خيارات البحث
النتائج 2061 - 2070 من 4,937
Analysis of teleconnection between the Arctic Oscillation and South American cryosphere reduction النص الكامل
2019
Bolaño Ortiz, Tomás Rafael | Pascual Flores, Romina María | López Noreña, Ana Isabel | Ruggeri, María Florencia | Lakkis, Susan Gabriela | Puliafito, Salvador E.
Abstract: The cryosphere in South America is a very important resource because it is the main source of water for 85 million inhabitants distributed in Colombia, Ecuador, Peru, Bolivia, Chile and Argentina [1-2]. To know the effects due to global phenomena such as arctic oscillation (AO) in the reduction of the cryosphere in this region, we proceeded to analyze sources of reanalysis information (ERA-40; NCEP/NCAR Reanalysis) and high resolution snow cover (MOD10 500m) from Moderate-Resolution Imaging Spectroradiometer (MODIS). Several linear adjustments were made to observe how snow cover variations (Y) responded to variations in AO (X1 ), surface temperature (X2 ) and snow precipitation (X3 ).
اظهر المزيد [+] اقل [-]Estimating particulate matter (PM) concentrations from a meteorological index for data-scarce regions: A pilot study النص الكامل
2019
de Lange, Anzel | Garland, Rebecca M. | Dyson, Liesl L.
Estimating particulate matter (PM) concentrations from a meteorological index for data-scarce regions: A pilot study النص الكامل
2019
de Lange, Anzel | Garland, Rebecca M. | Dyson, Liesl L.
In regions where air quality data are scarce or access thereto is limited, a comprehensive understanding of air pollution is hindered by a lack of emission data and ambient air pollution measurements. Therefore, in this pilot study, we assess the feasibility of estimating particulate matter (PM) mass concentrations from a meteorological index. Measured PM concentrations from air quality monitoring stations (2013–2016) situated in and around South African air pollution priority areas were analysed. Simulated meteorological parameters were used to calculate the newly-developed Air Dispersion Potential (ADP) index, which describes the meteorological potential for pollution dispersion in the atmosphere. For most conditions, there exists weak (r = 0.1–0.29) to moderate (r = 0.30–0.49) correlations between the ADP index and PM classes. At the three stations with adequate data availability, it was found that the ADP index was relatively successful in predicting conditions of high PM concentrations. An investigation of the effect of meteorological conditions on the diurnal variation of PM concentrations led to both the quantification of this effect, and the realization that at these diverse sites, up to 29% of variation in hourly PM concentrations can be explained by variations in meteorology. The application of the index in this way can play an important role in air quality management by quantifying the impacts of meteorological drivers on PM peaks.
اظهر المزيد [+] اقل [-]Decision support tool to improve the spatial distribution of air quality monitoring sites النص الكامل
2019
Castro, Marlene | Pires, José C.M.
The air quality is an increasingly concerning topic. Efficient air quality monitoring system is highly required in urban areas due to the existing different types of air pollution sources. Consequently, air pollution profiles of the monitored region should be regularly evaluated to infer the efficiency of the monitoring system. This study applied principal components analysis (PCA) to air quality data from Porto (Portugal), aiming to characterize the spatial distribution of NO₂, O₃ and PM₁₀ concentration profiles. In the analysed period (2006 and 2013), some of the selected monitoring sites have been closed and others were moved to other locations. PCA allowed the evaluation of these changes in geographical distribution of the monitoring sites and the definition of proposals to improve the efficiency of air quality monitoring system. The performed analysis concluded that these last changes were correctly performed, but the reduction of the monitoring sites for NO₂ and O₃is still possible, being optimized the current number for PM₁₀. In addition, the application of computational model HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) allowed analysing the air pollution transport over long distances in high pollutant concentration episodes, having found that the variation of NO₂ and O₃ concentrations may be strongly influenced by air masses from the north of Spain. For PM₁₀, there are two different air mass trajectories: the transport of air masses from the Galicia region and from North Africa.
