SensEURCity: A multi-city air quality dataset collected for 2020/2021 using open low-cost sensor systems.

Low-cost air quality sensor systems can be deployed at high density, making them a significant candidate of complementary tools for improved air quality assessment. However, they still suffer from poor or unknown data quality. In this paper, we report on a unique dataset including the raw sensor data of quality-controlled sensor networks along with co-located reference data sets. Sensor data are collected using the AirSensEUR sensor system, including sensors to monitor NO, NO2, O3, CO, PM2.5, PM10, PM1, CO2 and meteorological parameters. In total, 85 sensor systems were deployed throughout a year in three European cities (Antwerp, Oslo and Zagreb), resulting in a dataset comprising different meteorological and ambient conditions. The main data collection included two co-location campaigns in different seasons at an Air Quality Monitoring Station (AQMS) in each city and a deployment at various locations in each city (also including locations at other AQMSs). The dataset consists of data files with sensor and reference data, and metadata files with description of locations, deployment dates and description of sensors and reference instruments.

Air pollution levels near crossroads with different traffic density and the estimation of health risk.

The aim of this study was to determine the influence of traffic density on air pollutant levels as well as to analyse the spatial and temporal distribution of particulate pollutants and their health risk. The following species related to traffic pollution were measured: PM10, elemental and organic carbon and polycyclic aromatic hydrocarbons (PAHs) in PM10 and gas pollutants (SO2, NO2 and CO). The measurements were carried out at four crossroad sites in the city. Samples of PM10 were collected over three periods (6 am to 2 pm, 2 pm to 10 pm and 10 pm to 6 am) on working days and weekends. Statistically significant differences were found between sampling sites for all pollutant concentrations, except for NO2. The highest mass concentrations of PM10, carbon and PAHs were observed in the south of the city with the highest traffic density. Concentrations of gasses (CO and NO2) showed high values in morning and in the late afternoon and evening (west and east). At all measuring sites, the highest concentration of particle-bound pollutants was mostly recorded during morning and afternoon, except at the south, where elevated PAHs concentrations were recorded during night period, which indicated that residential heating takes up a portion of pollution sources in this area. Although for most of the pollutants the concentrations varied during the day, statistically significant differences between sampling periods were not found. The highest health risk was obtained at the south, where it was scored as significant.

Assessment of ozone concentration data from the northern Zagreb area, Croatia, for the period from 2003 to 2016.

A measurement station located in an urban area on the southern slope of the Medvednica Mountain (120 m a.s.l.), close to the Croatian capital Zagreb, provided data for an analysis of the photosmog in the city of Zagreb. Data for the period 2003-2016 obtained from this station and analysed in this work can also be compared with the nearby Puntijarka station (980 m a.s.l.) for which a similar analysis has already been carried out. In Puntijarka station analysis, it has been shown that there is most probably no significant change in ozone concentrations during the observed period. In this study the mean value of the annual ozone volume fractions showed a linear trend of 0.23 ppb yr-1, a growth that is in the worst case scenario among the lowest global prediction, while the seasonal (April-to-September) mean values had a trend of 0.32 ppb yr-1, which is a certain clearly observable growth. The 95-percentile values had trends of 0.009 ppb yr-1 (annual data) and -0.072 ppb yr-1 (seasonal data), respectively. Both of these values show very small changes if any at all. By using FT analysis, with the calculation of uncertainties, we have observed three prominent cycles of 169 ± 4 h (weekly cycle), 24 ± 1 h and 12 ± 1 h (diurnal cycles). Uncertainties were low which strongly indicate that the cycles are present. However, since high concentrations of ozone were observed only sporadically, ozone pollution in the northern part of Zagreb is at the present rather low. A Fourier transformation was used to analyse the data for periodic behaviour, which revealed the existence of diurnal and weekly modulations. Nevertheless, constant monitoring is important and will continue in the future as part of continuous monitoring of the ozone levels in the area.

Influence of lockdown caused by the COVID-19 pandemic on air pollution and carcinogenic content of particulate matter observed in Croatia.

Due to the pandemic of SARS-CoV-2 in Croatia, all unnecessary activities were prohibited during the designated lockdown period (March-May 2020). With reduced human activity, levels of some air pollutants decreased. In this study, mass concentrations of the PM1 particle fraction (particulate matter with an equivalent aerodynamic diameter < 1 µm) and polycyclic aromatic hydrocarbons (PAHs) in PM1 and NO2 were measured and compared with concentrations measured in the same period the year before. Air pollutant concentrations were measured at two measuring sites: urban residential and urban traffic. Our results show a concentration decrease by 35% for NO2 and PM1 particles and by 26% for total PAHs at the traffic measuring site. At the residential measuring site, only concentrations of NO2 decreased slightly, but PM1 particles and PAHs were similar to the year before.

