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- Improving air quality in Lisbon: modelling emission abatement scenariosPublication . Monjardino, J.; Barros, Nelson; Ferreira, F.; Tente, H.; Fontes, Tânia; Pereira, P.; Manso, M. ConceiçãoLisbon is one of the European cities where NO2 and PM10 legal limit values are still exceeded, leading to an Air Quality Plan applicable up to 2020. The developed work combined a detailed emission inventory, monitoring data, and modelling in order to assess if the proposed emission abatement scenarios, focused on the road transport sector, were able to tackle exceedances. A maximum decrease of 14% for PM10 concentrations was achieved, and of 21% for NO2, providing compliance. PM10 smallest reduction is related with higher weight of regional background sources, while for NO2 local traffic has more influence on concentrations.
- Impacte na qualidade do ar na saúde pública das grandes linhas de tráfego: o caso da VCI - projecto ImpactAIRPublication . Barros, Nelson; Brás, Catarina; Fontes, TâniaBetween 2004 and 2006 will be developed in CEMAS the ImpactAir Project - Impact in air quality and public health of the Urban highways: The case of the Via de Cintura Interna (VCI). In collaboration with the Ricardo Jorge National Health Institute and the Faculty of Medicine (University of Oporto), this project has the main objective the emissions impact evaluation from VCI traffic, on air quality and health of local populations. Entre 2004 e 2006 decorrerá no Centro de Estudos e Análise de Sistemas Ambientais (CEMAS) da Universidade Fernando Pessoa o Projecto ImpactAir - Impacte na qualidade do ar e na saúde das Grandes Linhas de Tráfego Urbano: O caso da Via de Cintura Interna (VCI). Em colaboração com o Instituto Nacional de Saúde Dr. Ricardo Jorge e a Faculdade de Medicina da Universidade do Porto, este projecto tem como objectivo proceder à avaliação do impacte das emissões do tráfego que circula na VCI, na qualidade do ar e na saúde das populações locais.
- Spatial prediction of air quality in an urban sensitive area: a seasonal overviewPublication . Fontes, Tânia; Barros, Nelson
- Spatio-temporal prediction of atmospheric benzene (Part I)Publication . Fontes, Tânia; Barros, NelsonBenzene is a carcinogenic and genotoxic pollutant which mainly affects the people health through the inhalation. Nevertheless, this pollutant is not frequently measured by air-quality networks. To solve this problem, some models have been published to estimate benzene concentrations in the atmosphere. However, the lack of measures makes difficult the application of complex models in order to get a detailed spatiotemporal analysis, namely in urban areas. In this work was developed a simple semi-empirical model to predict benzene concentrations based on the ratio of benzene and carbon monoxide concentrations in order to predict the concentrations of this pollutant in large areas and periods with lack of benzene measurements but with higher impact in the human health. The model was applied to an urban area, the Metropolitan Area of Oporto, for a period of 12 years (1995–2006). Monthly correlations between benzene and carbon monoxide concentrations at Custóias airquality station are significant (p = 0.01) and higher in winter (rs > 0.7) than in summer (0.3 >rs >0.7). Estimate of the monthly ratio of the concentration of these two pollutants range between 199 and 305. The methodology validation shows good results (rs = 0.81) which allow, assuming the availability of carbon monoxide data, the use of this tool for areas with low benzene recorded data. The application of this methodology in the study area shows an annual average trend decrease of benzene concentrations during the study period, which may be linked to a general trend decrease of benzene emissions in European urban areas, including the study domain.
- Trends of PM2.5 concentrations in China: a long term approachPublication . Fontes, Tânia; Li, Peilin; Barros, Nelson; Zhao, PengjunThe fast economic growth of China along the last two decades has created a strong impact on the environment. The occurrence of heavy haze pollution days is the most visible effect. Although many researchers have studied such problem, a high number of spatio-temporal limitations in the recent studies were identified. From our best knowledge the long trends of PM2.5 concentrations were not fully investigated in China, in particular the year-to-year trends and the seasonal and daily cycles. Therefore, in this work the PM2.5 concentrations collected from automatic monitors from five urban sites located in megacities with different climatic zones in China were analysed: Beijing (40 N), Chengdu (31 N), Guangzhou (23 N), Shanghai (31 N) and Shenyang (43 N). For an inter-comparison a meta-analysis was carried out. An evaluation conducted since 1999 demonstrates that PM2.5 concentrations have been reduced until 2008, period which match with the occurrence of the Olympic Games. However, a seasonal analysis highlight that such decrease occurs mostly during warmer seasons than cold seasons. During winter PM2.5 concentrations are typically 1.3 to 2.7 higher than in summer. The average daily cycle shows that the lowest and highest PM2.5 concentrations often occurs in the afternoon and evening hours respectively. Such daily variations are mostly driven by the daily variation of the boundary layer depth and emissions. Although the PM2.5 levels have showing signs of improvement, even during the warming season the values are still too high in comparison with the annual environmental standards of China (35 mg m3 ). Moreover, during cold seasons the north regions have values twice higher than this limit. Thus, to fulfil these standards the governmental mitigation measures need to be strongly reinforced in order to optimize the daily living energy consumption, primarily in the north regions of China and during the winter periods.
- Mobilidade e qualidade do ar: o caso da cidade do PortoPublication . Barros, Nelson; Fontes, TâniaApesar da evolução tecnológica dos últimos anos em matéria de controlo de emissões provenientes dos veículos automóveis a qualidade do ar junto a grandes linhas de tráfego (GLT) é ainda um problema pouco estudado. Para avaliar estes impactes numa das GLT da cidade do Porto, desenvolveram-se metodologias para efectuar a monitorização e a modelação das emissões de tráfego tendo em conta os fluxos e padrão de tráfego horário na Via de Cintura Interna usando o benzeno como indicador. Embora os resultados médios das campanhas de monitorização (2,1 µg.m-3 ) não se aproximem do valor limite legislado (5 µg.m-3 ), as concentrações anuais obtidas através da modelação indicam alguns locais críticos na VCI, nomeadamente junto da zona do Amial.
