Start to search for it with google scholar; otherwise I help you:

Then go to the web-site of dr Tami Bond and her group

Thank you, Prof. Harry, I have read Dr. Tami Bond and Ramanathan, V as well as Szidat, Sonke's article, but they use different definitions

OK

Seems you have done your home work

To put it simple

There are two methods to specify carbon

Chemical

This discriminates Elemental, Inorganic, Organic Carbon

Inorganic is easy to measure and it is alomot completely calcium carbonate.

Physical/optical

Black and Brown Carbon are defined by the fact that they absorb light

Black Carbon absorbs light over the whole visible spectrum

Brown carbon absorbs much more blue-UV light than red light: therefore the color is brown

Black Carbon is equivalent with elemental carbon

Brown Carbon is realterd with the light-absorbing Organic compounds like lignine

Very grateful for your guidance in such clear explanation. It's very kind of you, Prof. Harry

Chemical definitions of EC/OC are also closely related to their specific sampling and analytical procedures. For example, NIOSH 5040 or IMPROVE-A are both quartz-filter-sample and thermal-optical measurement methods and both indicate EC and OC but give somewhat different results due to differences in the analyses and corrections applied within the analyses.

To Prof. Joseph McDonald,

the variable chemical definitions of OC/EC are due to the different residence time, the NOISH protocol uses fixed residence time, whereas the IMPROVE method employs variable residence time to allow the FID peaks to return to baseline and to give rise to well-resolved peaks. (Cited from Gelencsér, A. 2004)

But I don't think the different analytical methods that lead to their different chemical definitions, the different analytical methods may have different results, but the results are comparable, and their chemical definitions have not changed when we use the above two different measurement methods.

thank you for your suggestion!

Joseph

I like to add that in Europe methods are in use that do not use an optical correction, but rely on chemistry only. One is known as the Cachier method and the other is VDI-1 and there is VDI-2 with an extra extraction step. I refer to the paper by Schmid et al. in Atmos. Environ. 2001; the results compare quite favorably with the NIOSH approach.

We have also found source measurements of EC/OC by TOT/TOR analysis of quartz membranes to be sensitive to the amount of time taken to ramp up temperature during the OC analysis, particularly in samples with high OC loading. In my experience, longer ramp times tended to result in less charring and a lower magnitude correction for charring as well as a better mass-balance of EC and OC mass relative to PM mass. This probably peculiar to source measurements - ambient OC filter loadings are typically orders of magnitude less.

I have no experience of source measurements, we monitor the ambient OC/EC concentrations and other pollutants of our concern in Shanghai, China, and we will measure the emission source——traffic exhausts or the cooking fumes in the near future.

There is a problem in the coreection with samples from China/Hong Kong, because the original urban sample often has a very high loading and blackness, so that the turning point later on for the EC is ill to non-defined. It is in a publication of Judy Chow et al.

Comparison of PM2.5 carbon measurement methods in Hong Kong, China

www.aseanenvironment.info/Abstract/41012244.pdf

I am currently developing the next-generation carbon analyzer (DRI version). According to my experience, the duration of each temperature step is not as influential as the ramp time (I totally agree with Joseph on this point). For regular users, the OC/EC analysis can be sometimes frustrating, simply because many factors can alter the measurment results. Let me know if you have any issues with carbon analysis.

OC and EC are sort of operational definitions (like PM2.5). I personally don't think there will be any EC standard or a perfect OC/EC splitting. Photoacoustic black carbon (BC) might be a good transfer standard for filter-based EC (thermal/optical method). A better OC/EC splitting is possible with improved optical correction (e.g., multi-wavelengths) and further refined temperature programs. But it takes time.

Are you using reflection or transmission for the correction?

The only way that I have been able to get the temperature ramp times set for specific source measurements has been to challenge the analysis procedure with quartz filters pre-doped with known organic compounds at filter loadings comparable to what would be expected in an actual sampling/analytical situation. That was relatively straightforward for pre-control diesel aerosols like the locomotive work I was doing but it could be a real challenge for other source measurements. We were using TOT for the char correction in the locomotive work. By the way, has anyone tried using the temperature ramps as a means of correcting for gas-phase OC artifact? I would think that would be relatively straight-forward to develop, it would eliminate the current need for dual sampling trains and duplicate analysis and it should help improve measurement uncertainty.

Joseph

It has been done by a first step in which the temp is kept at (I think) 50 C. Do not remember who did this, I thought Helene Cachier

Harry - Thanks. I will do a quick literature search on that name and see if I come up with something.

Joseph

You also may want to ask Barbara Turpin with her long track record in artefacts

The artifact issue may not be easily solved by temperature ramps, IMO. But if it is just for diesel or gasoline engine emission samples, it is worthy trying. I would suggest using a slightly higher temperature, e.g., 80 C to condition the filter sample in the instrument oven (we called it OC-zero).