Utilizing Nephelometers for Near Roadside John Carney Mark Phelps Andrew Tolley American Ecotech

Roadside Monitoring

Nephelometers 101 Light trap Sample outlet Sample inlet Temp RH sensor Measurement bench Reference shutter motor PMT,HV supply, pre amp PMT signal LED module Pressure sensor

Nephelometer Readings

Total light extinction = light scattering + light absorption Light scattering by particles (b sp ) - Urban visibility field studies indicated that particles ≤ to 2.5 microns in aerodynamic diameter (PM2.5) cause the vast majority of light scattering. Atmospheric, or Rayleigh scattering (b Rayleigh ) is natural scattering not related to air particulate. Light absorption - due to particles and gases, and is determined by analysis of elemental carbon. A nephelometer measures the light scattering component of light extinction.nephelometer Nephelometers 101

Inverse Megameter (Mm- 1 ) is the direct measurement unit for visibility impairment data. It is the amount of light scattered and absorbed as it travels over a distance of one million meters. Visual range (VR)Visual range (VR) - Visual range is an expression of visibility impairment defined as the distance in miles or kilometers at which a large, black object just disappears from view. Visual range values are calculated from direct measurement data, or are estimated directly by observers. Visual range can be calculated from extinction data as follows: Visual Range (km) = 3912 / b ext (Mm- 1 ) Mass Concentration (mg/m 3 µg/m 3 ) Nephelometer Units

The first generation in LED Light Source introduced in 2002 Evolution of LED Light Source Three Wavelength

Next Generation of LED Lightsource Evolution of LED Light Source

Advantages Stable light intensity Stable light wavelength generation Bandpass filters not required Negligible thermal interference during measurement Minimal mthly maint. (<10 minutes per month!) Evolution of LED Light Source

Disadvantage – Geometry of light source and diffusion lens led to an uneven light distribution within measurement cell Evolution of LED Light Source Result – Over estimation of scattering coefficients (by up to 10%)

Opal Diffuser in front of LED array Evolution of LED Light Source Result – Light intensity approaching Lambertian distribution resulting in negligible error.

New Generation of LED Lightsource Fewer LEDs – Three lamps per wavelength Compact Light Source Further reduction in measurement bench heating (between sample and ambient temperature) User adjustable intensity pots (extend lifetime of light source) Fully field serviceable Backwards compatible with older units. Evolution of LED Light Source

Near Roadside Monitoring Dust Monitoring Forest Fire/Smoke Monitoring PM Correlation Monitoring Solar Energy Site Assessment and Operation Field Applications

Near Roadside I-40 Station – Raleigh Gas Analyzers (NOx, Ozone) Particulate Monitors (BAM, Aethalometer, Ultrafine) Samplers (passive, TSP)

Installation

Preliminary Data

Dust Monitoring Sydney Dust Storm – September 2009

New South Wales EPA Air Monitoring Network

Field Applications

Victoria EPA Forest Fire alert categories based on PM10 and visibility

Smoke Monitoring Pollutants Ozone O3 Nitrogen dioxide NO2 Visibility NEPH Carbon monoxide CO Sulfur dioxide SO2 Particles PM10 Particles PM2.5 Averaging Periods 1-hour average 4-hour rolling average 1-hour average 8-hour rolling average 1-hour average 24-hour rolling average Sydney East Randwick Rozelle Lindfield Chullora Earlwood Sydney North- west Richmond St Marys Vineyard Prospect Sydney South- west Bargo Bringelly Camden Campbelltown West Liverpool Oakdale Illawarra Wollongong Kembla Grange Albion Park Sth Lower Hunter Wallsend Newcastle Beresfield Central Coast Wyong Central Tablelands Bathurst 63.7 North-west Slopes Tamworth 12.7 South-west Slopes Albury 27.9 Wagga Wagga Nth Upper Hunter - Muswellbrook Muswellbrook Upper Hunter - Singleton Singleton Air Quality Index VERY GOODGOODFAIRPOORVERY POORHAZARDOUS New South Wales Air Quality October 20, :00 – 9:00 AEST Brush Fire Event Nephelometer – hourly average based on 1 or 5 minute (high frequency) data, capturing smoke event as it occurs

Smoke Monitoring

Portable Functionality

Correlation of Nephelometers Correlation of PM2.5 measurements and scattering coefficients Puget Sound Clean Air Agency Study – Residential Area ◦Collocated Instruments:  American Ecotech Nephelometer  Radiance Research (RR) Nephelometer  Partisol (FRM) for PM 2.5  TEOM with PM 2.5 head  TEOM (FDMS-TEOM) PM 2.5 head  BAM 1020 PM 2.5

FRM vs. Nephelometer Particulate Monitors

FDMS TEOM vs. Nephelometer Particulate Monitors

BAM vs. Nephelometer Particulate Monitors

Results Nephelometer correlates well (r 2 > 0.94) with: ◦The US Federal Reference Method ◦FDMS-TEOM ◦FEM Beta Attenuation Monitor Particulate Monitors

Continuous Correlation – Aurora Neph and BAM-1020 Particulate Monitors

Renewable Energy Field Courtesy of yesRenewables

Site Evaluation involves up to a year long study of site conditions. Parameters to measure include: Solar Intensity Light Duration Cloud Cover Light Scattering Solar Site Evaluation

Solar Tower Courtesy AMBL

Evaluate degree of light scattering of both incoming light and reflected light. Need to evaluate scattering at several levels covering the height of the planned tower Solar Site Evaluation

Sue Kimbrough and Richard Snow – USEPA Office of Research and Development Acknowledgments

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