Atmósfera (Journal)
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Carbon fluxes above a deciduous forest in Greece
Get PDFPhotosynthetic production in forest ecosystems occurs through the absorption of light and CO2. The present work deals with CO2 and carbon flux densities above a deciduous forest in Greece, the southernmost monitoring site in Europe. Results show annual net carbon absorption of 7.6 t C ha–1 y–1, indicating that this forest is a strong carbon sink compared to other European sites. However, absorbance may be reduced by 1 μmol m–2 s–1 for every 1.5 ºC above-canopy air temperature increase or 0.015 cm3 cm–3 active root-zone moisture depletion, beyond estimated optimum values. The forest acts as a carbon sink from late April to early November and as a source of carbon in the remaining period of the year. The highest CO2 net absorption flux occurs during June-July (approximately 200 g C m–2 month–1)
Climatic analysis linked to land vegetation cover of Mexico by applying multivariate statistical and clustering analysis
Get PDFThe climate regions of Mexico are delimitated using hierarchical clustering analysis (HCA). The data used consists of monthly means of maximum and minimum temperatures and monthly-accumulated precipitation. The dataset was obtained from heterogeneously distributed climatic stations in Mexico for the period from 1961 to 2004. This cluster method assigns precipitation and temperature variables to groups of clusters based on similar statistical characteristics. We carried out a principal components analysis to obtain a standardized reduced matrix to be used in HCA. By applying two clustering criteria (K-means and Ward´s method) it was possible to define statistically groups of stations that delimit regions of similar climate. In addition, the applied methodology describes the dominant vegetation distribution for each climate region. This analysis may contribute to the generation of new climate scenarios, where the dynamics of land vegetation cover could be included as a biomarker of climate.
Concentration of heavy metals in condensed atmospheric water vapor at three Mexican localities
Get PDFThe condensation of water vapor is a very useful technique in mitigating the scarcity of water resources for human consumption; however, the quality of this water must meet the highest standards to avoid becoming a health hazard. The present study quantifies trace elements such as As, Ba, Cu, Cd, Cr, Fe, Hg, Mn, Pb, and Zn, as well as pH and electrical conductivity (EC), in condensed atmospheric water vapor at three localities in Mexico. Atmospheric water vapor was condensed with an atmospheric water generator prototype. A total of 108 samples were obtained from three survey sites over the course of two seasons (wet and dry) during day/night shifts. The concentration of heavy metals was analyzed using inductively coupled plasma mass spectrometry. The pH and EC parameters were measured with a potentiometer/conductometer. We found Pb, Fe, and Cd in 91.66, 58.33, and 33% of the samples, respectively, at concentrations exceeding those permitted by the World Health Organization (WHO) for water intended for human consumption. Both pH and EC were within the limits established by the Department of Water Affairs of Namibia. The concentrations of trace metals in condensed atmospheric water vapor samples were within the maximum permissible limits determined by WHO for most elements analyzed in this study
Preface to the thematic issue on Climate, economics and statistics
Get PDFEnvironmental problems are typically produced by the interactions of complex natural and human systems and can entail far-reaching and sometimes irreversible consequences. Their study is characterized by the existence of incomplete knowledge and high levels of uncertainty and, in some cases, ambiguousness in the definition of the problem itself and its boundaries. These so-called wicked problems openly challenge the traditional disciplinary approach commonly used in natural and social sciences and call for the development of interdisciplinary, integrated research, as well as for innovative methods and frameworks
Influences of boundary layer phenomena and meteorology on ambient air quality status of an urban area in eastern India
Get PDFMonitoring and analyses of various air pollutants like particulate matter (PM10), sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO) and ammonia (NH3), as well as meteorological parameters (temperature, humidity, wind speed and direction) have been performed for the period between April and May, 2014 at three different sites (an area with high vehicular density, a residential area and an industrial area) of an urban area in eastern India. The hourly average concentration of surface ozone is found maximum at the industrial site (70.085 µg/m3) followed by the residential site (39.067 µg/m3) and the site with high vehicular density (25.936 µg/m3). The site with high vehicular density shows the maximum 24 h average concentration of NO2 (86.112 µg/m3) and NH3 (109.673 µg/m3). Maximum daily (24 h) average concentration of PM10 (392.127 µg/m3) and SO2 (174.069 µg/m3), and highest hourly average of CO (3.846 mg/m3) at the industrial site can be attributed to emissions from the surrounding industries. Computation of air quality indices (AQI) show that both site I (a traffic congested area with AQI = 53.85) and site III (an industrial area with AQI = 71.68) fall under a moderately polluted category whereas site II (a residential area with AQI = 22.69) is found to be clean. This detailed study reveals that variations in the concentration of different air pollutants manifest the combined effect of emission sources and patterns, planetary boundary layer height and meteorology
Isoprene, benzene and toluene levels at the major landmarks of Rio de Janeiro during the 2014 FIFA World Cup
Get PDFAir samples were collected in the days before and during the 2014 FIFA World Cup at the major landmarks of Rio de Janeiro, Brazil. Samples were collected and analysed following Method TO-15 (US-EPA). Isoprene was selected as a marker of biogenic emissions, and benzene and toluene were selected as markers of anthropogenic emissions, primarily vehicular emissions. The isoprene, benzene, and toluene concentrations ranged from 0.39 to 2.32 µg m–3, 2.27 to 10.16 µg m–3, and 5.21 to 21.83 µg m–3, respectively. The kinetic and mechanistic reactivities of these compounds were also calculated to estimate the actual contribution of these compounds to atmospheric oxidant formation. The benzene and toluene concentrations indicated that greener areas of the city are strongly affected by urban emissions. Levels of isoprene were similar to those previously determined in other areas with vegetation
