Harmonized Counting of Atmospheric Ultrafine Particles Nordic Aerosol Symposium NOSA 2017
T. Tritscher1, J. Spielvogel1, O.F. Bischof1, J. Scheckman2, F. Dahlkötter1 and T. Krinke1 1TSI
Lund, Sweden March 20-22, 2017
GmbH, Neuköllner Str. 4, 52068 Aachen, Germany 2 TSI Inc., 500 Cardigan Road, 55126 Shoreview, MN, USA
Contact:
[email protected]
Introduction and Motivation • Assess impact of ultrafine particles (UFP) on human health and climate • Supplement regulated air quality mass measurements of PM2.5 or PM10 with time-resolved measurement of particle number concentration • First step: Harmonizing the continuous measurement of UFPs by Condensation Particle Counter (CPC) • Technical Specification CEN/TS 16976 by the European Committee for Standardization (CEN) • This progress is well aligned with ACTRIS ( www.actris.net ), which aims for a high quality-assurance of ambient aerosol measurements.
CEN/TS 16976 Technical Specification
Tab. 1: CPC performance criteria (Excerpt from [1])
Performance characteristic
Criteria
Contains general information about aerosol properties and the method:
Actual flow rate
5 % difference to the nominal flow rate
• Defines performance criteria and test procedures for suitable CPCs • Defines performance criteria and test procedures for the sampling system • Lists requirements for installation, initial checks and calibrations, and operation of a CPC and sampling system at a monitoring site • Suggests a standardized data reporting format • Describes Quality Assurance and Quality Control procedures
Concentration response Slope Linearity Performance characteristic Detection efficiency at low particle size Actual flow rate
2 % difference to the factory-certified flow rate
Detection efficiency (at intermediate particle sizes) Number concentration measurement range Lower limit Upper limit Dynamic range
1 0,05 all residuals < 4 % of the measured value Criteria D50 = 7 nm ± 0,7 nm difference to the nominal flow rate D905 95 %difference at (50 10) 100 cm–3 (based on at least 1500 particle counts) 10 000 cm–3 (including coincidence correction) at least 3 orders of magnitude
Concentration response Slope Linearity
1 0,05 all residuals < 4 % of the measured value
Zero count rate
< 1 min–1
Response time
trise < 5 s tfall < 5 s
New CPC: Model 3772-CEN
Characterization & Calibration
• • • •
• CPCs were carefully checked to make sure all CEN/TS requirements Detection efficiency at lowwere particle size D50 = 7 nm ± 0,7 nm and recommendations fulfilled D90 < 14 nm • WCCAP has independently calibrated and characterized the first of Detection efficiency (at intermediate particle sizes) > 95 % at (50 10) nm the newUpper CPCs for counting efficiency (Fig. 2). particle sizetheir detection limit > 90 % detection efficiency at 1000 nm 100 nm
Compliant to the new Technical Specification CEN/TS 16976 Full flow butanol-based CPC (1 L/min) Single particle counting up to 50 000 particles/cm3 Detection efficiency D50=7 nm (calibrated with silver particles by
• Pulse height monitor ensures high data quality • CEN data record format
Counting Efficiency
World Calibration Center for Aerosol Physics (WCCAP), TROPOS, Leipzig
𝑡 rise −𝑡 fall 𝑡 rise
< 10 % or < 0,5 s
TSI 3772-CEN S/N: 904 TSI 3772-CEN S/N: 903
New Sampling System Dp in nm
• Dedicated inlet for CPCs & fully compliant to CEN/TS 16976 • Consists of: • PM10 sampling inlet • Single tube Nafion® dryer • Built-in dilution of 3:1 (adaptable to other dilution ratios). • Temperature & humidity (RH) are measured and reported to the CPC
Fig. 2: Counting efficiency (D50 of 7 nm) for silver particles generated with the evaporation / condensation method
Fig. 3: Linearity. Data points show data for 4 different CEN-CPC units, black line shows 1:1 line
Fig. 4: Response time. Shown are rise and fall time with trise < 2 s and tfall < 2 s
Summary • CEN/TS 16976 harmonizes the continuous atmospheric measurements of UFPs by defining requirements for CPC, its sampling system, measurement procedure and result reporting • Important step forward for routine monitoring networks (e.g. GUAN, NABEL, DEFRA [2]) and for evaluation of abatement techniques e.g. low emission zones [3] • TSI released new CPC with dedicated sampling system compliant to CEN/TS 16976, calibrated and characterized by WCCAP, TROPOS Fig. 1: Schematic of CEN Sampling System, Model 3772200
• Same high accuracy and tight tolerances as EECPCs, used in PMP type approval testing for Euro legislation
References [1] CEN/TS 16976. Ambient air - Determination of the particle number concentration of atmospheric aerosol, published August 24, 2016 [2] Defra report (2012), Particle number concentrations and size distributions in UK ambient air, Chapter 6-5, 2012 [3] Wiedensohler et al. (2016), Assessment of the Effectiveness of the Low Emission Zone Leipzig by Measurements of Soot and the UFP Number Concentration, 20th ETH-Conference 2016
