CARBONACEOUS AEROSOL SPECIATION SYSTEM MODEL CASS
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CARBONACEOUS AEROSOL SPECIATION SYSTEM MODEL CASS
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 INFO
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.
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.
OPERATION
- Supply voltage: 100-240 V~, 50/60 Hz
- Max power consumption: for TCA08 600 W (Heaters 400 W, Sample pump 100 W, Analytic flow pump 25 W) and for AE33 90 W (25 W on average)
- Airflow: for TCA08 Sample Airflow 16.7 LPM (Analytic Airflow 0.5 LPM); for AE33 Sample Airflow from 2-5 LPM
- Time resolution: 60 min (default) and user-selectable 20 min to 24 hours for TCA08 and user selectable 1 s or 60 s for AE33
ENVIRONMENTAL OPERATING CONDITIONS
- Indoor use, rack or benchtop (instrument)
- Altitude: up to 3000 m with internal pump for AE33. Increased flow at very high altitudes possible with external pump on request.
- Temperature range: 10 – 40 degrees Celsius (instrument)
- Relative humidity range: non-condensing (Note that it is essential to prevent condensation of humid outdoor sample air, if the instrument is located in a chilled (air-conditioned) environment.)
ANALYTICAL PERFORMANCE
- TCA Sensitivity: 0.5 μg C/m³ at 60 min sample time base and 16.7 LPM Sample Airflow
- AE33 Sensitivity: 0.03 μg/m³ at 1 min and 5 LPM
MECHANICAL SPECIFICATION
- CASS is supplied in standard 19’’/9U, rack mount, constructed of sheet metal
- Dimensions: 78 x 48 x 57 cm
- Weight: 89 kg
- Inlet plumbing requirement: the minimum overall height of the Total Carbon Analyzer (TCA) chassis and inlet tubing is 1.20 m. See details under TCA08 Specifications
CONNECTORS
TCA08 Connectors:
Sampling air stream:
- inlet: inner diameter 14 mm, outer diameter 18 mm, custom connectors. See Figure 2.
- outlet: .1/4” NTPF
Analytic air stream:
- inlet: 1/8’’’ NTPF
- outlet: (internal, not brought to panel connector)
Communications:
- 6x COM, 4x USB 2.0, 1x USB 3.0, 3x power USB, Ethernet
AE33 Connectors:
Sampling air:
- inlet / outlet type – ¼” NTPF
- Communication: 3x USB type A, 3x COM, 1x Ethernet
USER INTERFACE
CASS User Interface:
- 2x 8.4” SVGA display with LED backlight
- Basic control: touch-screen
- Optional control: standard PC keyboard and mouse
- Red, Yellow, Green status
PUBLICATIONS
| Title | Author | Publication | Year | Link |
|---|---|---|---|---|
| The new TC-BC method and online instrument for the measurement of carbonaceous aerosols | M. Rigler et.al. | Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-13-4333-2020 | 2020 | Download |
| Rigler (2017) Offline validation of the New Total Carbon Analyzer | M. Rigler et.al. | POSTER | 2017 | Download |
VIDEO RELATED TO CASS
Magee Scientific Total Carbon Analyzer Model TCA08
Dr. Tony Hansen (Magee Scientific Co.) about Black Carbon and the Magee Scientific Aethalometer®
For more video content please visit Magee Scientific YouTube channel or VIDEO tab of AE33 and TCA08.
ACCESSORIES
Magee Scientific offers accessories and routine supplies. Please contact our sales team to discuss your specific needs.
BGI TETRACAL® AIR FLOW CALIBRATOR
The BGI ‘TetraCal’® is a simple-to-use, NIST-traceable Standard for volumetric air flow, barometric pressure, and ambient temperature. The TetraCal is a venturi based system with built-in compensation for changes in ambient temperature and pressure. The TetraCal® may be directly connected to the Model TCA08 Total Carbon Analyzer for both air flow and data transmission: and used in automatic software routines for flow calibration of the TCA08.
PM2.5 SHARP CUT CYCLONE (SCC)
The Sharp Cut Cyclone (SCC) is designed to replace the US EPA WINS Impactor for PM2.5 sampling. It has proven advantages over the WINS because it is a dry system and does not require cleaning at frequent intervals. Since speciation sampling for particulates is not governed by an EPA FRM, the SCC may be freely utilized.
