This document summarizes research investigating aerosol sources in Colorado during the DISCOVER-AQ 2014 field study. Chemical composition measurements of particulate matter were collected using a particle-into-liquid sampler coupled with an ion chromatograph. The measurements showed that nitrate and ammonium concentrations varied more than sulfate and were influenced by temperature and humidity, suggesting they originate from local pollution. Potassium and calcium levels indicated potential biomass burning and dust transport events. The composition data and meteorological parameters will be analyzed further to characterize aerosols as anthropogenic, biogenic or marine in origin.

1. Investigating Aerosol Sources in Colorado during DISCOVER-AQ
Background Information
DISCOVER-AQ 2014 Data (Continued)
Jared J. Johnson, Jessica Izumi, Raymond Hoff, Ruben Delgado, Christopher J. Hennigan
University of Maryland, Baltimore County
Purpose
The purpose of this research is to characterize aerosol properties
as predominantly anthropogenic, biogenic, and marine by
coupling detailed chemical composition measurements with
intensive and extensive aerosol parameters (e.g. atmospheric
profile, relative humidity, anthropogenic events, etc.).
Methods
A particle-into-liquid sampler was coupled with an ion
chromatograph (PILS-IC) to measure the inorganic composition of
water soluble PM2.5 (Na+, NH4
+, K+, Mg2+, Ca2+, Cl-, NO3
-, and SO4
2-) in
Golden, Colorado. These data were paired with meteorological
measurements from a Vaisala MAWS201 Meteorological Station to
establish relationships between the compositions and the ambient
temperature, relative humidity, wind speed, and wind direction.
Figure 3. The PILS-IC setup
inside of the UMBC trailer.
Figure 4. Particle-into-Liquid sampler
(PILS).
PM2.5 samples were taken adjacently to an urban setting in Golden,
Colorado. Measurements of gaseous and particulate pollutants
were simultaneously taken between 1,000 and 5,000 feet over
selected monitoring sites on the ground.
Figure 1. DISCOVER-AQ
flight paths. (NASA)
Denver Golden
Figure 2. The NREL S. Golden ground site
from Figure 1.
DISCOVER-AQ 2014 Data
2.0
1.5
1.0
0.5
0.0
Concentration(ug/m
3
)
12:00 AM
1/1/1904
6:00 AM 12:00 PM 6:00 PM
Time (MDT)
NO3
-
NH4
+
SO4
2-
Figure 5. Diurnal profile of NO3
-, NH4
+,
and SO4
2- during the study.
0.3
0.2
0.1
0.0
Concentration(ug/m
3
)
12:00 AM
1/1/1904
6:00 AM 12:00 PM 6:00 PM
Time (MDT)
K
+
Ca
2+
Figure 6. Diurnal profile of K+ and Ca2+
during the study.
Figures 5, 6:
• NH4
+ and NO3
- concentrations exhibited more variance which suggests
that they are local pollutants.
• Cl- levels remained below its lower limit of detection (0.05 𝛍g/m3)
throughout the campaign.
• SO4
2- concentrations remained constant throughout the day which
suggests that it is likely a regional pollutant.
6
5
4
3
2
1
Concentration(ug/m
3
)
10080604020
Relative Humidity (%)
NO3
-
6
5
4
3
2
1
Concentration(ug/m
3
)
30252015
Ambient Temperature (ºC)
NO3
-
4
3
2
1
0
Concentration(ug/m
3
)
10080604020
Relative Humidity (%)
NH4
+
4
3
2
1
0
Concentration(ug/m
3
)
30252015
Ambient Temperature (ºC)
NH4
+
Figure 7. NO3
- concentration as a
function of relative humidity.
Figure 8. NO3
- concentration as a
function of ambient temperature.
Figure 9. NH4
+ concentration as a
function of relative humidity.
5
4
3
2
1
0
Concentration(ug/m
3
)
10080604020
Relative Humidity (%)
SO4
2-
Figure 10. NH4
+ concentration as a
function of ambient temperature.
Figure 11. SO4
2- concentration as a
function of relative humidity.
Figure 12. SO4
2- concentration as a
function of ambient temperature.
5
4
3
2
1
0
Concentration(ug/m
3
)
30252015
Ambient Temperature (ºC)
SO4
2-
Figures 8 through 13:
• For NO3
- and NH4
+, the mirrored relationship between concentration, relative
humidity, and ambient temperature suggests that NH4NO3 is produced at low
temperatures and is favored when aerosol liquid water is high.
• SO4
2- is less sensitive to temperature and relative humidity. This reinforces the
possibility that it is a regional pollutant.
0.5
0.4
0.3
0.2
0.1
Concentration(ug/m
3
)
7/16/2014 7/21/2014 7/26/2014 7/31/2014 8/5/2014 8/10/2014
Date (MDT)
K
+
Possible biomass
burning event
1.2
1.0
0.8
0.6
0.4
0.2
Concentration(ug/m
3
)
7/16/2014 7/21/2014 7/26/2014 7/31/2014 8/5/2014 8/10/2014
Date (MDT)
Ca
2+
Possible dust
transport events
Figure 13. Time series of Ca2+
concentration during the study.
Figure 14. Time series of K+
concentration during the study.
Figure 15. Ca2+ concentration as a
function of wind speed.
1.2
1.0
0.8
0.6
0.4
0.2
Concentration(ug/m
3
)
8642
Wind Speed (m/s)
Ca
2+
0.5
0.4
0.3
0.2
0.1
Concentration(ug/m
3
)
7654321
Wind Speed (m/s)
K
+
Figure 16. K+ concentration as a
function of wind speed.
0.5
0.4
0.3
0.2
0.1
Concentration(ug/m
3
)
35030025020015010050
Wind Direction (° from True North)
K
+
1.2
1.0
0.8
0.6
0.4
0.2
Concentration(ug/m
3
)
35030025020015010050
Wind Direction (° from True North)
Ca
2+
Figure 17. Ca2+ concentration as a
function of wind direction.
Figure 18. K+ concentration as a
function of wind direction.
Figures 13 through 18:
• The possibilities of local dust and long range transport from biomass burning
events will be investigated further.
Acknowledgements
NOAA-CREST