Naděžda Zíková

Deposition of suspended fine particulate matter in a library

To analyse deposition of fine particulate matter (PM) on book surfaces we put twelve bunches of cellulose filters on a free shelf of the National Library in Prague, exposed them for three, six, nine, and twelve months to indoor air and analysed them after each period by Scanning Electron Microscopy (SEM) and Ion Chromatography (IC). Results showed that fine particles were deposited predominantly on the surface of the top filter but partly also on the surfaces of inner filters. It indicates fine particles penetrated between filters. The penetration and deposition of particles was also modelled as Brownian diffusion between two parallel filters. The model prediction demonstrated that fine particles penetrate between filters, with the depth of penetration limited by parallel diffusional deposition on filter surfaces. This is in qualitative agreement with SEM and IC investigations. The results show that beside the top part fine PM can deposit onto all available surfaces of books.

Size-Resolved Penetration Through High-Efficiency Filter Media Typically Used for Aerosol Sampling

We have developed a new, fully controlled filter testing device and have used it to measure size-resolved penetration through a typically used filtration media for (but not only) atmospheric aerosol sampling. Twenty membrane and fiber filter pieces (mixed cellulose ester filters, polytetrafluoroethylene filters, quartz fiber filters, glass fiber filters, and polycarbonate filters) of various manufacturers and filter codes were examined. High variability in the penetration curve shapes, most penetrating particle size (MPPS) (from 20 nm to 90 nm) and penetration maxima (from 0.001% to almost 100%) has been found. The dependence of pressure drop on face velocity generally agrees with theory, the comparison of penetration at various face velocities proved the theoretical equations being able to determine MPPS only partially correctly. Although the variability within an individual filter of the same code is not negligible, it is small compared to the differences between the various filter types. The results not only differed from the information provided by the manufacturers, but in many cases also provided information otherwise unavailable, although affecting the sampling and also the ability of comparison with theory. To have enough information for the proper choice of the filter for a given purpose, it would be necessary to have not only total penetration given from the DOP standard measurement, but the MPPS, penetration maximum value and pressure drop as well. Copyright 2015 American Association for Aerosol Research

Aerosol Distribution in The Planetary Boundary Layer Aloft a Residential Area

Atmospheric aerosol is an omnipresent component of the Earth atmosphere. Aerosol particle of diameters 1 μm defines ultrafine or coarse aerosol particles, respectively. Aerosol particle concentrations within the planetary boundary layer - PBL are measured at the ground level while their vertical profiles in the PBL are usually estimated by modelling. The aim of this study was to construct vertical concentration profiles of ultrafine and coarse aerosol particles from airborne and ground measurements conducted in an urban airshed. Airborne measurements were done by an unmanned airship, remotely controlled with GPS 10 Hz position tracking, and electrically powered with propulsion vectoring, which allows average cruising speed of 6 m.s-1. The airship carried three aerosol monitors and a temperature sensor. The monitors acquired 1 Hz data on mass concentration of coarse and number concentration of ultrafine particles. Four flight sequences were conducted on the 2nd of March 2014 above Plesna village, up-wind suburb of Ostrava in the Moravian-Silesian region of the Czech Republic. The region is a European air pollution hot-spot. Repeated flights were carried out in several height levels up to 570 m above ground level - a.g.l. Early morning flight revealed a temperature inversion in the PBL up to 70 m a.g.l. This lead to coarse particle concentrations of 50 μgm-3 below the inversion layer and 10 μgm-3 above it. Concurrently, air masses at 90-120 m a.g.l. were enriched with ultrafine particles up to 2.5x104 cm-3, which may indicate a fanning plume from a distant emission source with high emission height. During the course of the day, concentrations of ultrafine and coarse particle gradually decreased. Nevertheless, a sudden increase of ultrafine particle concentrations up to 3.7x104 cm-3 was registered at 400 m a.g.l. at noon and also after a lag of 20 min at the ground. This may indicate formation of new aerosol particles at higher altitudes, which are then transported downward by evolved convective mixing. Detailed information acquired by the airship measurements allow us to better understand processes resulting in the increase of aerosol particle concentrations at ground level in urban air.

On the use of the field Sunset semi-continuous analyzer to measure equivalent black carbon concentrations

ABSTRACT This study describes a method to calculate equivalent black carbon (EBC) concentrations comparable to those obtained from optical filter-based EBC instrumentation from data obtained with a semi-continuous thermo-optical analyzer (Sunset Laboratory Inc., USA) without any need of instrument alterations or extra costs. A correction for the reflection of the Sunset analyzer laser beam by the walls of the sampling tube is introduced. EBCSunset concentrations obtained during two intensive campaigns in Prague (one in winter and one in summer) were compared also to EBC measured by an AE31 Aethalometer (EBCaeth), an AE51 MicroAethalometer (EBCmicro), and a Multi Angle Absorption Photometer (EBCMAAP). Good agreement was observed in both campaigns. The EBCSunset data were also corrected for loading effects in two ways—a simple loading correction and a total correction using data also from the MAAP and a nephelometer. The loading corrections gave similar results for EBCSunset and the aethalometer data except for the simple correction for summer EBCSunset data. The multiple scattering correction factors computed for EBCSunset agreed well with those calculated for EBCaeth. The wall reflection correction for the Sunset analyzer data further improves the agreement between EBCSunset and EBCMAAP. Copyright

Hourly land-use regression models based on low-cost PM monitor data

ABSTRACT Land‐use regression (LUR) models provide location and time specific estimates of exposure to air pollution and thereby improve the sensitivity of health effects models. However, they require pollutant concentrations at multiple locations along with land‐use variables. Often, monitoring is performed over short durations using mobile monitoring with research‐grade instruments. Low‐cost PM monitors provide an alternative approach that increases the spatial and temporal resolution of the air quality data. LUR models were developed to predict hourly PM concentrations across a metropolitan area using PM concentrations measured simultaneously at multiple locations with low‐cost monitors. Monitors were placed at 23 sites during the 2015/16 heating season. Monitors were externally calibrated using co‐located measurements including a reference instrument (GRIMM particle spectrometer). LUR models for each hour of the day and weekdays/weekend days were developed using the deletion/substitution/addition algorithm. Coefficients of determination for hourly PM predictions ranged from 0.66 and 0.76 (average 0.7). The hourly‐resolved LUR model results will be used in epidemiological studies to examine if and how quickly, increases in ambient PM concentrations trigger adverse health events by reducing the exposure misclassification that arises from using less time resolved exposure estimates. HighlightsA network of 23 low‐cost PM monitors was deployed across an urban area.Land use regression models predict the hourly intra‐urban PM variations.Coefficients of determination for hourly PM predictions ranged 0.66–0.76.Low‐cost PM monitor data need to be carefully evaluated before use.The combination of low‐cost monitors and modeling provides useful PM estimates.