Atmospheric Chemistry Related Research at Texas Tech University

1
Atmospheric Chemistry RelatedResearch at Texas
Tech University
2
Flux 20 Hz Microfabricated Moisture Sensors
Ozone
Inexpensive and versatile, fully automated,
lt500, 1 ppb sensitivity, 2-5 min integr time
(Also for NO2)
Fast and Sensitive, 10 Hz, Solution
Chemiluminescence
Other Gases Hydrogen peroxide, Methyl
hydroperoxide, Formaldehyde, Ammonia, all
fluorescence based, mid-low ppt LODs
Developing capabilities Acetone, alkenes, Fast
NO2
3
Ionogenic Gases
Organic Acids, HF, HCl, HONO, HNO3, SO2, H2C2O4,
NH3 10-15 min time resolution, low to sub-ppt
LODs
Ionogenic Particles
Ammonium, organic acid anions, fluoride,
chloride, nitrite, nitrate, sulfate, oxalate
10-15 min time resolution, low ng/m3 LODs
4
Size and wavelength multiplexed Aethalometry
Light attenuation as a function of particle size
and wavelength
5
In Progress EPA Carbonaceous PM Project
On-line Liquid Chromatographic Mass Spectrometric
Characterization of PM2.5
6
Rh moisture sensor deposit Ni/Ti electroplate
Rh spincoat Nafion
7
Rh Sensor Response Speed Data points 10 msec
Apart Speed increases with increasing applied
voltage
8
Intermediate range humidity calibration
9
(No Transcript)
10
Porous membranes carry 10-20 as much light as
Teflon AF but has 10-20 times higher gas transfer
rate!
11
Analytical reaction Indigosulfonate ozone
Colorless Product Use Yellow Food Dye as
ReferenceWater evaporation compensation
12
Renew the reagents at fix time or renew it when
?A0.05 AU
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
Measurement of Atmospheric O3
17
Gas inlet
Aluminum block
Black plexi
Liquid in
Liquid out
Pantyhose
Clear plexiglas
Signal out
PMT
Pump
Gas outlet
PMT cell
Lamp
Dark housing
Fresh CA soln.
18
Response time
Rise time 0.14 s
Fall time 0.12 s
CL responses for ozone. Left 0 ppb to 110 ppb
ozone right 110 ppb to 0 ppb ozone.
19
An Instrument that measures Gas phase Hydrogen
Peroxide and Methyl hydroperoxide
Nafion
ePTFE
Pulsating
LEDs Multiplexed Detector
20
(No Transcript)
21
Instrument Schematic for HCHO
22
(No Transcript)
23
(No Transcript)
24
Stability of response to 7.9 ppbv HCHO, 3/7 min
sample/zero.
25
2.0 ppbv H2O2 and 3.4 ppbv MHP.
26
Aircraft measurement data
27
Different origin of air mass
28
Gas Particle Analysis Systems
29
Separating Gases From Particles
Principles of Diffusion Based Collection      
  Gormley, P.
G. and Kennedy, M. Proc. Roy. Soc. Ir. Acad.
Sci. 52A163 (1949)  For high Collection
Efficiencies (f) 1-f 0.819 exp(-3.657?)
0.097 exp (-22.3?) 0.033 exp (-57?)
.....  where ? ?DL/Q D Diffusion
Coefficient, cm2/s L Active length of
denuder Q sampling rate, cm3/s
 
 
FILTER
Gas

Particle
30
Parallel Plate

s
w
1-f 0.91 exp (-2.4w?/s)) where w is the width
of the plate and s is the separation between
them see Simon, P. K. Dasgupta, P. K. Anal.
Chem. 65, 1134 (1993). Amendments De
Santis, F. Anal. Chem. 66, 3503 (1994).  Example
L 30 cm, w 5 cm, s 3 mm Test gas SO2 Q
5L/min f 99.8 Q 10 L/min f 95.2
31
(No Transcript)
32
In our laboratory, we have chosen to work with
the parallel plate denuders The current versions
are made from plastic, rather than glass and
simple field deployable stands are used.
33
Tampa 2003
34
95 mm
76 mm
35
A Continuous Analyzer for Soluble Anionic
Constituents and Ammonium in Atmospheric
Particulate Matter R. Al-Horr, G. Samanta and P.
K. Dasgupta Environmental Science and Technology
(ASAP, on web)
36
To get meaningful results for sticky gases like
HNO3, must operate a separate denuder without
cyclone or other inlet
37
(No Transcript)
38
(No Transcript)
39
Thank You!