Environmental Data Analysis BC ENV 3017
Indoor - Outdoor PM lab
The goal of this lab is to build a mathematical model of the experiment
that was conducted innorder to better understand the processes controlling
the indoor PM concentrations.
Part 1
-
In order to determine the air exchange rate between inside and outside,
a small quantity of SF6 was injected into the air of all
rooms in the appartment and the concentrations were measured as a function
of time. As we discussed in class the result of this is an exponential
drop of the indoor SF6 concentration as a function of time.
We can derive the characteristic time constant of this decay by fitting
the concentration as a function of time (t) with an exponential function:
C(t) = C(t=0) * exp(-lt)
-
this experiment was conducted several times during the PM measurement period.
-
download the SF6 data , and
standardize the measurements as discussed in class. Assume that the measured
area under the SF6 peak in the gaschromatograph is proportional to the
SF6 concentration:
-
C = a*(area - blank), a being a constant
-
determine the average blank and substract it from all measurements
-
determine a for the standard that has a known concentration (321 ppt, parts
per trillion)
-
plot the SF6 concentrations as a function of t and
fit them with an exponential function and derive the characteristic air
exchange rate l for the 4 gas exchange
experiments and put them into the table below
-
note that you have to convert l from hour-1
to day-1
-
convert the date and time into fraction of days after midnight of 7/2/1999.
|
Experiment
|
Date |
Time |
days>7/2/99 |
l (day-1) |
action
|
|
1
|
7/2/99
|
16:00
|
|
|
sealed windows
|
|
2
|
7/3/99
|
14:00
|
|
|
|
|
3
|
7/5/99
|
12:00
|
|
|
|
|
4
|
7/5/99
|
12:45
|
|
|
unsealed
|
-
Is the air exchange rate affected by the fact that the windows were sealed
with plastic foil from 7/2/99 16:00 until 7/5/99, 12:45? Windows were unsealed
until 7/2/99 16:00 and after 7/5/99 12:45.