Grimm Aerosol Technik (Germany)

Abstract. Sub-10 nm aerosol particles play a critical role in the atmosphere through their involvement in new particle formation, a key process influencing the availability of cloud condensation nuclei. In recognition of their significance, international observation frameworks such as the Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS) engage in the process of integrating their observations into standardized protocols. ACTRIS aims to enhance the understanding of atmospheric processes, including those related to particle dynamics and their interactions with clouds and climate through harmonized long-term observations. To evaluate the performance of current instrumentation for sub-10 nm particle measurements, as well as the procedures for doing so, in November 2023, the ACTRIS Cluster Calibration Center in Helsinki, Finland, held its first workshop on the intercomparison of instrumentation for sub-10 nm aerosol particle number size distribution measurements. In this workshop, three mobility-based systems (GRIMM PSMPS, TSI 1 nm SMPS and TSI 3938N56) and five activation-based systems (three Airmodus A11s and two Airmodus A12s) were evaluated. The focus lay on assessing their number concentration response and size-dependent detection efficiency – including the determination of the diameter with 50 % detection efficiency – and sizing accuracy. In addition to these parameters, the instruments were compared with each other while measuring aerosol particle number size distributions side by side from an aerosol chamber. Beyond the evaluation of instrument performance, the workshop aimed to test and assess calibration and comparison methods to identify aspects of ACTRIS compliance requiring further refinement. Although this work highlights the key strengths of the different measurement techniques and instruments, several challenges remain. Mobility-based systems showed high sizing accuracy, especially for particles larger than 2 nm, while encountering challenges in measuring particles in the lower atmospheric concentration range. Activation-based systems proved more sensitive at lower particle number concentrations and particle sizes, with the drawback of slight unit-to-unit variability. Additionally, a systematic size shift was identified in aerosols generated by 4-way-cross glowing wire generator setups, indicating a need for further investigation on this effect and the development of calibration equipment in the sub-10 nm size range.

Abstract. The working fluid of a condensation particle counter (CPC) is one of its essential characteristics. Butanol is commonly used as the working fluid in alcohol-based CPCs due to its proven performance in various applications and a wide range of working conditions over the past almost five decades. At the same time, butanol has several disadvantages including its strong, unpleasant odour, negative effects when inhaled over prolonged periods, and flammability, making it troublesome to use in all places with strict safety regulations. We are proposing to address these negative issues by replacing it with dimethyl-sulfoxide (DMSO), a substance that has not been used as the working fluid in a CPC up to now. DMSO is an odourless, non-flammable, non-toxic substance that is easily accessible and inexpensive. During thorough experiments, this new substitute working fluid has proven to be stable in its performance in CPC and storage. We could show that DMSO behaves equivalent to butanol when used to operate a CPC in terms of the instrument's counting efficiency, D50 cut-off diameter and concentration linearity. In addition, we have demonstrated this for operating pressures ranging from ambient down to 200 hPa without the need for any safety precautions. Our new working fluid was tested on three CPC units representing two different models, almost always in side-by-side measurements. So far, we have achieved the best results with operating temperatures of 40 °C for the CPC’s saturator and 5 °C for its condenser. To address a less desirable property of DMSO, it could be mixed with a slight amount of water to decrease its freezing point significantly. When mixed accordingly, the substance stays liquid even in work environments with temperatures ≤ −10 °C and without any impact on the CPC's counting efficiency performance.

