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371.
László Bencs Khaiwal Ravindra Johan de Hoog Nico Bleux Felix Deutsch René Van Grieken 《Environmental pollution (Barking, Essex : 1987)》2010,158(11):3421-3430
Daily and seasonal variation in the total elemental, organic carbon (OC) and elemental carbon (EC) content and mass of PM2.5 were studied at industrial, urban, suburban and agricultural/rural areas. Continuous (optical Dustscan, standard tapered element oscillating micro-balance (TEOM), TEOM with filter dynamics measurement system), semi-continuous (Partisol filter-sampling) and non-continuous (Dekati-impactor sampling and gravimetry) methods of PM2.5 mass monitoring were critically evaluated. The average elemental fraction accounted for 2-6% of the PM2.5 mass measured by gravimetry. Metals, like K, Mn, Fe, Cu, Zn and Pb were strongly inter-correlated, also frequently with non-metallic elements (P, S, Cl and/or Br) and EC/OC. A high OC/EC ratio (2-9) was generally observed. The total carbon content of PM2.5 ranged between 3 and 77% (averages: 12-32%), peaking near industrial/heavy trafficked sites. Principal component analysis identified heavy oil burning, ferrous/non-ferrous industry and vehicular emissions as the main sources of metal pollution. 相似文献
372.
In this study, we analyze the evolution of Canada's mining industry from 1929 to 2006, focussing on the determinants of the number of firms in the industry and why this number changed over that period. Most empirical studies of industry evolution have focused on manufacturing industries that share similar structural characteristics. Perhaps because of this, extant models of industry evolution tend to ignore industry-specific and national-specific factors that can cause atypical trajectories, that is, heterogeneous industry evolution. Initial inspection of the Canadian mining industry shows that it is atypical in that it exhibits “negative skew” over time in the number of firms rather than the typical “positive skew.” We review two dominant theoretical approaches to industry evolution: the density-dependence theory and variants of industrial organization economics. We also consider possible sources of industry evolution heterogeneity, focussing particularly on “regulatory punctuation”. Using Canadian mining data, we find that the traditional models do not fully explain the changes in population size in Canada's mining industry. As a result, we introduce a number of hybrid models. The results from these hybrid models suggest that Canadian-specific regulatory punctuations, particularly the introduction of significant new taxes, environmental legislation, and incentives have shaped the trajectory of mining firm participation. 相似文献
373.
This paper investigates and compares the performances of polylactic acid (PLA)/kenaf (PLA-K) and PLA/rice husk (PLA-RH) composites
in terms of biodegradability, mechanical and thermal properties. Composites with natural fiber weight content of 20% with
fiber sizes of less than 100 μm were produced for testing and characterization. A twin-screw extrusion was used to compound
PLA and natural fibers, and extruded composites were injection molded to test samples. Flexural and Izod impact test, TGA,
soil burial test and SEM were used to investigate properties. All results were compared to a pure PLA matrix sample. The flexural
modulus of the PLA increased with the addition of natural fibers, while the flexural strength decreased. The highest impact
strength (34 J m−1), flexural modulus (4.5 GPa) and flexural strength (90 MPa) were obtained for the composite made of PLA/kenaf (PLA-K), which
means kenaf natural fibers are potential to be used as an alternative filler to enhance mechanical properties. On the other
hand PLA-RH composite exhibits lower mechanical properties. The impact strength of PLA has decreased when filled with natural
fibers; this decrease is more pronounced in the PLA-RH composite. In terms of thermal stability it has been found that the
addition of natural fibers decreased the thermal stability of virgin PLA and the decrement was more prominent in the PLA-RH
composite. Biodegradability of the composites slightly increased and reached 1.2 and 0.8% for PLA-K and PLA-RH respectively
for a period of 90 days. SEM micrographs showed poor interfacial between the polymer matrix and natural fibers. 相似文献
374.
Ika Paul-Pont Xavier de Montaudouin Patrice Gonzalez Philippe Soudant Magalie Baudrimont 《Environmental science and pollution research international》2010,17(4):987-998
Introduction
Within the last decade, numerous studies have investigated the role of environmental history on tolerance to stress of many organisms. This study aims to assess if Manila clams Ruditapes philippinarum may react differently to cadmium exposure and trematode parasite infection (Himasthla elongata) depending on their origin and environmental history in Arcachon Bay (France). 相似文献375.
C. Borrego J. Valente A. Carvalho E. Sá M. Lopes A.I. Miranda 《Atmospheric environment (Oxford, England : 1994)》2010,44(5):642-651
Wood is commonly used in residential combustion for heating purposes; however, it can be a major source of air pollutants, namely fine particles, volatile organic compounds and carbon monoxide. Since 2004, the PM10 daily limit value has been surpassed in Portugal, and the European Commission has stated that plans and programs must be designed in order to reduce these levels. In Portugal, 18% of PM10 emissions are due to residential wood combustion, which may deeply impact the PM10 levels in the atmosphere. The main aim of this study is to investigate the impact of residential wood combustion on the air quality in Portugal. The air quality modelling system MM5/CHIMERE was applied over Portugal for a winter month, for the following three scenarios: the reference scenario, considering the actual emissions of PM10; scenario 1, where residential wood combustion emissions are not considered; and scenario 2, which takes into account a complete conversion from traditional fireplaces to certified appliances (with a 90% reduction in PM emissions). The residential wood combustion contribution to PM10 air quality concentration values during January 2007 ranges from 0 to 14 μg m?3, with a mean contribution of 10 μg m?3 in the Lisboa area and 6 μg m?3 in the Porto region. Concerning the legislated values, the area where the daily average limit value (50 μg m?3) is exceeded decreases by 46% in the simulation when residential combustion is not considered. The modelling results for scenario 2 are not significantly different from those for scenario 1. In summary, the regulation of the residential wood combustion sector is as an effective way to reduce the PM10 levels in the atmosphere as regards air quality plans and programs. 相似文献
376.