Pollution Sources and Carcinogenic Risk of PAHs in PM1 Particle Fraction in an Urban Area.

Airborne particles are composed of inorganic species and organic compounds. PM1 particles, with an aerodynamic diameter smaller than 1 µm, are considered to be important in the context of adverse health effects. Many compounds bound to particulate matter, such as polycyclic aromatic hydrocarbons (PAH), are suspected to be genotoxic, mutagenic, and carcinogenic. In this study, PAHs in the PM1 particle fraction were measured for one year (1/1/2018-31/12/2018). The measuring station was located in the northern residential part of Zagreb, the Croatian capital, close to a street with modest traffic. Significant differences were found between PAH concentrations during cold (January-March, October-December) and warm (April-September) periods of the year. In general, the mass concentrations of PAHs characteristic for car exhausts (benzo(ghi)perylene (BghiP), indeno(1,2,3-cd)pyrene (IP), and benzo(b)fluoranthene (BbF)) were higher during the whole year than concentrations of fluoranthene (Flu) and pyrene (Pyr), which originated mostly from domestic heating and biomass burning. Combustion of diesel and gasoline from vehicles was found to be one of the main PAH sources. The incremental lifetime cancer risk (ILCR) was estimated for three age groups of populations and the results were much lower than the acceptable risk level (1 × 10-6). However, more than ten times higher PAH concentrations in the cold part of the year, as well as associated health risk, emphasize the need for monitoring of PAHs in PM1. These data represent a valuable tool in future plans and actions to control PAH sources and to improve the quality of life of urban populations.

ESTIMATION OF AIRBORNE 106RU ACTIVITY CONCENTRATION FROM TOTAL BETA ACTIVITY OF PM10 PARTICLE FRACTIONS.

Airborne radioruthenium, as a result of an accidental release, presents a risk for occupational and public exposure. In fall 2017, a detection of 106Ru was reported by the European atmospheric radioactive contamination monitoring networks. We investigated the daily specific total beta activity of PM10 particle fractions samples. The presented method enables indirect determination of airborne 106Ru activity concentration from total beta activity, in case 106Ru was confirmed as single excess radiological pollutant. This allows for daily measurements and time-resolved 106Ru activity concentration data. We estimated the indicative committed effective dose due to 106Ru inhalation for the Croatian population during the exposure period. Although the estimated dose value of ~169.7 nSv, for ~6-d duration of ruthenium air pollution, was very low, it was ~40 times higher than the value for Hinh from inhalation of other radionuclides (90Sr + 137Cs + 40K + 7Be).

Spatial and temporal distribution of platinum, palladium and rhodium in Zagreb air.

Platinum (Pt), palladium (Pd) and rhodium (Rh) are most widely used in the production of automotive catalytic converters that serve to reduce toxic emissions from motor vehicles. The aim of this study was to quantitatively determine the levels of platinum, palladium and rhodium in the PM10 and PM2.5 fraction of airborne particle matter and find their spatial and temporal distribution at different polluted areas of the city of Zagreb, Croatia. The method used in this paper included weekly sampling of airborne particle matter on quartz filters, microwave digestion in acid under high pressure and temperature, and analysis by inductively coupled plasma mass spectrometry (ICP MS). The results have shown that the highest mean values at all three sampling stations (North, Center, South) were obtained for palladium (3.856 pg m-3, 5.396 pg m-3, 5.600 pg m-3) and the lowest for rhodium (0.444 pg m-3, 0.643 pg m-3, 0.750 pg m-3). The average mass concentrations of platinum group elements (PGE) in PM10 increased for all three elements in the direction North < Center < South which had to do with the traffic load nearby the monitoring stations. The ratio of measured mass concentrations to all measuring stations was similar to platinum, palladium and rhodium content in automotive catalytic converters. Factor analysis grouped platinum, palladium and rhodium at all of the monitoring stations, and their relation to other metals together with the aforementioned results indicate that their main source of pollution is traffic or precisely automotive catalytic converters. At all three of the monitoring sites, higher values were measured during the colder part of the year. The results of measuring platinum, palladium and rhodium levels in the city of Zagreb are the first results of their kind for this area and will provide insights into the contribution of catalytic converters to the presence of these elements in the environment.

Carbon species in PM10 particle fraction at different monitoring sites.