اظهر المزيد [+] اقل [-]Comparison of the epiphyte Tillandsia bergeri and the XAD-resin based passive air sampler for monitoring airborne pesticides النص الكامل
2019
Silva-Barni, María Florencia | González, Mariana | Miglioranza, Karina Silvia Beatriz
The aim of this study was to assess if the epiphyte Tillandsia bergeri is feasible to be used as a biomonitor of pesticides in the air by comparing with the results of the artificial XAD-resin based passive air sampler (XAD-PAS). Biomonitors and XAD-PAS were deployed at 10 sites of Quequén Grande River watershed (Buenos Aires province, Argentina) during three exposure periods. Endosulfan was the main pesticide found in T. bergeri as well as in XAD-PAS, even after the ban was in effect. Higher endosulfan levels were observed during pesticide application period in XAD-PAS, while T. bergeri showed a decreasing trend during this period. Chlorpyrifos concentrations were in the same order than endosulfan in XAD-PAS, while T. bergeri showed significantly lower levels. Concentrations of legacy pesticides (hexachlorocyclohexanes, chlordanes, dieldrin, heptachlors) registered a low contribution to total pesticides analyzed both in T. bergeri and XAD-PAS, reflecting the past use of organochlorine pesticides in the region. Trifluralin showed the lowest concentrations in T. bergeri while XAD-PAS exhibited a higher proportion in some sites. Even both samplers showed that endosulfan was the most frequent pesticide found, environmental processes such as volatilization and photodegradation, as well as biological processes in T. bergeri have probably occurred and therefore pesticides accumulation was altered. Results demonstrate the importance of taking into account the type of sampling media when analyzing atmospheric pesticide composition. Nevertheless, the use of T. bergeri and XAD-PAS allowed discriminating efficiently the relative contribution of currently used pesticides versus legacy pesticides to air pollution.
اظهر المزيد [+] اقل [-]Polycyclic aromatic hydrocarbons in two polluted lagoons, eastern coast of the Red Sea: Levels, probable sources, dry deposition fluxes and air-water exchange النص الكامل
2019
Rasiq, K.T. | El-Maradny, Amr | Orif, Mohammed | Bashir, Mohammed Elamin | Turki, Adnan J.
The air-water exchange of polycyclic aromatic hydrocarbons (PAHs) is an important process in determining the fate, transport and chemical loadings of these contaminants in the atmosphere and water bodies. Concentration levels of PAHs in air (gaseous and particulate) and surface water were investigated in the environments of two polluted lagoons along the eastern coast of the Red Sea to study air water exchange and dry deposition fluxes. Nine priority parent PAHs and nine methylated PAHs were identified and quantified by GC-MS. The range of total PAHs in surface water was from 120.29 ng L⁻¹ to 524.45 ng L⁻¹ (average: 308.7 ng L⁻¹, n = 19). The PAHs levels in air recorded significant rise form the previous study. The probable sources of dissolved PAHs in water were found predominantly to be of petrogenic origin in one lagoon and of pyrogenic origin in the other lagoon. The dry deposition fluxes for individual congeners ranged between 0.01 ng m⁻²d⁻¹ to 2.82 μg m⁻²d⁻¹. After Henry's law constant corrections for temperature and salinity; the air-water exchange fluxes were found in the range of −9.7 × 10⁴ to 8.6 × 10⁶ ngm⁻²d⁻¹ with an average of 6.8 × 10⁵ ngm⁻²d⁻¹. Beside the other sources of PAHs in the studied lagoons, high temperature and wastewater dumping might affect the magnitude and direction of air-water exchange fluxes.
اظهر المزيد [+] اقل [-]Characterisation of ambient Total Gaseous Mercury concentrations over the South African Highveld النص الكامل
2019
Belelie, M.D. | Piketh, S.J. | Burger, R.P. | Venter, A.D. | Naidoo, M.
