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491.
David A. Olson Stephen R. McDow 《Atmospheric environment (Oxford, England : 1994)》2009,43(18):2862-2867
Concentrations of elemental carbon (EC), organic carbon (OC), and 33 organic source markers (12 alkanes, 18 polycyclic aromatic hydrocarbons and ketones, and 3 hopanes) are reported near a highway in Raleigh, NC with an annual average daily traffic count of approximately 125,000 vehicles. Daily samples (24-h) were collected at two locations, one approximately 10 m and the other 275 m perpendicular from the road. Concentrations of OC were similar between near (mean = 7.6 μg m?3) and far (8.0 μg m?3) locations, but concentrations of most organic species at the near site were between 1.5 and 2 times higher than those at the far site. 相似文献
492.
Yifang Zhu Jayanth Pudota Donald Collins David Allen Andrea Clements Allison DenBleyker Matt Fraser Yuling Jia Elena McDonald-Buller Edward Michel 《Atmospheric environment (Oxford, England : 1994)》2009,43(30):4513-4522
Vehicular emitted air pollutant concentrations were studied near three types of roadways in Austin, Texas: (1) State Highway 71 (SH-71), a heavily traveled arterial highway dominated by passenger vehicles; (2) Interstate 35 (I-35), a limited access highway north of Austin in Georgetown; and (3) Farm to Market Road 973 (FM-973), a heavily traveled surface roadway dominated by truck traffic. Air pollutants examined include carbon monoxide (CO), oxides of nitrogen (NOx), and carbonyl species in the gas-phase. In the particle phase, ultrafine particle (UFP) concentrations (diameter < 100 nm), fine particulate matter (PM2.5, diameter < 2.5 μm) mass and carbon content and several particle-bound organics were examined. All roadways had an upwind stationary sampling location, one or two fixed downwind sample locations and a mobile monitoring platform that characterized pollutant concentrations fall-off with increased distance from the roadways. Data reported in this paper focus on UFP while other pollutants and near-roadway chemical processes are examined in a companion paper. Traffic volume, especially heavy-duty traffic, wind speed, and proximity to the road were found to be the most important factors determining UFP concentrations near the roadways. Since wind directions were not consistent during the sampling periods, distances along wind trajectories from the roadway to the sampling points were used to study the decay characteristics of UFPs. Under perpendicular wind conditions, for all studied roadway types, particle number concentrations increased dramatically moving from the upwind side to the downwind side. The elevated particle number concentrations decay exponentially with increasing distances from the roadway with sharp concentration gradients observed within 100–150 m, similar to previously reported studies. A single exponential decay curve was found to fit the data collected from all three roadways very well under perpendicular wind conditions. No consistent pattern was observed for UFPs under parallel wind conditions. However, regardless of wind conditions, particle concentrations returned to background levels within a few hundred meters of the roadway. Within measured UFP size ranges, smaller particles (6–25 nm) decayed faster than larger ones (100–300 nm). Similar decay rates were observed among UFP number, surface, and volume. 相似文献
493.
Bethany Warren Rebecca L. Austin David R. Cocker 《Atmospheric environment (Oxford, England : 1994)》2009,43(22-23):3548-3555
Temperature was found to have a dramatic effect on secondary organic aerosol formation from two ozonolysis systems, cyclohexene and α-pinene. Isothermal experiments were conducted for both systems where the lowest temperature, 278 K, formed approximately 2.5–3 times and 5–6 times the SOA formed at 300 K and 318 K, respectively. Changing the cyclohexene system temperature to a different isothermal experimental set point after completion of SOA formation did not lead to sufficient condensation/evaporation to reproduce the SOA formation at other temperature set points. When the system temperature was cycled between two set points at the end of an experiment, the α-pinene system showed reversibility between the initial temperature 318 K and 300 K. For temperature cycles between the initial temperature of 300 K–318 K, an irreversible loss of mass is observed after the first heating cycle with reversibility observed between subsequent temperature cycles. The SOA formed at 278 K was reversible over a 22 K range but was unable to evaporate sufficiently to match the SOA mass formed at 300 K. Hygroscopicity measurements, taken after the completion of SOA formation, indicate that hygroscopicity of the aerosol is also a function of temperature and that the aerosol does not continue to be oxidized after initial growth is complete. The differing hygroscopicity of the semi-volatile component of the aerosol is evident during system temperature changes after completion of the experiment. 相似文献
494.
