Nephelometers

Global Dimming or Global warming? a BBC documentary
An interesting documentary about global dimming describing how aerosols in the air are reflecting light back into space and reducing the solar energy reaching the earth, masking the effects of Global warming. The Nephelometer is the principal instrument used to measure backscatter of light back into space and global diming.

Recently the American Association for Aerosol Research (AAAR), co-sponsored by the Air & Waste Management Association, held the 3rd International speciality conference "Air Pollution and Health: Bridging the gap from sources to health outcomes".

This conference was attended by many health officials, aerosol researchers and instrument manufacturers and provided a forum with which information could be shared and relationships formed.

Ecotech, in association with its distributor American Ecotech, attended the conference displaying the Aurora Nephelometer to attending parties. Ecotech's representative was Head of Research and Development Mr Grant Kassell. Mr Kassell met with many eminent aerosol and atmospheric researchers and discussed ways in which the measurement of light scattering and global dimming can be better performed. These discussions involved how instrumentation, such as the nephelometer, can be improved to enhance the information that they produce.

We hope that this conference, and these meetings, will help improve the performance and broaden the scope of what nephelometers are capable of in air quality and global dimming studies.

The Aurora 2000 PM correlation nephelometer uses a single wavelength to measure aerosol light scattering and derive particulate concentrations. The Aurora 2000 nephelometer is available in two configurations.
PM2.5 Size Selective Inlet (SSI) to sample PM2.5, ideal in areas with stable aerosol chemistry Communicates directly with a BAM1020, ideal in areas with multiple aerosol sources

More info at = www.ecotech.com

---

Configuration 1

The Aurora 2000 nepheleometer is available with automatic flow control and a PM2.5 Size Selective Inlet. This configuration improves the correlation between the Aurora 2000 nephelometer and Federal Equivalent PM2.5 Methods.

This sampling method enables a manual correction factor to be entered in order to derive real time (1 minute) PM_2.5 concentrations. In applications where the aerosol chemistry is stable this configuration provides excellent results with minimal maintenance and a high degree of correlation.

The Aurora Nephelometer employs a smart heater controlled by a relative humidity sensor, this allows the user to set the maximum relative humidity of the sampled air, eliminating the influence of water vapour on the measurement and thus performing a “dry measurement”.

---

Configuration 2

In applications where aerosol chemistry is subject to change, a correction factor derived from manual sampling may be unreliable.

The Automatic correlation PM nephelometer connects directly to the Met One BAM1020 in order to monitor and log PM hourly averages generated by a BAM1020 (PM_BAM). These hourly averages are compared to the Aurora nephelometer’s hourly average scattering coefficient (σ_scat) and a scattering to PM coefficient factor (Coef_Scat/PM) is calculated. This factor is then applied to the next hour of 1 min scattering coefficients measured in order to determine a 1 minute average for PM concentrations (PM_aurora). This data can also be used to determine changes in aerosol source through deviations in light scattering from the expected values.