Aerosol deposition velocities can be estimated from measurements of the ratio of the concentration of a depositing species, such as Pb, to a non-depositing (conserved) species, such as CO, when both originate from the same source (dual tracer method). This method has been applied to size-segregated aerosol samples collected in Los Angeles, CA during the Southern California Air Quality Study, summer 1987. Lead size distributions were measured in ambient and tunnel samples using an eight-stage low pressure impactor. A new parameter, the fraction of aerosol remaining airborne, was directly determined. This fraction is of great importance receptor modelling. Dry deposition velocities calculated using a stirred atmosphere (box) model, varied over three orders of magnitude depending on particle size. The calculated deposition velocity for unit density particles > 0.5 μm, was approximately proportional to Dp2 as expected for deposition by an interception mechanism (dp = particle aerodynamic diameter). 相似文献
Human-induced urban growth and sprawl have implications for greenhouse gas (GHG) emissions that may not be included in conventional GHG accounting methods. Improved understanding of this issue requires use of interactive, spatial-explicit social–ecological systems modeling. This paper develops a comprehensive approach to modeling GHG emissions from urban developments, considering Stockholm County, Sweden as a case study. GHG projections to 2040 with a social–ecological system model yield overall greater emissions than simple extrapolations in official climate action planning. The most pronounced difference in emissions (39% higher) from energy use single-residence buildings resulting from urban sprawl. And this difference is not accounted for in the simple extrapolations. Scenario results indicate that a zoning policy, restricting urban development in certain areas, can mitigate 72% of the total emission effects of the model-projected urban sprawl. The study outcomes include a decision support interface for communicating results and policy implications with policymakers.
The Chi-Chi earthquake (ML = 7.3) occurred in the central part of Taiwan on September 21, 1999. After the earthquake, typhoons Xangsane and Toraji produced
heavy rainfall that fell across the eastern and central parts of Taiwan on November 2000 and July 2001. This study uses remote
sensing data, landscape metrics, multivariate statistical analysis, and spatial autocorrelation to assess how earthquake and
typhoons affect landscape patterns. It addresses variations of the Chenyulan watershed in Nantou County, near the earthquake’s
epicenter and crossed by Typhoon Toraji. The subsequent disturbances have gradually changed landscape of the Chenyulan watershed.
Disturbances of various types, sizes, and intensities, following various tracks, have various effects on the landscape patterns
and variations of the Chenyulan watershed. The landscape metrics that are obtained by multivariate statistical analyses showed
that the disturbances produced variously fragmented patches, interspersed with other patches and isolated from patches of
the same type across the entire Chenyulan watershed. The disturbances also affected the isolation, size, and shape-complexity
of patches at the landscape and class levels. The disturbances at the class level more strongly affected spatial variations
in the landscape as well as patterns of grasslands and bare land, than variations in the watershed farmland and forest. Moreover,
the earthquake with high magnitude was a starter to create these landscape variations in space in the Chenyulan watershed.
The cumulative impacts of the disturbances on the watershed landscape pattern had existed, especially landslides and grassland
in the study area, but were not always evident in space and time in landscape and other class levels. 相似文献
Identifying and communicating uncertainty is core to effective environmental assessment (EA). This study evaluates the extent to which uncertainties are considered and addressed in Canadian EA practice. We reviewed the environmental protection plans, follow-up programs, and panel reports (where applicable) of 12 EAs between 1995 and 2012. The types of uncertainties and levels of disclosure varied greatly. When uncertainties were acknowledged, practitioners adopted five different approaches to address them. However, uncertainties were never discussed or addressed in depth. We found a lack of suitable terminology and consistency in how uncertainties are disclosed, reflecting the need for explicit guidance, and we present recommendations for improvement. Canadian Environmental Impact Statements are not as transparent with respect to uncertainties as they should be, and uncertainties in EA need to be better considered and communicated. 相似文献
This paper contributes to an enhanced understanding of present climatic conditions, observed climate trends and regional climate vulnerability of the Bhutan Himalayas. Bhutan’s complex, often high-altitude terrain and the severe impact of the Indian summer monsoon leads to a strong exposure of the countries’ key economic sectors (agriculture, forestry, hydropower generation and tourism) to climatic changes. Climate change also threatens Bhutan’s vast biodiversity and increases the likelihood of natural hazards (e.g. glacier lake outburst floods, flash floods, droughts and forest fires). A better understanding of Bhutan’s climate and its variability, as well as observed and possible climate impacts, will help in improving the handling of regional social, economic and ecologic challenges not limited to the Himalayas. Only a few climatological studies exist for the eastern Himalayas. They mainly focus on adaptation to immediate threats by glacier lake outbursts. In contrast, this paper (1) investigates the average spatial and inner-annual diversity of the air temperature regime of Bhutan, based on local meteorological observations, (2) discusses past temperature variability, based on global datasets, and (3) relates effects of observed warming to water availability, hydropower development, natural hazards, forests, biodiversity, agriculture, human health and tourism in the Bhutan Himalayas. Results indicate a large spatial and temporal temperature variability within Bhutan and considerably increasing temperatures especially over recent decades. Implications of regional climatic changes on various socio-economic sectors and possible adaptation efforts are discussed. 相似文献
In a laboratory study we investigated 1) the potential production of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) and 2) the effect of nitrate (NO3?) and anaerobic N2O development on CH4 production in sediment from a recently recreated free surface water wetland (FSWW) and in soil from an adjacent meadow. We designed an experiment where production of greenhouse gases was registered at the time of maximum net development of N2O. We made additions of biodegradable carbon (glucose) and/or NO3? to sediment and soil slurries and incubated them at four temperatures (4, 13, 20, 28 °C). Gas production from both substrates was positively correlated with temperature. We also found that the sediment produced more N2O than the soil. N2O production in sediment was NO3? limited, whereas in soil carbon availability was lower and only combined additions of NO3? and glucose supported increased N2O development. CH4 production was generally low and did not differ between soil and sediment. Nor did glucose addition increase CH4 rates. The results suggest that neither soil nor sediment environment did support development of methanogenic populations. There were no clear effects of NO3? on CH4 production. However, the highest records of CH4 were found in incubations with low N2O production, which indicates that N2O might be toxic to methanogens. In summary, our study showed that transforming meadows into FSWWs implies a risk of increased N2O emissions. This does not seem to be valid for CH4. However, since N2O is almost always produced wherever NO3? is denitrified, increased N2O production in wetlands leads to reduced rates in downstream environments. Hence, we conclude that when balancing NO3? retention and global warming aspects, we find no reason to discourage future creation or restoration of wetlands. 相似文献