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701.
Jean L. Graf 《Environment international》1981,5(4-6)
Bioassays of diesel engine exhaust components are being conducted at IITRI to determine toxic and carcinogenic potentials of the exhaust. The bioassay method, intracheal instillation of saline suspensions of test materials in hamsters, requires preparation of stable suspensions of test materials. A method to prepare suspensions of whole particle diesel exhaust in saline has been developed. The diesel exhaust particle material was supplied to IITRI as a dry, loose powder by the U.S. EPA from a light duty diesel test engine. Preliminary characterizations of the powders indicated aggregation of exhaust particles had occurred both before and during capture on collection substrates. Flake-like sheets and hollow spheres of aggregated particles up to 150 μm in sie present in the powders. Therefore, the powder were ball-milled to geometric particle sizes more amenable to the animal administration technique to be employed. Grinding, suspension preparation and particle concentration assaying methods have been developed. Particle (geometric) size and morphological characterizations have also been performed on the as-received powders and prepared suspensions. A method to prepare emulsions (liquid-liquid suspensions) of the dichloromethane extracts of whole particle diesel exhaust has also been developed. 相似文献
702.
Objective
To evaluate CarFit, an educational program designed to promote optimal alignment of driver with vehicle.Methods
A driving activity survey was sent to 727 randomly selected participants living in retirement communities. Drivers (n = 195) were assigned randomly to CarFit intervention (n = 83, M age = 78.1) or Comparison (n = 112, M age = 79.6) groups. After 6 months, participants completed a post-test of driving activity and CarFit recommendations.Results
Nonconsenting drivers were older and participated in fewer driving activities. CarFit participation was moderate (71%) with 86% of the participants receiving recommendations. 60% followed the recommendations at the 6-month re-evaluation). The CarFit (67.6%) and Comparison (59.3%) groups reported at least one type of self-regulation of driving activity at baseline. There was no significant change in the driving behaviors at the six-month follow-up.Conclusion
CarFit was able to detect addressable opportunities that may contribute to the safety of older drivers.Impact on industry
CarFit recommendations may need stronger reinforcement in order to be enacted by a participant. 相似文献703.
Filippi-Codaccioni Ondine Clobert Jean Julliard Romain 《Agriculture, ecosystems & environment》2009,129(1-3):140-143
Bird abundance was assessed on a total of 58 farms across the Seine-et-Marne department, France (12 organic, 19 conservation-tillage and 27 conventional farms). Local abundance variations among the three farming systems were related to two species traits, i.e. habitat specialisation and diet, considering both farmland and non-farmland species. It was found that organic farming favoured specialist birds, either considering the whole community or non-farmland birds only. On the opposite, specialist farmland species were found to be less abundant in conservation-tillage farms than in conventional ones. Invertebrate-feeders were found to benefit from conservation-tillage practices compared to omnivorous species but not compared to granivorous ones; an interaction between species diet and the species specialisation level was also found. Granivorous species tended to increase with the conservation-tillage duration and in particular specialist birds. 相似文献
704.
Vanesa L. Negrin Carla V. Spetter Ra′ul O. Asteasuain Gerardo M. E. Perillo Jorge E. Marcovecchio 《环境科学学报(英文版)》2011,23(2):212-221
Four sites were selected in a salt marsh in the Bah′?a Blanca Estuary (Argentina): (1) low marsh (flooded by the tide twice daily)
vegetated by S. alterniflora; (2) non-vegetated low marsh; (3) high marsh (flooded only in spring tides) vegetated by S. alterniflora;
(4) non-vegetated high marsh. The pH and Eh were measured in sediments, while dissolved nutrients (ammonium, nitrate, nitrite and
phosphate) and particulate organic matter (POM) were determined in pore water. pH (6.2–8.7) was only a ected by vegetation in low
areas. Eh (from –300 to 250 mV) was lower at low sites than at high ones; in the latter, the values were higher in the non-vegetated
sediments. The POM concentration was greater in the high marsh than in the low marsh, with no e ect of vegetation. Ammonium
was the most abundant nitrogen nutrient species in pore water, except in the non-vegetated high marsh where nitrate concentration
was higher. All nitrogen nutrients were a ected by both flooding and vegetation. Phosphate was always present in pore water at all
sites throughout the year and its concentration varied within narrow limits, with no e ect of flooding and greater values always at
non-vegetated sites. Our results showed that the variability of the pore water composition within the marsh is greater than the temporal
variation, meaning that both tidal flooding and vegetation are important in the dynamics of nutrients and organic matter in the sediment
pore water. 相似文献
705.
Compared with natural ecosystems and managed agricultural systems, engineered landfills represent a highly managed soil system for which there has been no systematic quantification of emissions from coexisting daily, intermediate, and final cover materials. We quantified the seasonal variability of CH, CO, and NO emissions from fresh refuse (no cover) and daily, intermediate, and final cover materials at northern and southern California landfill sites with engineered gas extraction systems. Fresh refuse fluxes (g m d [± SD]) averaged CH 0.053 (± 0.03), CO 135 (± 117), and NO 0.063 (± 0.059). Average CH emissions across all cover types and wet/dry seasons ranged over more than four orders of magnitude (<0.01-100 g m d) with most cover types, including both final covers, averaging <0.1 g m d with 10 to 40% of surface areas characterized by negative fluxes (uptake of atmospheric CH). The northern California intermediate cover (50 cm) had the highest CH fluxes. For both the intermediate (50-100 cm) and final (>200 cm) cover materials, below which methanogenesis was well established, the variability in gaseous fluxes was attributable to cover thickness, texture, density, and seasonally variable soil moisture and temperature at suboptimal conditions for CH oxidation. Thin daily covers (30 cm local soil) and fresh refuse generally had the highest CO and NO fluxes, indicating rapid onset of aerobic and semi-aerobic processes in recently buried refuse, with rates similar to soil ecosystems and windrow composting of organic waste. This study has emphasized the need for more systematic field quantification of seasonal emissions from multiple types of engineered covers. 相似文献
706.