<p>With the EDM264, GRIMM offers a [A1] solution for mobile short- and long-term measurements in outdoor areas and at production sites. For research as well as permanent areal observations on a near reference quality base.</p><p>The model EDM264 features a powerful and robust measuring cell based on optical particle counting (OPC) principle with all the advantages that users of GRIMM‘s portable aerosol spectrometers  are used to. The system is embedded in a compact weather-protection housing with all-weather sampling, heated inlet system, data logger and meteorological sensor.</p><p>With TSP, PM10, PM4, PM2.5, PM1 and PMcoarse, the EDM264  provides all fine dust fractions real-time, valid for outdoor applications and calculated with the proven GRIMM enviro-algorithm, as well as six additional dust mass fractions pm10, pm2.5, pm1, inhalable, thoracic and respirable for IAQ and workplace measurements.</p><p>This highly versatile instrument performs real-time monitoring of particle number, particle size and provides information on particle surface distribution as well as dust mass distribution. GRIMM‘s EDM264 has 31 equidistant size channels, which are PSL traceable.</p><p>A high-end data logger enables data acquisition and wireless communication via LTE, WLAN or wired via Ethernet. Backup copies of the measurement data are stored in the device directly.</p><p>The rinsing air function, which protects the laser and detector in the optical cell, further increases the reliability and long term stability of the EDM264 under different environmental and climatic conditions.</p><p>The entire sample volume flow of 1.2 L/min is analyzed by 100% in the optical cell, which assures excellent counting efficiency at low and high concentrations and complies to the ISO 21501-1standard for OPCs.</p><p>With  all  these  features,  the  EDM264 is a world-leading dust monitor for precise monitoring of particulate matter and particle number concentration. This highly reliable instrument is an indispensable tool for many users, who need to measure aerosol levels and air quality outdoors, on construction sites, or at production facilities.</p><p>Keywords — aerosol research, aerial observation, fence line monitoring, wild fire detection   </p>

The study investigates the spatial pattern of black carbon (BC) at a high spatial resolution in Augsburg, Germany. Sixty two walks were performed to assess the concentrations of equivalent black carbon (eBC), ultraviolet particulate matter (UVPM), and equivalent brown carbon (eBrC) in different seasons and at different times of the day with a mobile platform (i.e., trolley). Along with BC measurements, images of street microenvironments were recorded. Meteorological parameters, including temperature, relative humidity, and wind speed, were monitored. The BC concentrations showed significant spatial heterogeneity and diurnal variations peaking in the morning and at night. The highest BC concentrations were observed near dense traffic. The correlations between BC and street views (buildings, roads, cars, and vegetation) were weak but highly significant. Moreover, meteorological factors also influenced the BC concentration. A model based on street view images and meteorological data was developed to examine the driving factors of the spatial variability of BC concentrations at a higher spatial resolution as different microenvironments based on traffic density. The best results were obtained for UVPM and eBC (71 and 70% explained variability). eBrC (53%), to which other sources besides road traffic can also make significant contributions, is modeled less well.

Abstract. Highly oxygenated organic molecules (HOMs) contribute substantially to the formation and growth of atmospheric aerosol particles, which affect air quality, human health and Earth's climate. HOMs are formed by rapid, gas-phase autoxidation of volatile organic compounds (VOCs) such as α-pinene, the most abundant monoterpene in the atmosphere. Due to their abundance and low volatility, HOMs can play an important role in new-particle formation (NPF) and the early growth of atmospheric aerosols, even without any further assistance of other low-volatility compounds such as sulfuric acid. Both the autoxidation reaction forming HOMs and their NPF rates are expected to be strongly dependent on temperature. However, experimental data on both effects are limited. Dedicated experiments were performed at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN to address this question. In this study, we show that a decrease in temperature (from +25 to −50 ∘C) results in a reduced HOM yield and reduced oxidation state of the products, whereas the NPF rates (J1.7 nm) increase substantially. Measurements with two different chemical ionization mass spectrometers (using nitrate and protonated water as reagent ion, respectively) provide the molecular composition of the gaseous oxidation products, and a two-dimensional volatility basis set (2D VBS) model provides their volatility distribution. The HOM yield decreases with temperature from 6.2 % at 25 ∘C to 0.7 % at −50 ∘C. However, there is a strong reduction of the saturation vapor pressure of each oxidation state as the temperature is reduced. Overall, the reduction in volatility with temperature leads to an increase in the nucleation rates by up to 3 orders of magnitude at −50 ∘C compared with 25 ∘C. In addition, the enhancement of the nucleation rates by ions decreases with decreasing temperature, since the neutral molecular clusters have increased stability against evaporation. The resulting data quantify how the interplay between the temperature-dependent oxidation pathways and the associated vapor pressures affect biogenic NPF at the molecular level. Our measurements, therefore, improve our understanding of pure biogenic NPF for a wide range of tropospheric temperatures and precursor concentrations.