Characterisation of ambient Total Gaseous Mercury concentrations over the South African Highveld النص الكامل
2019
Belelie, M.D. | Piketh, S.J. | Burger, R.P. | Venter, A.D. | Naidoo, M.
Mercury is considered a ubiquitous, toxic, and global pollutant. In this study, ambient Total Gaseous Mercury (TGM) concentrations over the South African Highveld are characterised. Studies on ambient mercury in this region is important because of various anthropogenic emission sources. In this pilot study, concentrations of TGM and criteria pollutants (O3, SO2, NO, NO2, and CO) were measured concurrently with meteorological parameters at Balfour (BF), Middelburg (MB), and Standerton (ST) from January 2009 to December 2009. The spatial variation of TGM concentrations ranged from 0.40 to 28.72 ng/m3 (1.99 0.94 ng/m3), 0.12–9.91 ng/m3 (1.04 0.62 ng/m3), and 0.21–32.10 ng/m3 (1.25 1.38 ng/m3), at BF, MB, and ST, respectively. Generally, concentrations fell within the Northern Hemisphere background range of 1.5–1.7 ng/m3 and Cape Point, South Africa background of 1.2–1.4 ng/m3, with the exception of outliers. The outliers were much higher than the background values and may be the result of pollution events. Seasonal variation varied with descending orders of summer, spring, winter, autumn, at BF; summer, winter, autumn, spring at MB; and winter, spring, summer at ST (no data available for autumn). This study observed no profound diurnal patterns at BF and MB where sparse local and regional sources appear to have been the predominant sources. An interesting phenomena, however, was observed at ST where the diurnal cycle suggests a potential significant influence from local domestic combustion sources.
اظهر المزيد [+] اقل [-]Characterisation of ambient Total Gaseous Mercury concentrations over the South African Highveld
VOCs emission characteristics in motorcycle exhaust with different emission control devices النص الكامل
2019
Dhital, Narayan Babu | Yang, Hsi-Hsien | Wang, Lin-Chi | Hsu, Ya-Tin | Zhang, Han-Yu | Young, Li-Hao | Lu, Jau-Huai
Speciated VOCs and regulated air pollutant emissions (CO, HC and NO) of carburetor (CB) and fuel injection (FI) motorcycles were evaluated based on engine dynamometer tests. Effects of engine loads and emission control systems were evaluated. CB was equipped with oxidation catalytic converter (OCC) and secondary air system (SAS) while FI had three-way catalytic converter (TWC) and oxygen sensor (OS). Under normal operation of the control devices, the emissions of regulated pollutants and the sum of detected VOCs (ΣVOC) were higher in CB than in FI motorcycle. Alkanes and aromatics had the highest concentrations contributing approximately 90% to the ΣVOC while xylene and toluene were most abundant among the BTEX, in both motorcycles. Emissions of all regulated pollutants and ΣVOC increased with increase in engine load. The emission control devices showed differential efficiencies on different VOC groups. Average emission reduction efficiencies of OCC with SAS (CB motorcycle) were 45.4% (ΣVOC) and 48.6% (BTEX) and TWC with OS (FI motorcycle) were 74.4% (ΣVOC) and 88.0% (BTEX). Without SAS, the efficiency of OCC dropped to 30.2% (ΣVOC) and 34.9% (BTEX) in CB motorcycle. Similarly, the efficiency of TWC reduced to 69.0% (ΣVOC) and 85.2% (BTEX) when the OS was blocked in FI motorcycle. The ozone formation potentials of VOCs ranged from 500 mg-O3/m3 (FI motorcycle with TWC and OS, TO 20%) to 2218 mg-O3/m3 (CB motorcycle without control system, TO 30%).
