Environmental Data Analysis BC ENV 3017
Indoor - Outdoor PM lab 1
A significant amount of our time we spend indoors. In order to better understand
what controls indoor concentrations of particulate matter an experiment
was performed this summer in the appartment of Steve Chillrud, a researcher
at LDEO. Steve lives on the 5th floor of 720
W 181th St in Washington Heights.
Download the spreadsheet with the data (it appears that some versions
of Netscape have problems with downloading MS Excel files).
Particles were collected outside and inside (bedroom
1, volume: 33 m3) using a set of filters and a pump (Fig).
We will focus on the particle sizes between 0.3 and 0.5mm.
Download the data and plot the
time series of indoor and outdoor PM concentrations from 7/2/99 to 7/7/99.
Describe the patterns that you see in the graph. We will try to understand
the processes controlling the PM concentrations by constructing a simple
two box model:
That means we envision two processes controlling the PM concentrations
indoors
-
exchange of particles between indoors and outdoors,
-
and deposition of particles on to surfaces.
How can we determine the exchange rate between outside and inside? In the
experiment, 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. We can derive the characteristic time
constant of this decay by fitting the concentration as a function of time
with an exponential function:
C(t) = C(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 in the Gaschromatograph is proportional to the SF6
concentration:
area = a * C + blank
Plot the SF6 concentrations as a function of t on
a logarithmic Y axis and fit them with an exponential function and derive
the characteristic time constant l (AER = Air
Exchange Rate) and put them into the table below.
|
Point
|
Date |
Time |
l or AER (hour-1) |
|
|
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
|
Are the AER affected by the fact that the windows were sealed with plastic
foil from 7/2/99 16:00 until 7/5/99, 12:45?
