Samples of aerosols were collected at a particular location on the open ocean on three consecutive

Days. The accompanying table give the atomic elemental ratios for these three samples and for

Seawater. A polluted air mass with a high burden of sulfur dioxide moved into the area during the

time the samples were collected.

a$.$ Interpret sample $1$ and sample $3$ in terms of source and aerosol modification.

b$.$ Interpret sample $2.$ If you believe this is a mixed sample, identify and calculate the percents of the

end members.

A sulfuric acid aerosol particle has density of $1100kg{m}^{-3}$ and a diameter of $30m.$

A dust particle has a density of $2300kg{m}^{-3}$ and a diameter of $30m.$

a$.$ Calculate the settling velocity for both particles using Stokes' law. How do they compare?

b$.$ Calculate the diameter of a sulfuric aerosol particle settling at the same velocity as the dust particle.

Stokes' law: $v_s=\frac{g({}_s-{}_f)d^2}{18}$

Where $,v_s=$ terminal velocity

$g=$ acceleration due to gravity $(9\mathrm{.}81\frac{m}{s^2})$

${}_s=$ density of the solid particle

${}_f=$ density of the fluid $($density of the atmosphere $=1\mathrm{.}225k\frac{g}{m^3}.$

$=$ viscosity $($viscosity of the atmosphere $=1\mathrm{.}789{10}^{-5}$Pas.

An air sampler is used to collect particles less than $10m$ in diameter. The sampler is located

downwind from a steel plant. The accompanying data are for particulate samples collected on two

different days.

a$.$ For both samples, calculate the non$-$crustal abundance of $Fe,Mn,Cr$ and $Ni.$ Use Al as the reference

element. Use the upper crust values.

b$.$ For particles emitted by the steel plant, $M\frac{n}{F}e=0\mathrm{.}009,C\frac{r}{F}e=0\mathrm{.}003,$ and $N\frac{i}{F}e=0\mathrm{.}002.$ Using the

non$-$crustal abundances of $Fe,Mn,Cr$ and $Ni,$ do emissions from the steel plant contribute to the

aerosol chemistry? Explain.

c$.$ If your answer to part $($b$)$ is yes, what percent of aerosol sample $1$ and aerosol sample $2$ is due to

emissions from the steel plant?

$Pb$ isotopic measurements of an aerosol sample give ${?}^{206}P\frac{b}{{?}^{204}}Pb=18\mathrm{.}673,{?}^{207}P\frac{b}{{?}^{204}}Pb=15\mathrm{.}667$ and

${?}^{208}P\frac{b}{{?}^{204}}Pb=38\mathrm{.}857.$ Calculate the ${?}^{206}P\frac{b}{{?}^{207}}Pb$ and ${?}^{208}P\frac{b}{{?}^{206}}Pb$ ratios for this sample.

Formic acid collected in an aerosol sample at Anholt, Denmark, had ${?}^{14}C=98\mathrm{.}6pmc($Glasius et al$.,$

$.$ At the time this sample was collected, ${?}^{14}C=110\mathrm{.}5pmc$ for the atmosphere. Calculate the

percent biogenic carbon in the formic acid sample.