Transcript ADVANCES IN MONITORING METHODS FOR AIRBORNE PARTICLES

ADVANCES IN
MONITORING METHODS
FOR AIRBORNE PARTICLES
Philip K. Hopke
Department of Chemical Engineering, Clarkson
University, Potsdam, NY 13699-5705 USA
[email protected]
Air Quality Standards
• In 1997, the U.S. Environmental Protection
Agency promulgated new National
Ambient Air Quality Standards (NAAQS)
for airborne particulate matter.
– New standards were established for PM2.5
– Revised standards were set for PM10
Air Quality Standards
• The PM2.5 standards were set as:
– Annual arithmetic average standard
• 15 µg m-3
• Averaged over three years
– Each quarter must have 75% collection
– Quarterly averages are averaged over the 3 years
• Value >15.1 µg m-3 is in non-attainment.
Air Quality Standards
• The PM2.5 standards were set as:
– 24-Hour standard
• 65 µg m-3
• 98th Percentile Standard based on 3-years of data
– Determine the 98th percentile value for each of the three
years
– Average these three values
– If it is greater than 66 µg m-3, the site is in non-attainment
Air Quality Standards
• The PM2.5 standards were set to be:
• Measured with a standard design Federal
Reference Method sampler
• Samplers deployed based on population density
• Measurements at least every third day
• Teflon filters
– Equilibrated and weighed prior to and after exposure.
Air Quality Standards
• The PM10 standards were set to be:
– Maintain the 1987 annual arithmetic mean
value of 50 µg m-3
– Set a new 24-hour standard of 150 µg m-3
which is the same as the 1987 value, but now
as the 99th percentile value
– Three years of data needed as in the PM2.5
standard
Air Quality Standards
• Lawsuit was filed against the
Administrator by the American Truckers
Associations with a number of coplaintiffs
• Alleged that the EPA had exceeded
their authority by creating the PM2.5
standard as well as raising a number of
points with respect to the new 8-hour O3
standard that was also promulgated in
1997.
Air Quality Standards
• The PM10 NAAQS was promulgated to
protect public health from coarse
particles that would not be part of PM2.5,
• The suit alleged PM10 to be illegal since
it included PM2.5 and the effects of the
two cannot be adequately separated.
• PM10 is thus not an effective indicator of
coarse particle exposure
Air Quality Standards
• A 3 judge panel of the Court of Appeals for
the Third Circuit (Washington, DC) upheld
the entire suit by a 2 to 1 majority
• EPA chose to contest the decision
except for the part of regarding the
invalidation of the PM10 standard.
Air Quality Standards
• The Supreme Court found for the EPA and
remanded the case back to the Court of
Appeals with specific instructions
regarding the outcome
• The Court of Appeals then dismissed all
of the remaining parts of the suit.
Air Quality Standards
• Thus, at this time the NAAQS in the
United States include the
– 1997 PM2.5 standard (both annual average
and 24-hour standards).
– 1997 eight-hour ozone standard
– 1987 PM10 NAAQS remains in effect since
it was not part of the lawsuit and thus, is
not affected
– However, a new coarse particle standard
will be set in this round of NAAQS review.
PM2.5 Monitoring Program

PM2.5 Program Objectives: Why Monitor?
 Comparison With Air Quality Standards
 Development of Emission Control Strategies
 Support Modeling & Emissions
 Continued Assessment of Strategies and Trends
 Public Awareness
 Research On:
 Atmospheric Processes and Emissions
 Source-Receptor Relationships
 Health Effects/Exposure
Supersites
Speciation
Network
Mass
Monitoring
Network
7
sites
300 State Sites
+
150 IMPROVE
>1100 Sites
EPA PM2.5
Monitoring
Network
Airborne Mass Concentration
Measurement
• Approved method is the Federal
Reference Sampler
• Equivalent manual samplers can be
developed from the same sampler plans
• Very difficult to develop an equivalent
continuous sampler because of the
stringent requirements
FRM Sampler
• Designed to
– Have sharp cutpoint
– Volumetric flow control
– Have high precision
• However, it has
– Unknown loss of semivolatile components
• Ammonium nitrate
• Organic compounds
• Thus, it has unknown accuracy and it is
only right by REGULATION!
FRM Monitoring Network
FRM Sampler
Problems with FRM
• Accuracy
• Cost
– High labor and time cost
• Equilibration
• Transport to site
• Weighing
• Only 33% of the days sampled even
when everything goes right!
Problems with FRM
• WINS impactor uses oil to prevent
particle bounce
– Freezes in the winter although a
replacement oil type has now been
approved.
