Week #4 Report

This week more samples are here to be analyzed! The ones specific I would like to share are some filter samples. The major difference of these samples from the samples I have analyzed before is that they are collected in a laboratory rather than on the field. The samples to be discussed are collected from the fumes emitted from a burning of Douglas fir in a controlled environment. Those laboratory samples are able to help us to understand the composition and behavior of aerosols coming from a single source (in this case, a biomass burning aerosol ). Such knowledge can play an important role in our analysis of ambient (field) aerosol samples.

 

Another advantage of the filter sample is that we can perform chemistry on the filter to probe the probable chemical change of aerosols under certain atmospheric conditions. For the present samples, we decided to investigate the photochemical aging effect on biomass burning aerosols (i.e. see how the chemical composition of aerosol changes due to sunlight). What we did is to cut the original filter with fresh aerosols into 4 pieces and labelled them 0, 1, 2, 3. Filter #0 remains in a controlled chamber with no light, while the rest are irradiated with a lamp simulating sunlight for 1, 2, 3 days, respectively. After that, the chemicals on the filters are extracted and investigated using the AMS.

 

The following picture is the AMS spectra of filter 0-3. We can see a major increase in the signal of CO+ and CO2+ (which represent organic acids), and a decrease in CHO+ signal (may represent alcohol groups). Therefore, we can say that the biomass burning aerosols are oxidized during the photolysis process. Another significant change is the decrease of m/z 60 signal (C2H4O2+). From literature research, we know that a strong C2H4O2+ signal serves as a marker of biomass burning aerosol source (as it is in filter 0). Its decrease over time due to photolytic aging indicates a challenge facing environmental chemists: it might be hard to distinguish an aged aerosol influenced by biomass burning from those influenced by other possible sources.

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Comments

  1. Great post.

  2. Hi Mark! Thank you for your compliment!

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