- Can artificial neural networks be used to predict the origin of ozone episodes?Publication . Fontes, Tânia; Silva, Luís; Silva, Márcia; Barros, Nelson; Carvalho, Ana CristinaTropospheric ozone is a secondary pollutant having a negative impact on health and environment. To control and minimize such impact the European Community established regulations to promote a clean air all over Europe. However, when an episode is related with natural mechanisms as Stratosphere–Troposphere Exchanges (STE), the benefits of an action plan to minimize precursor emissions are inefficient. Therefore, this work aims to develop a tool to identify the sources of ozone episodes in order to minimize misclassification and thus avoid the implementation of inappropriate air quality plans. For this purpose, an artificial neural network model – the Multilayer Perceptron – is used as a binary classifier of the source of an ozone episode. Long data series, between 2001 and 2010, considering the ozone precursors, 7 Be activity and meteorological conditions were used. With this model, 2–7% of a mean error was achieved, which is considered as a good generalization. Accuracy measures for imbalanced data are also discussed. The MCC values show a good performance of the model (0.65–0.92). Precision and F1-measure indicate that the model specifies a little better the rare class. Thus, the results demonstrate that such a tool can be used to help authorities in the management of ozone, namely when its thresholds are exceeded due natural causes, as the above mentioned STE. Therefore, the resources used to implement an action plan to minimize ozone precursors could be better managed avoiding the implementation of inappropriate measures.
- Learning from 24 years of ozone data in PortugalPublication . Barros, Nelson; Silva, M.P.; Fontes, Tânia; Manso, M. Conceição; Carvalho, Ana CristinaOzone (O3) is a secondary pollutant mainly produced in the troposphere by photochemical reactions with high impact on human health. In this work hourly average O3 concentrations from the Portuguese air quality network collected during 24 years (1988–2011) were analysed. The background time series were assessed by environment type (urban, suburban and rural) and considering several criteria: the annual mean O3 concentration, the Directive 2008/50/EC O3 long-term objective and the 2005 WHO Guideline for protection of human health and, finally, the hourly information threshold exceedances. The trend of annual mean O3 concentration data and the maximum daily eight-hour mean ozone concentration data were both annually compared using an one-way ANOVA followed by a Tamhane post-hoc comparison test. In both series, although of an instable trend, a tendency for an increase of the mean O3 concentrations was found. On the other hand, after 2006, for all stations types, the normalized number of exceedances for public O3 information are significantly decreasing (p<0.05). In this paper, the O3 trend will be analyzed and discussed, contributing to improve knowledge of long time series of O3 concentrations in Portugal.
- Comparação das emissões do tráfego rodoviário por análise dos factores de emissãoPublication . Barros, Nelson; Fontes, Tânia; Brás, CatarinaAn estimate of weighed emission factors (g.Km-1) was made to compare atmospheric emissions from diesel and gasoline vehicles in Portugal, on the basis of EMEP/CORINAIR and NAEI methodologies, considering an average speed in 3 representative types of roads, urban roads, rural roads and highways. The results obtained show that traffic emissions are dependent on diverse factors which make their comparison non linear and as such, hardly conclusive. No sentido de comparar as emissões atmosféricas dos veículos do parque automóvel português, foi efectuada uma estimativa dos factores de emissão ponderados (g.Km-1) por categoria de veículo e poluente, com base nas metodologias EMEP/CORINAIR e NAEI, considerando uma velocidade média de circulação de veículos em 3 tipos de estradas representativos, estradas urbanas, estradas rurais e auto-estradas. Verificou-se que as emissões associadas ao tráfego estão dependentes de diversos factores que tornam a sua intercomparação complexa e, como tal, dificilmente conclusiva.
- A proposed methodology for impact assessment of air quality trafficrelated measures: the case of PM2.5 in BeijingPublication . Fontes, Tânia; Li, Peilin; Barros, Nelson; Zhao, PengjunAir quality traffic-related measures have been implemented worldwide to control the pollution levels of urban areas. Although some of those measures are claiming environmental improvements, few studies have checked their real impact. In fact, quantitative estimates are often focused on reducing emissions, rather than on evaluating the actual measures’ effect on air quality. Even when air quality studies are conducted, results are frequently unclear. In order to properly assess the real impact on air quality of traffic-related measures, a statistical method is proposed. The method compares the pollutant concentration levels observed after the implementation of a measure with the concentration values of the previous year. Short- and long-term impact is assessed considering not only their influence on the average pollutant concentration, but also on its maximum level. To control the effect of the main confounding factors, only the days with similar environmental conditions are analysed. The changeability of the key meteorological variables that affect the transport and dispersion of the pollutant studied are used to identify and group the days categorized as similar. Resemblance of the pollutants' concentration of the previous day is also taken into account. The impact of the road traffic measures on the air pollutants’ concentration is then checked for those similar days using specific statistical functions. To evaluate the proposed method, the impact on PM2.5 concentrations of two air quality traffic-related measures (M1 and M2) implemented in the city of Beijing are taken into consideration: M1 was implemented in 2009, restricting the circulation of yellow-labelled vehicles, while M2 was implemented in 2014, restricting the circulation of heavy-duty vehicles. To compare the results of each measure, a time-period when these measures were not applied is used as case-control.
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