• WINS impactor can now be replaced by
the sharp cut cyclone
– No oil
– Less maintenance
Continuous Mass Monitors
• Need systems that provide continuous
measurements of the particle mass
– Lower operating costs
– Complete data
• More accurate determination of attainment status
– Provide better data for epidemiology and
atmospheric process understanding.
Continuous Mass Monitors
• Need a response to collected particle
mass
– TEOM
– Beta Attenuation Monitors
– Pressure across over a filter
• Commercial systems are available
Continuous Mass Monitors
• Problem is not with the detector, but
deciding what to measure
• Water associated with the particle is
assumed to be non-toxic and thus,
should be removed.
• Desire to match the FRM measured
values
Continuous Mass Monitors
• How to remove the water without removing
semivolatiles?
• Do we want to match the FRM when we
know it is inaccurate?
• What is currently available?
30ºC TEOM with SES
• Operate TEOM at 30ºC
• Sample Equilibration System uses a
Nafion dryer to remove water
Continuous Aerosol Mass
Monitor (CAMM)
• Pressure drop over a filter
• Uses Nafion® dryer
• Attempts to match FRM values
• Has a serious problem if there is much
mass in the 1.5 to 2.5 µm range.
Research Systems
The problem is to deal with both the
positive and negative artifacts
Adsorption of organics on filter
Volatilization of ammonium nitrate and SVOCs
• Real-time Aerosol Mass System
(RAMS)
– Developed by Delbert Eatough at BYU
– Uses a concentrator to increase the S/N
ratio
– Dual monitoring system
Differential Systems
• RAMS is too large and too complex to
be a useful monitoring tool.
• However, suggested the idea of a
differential system in which
comparisons are made between
collection of gases and particles and
removal of particles. This comparison
permits the estimation of artifacts, both
positive and negative
Differential TEOM
Filter Dynamics Measurement
System (FDMS)
• The Filter Dynamics Measurement System
quantifies both the volatile and non-volatile
components of particulate matter (PM),
and reporting the combination as a mass
concentration result by measuring the
volatile portion of the sample
independently from the total incoming
sample, and accounting for this fraction in
calculating the PM mass concentration.
Continuous Mass Monitors
X
Y
Intercept
slope
r
# samples
RAAS
-0.57
0.98
1.0
33
And-BAM3 And-BAM 0.69
0.98
0.98
99
Met-BAM4 Met BAM
-1.19
0.98
1.0
105
FDMS5
FDMS
0.88
1.04
0.99
55
CAMM6
CAMM
2.32
0.97
0.91
96
Precision
RAAS2
Accuracy
RAAS
And-BAM -1.32
1.02
0.98
102
RAAS
Met-BAM -1.58
1.03
1.0
102
RAAS
FDMS
3.73
1.01
0.99
102
RASS
CAMM
9.79
0.68
0.87
93
2
Continuous Mass Monitors
• New guidelines are being developed to
permit regional relationships to be
developed between the continuous
monitor and a collocated FRM.
• We should start to see a significant
number of continuous monitors in the
compliance monitoring network within the
next 1 to 2 years.
Speciation Network
• Chemical composition data to support
• ~190 PM2.5 filter-based chemical
speciation monitoring sites operating, or
identified and scheduled to start
operating, by December 31, 2001
• 110 IMPROVE sites and 34 IMPROVE
protocol sites
Speciation Network
• XRF for elements
• Ion Chromatography for major anions
and cations
• OC/EC using a modified NIOSH 5040
method
Speciation Network Data
• Trends in composition over time
• Source apportionment for State
Implementation Plan development
• Potential for epidemiology on chemical
species or apportioned source
contributions
Continuous Chemical Data
• Improved time resolution permits
identification of atmospheric process
details,
• Identification of plumes from point
sources,
• Improved source resolution, and
• Better air quality planning.
Continuous Chemical
Measurements
• Continuous measurement of chemical
constituents (commercial systems)
–
–
–
–
Sulfate
Nitrate
OC/EC
Single Particle Mass Spectrometry
• Research Systems
– Particle into Liquid System (PILS)
– Semi-continuous Elements in Aerosol System (SEAS)
Illustrative Results
• Rochester, NY
• Sampled through a 4” duct inlet
Illustrative Results
Semi-continuous Elements in
Aerosol System (SEAS)
• Developed by John Ondov at the
University of Maryland at College Park
• Uses steam injection to cause hygroscopic
growth
• Collected samples can then be analyzed
• Half-hour time resolution is possible
Semi-continuous Elements in
Aerosol System (SEAS)
SEAS
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