Thursday, September 13, 2007

Questionable paper in Science on carbon emissions

The 7 Sept 07 issue of Science has a paper titled "20th-Century Industrial Black Carbon Emissions Altered Arctic Climate Forcing," by Joseph R. McConnell, et al. [317 Science 1381]. Within the abstract, one has: Beginning about 1850, industrial emissions resulted in a sevenfold increase in ice-core BC [black carbon] concentrations, with most change occurring in winter.

The paper does NOT define the term black carbon, and one infers "black carbon" is whatever the "laser based atmospheric analyzer" says it is. To distinguish "black carbon" arising from biomass (e.g., forest fires) from black carbon from burning of coal, the paper relies on non-sea-salt sulfur (nss-S). The paper does not recognize that the amount of sulfur in combustion soots depends greatly on the amount of sulfur in the initial fuel, which is different amoung coals (compare anthracite (low S) to some bituminous coals (high S) to lignites and peats) and is different for petroluem-based fuels again (typically much lower than for some bituminous coals).

Supporting material is stated to be at

This supporting material mentions a BC analyzer (SP2 from Droplet Measurement Technologies). This seems to be directed to measuring number of particles and their sizes, but NOT what the particles are comprised of. The method is based on laser-induced incandescence. The mass of the particles is proportional to the area of the incandescence signal. A highly problematic aspect is this: the SP2 machine was calibrated against glassy carbon of known density. IPBiz notes that glassy carbon possesses physical and chemical properties TOTALLY UNLIKE those of combustion soots. Different density, different porosity, different chemical composition. Thus, the results of the McConnell paper on "industrial black carbon emissions" are based on a calibration to something unlike an "industrial black carbon emission."

The McConnell supplementary material has a most interesting footnote, S12, which is to M. Stephens, N. Turner, and J. Sandberg, Appl. Optics, 42, 3726 (2003) even though the McConnell text for this footnote states "The SP2 uses a patented technique (S12)..."

For those interested, the involved patent is US 5,920,388 titled Small particle characteristic determination assigned to Research Electro-Optics, Inc.

The first claim is

A device for small particle characteristic determination, said device comprising:

a region capable of having the small particles thereat with at least a portion of the small particles being optically absorbing particles;

a high intensity laser light source including a laser cavity having said region within said laser cavity, said high intensity laser light source providing laser light at said region for contact with the small particles thereat to cause heating of said optically absorbing particles to incandescence at said region to cause resulting light to be emitted from within said region where said heating occurs with said resulting light being indicative of said heating to incandescence of said optically absorbing particles; and

at least one optical detecting unit for sensing said resulting light emitted from within said region where said heating occurs thereby enabling predetermined particle characteristic determination, other than size determination, of the small particles.

The '388 patent is cited by US 7,167,240, titled Carbon black sampling for particle surface area measurement using laser-induced incandescence and reactor process control based thereon. The '240 patent contains the text:

Laser-induced incandescence (LII) has been used as a soot diagnostic technique since about the 1980s. The basic principle of LII is to rapidly heat up particles with ultra-short laser pulses (laser pulse is typically <20 ns duration) of high energy. Particle temperature is increased to a point to produce significant incandescence of the particle, or even up to vaporization temperature (for carbon blacks, about 4000 K). Particles lose this added energy via 3 paths: vaporization, heat conduction to the surrounding medium, and thermal radiation. The enhanced thermal radiation is then detected (emission signal). The incandescence from the particles is measured using collection optics and photo detectors. Using appropriate calibration and analysis of the incandescence signal, information such as the soot volume fraction (svf) or the primary soot particle size may be obtained. The method is essentially non-intrusive and is capable of making in-situ measurements.

LII measurement is an emerging technology that has promise to be a reliable means for spatially and temporally measuring the concentration of carbonaceous particles and their spherule size. LII has been developed primarily for monitoring particulate emissions produced by combustion of hydrocarbon fuels. In the past 10 years or so, academic researchers have utilized LII to resolve spatial concentrations of soot in laboratory flames and diesel engines (See, e.g., Dec, J. E., zur Loye, A. O., and Siebers, D. L., "Soot distribution in a D.I. Diesel Engine Using 2-D Laser Induced Incandescence Imaging," SAE Transactions, 100, pp. 277 288, 1991).

LII is suitable for soot particulate measurements since the LII signal is proportional to particulate volume faction over a wide dynamic range. LII provides a relative measure of soot concentrations and requires a calibration for quantification of soot particulate concentrations. LII has been used to measure soot particle volume fraction in steady-state and time-varying diffusion flames, premixed flames within engines and in diesel engine exhaust streams, and gas turbine exhausts. These LII applications are with relatively dilute (low concentration) streams of soot.

Recently, a technique for performing absolute light intensity measurement in LII has been presented, thus avoiding the need for a calibration in a source of soot particulates with a known concentration (U.S. Pat. No. 6,154, 277), and, thus, extending the capabilities of LII for making practical quantitative measurements of soot. Using this in-situ absolute intensity self-calibration technique, LII has been applied to measure soot particle volume fraction in laminar diffusion flames, carbon black, and in diesel engine exhaust streams. See, e.g., Snelling, D. R., Smallwood, G. J., Gulder, O. L., Liu, F., and Bachalo, W. D., "A Calibration-Independent Technique of Measuring Soot by Laser-Induced Incandescence Using Absolute Light Intensity," The Second Joint Meeting of the U.S. Sections of the Combustion Institute, Oakland, Calif., Mar. 25 28, 2001.

It has also been theorized that LII could be used to measure primary particle size. Some work toward using LII for size (sample particle diameter) measurements of soot and carbon black were published by various academic groups. See, e.g., U.S. Pat. No. 6,181,419; WO 97/30335; and Starke, R. and Roth, P., "Soot Particle Sizing by LII During Shock Tube Pyrolysis of C.sub.6H.sub.6," Combustion and Flame, 127:2278 2285 (2002) (the disclosures of which are hereby incorporated by reference for their general teaching on LII methods for determining particle size and LII apparatus/instrumentation used in determining particle size).

See also


Also in the 7 Sept 07 Science:

Puzzling Decline of US Bees Linked to Virus from Australia (317 Science 1304). Discusses colony collapse disorder (CCD) and the Israel acute paralysis virus (IAPV).

The Brain/Education Barrier, which begins: "In an era of translational science, researchers often find themselves in the mixed company of policy-makers, legislators, and educators looking for "evidence-based" practice. Hmmm, sounds like Proposition 71 and embryonic stem cell research, doesn't it?

"Lights, Camera, Clarify" which discusses SciVee, a new video-sharing site form the Public Library of Science and the National Science Foundation (NSF). It's at


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