from coal combustion, aerosol from oil combustion, secondary sulfate aerosol, secondary organic carbon, elemental carbon, as well as particles with high loadings of nitrates, and Zn-Cu. Potential Source Contribution Function (PSCF) method was applied to identify possible source areas. It is concluded that emissions from different anthropogenic activities and the secondary aerosol production are the main sources of fine particles measured in the Eastern US. It was found that sulfate aerosol from coal combustion in the Midwestern United States account for more than 50% of annual average fine mass. The study indicated that the combination of the two receptor modeling methods, PMF3 and PSCF, provides an effective way in identifying possible aerosol sources and their likely locations.

----

cancel ×

comment

Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Create a Slashdot Account

Loading...