Transcript Strong Air-Sea Interactions in the North Atlantic During

Photolysis of Particulate Nitrate: a Daytime HONO Source
and a Re-NOx-ification Pathway in the Troposphere
(TROPospheic HONO: TROPHONO)
A Component of NOMADSS (Nitrogen, Oxidants, Mercury,
and Aerosol Distributions, Sources and Sinks) Field
Campaign
Xianliang Zhou (Wadsworth Center and SUNY Albany)
Jochen Stutz (University of California, Los Angeles)
Objective: To investigate the role of particulate nitrate photolysis
in the cycling of reactive nitrogen species in the troposphere,
focusing on HONO as an intermediate product.
Hypothesis 1: Photolysis of particulate nitrate in aerosol particles,
and, to a lesser extent, NO2 conversion on organic aerosol, are
major sources of HONO in the low-NOx troposphere above
the surface boundary layer.
Hypothesis 2: Photolysis of particulate nitrate in aerosol particles
represents an important pathway to recycle HNO3/nitrate back
to photochemically reactive NOx (re-NOx-ification) in the
troposphere.
Supporting Evidences
Potential Temperature, K
302
301
July 30
12:02-14:09
2500
306
y = 0.0002e-0.078x
R² = 0.70
August 1
13:54-17:07
JHONO+NO2, s-1
297
1.0E-03
Altitude (m agl)
2000
1500
1.0E-04
1.0E-05
AlbSum
AlbWin
AlbNov
Del
WFM
1000
1.0E-06
0
500
1
[NO3 -], nmol/m3 10
0
0
20
40
60
0
20
40
60
HONO, pptv

Substantial daytime HONO exists in the upper atmospheric boundary layer and
free troposphere  require a strong daytime HONO source in the air column.

Photolysis of particulate nitrate (pNO3) in aerosol is fast, with a lifetime of ~1.4
hr for pNO3, with HONO as a dominant product (HONO/NO2 = 3 - 9)
100
Potential impact of p-NO3 photolysis on
tropospheric photochemistry
OH
HNO3
NO2
hv
O2
hv
OH
p-NO3Organics
O3
hv
hv
HO2
hv
HONO
OH + NO
Flight Strategy/Experimental Designs
1. Daytime horizontal transects and vertical profiling over land and ocean:
To establish daytime distributions of HONO and its production rate, and their
relationships with pNO3, NOx, pOrganics, aerosols, and O3 in different air
masses.
2. Daytime HONO production in urban plumes:
To study daytime HONO production in the urban plumes as a function of
photochemical ages, and to establish the maximum HONO contribution from
the NOx precursor.
3. Nighttime HONO accumulation/early morning decay:
To study nighttime accumulation and morning hour decay of HONO . The
HONO formation rates during the day and the night will be compared.
4. Bulk aerosol sampling:
To collect aerosol samples for laboratory pNO3 photolysis experiments.
horizontal transects and vertical profiles
*
HONO system
air pump
Solenoid valve
MFC
Ambient air
coil sampler
annular denuder
• Aqueous scrubbing
• Azo dye derivatization
• Long-Path Absorption
Photometric (LPAP)
detection of azo dye
peristaltic pump
o
55 C
H2O
SA/
NED
light source
• Detection limit ~1 pptv
• 90% response time ~1 min
long-path flow cell
spectrometer
Ambient air
HONO system
Valve/sampler box
MFC
MFC
Relays
Relays
SA/NED
H2O
H2O
SA/NE
D
HONO Signal, pptv equavalent
HONO data from two HONO systems
0.3
system 1
system 2
0.2
0.1
0.0
9:50
10:20
10:50
11:20
Local Time of 5/19/2010
11:50
HNO3 system
Ambient air
• Aqueous scrubbing
• NO3- to NO2- conversion on
Cd-reductor
• Azo dye derivatization
• Long-Path Absorption
Photometric (LPAP)
detection of azo dye
• Detection limit ~20 pptv
• 90% response time ~1 min
Valve/sampler box
MFC
Relays
Cd reductor
NH4Cl
buffer
SA/NE
D
PNO3 system
Ambient air
Valve/sampler box
• Aqueous scrubbing
• NO3- to NO2- conversion on
Cd-reductor
• Azo dye derivatization
• Long-Path Absorption
Photometric (LPAP)
detection of azo dye
• Detection limit ~20 pptv
• 90% response time ~1 min
MFC
Relays
NH4Cl
buffer
Cd reductor
SA/NE
D
P-Organics system
Valve/sampler box
Ambient air
• Aqueous scrubbing
• Long-Path Absorption
measurement a 300 nm
MFC
Relays
H2O/AcN