The aim of this study was to determine and compare the levels of elemental carbon (EC), organic carbon (OC) and polycyclic aromatic hydrocarbons (PAHs) mass concentrations in PM10 particles (particles with aerodynamic diameter less than 10 µm) between seasons (winter and summer) and at different monitoring sites (urban background and rural industrial). Daily samples of airborne particles were collected on pre-fired quartz fibre filters. PM10 mass concentrations were determined gravimetrically. Samples were analysed for OC and EC with the thermal/optical transmittance method (TOT) and for PAHs by high-performance liquid chromatography (HPLC) with a fluorescence detector. Measurements showed seasonal and spatial variations of mass concentrations for carbon species and for all of the measured PAHs (Flu, Pyr, Chry, BaA, BbF, BaP, BkF, BghiP and IP) in PM10 at the urban site and rural monitoring site described here. Diagnostic PAH ratios (Flu/(Flu + Pyr), BaA/(BaA + Cry), IP/(IP + BghiP), BaP/BghiP, IP/BghiP and BaP/(BaP + Chry)) make it possible to assess the sources of pollution, and these showed that diesel vehicles accounted for most pollution at the rural-industrial (RI) site in the summer, whereas coal and wood combustion were the causes of winter pollution. This difference between winter and summer PAH ratios were more expressed at the RI site than at the UB site because at the UB site the predominant heating fuel was gas. The OC/EC ratio yielded the same conclusion. Factor analysis showed that EC and OC originated from traffic at both sites, PAHs with 5 or more benzene rings originated from wood pellets industry or biomass burning, while Pyr and Flu originated from diesel combustion or as a consequence of different atmospheric behaviour - evaporation and participation in oxidation and photo oxidation processes.

Concentrations of PAHs and other gaseous pollutants in the atmosphere of a rural area.

In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) bound to PM10 particles were measured in a Croatian rural area. Considering that by now only a limited number of studies have provided data on pollutant concentrations for rural areas, our aim was to do so by determining the PAH levels, their mutagenic effect and relationship with meteorological conditions and other gaseous pollutants (NO, NO2, NH3). In this investigation, samples of PM10 particles were collected on quartz filters for 1 month in the cold period and 1 month in the warm period of the year, 24 h a day. Diagnostic PAH concentration ratios and factor analysis were used as tools to identify and characterize the PAH sources. The PAHs found in the warm period of the year were characteristic for car exhaust emissions while the predominant source of these pollutants in the cold period was wood burning. The measurements showed much higher average concentrations of all PAHs in the cold period, most pronounced for fluoranthene 0.347 ng m(-3) and pyrene 0.223 ng m(-3). Mass concentrations of benzo(a)pyrene in the cold period ranged from 0.057 to 1.526 ng m(-3), while in the warm period they varied from 0.009 to 0.111 ng m(-3). Mutagenicity related to BaP (BaPMeq) was significantly higher during the cold period (1.095 ng m(-3)) than in the warm period (0.101 ng m(-3)).

Real-time dissemination of air quality information using data streams and Web technologies: linking air quality to health risks in urban areas.

This article presents a new, original application of modern information and communication technology to provide effective real-time dissemination of air quality information and related health risks to the general public. Our on-line subsystem for urban real-time air quality monitoring is a crucial component of a more comprehensive integrated information system, which has been developed by the Institute for Medical Research and Occupational Health. It relies on a StreamInsight data stream management system and service-oriented architecture to process data streamed from seven monitoring stations across Zagreb. Parameters that are monitored include gases (NO, NO2, CO, O3, H2S, SO2, benzene, NH3), particulate matter (PM10 and PM2.5), and meteorological data (wind speed and direction, temperature and pressure). Streamed data are processed in real-time using complex continuous queries. They first go through automated validation, then hourly air quality index is calculated for every station, and a report sent to the Croatian Environment Agency. If the parameter values exceed the corresponding regulation limits for three consecutive hours, the web service generates an alert for population groups at risk. Coupled with the Common Air Quality Index model, our web application brings air pollution information closer to the general population and raises awareness about environmental and health issues. Soon we intend to expand the service to a mobile application that is being developed.

Carcinogenic activity of polycyclic aromatic hydrocarbons bounded on particle fraction.

Polycyclic aromatic hydrocarbons (PAHs) originate from a variety of natural and industrial processes. In this paper, concentrations of nine PAHs in PM10 particle fraction were measured concurrently at four different sites (rural, urban residential, urban traffic, and residential-industrial) in continental Croatia. Measurements at all of the four sites showed much higher average concentrations for all of the PAHs in the winter period. The highest winter average values were measured at the industrial site and the lowest at the rural and the urban residential site. In the summer, the highest average values were also measured in the industrial area, except for benzo(ghi)perylene and indeno(1,2,3-cd)pyrene, which showed the highest average values in the rural area. Factor analysis has been applied to PAH concentrations to identify their potential sources. Extracted factors have been interpreted on basis of previous studies and weather conditions. The diagnostic ratios calculated in this study indicated mixed sources at all of the sites. The contribution of gasoline and diesel from traffic was significant at all of the sites except for the urban industrial. In the winter, potential PAH sources also arose from wood combustion. The industrial site differed from the other sites with the highest influence of diesel sources and refinery during the summer months. The contribution of BaP in total carcinogenic activity exceeded 50 % in both seasons at all of the measured sites, which suggests that BaP could be suitable as a marker of the carcinogenic potential of a PAH mixture.