Design and Application of an Unattended Multifunctional H-TDMA System

Abstract

The hygroscopic properties of aerosols have a significant impact on aerosol particle number size distributions (PNSD), formation of cloud condensation nuclei, climate forcing, and atmospheric visibility, as well as human health. To allow for the observation of the hygroscopic growth of aerosols with long-term accuracy, an unattended multifunctional hygroscopicity-tandem differential mobility analyzer (H-TDMA) system was designed and built by the Institute of Tropical and Marine Meteorology (ITMM), China Meteorological Administration (CMA), in Guangzhou, China. The system is capable of measuring dry and wet PNSD, hygroscopic growth factor by particle size, and mixing states. This article describes in detail the working principles, components, and calibration methods of the system. Standard polystyrene latex (PSL) spheres with flve different diameters were chosen to test the system's precision and accuracy of particle size measurement. Ammonium sulfate was used to test the hygroscopic response of the system for accurate growth factor measurement. The test results show that the deviation of the growth factor measured by the system is within a scope of -0.01 to -0.03 compared to Köhler theoretical curves. Results of temperature and humidity control performance tests indicate that the system is robust. An internal temperature gradient of less than 0.2 K for a second differential mobility analyzer (DMA2) makes it possible to reach a set-point relative humidity (RH) value of 90% and with a standard deviation of ±0.44%, sufficient for unattended field observation.

Distinct Ultrafine‐ and Accumulation‐Mode Particle Properties in Clean and Polluted Urban Environments

“…The H‐TDMA system used in this study was custom built (Tan et al, ; Y. Wang, Li, et al, ). Briefly, this system mainly includes two differential mobility analyzers (DMA, model 3081L, TSI Inc.) and a water‐based condensation particle counter (WCPC, model 3787, TSI Inc.).…”

Simultaneous measurements of particle number size distributions at ground level and 260 m on a meteorological tower in urban Beijing, China

“…Comparatively, an SMPS as part of an unattended multifunctional hygroscopicity tandem differential mobility analyzer (H-TDMA) developed by the Guangzhou Institute of Tropical and Marine Meteorology, China Meteorological Administration (ITMM, CMA) was used to mea- sure particle number concentrations (10-400 nm) at ground level. A detailed description of the H-TDMA was given in Tan et al (2013). According to previous comparisons of particle number size distributions between different SMPSs or differential mobility particle sizers, the measurement uncertainties between 20 and 200 nm can be ∼ 10 %, and even larger for particles outside this range (Wiedensohler et al, 2012).…”

“…Positive matrix factorization (PMF, 2.exe, v 4.2) was performed on the size-resolved number concentrations (Ulbrich et al, 2009;Paatero and Tapper, 1994) to resolve potential sources. In this study, the measurement uncertainties were estimated using an equation-based approach that was detailed in Ogulei et al (2007).…”

Comparison of Aerosol Hygroscopcity, Volatility, and Chemical Composition between a Suburban Site in the Pearl River Delta Region and a Marine Site in Okinawa

“…The instrument was self-developed by the Guangzhou Institute of Tropical and Marine Meteorology (ITMM) (Tan et al, 2013b) and upgraded to include both H-and V-mode, instrumentation and algorithm (Cheung et al, 2016). Here only configuration relevant to the measurements was described.…”