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991.
I. Vigano T. Rckmann R. Holzinger A. van Dijk F. Keppler M. Greule W.A. Brand H. Geilmann H. van Weelden 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5637-5646
Recent experiments have shown that dry and fresh leaves, other plant matter, as well as several structural plant components, emit methane upon irradiation with UV light. Here we present the source isotope signatures of the methane emitted from a range of dry natural plant leaves and structural compounds. UV-induced methane from organic matter is strongly depleted in both 13C and D compared to the bulk biomass. The isotopic content of plant methoxyl groups, which have been identified as important precursors of aerobic methane formation in plants, falls roughly halfway between the bulk and CH4 isotopic composition. C3 and C4/CAM plants show the well-established isotope difference in bulk 13C content. Our results show that they also emit CH4 with different δ13C value. Furthermore, δ13C of methoxyl groups in the plant material, and ester methoxyl groups only, show a similar difference between C3 and C4/CAM plants. The correlation between the δ13C of emitted CH4 and methoxyl groups implies that methoxyl groups are not the only source substrate of CH4.Interestingly, δD values of the emitted CH4 are also found to be different for C3 and C4 plants, although there is no significant difference in the bulk material. Bulk δD analyses may be compromised by a large reservoir of exchangeable hydrogen, but no significant δD difference is found either for the methoxyl groups, which do not contain exchangeable hydrogen. The δD difference in CH4 between C3 and C4 plants indicates that at least two different reservoirs are involved in CH4 emission. One of them is the OCH3 group, the other one must be significantly depleted, and contribute more to the emissions of C3 plants compared to C4 plants. In qualitative agreement with this hypothesis, CH4 emission rates are higher for C3 plants than for C4 plants. 相似文献
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A. M. Rusanov 《Russian Journal of Ecology》2012,43(1):33-39
Results are presented that have been obtained in studies on the effect of forests growing in the steppe zone on the conditions
of formation and qualitative and quantitative composition of organic matter and on the properties of humus in chernozem soils
of neighboring biogeocenoses. 相似文献
995.
Stormwater discharged from highly urbanised catchments on the southern shore of Sydney estuary, Australia, has been identified
as the primary source of contaminants responsible for ecological degradation and reduction in recreational value of the waterway.
Effective management of this pollution requires knowledge of contaminant loads associated with various stormwater flow conditions
in three highly urbanised catchments in Sydney estuary catchment. The majority (>90%) of metal (Cu, Pb and Zn) and total suspended
solid annual loads were contributed during high-flow conditions (>50 mm rainfall dayt1), whereas ≤55% of TN and ≤21% of total phosphorus were contributed to annual loading by dry weather base-flow conditions.
All flow conditions posed an in-stream ecological threat because contaminant concentrations exceeded water quality guidelines
for all analytes measured, except Pb. Irregular, temporal variability in contaminant concentrations associated with base-flow
(within day and amongst days), high-flow (amongst events) and irregular discharges indicated that contaminant contributions
in stormwater were strongly controlled by human activity in the three catchments. Significant variation in contaminant concentrations
under all flow conditions revealed unique chemical signatures for each catchment despite similarities in land uses, location
and geology amongst catchments. These characteristics indicate that assessment and management of stormwater pollution needs
to be conducted on an individual-catchment basis for highly urbanised regions of Sydney estuary catchment. 相似文献
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Rapid urbanization in the developing world calls for attention to address the issue of urban sustainability, especially in emerging countries such as China, where social equity and environmental conditions have been marginalized by the rapid economic development. In this paper, we addressed the above issue with an attempt to answer the following questions: (1) How did the sustainability of Chinese cities evolve over time? (2) What are the driving forces for the evolution? By constructing a composite index that incorporates three major aspects of sustainability, economy, environment, and social equity, we characterized the recent evolution of Chinese cities and assessed the disparity among regions in terms of the sustainability measures. Further, we analyzed the driving forces for the change of sustainability indices through a driving force-pressure-state-effect model. We substantiate our numerical analysis of Chinese cities with a detailed case study of Urumqi, the capital of Xinjiang Autonomous Region, which has experienced significant change over the past 3 decades in every aspect of sustainability. We highlight some fundamental socioeconomic driving forces that have caused spatial restructuring, reflected by land-use change, and consequently impacted the urban environment of Urumqi. A brief case analysis of Guangzhou is also provided. 相似文献
1000.
Richard C. Foltz 《Journal of Agricultural and Environmental Ethics》2007,20(6):533-542