2. The need to measure carbonaceous aerosols
Carbonaceous aerosols are harmful in every way; obvious to everyone; and not defended by any industry or political power. It’s easy to measure them, and
easy to explain the reasons as follows:
1. Black Carbon is the primary component of Diesel Particulate Matter (‘DPM’), an ‘Air Toxic’ that has been designated as a Hazardous Air Pollutant and
which is regulated in both ambient and occupational (workplace) environments.
2. Black Carbon has the highest statistical correlation to adverse health effects such as asthma attacks, bronchitis, respiratory and cardiovascular symptoms,
hospitalization and premature death.
3. Black Carbon is the second leading forcing agent for Climate Change.
4. Combustion-derived aerosols can modify the properties of clouds and precipitation; can melt snow and ice when deposited; and can reduce visibility.
5. Black Carbon emissions can not be modeled or predicted: since BC is produced by the incomplete combustion of fuel, its emissions depend entirely on
the nature of the source. BC emissions and ambient concentrations can not be modeled or predicted, they must be measured.
6. Black Carbon is NOT adequately characterized through PM-2.5 mass measurements. The BC fraction of PM-2.5 mass can be highly variable. Actual
measurements and speciation are necessary.
7. BC aerosols can cross national boundaries and can be transported over long distances. Air Quality measurements at a receptor location may be
dominated by emissions from upwind sources, even in another State or Country.
3. Why measure Carbonaceous Aersosols with high
time resolution?
1. Carbonaceous aerosols account for a large and often dominant fraction of PM2.5 and are extremely diverse.
2. Particulate carbon (Total Carbon, TC) is commonly characterized by its organic carbon (OC) and elemental carbon (EC) content.
3. Organic carbon (‘OC’) usually compromises the largest carbon-containing fraction of ambient aerosols; often more than 50 % of the PM2.5 mass.
4. Organic aerosols are a complex mixture of chemical compounds including those with possible mutagenic and carcinogenic effects.
5. OC aerosols are produced as primary aerosol particles from fossil fuel and biomass burning; natural biogenic emissions; and other sources: or formed
as secondary aerosol particles from precursors in the atmosphere.
6. In contrast, EC aerosols are exclusively of primary origin and are emitted directly from the incomplete combustion of carbonaceous fuels.
7. The TC-BC method combines an optical method for measuring Black Carbon (BC, closely related to EC) by the AE33 Aethalometer; together with a
thermal method for measuring Total Carbon (TC) by the TCA08 Total Carbon Analyzer. This provides a complete characterization of carbonaceous aerosols
with high time resolution.
8. Measurements with high time resolution permit the identification of time-activity patterns; correlation with meteorological conditions including
stagnation, ventilation, and advection; identification of individual sources; infiltration into occupied buildings; real-time pollution alerts; and the
management of worker exposure in occupational environments.
8. A REVOLUTIONAIRY OC/EC ANALYZER
The Magee Scientific Carbonaceous
Aerosol Speciation System (CASS), is
a combined unit of a TCAO8 Total
Carbon Analyzer, and the Magee
Scientific Aethalometer® AE33, providing
a revolutionary scientific
instrument that measures
Total Carbon Content (“TC”)
Elemental Carbon Content (EC)
the Organic Carbon Content (OC)
Black Carbon Content (BC)
of suspended aerosol particles in
near-Real Time.
9. DETERMINATION OF TC, BC AND
EQUIVALENT OC AND EC FRACTION
TCAO8 instrument has 2 identical parallel
channels.
A continuous operation: while one channel is
collecting its sample, the other channel
analyzes an already collected one. At the end
of the collection period, the sample flow is
switched from one channel to the other
channel.
Collected sample is flash-heated (7O s, 950 -
1OOO°C) to convert all Carbon to COs;. The
CO, concentration is then integrated and
transformed to concentration (g/cm?) to give
the Total Carbon (TC) content of the sample.
In parallel Magee Scientific Aethalometer®
characterize a Black Carbon (BC/EC) aerosols
accumulated on a glass-fiber/PTFE filter tape.
On a defined time-base (1 s or 60 s) AE33
reports this BC/EC data to TCAO8
11. CASS MEASUREMENT PRINCIPLE
BC data from The Magee Scientific Aethalometer® AE33 is used to determine the equivalent EC fraction:
‘EC‘ = b * BC. The factor b is region specific and has to be determined in advance.
Equivalent OC is determined by a simple subtraction: ‘OC‘ = TC - ‘EC‘
17. CONCLUSIONS
• CASS — Carbonaceous Aerosol Speciation System is a revolutionary
OC/EC analyzer...Designed for routine and unattended analysis of
ambient aerosols.
• it provides complete speciation and quantitation of the carbonaceous
component of ambient aerosols in near-Real Time: BC (“EC”) ; BrC ;
OC: TC
• This equipment package is designed for operation at routine Air-
Quality monitoring stations; at scientific research project sites, even
at the most remote locations; and in laboratory studies.
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