اظهر المزيد [+] اقل [-]Differential impact of anthropogenic pressures on Caspian Sea ecoregions النص الكامل
2019
Lattuada, Matteo | Albrecht, Christian | Wilke, Thomas
Over the past decades, overall ecological conditions in the Caspian Sea have deteriorated. However, a comprehensive understanding of lake-wide spatial differences in anthropogenic pressures is lacking and the biological consequences of human impacts are poorly understood. This paper therefore aims at assessing the individual and combined effects of critical anthropogenic pressures on the Caspian Sea ecoregions. First, cumulative pressure scores were calculated with a cumulative environmental assessment (CEA) analysis. Then, the individual contribution of anthropogenic pressures was quantified. Finally, ecoregion-specific differences were assessed. The analyses show that both cumulative and individual pressure scores are unevenly distributed across the Caspian Sea. The most important individual pressures are invasive species, chemical pollution and poaching. This uneven distribution of pressure scores across Caspian Sea ecoregions creates new challenges for future conservation strategies, as different ecoregions usually require different conservation measures.
اظهر المزيد [+] اقل [-]Impact of financial development and economic growth on environmental quality: an empirical analysis from Belt and Road Initiative (BRI) countries النص الكامل
2019
Saud, Shah | Chen, Songsheng | Danish, | Haseeb, Abdul
This study aims to analyze the impact of financial development, foreign direct investment, economic growth, electricity consumption, and trade openness on environmental quality for a panel of 59 Belt and Road Initiative (BRI) countries, over the period of 1980–2016. The presence of the environmental Kuznets curve (EKC) hypothesis is investigated. The cross-sectional augmented Dickey-Fuller (CADF) and cross-sectional Im, Pesaran, and Shin panel unit root test; the Westerlund cointegration test, the dynamic seemingly unrelated regression (DSUR) approach; and the Dumitrescu and Hurlin (Econ Model 29:1450–1460, 2012) panel causality approach are employed. It is found that the analyzed variables are stationary at first differences and are cointegrated. It is also found that an increase in financial development, foreign direct investment, and trade openness enhance environmental quality, while the increase in economic growth and electricity consumption degrade environmental quality. The presence of the EKC hypothesis for the selected panel countries is validated. Furthermore, the Dumitrescu-Hurlin (DH) panel causality test result confirmed the presence of bidirectional causality among economic growth, foreign direct investment, financial development, electricity consumption, and trade openness with environmental quality.
اظهر المزيد [+] اقل [-]Indoor inhalation dose assessment for thoron-rich regions of Indian Himalayan belt النص الكامل
2019
Semwal, Poonam | Agarwal, Tarun Kumar | Singh, Kuldeep | Joshi, Manish | Gusain, Gurupad Singh | Sahoo, Bijay Kumar | Ramola, Rakesh Chand
²²²Rn, ²²⁰Rn, and their decay products are significant contributors to background radiation dose. Their concentration level, pertaining exposure, and consequent dose are prime concerns in indoor environments. The present study was performed in 101 dwellings of different villages of Almora district situated in Kumaun hills of Indian Himalayan belt. Measurement of gases and decay products were made in three different types of dwellings (i.e., mud, cemented, and stone with plaster) in three seasons (winter, summer, and rainy). Concentration values for ²²²Rn and EERC were found to be varying in the order of winter > summer > rainy while obtained least in rainy season for the case of ²²⁰Rn and EETC. Concentration values for ²²²Rn and EERC were found to be lesser for cemented houses. Relative standard deviation of concentration values was found to be higher for the rainy season. Yearly averaged concentration values for ²²²Rn, EERC, ²²⁰Rn, and EETC were noted to be higher than the global averages but comparable to some Indian studies. Annual inhalation dose due to ²²²Rn, ²²⁰Rn, and their progeny was found to be 0.55–4.71 mSv/year with an average value of 2.36 ± 0.83 mSv/year. These values were measured for the first time in the study area and provide a link for future studies in the dwellings representing higher concentration values.
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