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351.
A small fraction of the naphtha diluent used for oil sands processing escapes with tailings and supports methane (CH(4)) biogenesis in large anaerobic settling basins such as Mildred Lake Settling Basin (MLSB) in northern Alberta, Canada. Based on the rate of naphtha metabolism in tailings incubated in laboratory microcosms, a kinetic model comprising lag phase, rate of hydrocarbon metabolism and conversion to CH(4) was developed to predict CH(4) biogenesis and flux from MLSB. Zero- and first-order kinetic models, respectively predicted generation of 5.4 and 5.1 mmol CH(4) in naphtha-amended microcosms compared to 5.3 (+/-0.2) mmol CH(4) measured in microcosms during 46 weeks of incubation. These kinetic models also predicted well the CH(4) produced by tailings amended with either naphtha-range n-alkanes or BTEX compounds at concentrations similar to those expected in MLSB. Considering 25% of MLSB's 200 million m(3) tailings volume to be methanogenic, the zero- and first-order kinetic models applied over a wide range of naphtha concentrations (0.01-1.0 wt%) predicted production of 8.9-400 million l CH(4) day(-1) from MLSB, which exceeds the estimated production of 3-43 million l CH(4) day(-1). This discrepancy may result from heterogeneity and density of the tailings, presence of nutrients in the microcosms, and/or overestimation of the readily biodegradable fraction of the naphtha in MLSB tailings. 相似文献
352.
M. Dolores Garza-Gil Julia Torralba-Cano Manuel M. Varela-Lafuente 《Regional Environmental Change》2011,11(1):87-95
This study evaluates the economic effects of climate change on one of the most relevant fisheries of the Iberian Peninsula,
the European sardine fishery; a fishing ground that is particularly sensitive to environmental impacts. For this, the sea
surface temperature is introduced into the problem as an additional variable. This variable allows for the gathering of climate
change evidence and its repercussions on the oceans and, consequently, on the marine life and ecosystems. Various plausible
scenarios are posed with respect to the trends involving the sea surface temperature. The results show that if the trend of
rising surface temperatures continues in the Iberian-Atlantic fishing grounds, both the sardine biomass and the expected profits
will noticeably decrease. The biomass and profits will further decrease with greater intensity if the immediate effects of
global warming on sea surface temperature become more significant. On the other hand, in a palliation of global warming scenario,
both variables decrease to a lesser degree. 相似文献
353.
There has been a recent increase in the use of silver nanoparticles (Ag NPs) in a wide range of consumer products due to their highly effective antimicrobial properties. However, Ag NPs give cause for concern since their wide use makes them likely to be released into aquatic ecosystems and potentially affect natural bacterial communities. In this study marine biofilms were grown in situ in a coastal site (Singapore Harbour) and exposed in the laboratory for a further 24 h to 0-2000 μg L−1 of well characterised Ag NPs. Increasing concentrations of Ag NPs caused a significant decrease in biofilm volume and biomass, and Ag uptake by biofilms per unit of volume was also dependent on concentration. Terminal fragment length polymorphisms and subsequent cluster and phylogenetic analysis showed the presence of major bacterial groups in biofilms irrespective of treatment with Ag NPs. This implies that even at the highest concentrations studied these taxonomic groups were not displaced. Nevertheless, biofilm succession was impeded on Ag NP treated biofilms, affecting the relative abundance of major bacterial groups in the biofilm community, with potential longer term effects on biofilm development and function. 相似文献
354.
355.
356.
Dr. Fr. Lindner 《Die Naturwissenschaften》1916,4(16):205-210
357.
358.
Vondracek B Blann KL Cox CB Nerbonne JF Mumford KG Nerbonne BA Sovell LA Zimmerman JK 《Environmental management》2005,36(6):775-791
We synthesized nine studies that examined the influence of land use at different spatial scales in structuring biotic assemblages
and stream channel characteristics in southeastern Minnesota streams. Recent studies have disagreed about the relative importance
of catchment versus local characteristics in explaining variation in fish assemblages. Our synthesis indicates that both riparian-
and catchment-scale land use explained significant variation in water quality, channel morphology, and fish distribution and
density. Fish and macroinvertebrate assemblages can be positively affected by increasing the extent of perennial riparian
and upland vegetation. Our synthesis is robust; more than 425 stream reaches were examined in an area that includes a portion
of three ecoregions. Fishes ranged from coldwater to warmwater adapted. We suggest that efforts to rehabilitate stream system
form and function over the long term should focus on increasing perennial vegetation in both riparian areas and uplands and
on managing vegetation in large, contiguous blocks.
Minnesota Cooperative Fish and Wildlife Research Unit is jointly sponsered by U.S. Geological Survey Biological Resources
Division, the University of Minnesota, The Minnesota Department of Natural Resources, and the Wildlife Management Institute. 相似文献
359.
Julia B. Edwards 《Journal of Safety Research》1998,29(4):249-262
Road accident severity may be influenced by a number of factors. This article investigates the relationship between weather and road accidents in England and Wales. The weather information recorded on Police Accident Report Forms was taken as the prevailing weather at the time of the accident. At the local authority level, accident severity for the various adverse weather categories of rain, fog, and high winds is compared with the nonhazardous condition of fine weather. Severity ratios are then calculated. Findings establish that accident severity decreases significantly in rain compared with fine weather, while severity in fog shows geographical variation. Evidence for accident severity in high winds remains inconclusive. 相似文献
360.
Temporal variability of soil gas composition in landfill covers 总被引:1,自引:0,他引:1
In order to assess the temporal variability of the conditions for the microbial oxidation of methane in landfill cover soils and their driving variables, gas composition at non-emissive and strongly emissive locations (hotspots) was monitored on a seasonal, daily and hourly time scale on an old, unlined landfill in northern Germany. Our study showed that the impact of the various environmental factors varied with the mode of gas transport and with the time scale considered. At non-emissive sites, governed by diffusive gas transport, soil gas composition was subject to a pronounced seasonal variation. A high extent of aeration, low methane concentrations and a high ratio of CO2 to CH4 were found across the entire depth of the soil cover during the warm and dry period, whereas in the cool and moist period aeration was less and landfill gas migrated further upward. Statistically, variation in soil gas composition was best explained by the variation in soil temperature. At locations dominated by advective gas transport and showing considerable emissions of methane, this pattern was far less pronounced with only little increase in the extent of aeration during drier periods. Here, the change of barometric pressure was found to impact soil gas composition. On a daily scale under constant conditions of temperature, gas transport at both types of locations was strongly impacted by the change in soil moisture. On an hourly scale, under constant conditions of temperature and moisture, gas migration was impacted most by the change in barometric pressure. It was shown that at diffusion-dominated sites complete methane oxidation was achieved even under adverse wintry conditions, whereas at hotspots, even under favorable dry and warm conditions, aerobic biological activity can be limited to the upper crust of the soil. 相似文献