Secondly, because of the time between sample collection and analysis, volatile components of the aerosol may evaporate and be lost or chemically unstable compounds may react. First, a measurable amount of material has to be collected, and the detection limits of laboratory chemical analysis instrumentation usually require sampling times from several hours to days, so temporal resolution is generally poor. The most direct method is to collect particulate matter on a filter or impactor substrate over a period of hours and to analyze the material using standard analytical procedures, but this carries many intrinsic limitations. The technology to accurately count, size, and determine the mass concentration of particles in real time is well established, but the chemical analysis of aerosol is not as easily performed. For a detailed review of such instrumentation, the reader is directed to McMurry. Our level of understanding of the nature, sources, processes and effects of atmospheric aerosols has so far been limited by the instrumentation that is available to study them. This has led to the increased interest in fine PM and the adoption of the PM 2.5 standard in some areas such as the USA. However, it has been suggested that the smaller particles, known as fine particles (the widely accepted definition being those of sizes less than 2.5 μm), are the more damaging to health, as they tend to have a higher toxicity and can penetrate deeper into the alveolar region of the lungs. The majority of environmental monitoring and control has been based around measuring the total mass of particulate matter based on the PM 10 standard (particles of an aerodynamic diameter less than 10 μm), as these particles are more likely to pass the throat when inhaled.
Urban areas in particular are known to be major sources of anthropogenic aerosol, and the detrimental effects ambient particulate matter (PM) in cities has on visibility and the health of their inhabitants have long been studied. Atmospheric particulate matter is known to have a major impact on phenomena such as climate forcing, heterogeneous chemistry, cloud formation, and the hydrological cycle.
This paper is accompanied by part 2 of this series, in which these methods are used to process and analyze AMS results on ambient aerosol from two U.K. It is also possible to quantify the uncertainties in both MS and TOF data by evaluating the ion counting statistics and variability of the background signal, respectively. The techniques for applying particle velocity calibration data and transforming signals from time of flight (TOF) mode to chemical mass distributions in terms of aerodynamic diameter (d M/dlog( D a) distributions) are also presented. It is also necessary to correct for variations in the electron multiplier performance, and a method involving the measurement of the instrument's response to gas phase signals is also presented. These include the conversion of detected ion rates from the quadrupole mass spectrometer during the mass spectrum (MS) mode of operation to atmospheric mass concentrations of chemical species (in μg m −3) by applying calibration data.
#Use mmass to analyze data software
Analytical and software tools for interpreting the data from this instrument and generating meaningful, quantitative results have been developed and are presented here with a brief description of the instrument. The aerosol mass spectrometer (AMS), manufactured by Aerodyne Research, Inc., has been shown to be capable of delivering quantitative information on the chemical composition and size of volatile and semivolatile fine airborne particulate matter with high time resolution.
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