ADVANCES IN MONITORING METHODS FOR AIRBORNE PARTICLES Philip K. Hopke Department of Chemical...

ADVANCES IN MONITORING METHODS

FOR AIRBORNE PARTICLES

Philip K. HopkeDepartment of Chemical Engineering, Clarkson University, Potsdam, NY 13699-5705 USA

hopkepk@clarkson.edu

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 co-plaintiffs

• 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

Mass Monitoring Network >1100 Sites

7 sites

300 State Sites

+

150 IMPROVE

Speciation Network

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

• Real-time Aerosol Mass System (RAMS)– Developed by Delbert Eatough at BYU– Uses a concentrator to increase the S/N ratio– Dual monitoring system

The problem is to deal with both the positive and negative artifacts

Adsorption of organics on filter

Volatilization of ammonium nitrate and SVOCs

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 MonitorsX Y Intercept slope r # samples

Precision

RAAS2 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

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

• 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)

Semi-continuous Elements in Aerosol System (SEAS)

SEAS

QUESTIONS?

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