Browsing by Subject "NOx"
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(2022)The aim of this thesis is to understand how restrictions and recommendations to limit the spread of Covid-19 pandemic affected air quality in Helsinki from January to September 2020 and examine the health benefits coming from the decreased pollutant levels. During that time many restrictions to people’s movements took place. This caused a decrease in traffic rates which in turn affected air quality. The air pollutants included in this study are nitrogen oxide (NOx), tropospheric ozone (O3) and particulate matter (PM2.5 and PM10). The data was uploaded from SMEAR III -station in Kumpula neighborhood and the results were obtained by comparing concentrations from 2020 to those of 2018-2019. The data were divided into three periods, which were studied separately. The first period was the time before the lockdown (1.1.-17.3.), 2nd period was during the lockdown (18.3.-15.6.), and the 3rd period was after the lockdown (16.6.-30.9.). In addition, the health effects caused by the changes in pollutant concentration were studied with a calculator for financial benefits of emission reductions made by Finnish Environment Institute. The change in NOx concentrations during 2020 compared to 2018-2019 were -36.4 % in 1st period, -26.5 % in 2nd period and +34.1 % in 3rd period. The changes for O3 were +4.8 % (1st period), -8.6 % (2nd period) and -11.6 % (3rd period). PM2.5 concentrations changed -39.4 % (2nd period) and 0.0 % (3rd period) and PM10 concentrations -46.9 % (2nd period) and -14.7 % (3rd period) during 2020 compared to 2018-2019. Decrease of NOx in 1st period caused 2 600 t€/y savings in costs of air pollution related health effects. The changes in PM2.5 and NOx generated savings of 38 000 t€/y during 2nd period and -2 400 t€/y during 3rd period. Even though the pollutant concentrations decreased in most periods, the decrease can’t be explained only by changes in traffic rates and human activities. Other factors contribute air pollutant levels as well, including atypical weather during 2020. The study could be continued by separating the effects of weather, traffic and other contributing factors in changes in air pollutant concentrations.
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(2023)Lichens are sensitive organisms widely used for environmental biomonitoring. Urban environments have been under heavy pollution, especially sulphur dioxide and nitrogen oxides, due to human activity which has led to the disappearance of lichens in city centres. Regulations and technological changes have led to cleaner air and less deposition of pollutants, especially sulphur dioxide on the vegetation in both rural and urban areas. This in turn has led to recolonization of lichens in former lichen deserted areas. In this study epiphytic macrolichens on park maples were surveyed using simple tree-based random sampling in three parks in Helsinki, and in one park in Loviisa, Siuntio and Raasepori each. The sampling and surveying methods were selected based on the SFS standard “Ambient air. Biomonitoring with lichens. Assessing epiphytic lichen diversity”. Species identification took place on site and in Botanical museum (Finnish Museum of Natural History). The results from parks in Helsinki were used to estimate if lichens have recolonized the trees. In addition, the results from the other Uusimaa municipalities were used to assess how different is the lichen species assemblage when comparing the relatively more polluted region of Helsinki to the less polluted regions in Uusimaa. The study found that pollution levels in Helsinki have declined enough to enable recolonization, of which there have been signs already in 1990s and 2000. The study used lichen diversity value of defined functional groups as one of the statistical methods which gave new information about how the species tolerance or sensitivity to pollutants shapes the recolonization. Comparison between the study areas in Uusimaa region revealed that concentrations of nitrogen oxides steer lichen species assemblage in Helsinki. Lichen surveys in Helsinki are scarce. This study brings topical information about the lichen situation in Helsinki, and it uses an as yet relatively unknown method to extract information from lichen assemblage. Regular, comparable lichen surveys are needed to further research the pressure that human activities cause on urban nature. Such time series would help to monitor both the urban nature loss and the impact of climate change on the urban nature.
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