- Particle Size Cut PM2.5 at 16.67 LPM
- Ambient PM2.5 sampling
- Indoor Air Quality sampling
- Speciation sampling
AMBIENT METEOROLOGICAL SENSOR
The Ambient Meteorological Sensor is a non-aspirated unit which measures air temperature, relative humidity and barometric pressure. It uses a Pt100 element for Temperature; a compensated solid-state capacitive sensor for Relative Humidity; and a piezo-resistive pressure transducer for Pressure. The sensing elements are protected by a UV-resistant polymer shield. A data cable (supplied in 10-m. or 20-m. lengths) connects the sensor to the AE33, and its data is automatically imported and merged with the Black Carbon measurements.
SAMPLE STREAM DRYER
Drying the aerosol sample stream is highly recommended to provide accurate measurement data and to protect the equipment from water condensation.
In hot, humid locations, the water vapor content of the ambient sample air may be very large. This can lead to inaccuracies in the BC measurement – but, more seriously, there is the possibility of water condensation inside the instrument which can lead to permanent damage. This issue is solved by the use of our Sample Stream Dryer.
The interaction of water with aerosol species changes their physical properties. Consequently, the World Meteorological Organization has recommended that all aerosol measurements should be performed under conditions where the Relative Humidity is 40% or lower (WMO/GAW 2003; Wiedensohler, 2014).
Many stations in hot, humid locations have air-conditioned interiors. If the indoor air-conditioning temperature Ta is comparable to or lower than the dewpoint (condensation temperature) Td of the outside ambient air, water will condense in the tubing and inside the instrument. This will not only completely in-validate the data, but it can also cause permanent damage to the instrument.
The Magee Scientific Sample Stream Dryer removes water vapor from the inlet flow by means of a semi-permeable Nafion membrane. This membrane selectively absorbs molecules of water vapor from the air-stream and passes them to a space on the other side of the membrane, maintained at a low absolute pressure by means of a vacuum pump.
The Magee Scientific Sample Stream Dryer can reduce the dew point temperature by up to 14 degrees Celsius at a flow rate of 5 LPM. The equipment is self-contained, automatic, and includes a display screen which shows the input and output hygrometric properties. A data cable can connect to the Model AE33 Aethalometer so that the temperature and humidity data are incorporated into the Aethalometer’s data files.
The Magee Scientific Sample Stream Dryer can be used to remove water vapor from the inlet stream to anyaerosol instrument, not just an Aethalometer.
NEUTRAL DENSITY OPTICAL VALIDATION KIT
The Neutral Density Optical Filter Kit provides validation of the reproducibility of the photometric detectors.
The optical performance of the Magee Scientific Aethalometer® Model AE33 may be validated in the field by the ‘Neutral Density Optical Filter Kit’, consisting of four precision optical elements containing precision glass whose absorbance is traceable to primary photometric standards maintained by national organizations such as NIST (USA), NPL (UK), BIPM (EU), etc. Software routines measure the optical intensities at all wavelengths and compare the analysis during the test, with the original reference values. This validates the reproducibility of the Aethalometer’s fundamental measurement of optical Attenuation.
FILTER TAPE
The Magee Scientific Aethalometer® Model AE33 collects its samples on a proprietary filter tape made of glass fibers coated with PTFE/PET, and supported on a mechanical backing for transport in the instrument. When the spot reaches a pre-set loading density, the tape is advanced to create a new spot. Each roll of tape is 10 m. in length and will last from a few weeks to a few months, depending on the average concentration of BC in the sampled atmosphere and the operational flow-rate that is chosen.
SIZE-SELECTIVE INLETS
Ambient atmospheres include suspended particles of large aerodynamic size such as pollen, dust, etc. These particles are not strongly optically absorbing and therefore do not interfere with the Aethalometer® analysis: however, after lengthy use a deposit of dust in the internal optics will degrade performance. To exclude large particles, and to provide analysis of a known respirable size fraction, we recommend use of size-selective inlets designed to exclude particles of aerodynamic size greater than a specified cut point at a specified sample air flow rate. We offer the ‘Sharp-Cut Cyclones’ designed by BGI (USA) and now manufactured by Mesa Labs (USA). These inlets are usually attached directly to the sample inlet tube at the point of entry, but may also be installed in-line closer to the Aethalometer..