707.
Janis A. Shandro Marcello M. Veiga Jean Shoveller Malcolm Scoble Mieke Koehoorn 《Resources Policy》2011,36(2):178-186
The health of mining communities is becoming a priority for the mining industry, governments, and researchers. This paper describes an exploratory qualitative study into community health issues and mining activities (associated with the mining boom-bust cycle) from the perspective of health and social service providers in the northern Canadian coal mining community of Tumbler Ridge, British Columbia. Health and social service providers report on increases in pregnancies, sexually transmitted infections, and mine related injuries during booming mine activities. During bust times, mental health issues such as depression and anxiety were reported. Overarching community health issues prominent during both boom and bust periods include burdens to health and social services, family stress, violence towards women, and addiction issues. This paper concludes by providing recommendations as to how the industry can enhance community health made by this important stakeholder group. 相似文献
708.
Tree cover in sub-Saharan Africa: rainfall and fire constrain forest and savanna as alternative stable states 总被引:1,自引:0,他引:1
Savannas are known as ecosystems with tree cover below climate-defined equilibrium values. However, a predictive framework for understanding constraints on tree cover is lacking. We present (a) a spatially extensive analysis of tree cover and fire distribution in sub-Saharan Africa, and (b) a model, based on empirical results, demonstrating that savanna and forest may be alternative stable states in parts of Africa, with implications for understanding savanna distributions. Tree cover does not increase continuously with rainfall, but rather is constrained to low (<50%, "savanna") or high tree cover (>75%, "forest"). Intermediate tree cover rarely occurs. Fire, which prevents trees from establishing, differentiates high and low tree cover, especially in areas with rainfall between 1000 mm and 2000 mm. Fire is less important at low rainfall (<1000 mm), where rainfall limits tree cover, and at high rainfall (>2000 mm), where fire is rare. This pattern suggests that complex interactions between climate and disturbance produce emergent alternative states in tree cover. The relationship between tree cover and fire was incorporated into a dynamic model including grass, savanna tree saplings, and savanna trees. Only recruitment from sapling to adult tree varied depending on the amount of grass in the system. Based on our empirical analysis and previous work, fires spread only at tree cover of 40% or less, producing a sigmoidal fire probability distribution as a function of grass cover and therefore a sigmoidal sapling to tree recruitment function. This model demonstrates that, given relatively conservative and empirically supported assumptions about the establishment of trees in savannas, alternative stable states for the same set of environmental conditions (i.e., model parameters) are possible via a fire feedback mechanism. Integrating alternative stable state dynamics into models of biome distributions could improve our ability to predict changes in biome distributions and in carbon storage under climate and global change scenarios. 相似文献
709.
Adriane Martins de Freitas Carla Sirtori Patricio Peralta-Zamora 《Environmental Chemistry Letters》2011,9(1):97-102
The degradation of camphor using titanium/ruthenium dioxide (TiO2/RuO2; 70:30) electrodes was investigated in a photoelectrochemical thin-film reactor under near UV light irradiation. Two different
electrolytes (Na2SO4 and NaCl) were used in this work. Camphor degradation was monitored by solvent extraction methods and gas chromatography
(GC) analysis. Comparative studies between photoelectrochemical, electrochemical, photolytic, and heterogeneous photocatalytical
process were carried out. When NaCl was used, the degradation efficiency of camphor was improved, probably on account of electrochemical
generation of active chlorine species and their photochemical conversion to chlorine radicals. Under these conditions camphor
was completely mineralized at reaction times of 30 min. 相似文献
710.
Oscar Amin Laura Comoglio Carla Spetter Claudia Duarte Ra��l Asteasuain Rub��n Hugo Freije Jorge Marcovecchio 《Environmental monitoring and assessment》2011,175(1-4):63-73
The study deals with the determination of physico-chemical parameters, inorganic nutrients, particulate organic matter, and photosynthetic pigments on a monthly basis during an annual cycle from nine sampling sites of the coastal zone of a high-latitude ecosystem (Tierra del Fuego, Argentina). Nitrites and phosphates concentrations were similar to other systems of the south Atlantic coast (median, 0.30 and 1.02 ??M, respectively), while nitrates were higher in all sampling periods (median, 45.37 ??M), and silicates were significantly smaller (median, 7.76 ??M). Chlorophyll a and phaeopigments have shown median values of 0.38 and 0.85 mg m???3, respectively, while saturated values of dissolved oxygen were recorded throughout the study. The analysis reflected that nutrient enrichment seems to be linked to an anthropogenic source, the presence of peatlands areas, and a sink of Nothofagus pumilio woods. The area could be characterized in three zones related to (1) high urban influence, (2) natural inputs of freshwater, and (3) mixed inputs coming from moderate urban impacts. 相似文献