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101.
Brian P. Bledsoe Chester C. Watson 《Journal of the American Water Resources Association》2001,37(2):255-270
ABSTRACT: Channel instability and aquatic ecosystem degradation have been linked to watershed imperviousness in humid regions of the U.S. In an effort to provide a more process‐based linkage between observed thresholds of aquatic ecosystem degradation and urbanization, standard single event approaches (U.S. Geological Survey Flood Regression Equations and rational) and continuous hydrologic models (HSPF and CASC2D) were used to examine potential changes in flow regime associated with varying levels of watershed imperviousness. The predicted changes in flow parameters were then interpreted in concert with risk‐based models of channel form and instability. Although low levels of imperviousness (10 to 20 percent) clearly have the potential to destabilize streams, changes in discharge, and thus stream power, associated with increased impervious area are highly variable and dependent upon watershed‐specific conditions. In addition to the storage characteristics of the pre‐development watershed, the magnitude of change is sensitive to the connectivity and conveyance of impervious areas as well as the specific characteristics of the receiving channels. Different stream types are likely to exhibit varying degrees and types of instability, depending on entrenchment, relative erodibility of bed and banks, riparian condition, mode of sediment transport (bedload versus suspended load), and proximity to geomorphic thresholds. Nonetheless, simple risk‐based analyses of the potential impacts of land use change on aquatic ecosystems have the potential to redirect and improve the effectiveness of watershed management strategies by facilitating the identification of channels that may be most sensitive to changes in stream power. 相似文献
102.
PM2.5 chemical source profiles for vehicle exhaust, vegetative burning, geological material, and coal burning in Northwestern Colorado during 1995 总被引:12,自引:0,他引:12
PM2.5 (particles with aerodynamic diameters less than 2.5 μm) chemical source profiles applicable to speciated emissions inventories and receptor model source apportionment are reported for geological material, motor vehicle exhaust, residential coal (RCC) and wood combustion (RWC), forest fires, geothermal hot springs; and coal-fired power generation units from northwestern Colorado during 1995. Fuels and combustion conditions are similar to those of other communities of the inland western US. Coal-fired power station profiles differed substantially between different units using similar coals, with the major difference being lack of selenium in emissions from the only unit that was equipped with a dry limestone sulfur dioxide (SO2) scrubber. SO2 abundances relative to fine particle mass emissions in power plant emissions were seven to nine times higher than hydrogen sulfide (H2S) abundances from geothermal springs, and one to two orders of magnitude higher than SO2 abundances in RCC emissions, implying that the SO2 abundance is an important marker for primary particle contributions of non-aged coal-fired power station contributions. The sum of organic and elemental carbon ranged from 1% to 10% of fine particle mass in coal-fired power plant emissions, from 5% to 10% in geological material, >50% in forest fire emissions, >60% in RWC emissions, and >95% in RCC and vehicle exhaust emissions. Water-soluble potassium (K+) was most abundant in vegetative burning profiles. K+/K ratios ranged from 0.1 in geological material profiles to 0.9 in vegetative burning emissions, confirming previous observations that soluble potassium is a good marker for vegetative burning. 相似文献
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Conservation of representative facets of geophysical diversity may help conserve biological diversity as the climate changes. We conducted a global classification of terrestrial geophysical diversity and analyzed how land protection varies across geophysical diversity types. Geophysical diversity was classified in terms of soil type, elevation, and biogeographic realm and then compared to the global distribution of protected areas in 2012. We found that 300 (45%) of 672 broad geophysical diversity types currently meet the Convention on Biological Diversity's Aichi Target 11 of 17% terrestrial areal protection, which suggested that efforts to implement geophysical diversity conservation have a substantive basis on which to build. However, current protected areas were heavily biased toward high elevation and low fertility soils. We assessed 3 scenarios of protected area expansion and found that protection focused on threatened species, if fully implemented, would also protect an additional 29% of geophysical diversity types, ecoregional‐focused protection would protect an additional 24%, and a combined scenario would protect an additional 42%. Future efforts need to specifically target low‐elevation sites with productive soils for protection and manage for connectivity among geophysical diversity types. These efforts may be hampered by the sheer number of geophysical diversity facets that the world contains, which makes clear target setting and prioritization an important next step. 相似文献
106.
Alan Watson Steve Martin Neal Christensen Gregg Fauth Dan Williams 《Environmental management》2015,56(3):653-663
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