PM2.5 Inlet
BGI model SCC-1.828. Provides a cut point of 2.5µm at a sample flow rate of 5 LPM.
PM1/2.5 Inlet
BGI model SCC-1.197. Provides a cut point of 2.5µm at a sample flow rate of 2 LPM, or 1µm at a sample flow rate of 5 LPM.
PM1 Inlet
BGI model SCC-0.732. Provides a cut point of 1µm at a sample flow rate of 2 LPM.
BGI ‘Mini-PM’ Inlet Kit
The BGI ‘Mini-PM’ Inlet Kit offers impaction jet inserts to provide size selective capabilities of TSP, PM-4, PM-2.5, and PM-1, when operated at a flow rate of 5 LPM.
GENERAL QUESTIONS ABOUT CASS - It consists of TCA08 and AE33, therefore FAQs below relate to separate instrument subunit.
Black Carbon is a primary pollutant produced by the incomplete combustion of fuel. Its association with toxic and carcinogenic compounds makes it the Number-1 pollutant species most associated with adverse health effects. Its absorption of light makes it the Number-2 climate forcing agent, second only to CO2. Unlike CO2, whose emissions are directly related to the carbon content of fuel, the emission of BC can differ by orders of magnitude from one combustion source to another. Consequently, the emission of BC cannot be predicted, and has to be measured.
The Aethalometer collects aerosol particles on a spot on a filter tape. The spot is illuminated from one side, and the transmitted light is measured on the other side. A blank, un-loaded portion of the filter is used as a reference. The ‘optical attenuation’, “ATN”, is a measure of the absorption of light, and is directly proportional to the density of absorbing material on the spot. The rate at which ATN increases is proportional to the rate of accumulation of absorbing material. Knowing the sample air flow rate, the concentration in the air stream is calculated. This analysis is performed at multiple optical wavelengths, since some aerosol species may have enhanced optical absorption at shorter wavelengths.
The Aethalometer collects aerosols on a filter tape – but gases pass through it. Aerosol “Black Carbon” is the only species with a very strong optical absorption at 880 nm (infra-red). Some compounds of organic aerosols – such as are associated with ‘brown Carbon’ and biomass smoke – may absorb more strongly at shorter wavelengths. The Aethalometer analyzes at 7 wavelengths and is able to discriminate “diesel” emissions from “wood smoke”.
The Aethalometer measures the Attenuation of the light transmitted through the sample-collecting spot, relative to the intensity of light transmitted through a blank portion of the tape acting as a Reference. This ratio is independent of .the absolute intensity of the source. Therefore, changes in the optical source intensity are irrelevant, and the source intensity never needs to be adjusted or calibrated.
Even if the output intensity of the light source changes, the ATN measurement is not affected, since it is the ratio of two signals. The optical source in the Aethalometer is an array of LED chips which are operated at much less than their maximum rated power. Consequently, these LED sources are expected to last almost indefinitely.
Offline validation is important (1) to confirm the simplified Total Carbon Analyzer 08 method and (2) to compare offline analysis of ambient samples with standardized OC/EC method. The new instrument does not use glass chamber, high purity gases and catalyst oxidation via MnO2. Experiments with series of different sucrose solutions and ambient filter punches showed that we have nearly 100% efficient combustion without glass, gas and catalyst.
Yes, we did. In Ljubljana, urban background location, we showed that online TC-BC method is equivalent to the standardized OC/EC method.
We are using two heating modules with heating wires in each chamber. In this way, we can rapidly heat up the filter up to 900 oC.
To get the combustion process as efficient as possible we developed a two-stage heating thermal protocol. Firstly, the lower heater is turned on (analytic flow stream goes in up-down direction, see Figure 3) which is rapidly heated up to 900 oC. In that way, we are sure that all the OC vapors passing the lower heater are converted to CO2. After lower heater reaches the temperature of 900 oC the upper heater is turned on so everything on the filter is really combusted.
These are used when instrument is measuring online. When for example CH1 is sampling PM on filter, CH2 is preforming analysis of previously collected PM. After the end of sampling timebase the flows are switched. Now CH1 is analyzing previously collected PM, CH2 is sampling new material. With that we achieve almost zero “dead time” in measuring.
