FCH 511
Homework #9 - Aerosols 2
Fall 2015
Exercises
A.
What are typical lifetimes for Aitken nuclei, accumulation mode, and coarse particles?
What controls the lifetimes of Aitken nuclei, accumulation mode, and coarse particles?
B.
Is sea-salt aerosol primary or secondary aerosol? What mode does it (mostly) belong to?
What mode is mineral dust?
Oxidation of gaseous toluene can form aerosol; is this aerosol primary or secondary?
What aerosol mode would probably have most of the mass of oxidized aromatic
hydrocarbons?
C. Order the compounds in terms of their tendency to partition to the organic aerosol phase,
based on your knowledge of how molecular size and structure affect vapor pressure.
5-hydroxydecanoic acid
heptanal cyclohexane 3-hydroxyhexanoic acid
D.
Use the data in HW09.xls (see Homework web page) to determine the total concentration
of particles, the total particle surface area concentration, and the total particle volume
concentration.
E.
The table on the next page (Table 2.20 from the 1st edition of the textbook). Using the
“best estimate” data, calculate the fraction of the flux of aerosol to the atmosphere comes from
anthropogenic sources.
Problems
I.
e
Use the data in the Excel File HW08.xls to compute nN(Dp), nN (lnDp), and nV(Dp).
E-mail me the Excel spreadsheet with these distributions.
II.
Given: Answers to Exercise A, B, and E. Additional information in Table below.
Question: Why should the EPA bother regulating anthropogenic aerosol emissions if
these only constitute a few percent of all aerosol emissions?
i)
ii)
iii)
iv)
Type of Answer: Qualitative. There are 4 reasons, one each based on:
knowledge of aerosol behavior from this course
geography
background knowledge of chemistry and human health
page 22 and Figure 2.12 in FP+P, or the Powerpoint file borrowed from Daniel Jacobs
Copyright T. S. Dibble 2015
1
FCH 511
Homework #9 - Aerosols 2
Fall 2015
Data from Seinfeld and Pandis, 1st edition, 1998.
Source
Primary
Soil dust (mineral aerosol)
Sea salt
Volcanic dust
Biological debris
Secondary
Sulfates from biogenic gases
Sulfates from volcanic SO2
Organic matter from biogenic VOC
Nitrates from NOx
Total Natural
Anthropogenic
Primary
Industrial dust etc. (except soot)
Soot
Secondary
Sulfates from SO2
Biomass burning
Nitrates from NOx
Organics from anthropogenic VOC
Total anthropogenic
Total
Copyright T. S. Dibble 2015
Estimate Flux (Tg/yr) Particle Size Category
1000-3000
1000-10000
2-10000
26-80
Mainly coarse
Coarse
Coarse
Coarse
80-150
5-60
40-200
15-50
2200-23500
Fine
Fine
Fine
Fine and coarse
Best estimate 3100
40-130
5-20
170-250
60-150
25-65
5-25
300-650
2500-24000
Fine and coarse
Mainly fine
Fine
Fine
Mainly coarse
Fine
Best estimate 450
Best estimate 3600
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