The Magee Scientific Carbonaceous Aerosol Speciation System, model CASS, is a combined unit of a Total Carbon Analyzer, model TCA08 and an Aethalometer, model AE33 providing a revolutionary scientific instrument that measures the Total Carbon Content(“TC”), the Elemental Carbon content(EC), the Organic Carbon content(OC) and the Black Carbon content(BC) of suspended aerosol particles in near-Real Time.
CONTINUOUS ANALYSIS of CARBONACEOUS AEROSOLS
NEAR REAL-TIME determination OC/EC, TC, BC, %BB
SAMPLING TIME 20 min to 24 hours
NO special GAS, NO CATALYST and NO special quartz GLASS
RUGGED and RELIABLE
SOURCE APPORTIONMENT
DUALSPOTTM – PATENTED technology
PRODUCT ADVANTAGES AND BENEFITS
- DUALSPOTTM TECHNOLOGY for yielding Black Carbon result independent of the so called “filter loading effects”.
- CONTINUOUS ANALYSIS OF TOTAL CARBON content by using 2 identical flow channels with 2 independent stainless steel combustion chambers.
- SOURCE APPORTIONMENT to discriminate Black Carbon from fossil fuel vs Black Carbon from biomass burning with built-in analysis by a 2-component model.
- CALIBRATION/VALIDATION against NIST STANDARD reference material to validate the data by a Neutral Density Optical Filter Kit. This procedure can be performed at the instrument site to maximize up-time and minimizes expenses.
- Using AMBIENT AIR in the combustion chamber as a carrier gas to create CO2 pulse and measures the level of TC in ambient air, therefore NO special GAS and NO special quartz GLASS is required.
- RUGGED and ALL STEEL CONSTRUCTION to fit the requirements of standardized 19” rack type mounting.
- EASY INSTALLATION and MAINTENANCE and VERY LONG AUTONOMOUS OPERATION
ONLINE TC, BC, OC/EC DETERMINATION
The Magee Scientific Carbonaceous Aerosol Speciation System CASS provides a real-time data for BC, closely related to EC, and automatically combines them with TC data from TCA to provide a complete characterization of the carbonaceous component of the aerosol in near-real-time: TC, BC, (or ´EC´) and OC. The characterization of all carbonaceous aerosol components is performed by including a simple mathematical relation: TC = BC (EC) + OC.
REAL-TIME SOURCE APPORTIONMENT (%BB)
The Magee Scientific Carbonaceous Aerosol Speciation System CASS instrument discriminates a Black Carbon fossil fuel from a Black Carbon biomass burning (%BB) in real-time through a sophisticated built-in SW analysis based on a two-component Aethalometer model.
SEVEN WAVELENGTH OPERATION: UV-IR, 1HZ DATA
The BC (´EC´) optical analysis is performed at 7 wavelengths from the near-infrared (950 nm) to the near-ultraviolet (370 nm) yielding optical absorption characteristics of collected aerosols on a teflon-coated glass fiber filter tape. Tape advances automatically when user selectable loading threshold is reached, typically once every few hours depending on aerosol concentration and air flow-rate.
RUGGED INSTRUMENT FOR LONGER AUTHONOMOUS OPERATION
The Magee Scientific Carbonaceous Aerosol Speciation System CASS is constructed in a rugged and compact design to fit AE33 and TCA08 into 19” rack type CASS housing package suitable for field-work, laboratory and routine Air Quality monitoring applications with limited space. CASS can operate for longer period of time (from weeks to months) without operator´s attention, only a roll of filter tape on AE33 and quartz fiber filter or denuder on TCA08 have to be replaced from time to time.
CASS MEASUREMENT PRINCIPLE
The Magee Scientific Carbonaceous Aerosol Speciation System CASS simultaneously controls an operation of 2 instruments, i.e. the Total Carbon Analyzer TCA08 and the Aethalometer AE33. The first one collects a sample of atmospheric aerosols on a quartz fiber filter positioned inside a small stainless-steel chamber, at a controlled sampling flow rate of 16.7 LPM. The default sampling time of TCA08 is 60 min, but can be set from 20 min – 24 h, depending on the ambient aerosol concentrations. TCA08 instrument has 2 identical parallel channels, through which air-flows are being controlled by ball valves and solenoids. A continuous operation is enabled and sustained by the following principle of operation: while one channel is collecting its sample, the other channel analyzes an already collected one and reports a Total Carbon TC level on a set time-base (from 20 min – 24h). After collection on the filter, two flash-heating elements combust the sample instantaneously in a small ‘analytic’ flow of filtered ambient air. This converts all the carbonaceous compounds into CO2 and creates a short but large-amplitude pulse of CO2 in the analytic flow passed to the NDIR CO2 detector. The background level of CO2 in ambient air during the heating cycle is determined before and after the heating cycle, the provide the baselines against which the combustion pulse is measured. The CO2 concentration over the baseline is integrated to give the Total Carbon (TC) content of the sample.
In parallel to TCA08, CASS instrument also performs a BC/EC monitoring with AE33 on a 1 Hz time base performing an optical attenuation analysis at 7 wavelengths from near UV (370 nm) to near IR range (950 nm) in order to characterize a Black Carbon (BC/EC) aerosols accumulated on a Teflon-coated glass fiber filter tape. The Aethalometer AE33 draws the sample air stream through a filter tape with a flow rate from 2 – 5 LPM. Aerosols are collected on two spots on the tape and are illuminated by a multi-wavelength light source. Detectors measure the attenuation of light by the absorbing components of the aerosols, relative to a reference through an un-exposed portion of the tape. On a defined time-base (1 s or 60 s) AE33 reports this BC/EC data to TCA08. BC/EC data is together with TC included into a simple mathematical formula (TC = BC (EC) + OC) in order to deduce the OC level on the same time-base as the TC level.
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