D. Vienneau K. de Hoogh R. Beelen P. Fischer G. Hoek D. Briggs 《Atmospheric environment (Oxford, England : 1994)》2010,44(5):688-696
Land-use regression models have increasingly been applied for air pollution mapping at typically the city level. Though models generally predict spatial variability well, the structure of models differs widely between studies. The observed differences in the models may be due to artefacts of data and methodology or underlying differences in source or dispersion characteristics. If the former, more standardised methods using common data sets could be beneficial. We compared land-use regression models for NO2 and PM10, developed with a consistent protocol in Great Britain (GB) and the Netherlands (NL).Models were constructed on the basis of 2001 annual mean concentrations from the national air quality networks. Predictor variables used for modelling related to traffic, population, land use and topography. Four sets of models were developed for each country. First, predictor variables derived from data sets common to both countries were used in a pooled analysis, including an indicator for country and interaction terms between country and the identified predictor variables. Second, the common data sets were used to develop individual baseline models for each country. Third, the country-specific baseline models were applied after calibration in the other country to explore transferability. The fourth model was developed using the best possible predictor variables for each country.A common model for GB and NL explained NO2 concentrations well (adjusted R2 0.64), with no significant differences in intercept and slopes between the two countries. The country-specific model developed on common variables for NL but not GB improved the prediction.The performance of models based upon common data was only slightly worse than models optimised with local data. Models transferred to the other country performed substantially worse than the country-specific models. In conclusion, care is needed both in transferring models across different study areas, and in developing large inter-regional LUR models. 相似文献
377.
Pablo R. Dalmasso Raúl A. Taccone Jorge D. Nieto Pablo M. Cometto Silvia I. Lane 《Atmospheric environment (Oxford, England : 1994)》2010,44(14):1749-1753
Using the relative rate technique, rate constants for the gas-phase reactions of hydroxyl radicals with 2-chloroethyl methyl ether (k1), 2-chloroethyl ethyl ether (k2) and bis(2-chloroethyl) ether (k3) have been measured. Experiments were carried out at (298 ± 2) K and atmospheric pressure using synthetic air as bath gas. Using n-pentane and n-heptane as reference compounds, the following rate constants were derived: k1 = (5.2 ± 1.2) × 10?12, k2 = (8.3 ± 1.9) × 10?12 and k3 = (7.6 ± 1.9) × 10?12, in units of cm3 molecule?1 s?1. This is the first experimental determination of k2 and k3 under atmospheric pressure. The rate constants obtained are compared with previous literature data and the observed trends in the relative rates of reaction of hydroxyl radicals with the ethers studied are discussed. The atmospheric implications of the results are considered in terms of lifetimes and fates of the hydrochloroethers studied. 相似文献
378.
Rokjin J. Park Minjoong J. Kim Jaein I. Jeong Daeok Youn Sangwoo Kim 《Atmospheric environment (Oxford, England : 1994)》2010,44(11):1414-1421
Brown carbon aerosols were recently found to be ubiquitous and effectively absorb solar radiation. We use a 3-D global chemical transport model (GEOS-Chem) together with aircraft and ground based observations from the TRACE-P and the ACE-Asia campaigns to examine the contribution of brown carbon aerosol to the aerosol light absorption and its climatic implication over East Asia in spring 2001. We estimated brown carbon aerosol concentrations in the model using the mass ratio of brown carbon to black carbon (BC) aerosols based on measurements in China and Europe. The comparison of simulated versus observed aerosol light absorption showed that the model accounting for brown carbon aerosol resulted in a better agreement with the observations in East Asian-Pacific outflow. We then used the model results to compute the radiative forcing of brown carbon, which amounts up to ?2.4 W m?2 and 0.24 W m?2 at the surface and at the top of the atmosphere (TOA), respectively, over East Asia. Mean radiative forcing of brown carbon aerosol is ?0.43 W m?2 and 0.05 W m?2 at the surface and at the TOA, accounting for about 15% of total radiative forcing (?2.2 W m?2 and 0.33 W m?2) by absorbing aerosols (BC + brown carbon aerosol), having a significant climatic implication in East Asia. 相似文献
379.
380.
The effect of invertebrate predation pressure by the cladoceran Leptodora kindti on the population structure of Daphnia galeata and D. hyalina has been estimated by analyzing the occurrence frequency of the normal and spined morphotypes in Lake Baikal. It is shown
that the growth of L. kindti population density leads to an increase in the proportion of the spined morphotype, while that of that of the normal morphotype
decreases. 相似文献