A method for convective storm detection using satellite data
Get PDFMoisture and instability, along with a triggering mechanism, are the main keys of deep convective storms initiation and evolution. Satellite data can provide indirect measurements of instability and moisture of a wide area in short periods of time. This paper studies the use of an objective method based on a blended use of multiple satellite-based convection estimation techniques. This method is based on different techniques arranged in a several layers approach of different convective features, aiming to stratify a cloud shield. Meteosat Second Generation (MSG) infrared (IR) 10.8 μm and water vapor (WV) 6.2 μm channels are explored together with tropopause temperature information provided by a numerical model. Threshold, brightness temperature differences (BTD), and time trends are applied to the information available resulting in a five layers product, highlighting areas of different convective activities. This cloud shield stratification method showed a great ability to better evaluate strong convection when compared with simpler techniques such as IR false color, and was especially useful to better identify the strongest convective cell in a large area with several convective outbreaks. A validation analysis was conducted using radar and lightning data, showing that this approach is very helpful in distinguishing very strong cases from weaker ones by pointing out subtle convective patterns only present in severe storms. Also, small changes in storm evolution were more pronounced in the method output. Besides some uncertainties that were observed, likely due to the large viewing angle, techniques derived from MSG spectral bands displayed good accuracy in studying large convective systems in the South America southern region
Efficient prediction of total column ozone based on support vector regression algorithms, numerical models and Suomi-satellite data
Get PDFThis paper proposes a novel prediction method for Total Column Ozone (TCO), based on the combination of Support Vector Regression (SVR) algorithms and different predictive variables coming from satellite data (Suomi National Polar-orbiting Partnership satellite), numerical models (Global Forecasting System model, GFS) and direct measurements. Data from satellite consists of temperature and humidity profiles at different heights, and TCO measurements the days before the prediction. GFS model provides predictions of temperature and humidity for the day of prediction. Alternative data measured in situ, such as aerosol optical depth at different wavelengths, are also considered in the system. The SVR methodology is able to obtain an accurate TCO prediction from these predictive variables, outperforming other regression methodologies such as neural networks. Analysis on the best subset of features in TCO prediction is also carried out in this paper. The experimental part of the paper consists in the application of the SVR to real data collected at the radiometric observatory of Madrid, Spain, where ozone measurements obtained with a Brewer spectrophotometer are available, and allow the system’s training and the evaluation of its performance
Determining heavy metal contamination of road dust in Delhi, India
Get PDFAir pollution has been considered one of the major environmental challenges because of its effect on ecosystems and human health. The concentration levels and sources of heavy metals contamination were studied in road dust samples collected from various locations including four different activity areas: industrial, highways, residential and mixed use in Delhi, India. Metal content in road dust was analyzed by inductively coupled plasma atomic emission spectroscopy. The results showed high concentration levels of Ni, Cr and Pb in industrial areas. Pearson’s correlations coupled with principal component analysis revealed that Cd, Cr, Ni and Pb are associated with industrial sources whereas Zn and Cu are mainly contributed by vehicular traffic. Road dust contamination was assessed by various methods: degree of contamination, potential ecological index and pollution index. Contamination factor analysis showed that road dust samples are significantly contaminated by Zn and Pb. The potential ecological indices indicated high contamination of Cd and moderate contamination of Pb in road dust, but low contamination of Cr, Cu, Ni and Zn. The pollution index of most of the metals was higher than 1, indicating deterioration of road dust quality of Delhi city due to anthropogenic emissions. The degree of contamination, the potential ecological index and the integrated pollution index reveal that road dust from industrial, mixed use and highway areas are highly contaminated by heavy metals. The road dust from the residential area is also contaminated considerably. Evaluations by various methods indicated that all assessment methods are important for environmental quality evaluation
Annual atmospheric corrosion rate and dose-response function for carbon steel in Bogotá
Get PDFThis paper presents an assessment on the behavior of plain carbon steel exposure to the atmosphere of Bogotá. The main climate and environmental parameters, including relative humidity (RH), temperature (T), sulphur dioxide deposition (DSO2) and particulate matter deposition (DPM) were measured. Furthermore, mass loss of AISI/SAE 1006 plain carbon steel coupons was measured along one year. In this case, coupons were exposed in eight test sites located across the city of Bogotá. Results show that the corrosion rate of carbon steel is less than 35 μm yr–1 after one year. It was found that the west part of the city has the greatest aggressivity, which has the highest levels of DPM and DSO2,related with the characteristics of the anthropogenic activities distribution across the city. A dose-response function of plain carbon steel exposure to the atmosphere of Bogotá, based on RH, T and DSO2, was obtained