BAM-1022 Continuous Beta Gauge David Gobeli, Ph.D., Thomas Pottberg Met One Instruments, Inc. Grants Pass Oregon USA

Agenda Challenges facing continuous aerosol monitors under real-world conditions Moisture effect on measurement EPA field test of BAM-1022 continuous beta gauge Additional field testing along Gulf Coast under very high dew point conditions

Design Challenges in Criteria PM Monitor Design Must provide accurate reliable results under a wide variety of climactic conditions and aerosol types Testing at additional sites besides those required by EPA are useful validate known operating range to include very hot, humid regions such as US Gulf Coast Complexity, reliability, sensitivity, and accuracy considerations/tradeoffs

Class 3 PM2.5 Field Test 5 Test Campaigns, 4 Test Sites Site A (Mira Loma CA) – winter, summer Site B (Salt Lake City UT) – winter Site C (Dearborn MI) – winter Site D (Elizabeth NJ) – summer Site “E” (Baton Rouge LA) – year round

Salt Lake City UT – Winter 2012

Baton Rouge LA

Moisture Effect Approach Cost Complexity Issues Control Lower Requires elevated temperature Compensation Higher Incomplete/unreliable Removal Very High High Reliability In-Situ Low Very Low None

Moisture Control Temperature – based (usually elevated) Humidity – temperature adjusted to maintain set point Combination of temperature and humidity

Moisture Compensation Background will vary based upon moisture content (instrument artifact) Artifacts can be subtracted out. Water could bind to PM and skew results if humidity too high. Cannot be subtracted out.

Moisture Removal Moisture removed using physical means (PermaPure Drier)

BAM-1022 Approach Extremely simple Measurement is made under near-ambient “in-situ” conditions. Only slight warming to prevent condensation Nearly eliminates moisture interference Eliminates under-measurement due to excessive heating

Mira Loma, CA (Winter, Summer 2012)

Salt Lake City UT (Winter, 2012)

Dearborn MI (Winter, 2012) Regression statistics Slope1 Intercept2 Correlation (r) Statistics for this test site:   0.947 -0.395 0.99035 Limits for Upper: 1.100 2.000 PM2.5 Class III Lower: 0.900 -1.346 0.93793 Test Results (Pass/Fail): PASS

Elizabeth NJ (Summer, 2012)

Ambient Moisture Measured as Partial pressure of H2O in the atmosphere Temperature and relative humidity Dew Point

Test Site Dew Point Conditions

Baton Rouge Test Site Indicative of Gulf Coast/Southeast US Weather Conditions Extremely high dew point during summer months Wildly varying dew point and temperature during winter months EPA “Class 3” style field test performed for almost 1 year Triplicate BAM-1022 monitors & FRM samplers Strict collocation, all Class 3 protocols followed

Baton Rouge – Dew Point

All Data

Summer Only

Winter Only

Summary Additional test sites demonstrates “in-situ” approach under expanded ambient/climactic conditions Baton Rouge site conditions unlikely to be duplicated in EPA sites A-D for Class 3 test. Additional testing currently underway for ultra-high sensitivity version with PTFE filter media.

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