Browsing by Author "Kos, GPA"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Open Access A high-flow turbulent cloud chamber(AEROSOL SCIENCE AND TECHNOLOGY, 1996) Khlystou, A; Kos, GPA; ten Brink, HMA large laboratory facility (cloud chamber) has been built to study cloud formation under reproducible conditions. The chamber was designed to assess the influence of anthropogenic aerosols on the microstructure of marine clouds in coastal Western Europe. For this reason the supersaturations in the chamber are low, in the order of 0.1\%, typical for coastal marine stratus. The very large size (30 m(3)) and flow (30 m(3)/min) of the chamber allow unperturbed use of conventional cloud instrumentation like Forward Scattering Spectrometer Probe (TSI Inc.) and high-flow cascade impactors for chemical analysis of aerosol and droplets. The performance of the cloud chamber was tested with laboratory-generated submicron-sized ammonium sulphate aerosol with a lognormal size distribution and varying the number concentrations. It was found that the sulphate particles above a threshold size of 0.07 or 0.1 mu m in diameter (dependent on the settings) grew into droplets (became `'activated''), which corresponds according to the Kohler theory to supersaturations of 0.26\% and 0.15\%, respectively. Estimates of the supersaturation in the chamber from the measured liquid water content (LWC) gave the same value. Tests showed that LWC, droplet spectra, and activation threshold were stable for hours and reproducible from day to day.Item Open Access Activation properties of ambient aerosol in the Netherlands(ATMOSPHERIC ENVIRONMENT, 1996) Khlystov, A; Kos, GPA; Ten Brink, HM; Kruisz, C; Berner, AA cloud chamber has been used to study the cloud activation of ambient aerosol in The Netherlands. The large dimensions and throughput of the chamber allowed unperturbed collection of aerosol and droplets with cascade impactors and on-line measurements with cloud monitors (FSSP) inside the facility. The study provided maxima for the number of man-made aerosol acting as cloud nuclei in marine clouds in The Netherlands. Emphasis was given to the investigation of cloud formation in marine air, since sensitivity studies had shown that such clouds are most effectively influenced by the (extra) anthropogenic aerosol particles. For this reason the supersaturations in the study were low (on average 0.12\%), similar to those in actual marine stratus. The effect of the anthropogenic aerosols on cloud formation was determined by comparing the number of droplets formed in `'clean'' arctic marine air to the number of droplets formed in `'polluted'' marine air (air which had travelled over the U.K.). Air masses with the total aerosol number concentration of the order of 100 cm(-3) were considered as `'clean'' marine air. Air masses with higher aerosol concentrations were divided into `'moderately'' and `'heavily'' polluted with total aerosol concentrations of the order of 1000 and 10,000 cm(-3), respectively. In the clean marine air all potential cloud nuclei (particles lar er than the threshold size of the smallest reference particles that were activated al given supersaturation) were activated and the number of cloud droplets formed was on average 45 cm(-3). In the moderately polluted air 72\% of potential cloud nuclei were activated and the average droplet number was 190 cm(-3). The difference in the actual cloud droplet number and the number of potential cloud nuclei could be explained by the presence of water-insoluble particles which do not activate. In the heavily polluted air the average droplet concentration was around 320 cm(-3) which is, on average, 24\% of the number of potential cloud nuclei. Copyright (C) 1996 Elsevier Science LtdItem Open Access Concentrations of ultrafine, fine and PM2.5 particles in three European cities(ATMOSPHERIC ENVIRONMENT, 2001) Ruuskanen, J; Tuch, Th; Ten Brink, H; Peters, A; Khlystov, A; Mirme, A; Kos, GPA; Brunekreef, B; Wichmann, HE; Buzorius, G; Vallius, M; Kreyling, WG; Pekkanen, JTotal number concentrations, number concentrations of ultrafine (0.01-0.1 mum) and accumulation (0.1-0.5 mum) particles, as well as mass concentration of PM2.5 particles and blackness of PM2.5 filters, which is related to Black Smoke were simultaneously monitored in three European cities during the winter period for three and a half months. The purpose of the study was to describe the differences in concentration levels and daily and diurnal variations in particle number and mass concentrations between European cities. The results show statistically significant differences in the concentrations of PM2.5 and the blackness of the PM2.5 filters between the cities, but not in the concentrations of ultrafine particles. Daily PM2.5 levels were found to be poorly correlated with the daily total and ultrafine number concentrations but better correlated with the number concentration of accumulation particles. According to the principal component analysis airborne particulate pollutants seem to be divided into two major source categories, one identified with particle number concentrations and the other related to mass-based information. The present results underline the importance of using both particle number and mass concentrations to evaluate urban air quality. (C) 2001 Elsevier Science Ltd. All rights reserved.Item Open Access Variability of particulate matter concentrations along roads and motorways determined by a moving measurement unit(Atmospheric Environment, 2004-06-01) Weijers, EP; Khlystov, AY; Kos, GPA; Erisman, JWThe spatial variability of aerosol number and mass along roads was determined in different regions (urban, rural and coastal-marine) of the Netherlands. A condensation particle counter (CPC) and an optical aerosol spectrometer (LAS-X) were installed in a van along with a global positioning system (GPS). Concentrations were measured with high-time resolutions while driving allowing investigations not possible with stationary equipment. In particular, this approach proves to be useful to identify those locations where numbers and mass attain high levels ('hot spots'). In general, concentrations of number and mass of particulate matter increase along with the degree of urbanisation, with number concentration being the more sensitive indicator. The lowest particle numbers and PM1-concentrations are encountered in a coastal and rural area: <5000cm-3 and 6μgm-3, respectively. The presence of sea-salt material along the North-Sea coast enhances PM>1-concentrations compared to inland levels. High-particle numbers are encountered on motorways correlating with traffic intensity; the largest average number concentration is measured on the ring motorway around Amsterdam: about 160000cm-3 (traffic intensity 100000vehday-1). Peak values occur in tunnels where numbers exceed 106cm-3. Enhanced PM1 levels (i.e. larger than 9μgm-3) exist on motorways, major traffic roads and in tunnels. The concentrations of PM>1 appear rather uniformly distributed (below 6μgm-3 for most observations). On the urban scale, (large) spatial variations in concentration can be explained by varying intensities of traffic and driving patterns. The highest particle numbers are measured while being in traffic congestions or when behind a heavy diesel-driven vehicle (up to 600×103cm-3). Relatively high numbers are observed during the passages of crossings and, at a decreasing rate, on main roads with much traffic, quiet streets and residential areas with limited traffic. The number concentration exhibits a larger variability than mass: the mass concentration on city roads with much traffic is 12% higher than in a residential area at the edge of the same city while the number of particles changes by a factor of two (due to the presence of the ultrafine particles (aerodynamic diameter <100nm). It is further indicated that people residing at some 100m downwind a major traffic source are exposed to (still) 40% more particles than those living in the urban background areas. © 2004 Elsevier Ltd. All rights reserved.