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Latest News Technical Papers presented by Ecotech at IUAPPA, Brisbane, Australia
Technical Papers presented by Ecotech at IUAPPA, Brisbane, Australia
Ecotech recently presented papers on its
Trace Gas Analyzers and the new 3 Wavelength Nephelometer. Below are the abstracts with full papers available from Ecotech's International website: www.ecotech.com
ADVANTAGES OF ECOTECH’S TRACE PRECURSOR MONITORING STATIONS
Robert Dal Sasso, Marie Laborde,
Abstract
The last ten years have seen environmental pollution levels decrease significantly in many countries including Australia and the USA. Thus the measurement of trace precursor gas levels becomes correspondingly more essential. Indeed, air quality model evaluation, greenhouse studies, scientific studies ranging across technological, health and atmospheric process disciplines, all require the development of trace gas analysis.
Ecotech is the only Australian company to have U.S. EPA approval for their range of ambient gas analysers and has extensive experience not only in the design and manufacture of monitoring stations but also in their operation.
Based on this field experience, Ecotech has developed analysers and systems for the accurate measurement of trace precursor concentrations. Ecotech’s standard range of ambient analysers have been modified and optimised for use in trace precursor monitoring applications.
In addition Ecotech has recognised that station design is just as important as the analyser design with issues such as sample path length, use of inert materials, calibration and data acquisition using digital communication considered in the overall design.
These developments have produced systems that are capable of monitoring concentrations as low as 50 ppt for NOX, 100 ppt for SO2 and 25 ppb for CO.
This technical paper will describe more specifically the improvements in technology and design that has enabled these detection limits to be achieved. It will also examine the complete setup of the system and data from a number of case studies will be presented.
Keywords: Precursor Gas analyser, trace station design, data logger
communication, analyser specification.
ADVANTAGES OF USING THE ECOTECH THREE WAVELENGTH NEPHELOMETER FOR AEROSOL MEASUREMENTS
Marie Laborde, Marta Salek and David Logan
Abstract
The measurement of the scattering properties of aerosols is limited by the errors introduced by typical single wavelength integrating nephelometers.
These limitations, however, can be reduced by implementing the features of the Ecotech Three Wavelength Integrating Nephelometer. These limitations are predominantly contributed by particle size, relative humidity, Lambertian distribution of the light source, truncation error and the wavelength of the nephelometer.
Fitting a PM2.5 size selective inlet and controlling the relative humidity of the sample reduces the effects of larger particle sizes and moisture. The errors introduced by a non-Lambertian light source can be reduced by calibrating the light source distribution.
This feature is unique to the Ecotech design.
The truncation errors introduced by the physical constraints of the nephelometer’s measurement cell can also be corrected by measuring the sample at three distinct wavelengths (450nm, 520nm & 700nm). The Ecotech Three Wavelength Integrating Nephelometer also has the added advantage of a compact three wavelength light source, which eliminates the need for complex optics and multiple photomultiplier tubes, making the instrument more portable and robust.
Theoretical studies have shown that the use of a size selective inlet can improve the uncertainty of the scattering measurement by an order of up to 30% at a particle size of < 1 m.
Further studies have shown that correcting the truncation errors by measuring at different wavelengths can reduce this error a further 10%. These conclusions highlight that the Ecotech Three Wavelength Integrating Nephelometer can be used for very precise measurements of aerosol properties in varying conditions.
Keywords: nephelometer, Lambertian, Ångström exponent, humidity,
calibration, Mie Theory, scattering coefficient, aerosol.