Abstract. Cloud condensation nuclei (CCN) play an important role in cloud microphysics and are crucial for the second indirect effect of aerosols on global climate. One of the uncertainties in calculations of the indirect effect is due to insufficient data on CCN activation. The formation and growth processes of aerosol particles which subsequently become CCN determine their chemical composition. Due to the numerous organic and inorganic components present in atmospheric aerosol particles, a determination of the chemical composition of individual CCN is still challenging. To expand our understanding of activation of real-world CCN we introduce a novel method to characterize the chemical composition of single activated CCN in their droplet state. This method consists of a coupling of two essential instruments, a CCN-VACES (Cloud Condensation Nuclei-Versatile Aerosol Concentration Enrichment System) which is a modification of the original VACES to select and enrich CCN concentrations, and a Laser Ablation Aerosol Particle Time of Flight mass spectrometer (LAAPTOF), a single particle mass spectrometer. In the CCN-VACES, an aerosol flow is exposed to a specific water vapour supersaturation (in this study: 0.035 %, 0.054 %, 0.1 % and 0.6 %, respectively) and the CCN in the flow grow to droplets if their critical supersaturation is exceeded. These grown droplets are subsequently enriched in concentration by means of a virtual impactor at the end of the growth region by a factor of ca. 16 and pass directly into a LAAPTOF to measure the chemical composition of individual activated droplets. Contrary to widely held beliefs, the LAAPTOF is able to analyse refractory and non-refractory components even in aqueous droplets and can therefore be used to determine the chemical composition of actually activated CCN in their droplet state. Single particle spectra (for both positive and negative ions) were obtained from activated CCN in the ambient aerosol as well as activated CCN originating from aerosolized sea water samples collected at two different regions (Palma de Mallorca and San Sebastián, Spain). Ambient CCN were found to contain sometimes highly complex mixtures of different carbonaceous and non-carbonaceous components. Sea water derived CCN show the expected content of sea salt constituents, but the presence of organics is also observed. Activated CCN from the San Sebastián water samples have stronger sulphate signals than the Mallorca water sample. The LAAPTOF was found to provide insights into the composition of individual activated CCN.

Molecular singly charged clusters generated by electrospray sources are commonly used for calibration measurements of ultrafine Condensation Particle Counters (CPCs) in the sub-2 nm size range. This technique has been limited to the smallest singly charged clusters. In this study, we used a bipolar electrospray source combining two electrosprays of opposite polarities to generate singly charged clusters of ammonium salts dissolved in acetonitrile, i.e., tetra-heptyl ammonium bromide (THABr) and tetra-butyl ammonium iodide (TBAI) clusters. A high-resolution UDMA acts as a classifier for positively and negatively charged clusters which are used as mobility standards for the measurement of the complete ascent of the detection efficiency curve of three ultrafine CPCs. The CPCs characterized in this work are two laminar flow-type CPCs using n-butanol (TSI UCPC Model 3776, TSI Inc., Minneapolis, MN USA) and diethylene glycol (DEG) (TSI UCPC Model 3777, TSI Inc.) as working fluid and the turbulent mixing-type DEG-based Particle Size Magnifier (Airmodus A10 PSM). The clusters generated by the bipolar electrospray source are analyzed for their elemental composition using the Atmospheric Pressure interface Time-Of-Flight mass spectrometer (ioniAPi-TOF, Ionicon Analytik GmbH, Austria) in positive and negative ion mode. We present mobility-dependent mass spectra from experiments using the UDMA and the ioniAPi-TOF in series for the analysis of positively charged clusters when operating the electrospray source in unipolar and in bipolar mode to demonstrate the charge reduction and purity of the sample.