Soot From Ships Worse Than Expected
WASHINGTON—Large cargo ships emit more than twice as much soot as previously estimated, and tugboats puff out more soot for the amount of fuel used than other commercial vessels, according to the first extensive study of commercial vessel emissions.
In the Arctic, an increase in soot may contribute to climate change if shipping routes expand, according to the study.
Oceangoing tankers and container ships emit half a gram of soot per kilogram of fuel burned when at dock and slightly less when traveling, according to scientists from the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado (CU) who conducted the new study. Tugs emit nearly a gram of soot per kilogram of fuel burned—twice as much as any other vessel type, the authors find.
"Tugboats are a huge source of black carbon that may be under-reported or not reported at all in emissions inventories compiled by ports," says the study lead author Daniel Lack of NOAA's Earth System Research Laboratory and the NOAA-CU Cooperative Institute for Research in Environmental Sciences.
He and his colleagues will present their findings on 11 July 2008 in Geophysical Research Letters, a journal of the American Geophysical Union, or AGU.
Commercial shipping releases roughly 130, 000 metric tons of soot per year, or 1.7 percent of the global total—much of it near highly populated coastlines, the authors estimate. In the coming years global shipping is expected to grow two to six percent annually.
Exceptionally high soot levels from tugboats point to their low-quality fuel—a thick, black tar left over from crude oil after the gasoline and kerosene have been removed. Engine age and maintenance also play a role. Tugboats have a disproportionate impact on air quality because they travel within ports, emitting potentially harmful particles near populous urban areas, according to the authors.
To investigate ship emissions, the researchers observed plumes from commercial vessels in open ocean waters, channels, and ports along the southeastern United States and Texas during the summer of 2006. From the NOAA research vessel, Ronald H. Brown, the team measured black carbon emitted by tankers, cargo and container ships, large fishing boats, tug boats, and ferries, many of them in the Houston Ship Channel.
"Commercial shipping emissions have been one of the least studied areas of all combustion emissions," says Lack. "The two previous studies of soot emissions examined a total of three ships. We reviewed plumes from 96 different vessels."
A 2007 study by American and German scientists linked particle pollution from shipping to tens of thousands of premature deaths each year, most of them along coastlines in Europe, East Asia, and South Asia. Soot makes up a quarter of that pollution, says Lack.
The primary sources of soot, or small particles of black carbon, are fossil fuel combustion, wildfires, and burning vegetation for agricultural purposes. On a global scale, soot currently traps about 30 percent as much heat as does carbon dioxide, the most important greenhouse gas, according to the latest assessment of the Intergovernmental Panel on Climate Change.
Small dark soot particles absorb sunlight, create haze, and affect how clouds form and make rain, further altering a region’s heat balance, according to the new study. If commercial shipping extends new routes through Arctic waters as they become navigable, soot emissions there could increase.
The NOAA program for climate change funded this study.
Notes for Journalists
As of the date of this press release, this study by Lack and his colleagues is still "in press" (i.e. not yet published). However, you may receive the final, copy-edited and formatted PDF of the paper by emailing your request to Peter Weiss at pweiss@agu.org. Please provide your name, the name of your media outlet, and your phone number.
From now through 10 July, journalists and public information officers (PIOs) of educational and scientific institutions who have registered with AGU can directly download a PDF copy of a manuscript of this paper by clicking on this link: http://www.agu.org/journals/pip/gl/2008GL033906-pip.pdf
Beginning Friday, 11 July, registered news media and PIOs may directly download the final, copy-edited and formatted PDF of the paper by clicking on the following link: http://dx.doi.org/10.1029/2008GL033906
(If you need instructions for downloading, please see: http://www.agu.org/jinstructions.shtml)
Neither the paper nor this press release are under embargo.
Images:
Available for download at http://www.noaanews.noaa.gov/stories2008/20080709_soot.html are print-quality, high-resolution images: one of researcher Daniel Lack standing in front of the ship on which the study was conducted, and the other of tugboats with a cargo ship.
Title:
"Light absorbing carbon emissions from commercial shipping"
Authors:
Daniel Lack, Brian Lerner, Claire Granier, Edward Lovejoy, Paola Massoli, A. R. Ravishankara, and Eric Williams: NOAA Earth System Research Laboratory, Boulder, Colorado, USA; Lack, Lerner, Granier, Massoli, and Williams also at Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA.
Granier also at Service d'Aéronomie, CNRS, Université Pierre et Marie Curie-Paris 6, UMR7620, Paris, France.
Tahllee Baynard is at LockheedMartin Coherent Technologies, Longmont, Colorado,USA; Baynard had been at NOAA Earth System Research Laboratory, Boulder, Colorado, USA, and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA.
Citation:
Lack, D., B. Lerner, C. Granier, T. Baynard, E. Lovejoy, P. Massoli, A. R. Ravishankara, and E. Williams (2008), Light absorbing carbon emissions from commercial shipping, Geophys. Res. Lett., 35, L13815, doi:10.1029/2008GL033906.
Contact information for coauthors:
Daniel Lack, atmospheric scientist, NOAA Earth System Research Laboratory and Cooperative Institute for Research in Environmental Sciences, +1 (802) 338-1250 (Wed., 9 July), +1 (720) 635-2039 (starting 10 July), office +1 (303) 497-5820, daniel.lack@noaa.gov
A.R. Ravishankara, Director, Chemical Sciences Division, NOAA Earth System Research Laboratory, +1 (303)-497-5821 a.r.ravishankara@noaa.gov