Bustamante J Pacios F Díaz-Delgado R Aragonés D 《Journal of environmental management》2009,90(7):2219-2225
We have used Landsat-5 TM and Landsat-7 ETM+ images together with simultaneous ground-truth data at sample points in the Doñana marshes to predict water turbidity and depth from band reflectance using Generalized Additive Models. We have point samples for 12 different dates simultaneous with 7 Landsat-5 and 5 Landsat-7 overpasses. The best model for water turbidity in the marsh explained 38% of variance in ground-truth data and included as predictors band 3 (630–690 nm), band 5 (1550–1750 nm) and the ratio between bands 1 (450–520 nm) and 4 (760–900 nm). Water turbidity is easier to predict for water bodies like the Guadalquivir River and artificial ponds that are deep and not affected by bottom soil reflectance and aquatic vegetation. For the latter, a simple model using band 3 reflectance explains 78.6% of the variance. Water depth is easier to predict than turbidity. The best model for water depth in the marsh explains 78% of the variance and includes as predictors band 1, band 5, the ratio between band 2 (520–600 nm) and band 4, and bottom soil reflectance in band 4 in September, when the marsh is dry. The water turbidity and water depth models have been developed in order to reconstruct historical changes in Doñana wetlands during the last 30 years using the Landsat satellite images time series. 相似文献
495.
There are two principal strategies for managing climate change risks: mitigation and adaptation. Until recently, mitigation
and adaptation have been considered separately in both climate change science and policy. Mitigation has been treated as an
issue for developed countries, which hold the greatest responsibility for climate change, while adaptation is seen as a priority
for the South, where mitigative capacity is low and vulnerability is high. This conceptual divide has hindered progress against
the achievement of the fundamental sustainable development challenges of climate change. Recent attention to exploring the
synergies between mitigation and adaptation suggests that an integrated approach could go some way to bridging the gap between
the development and adaptation priorities of the South and the need to achieve global engagement in mitigation. These issues
are explored through a case study analysis of climate change policy and practice in Bangladesh. Using the example of waste-to-compost
projects, a mitigation-adaptation-development nexus is demonstrated, as projects contribute to mitigation through reducing
methane emissions; adaptation through soil improvement in drought-prone areas; and sustainable development, because poverty
is exacerbated when climate change reduces the flows of ecosystem services. Further, linking adaptation to mitigation makes
mitigation action more relevant to policymakers in Bangladesh, increasing engagement in the international climate change agenda
in preparation for a post-Kyoto global strategy. This case study strengthens the argument that while combining mitigation
and adaptation is not a magic bullet for climate policy, synergies, particularly at the project level, can contribute to the
sustainable development goals of climate change and are worth exploring. 相似文献
496.
The fate and transport processes of a toxic chemical such as atrazine, an herbicide, in a reservoir are significantly influenced
by hydrodynamic regimes of the reservoir. The two-dimensional (2D) laterally-integrated hydrodynamics and mass transport model,
CE-QUAL-W2, was enhanced by incorporating a submodel for toxic contaminants and applied to Saylorville Reservoir, Iowa. The
submodel describes the physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions
of a toxic chemical. The simulation results from the enhanced 2D reservoir model were validated by measured temperatures and
atrazine concentrations in the reservoir. Although a strong thermal stratification was not identified from both observed and
predicted water temperatures, the spatial variation of atrazine concentrations was largely affected by seasonal flow circulation
patterns in the reservoir. In particular, the results showed the effect of flow circulation on spatial distribution of atrazine
during summer months as the river flow formed an underflow within the reservoir and resulted in greater concentrations near
the surface of the reservoir. Atrazine concentrations in the reservoir peaked around the end of May and early June. A good
agreement between predicted and observed times and magnitudes of peak concentrations was obtained. The use of time-variable
decay rates of atrazine led to more accurate prediction of atrazine concentrations, while the use of a constant half-life
(60 days) over the entire period resulted in a 40% overestimation of peak concentrations. The results provide a better understanding
of the fate and transport of atrazine in the reservoir and information useful in the development of reservoir operation strategies
with respect to timing, amount, and depth of withdrawal. 相似文献
497.
Understanding how setting attributes influence the nature of the visitor experience is crucial to effective recreation management.
Highly influential attributes are useful indicators to monitor within a planning framework, such as Limits of Acceptable Change.
This study sought to identify the setting attributes perceived to have the most profound effect on the ability to have “a
real wilderness experience” and to assess the degree to which attribute importance varied with situational context and visitor
characteristics. To this end, exiting hikers were surveyed at moderate and very high use trailheads in Alpine Lakes Wilderness,
WA (USA), and Three Sisters Wilderness, OR (USA). They were asked about the degree to which encountering varying levels of
different setting attributes would add to or detract from their experience. Attributes with the largest range of effect on
experience, based on evaluations of different levels, were considered most important. The most influential attributes were
litter and several types of campsite interaction—people walking through camp and number of other groups camping close by.
The perceived importance of setting attributes did not vary much between wilderness locations with substantially different
use levels, suggesting that conclusions are robust and generalizable across wilderness areas. There also was little difference
in the perceptions of day and overnight visitors. In contrast, we found substantial variation in the perceived importance
of setting attributes with variation in wilderness experience, knowledge, attachment, and motivation. Our results validate
the emphasis of many wilderness management plans on indicators of social interaction, such as number of encounters. 相似文献
498.
The Effect of Water Harvesting Techniques on Runoff,Sedimentation, and Soil Properties 总被引:1,自引:0,他引:1
This study addressed the hydrological processes of runoff and sedimentation, soil moisture content, and properties under the
effect of different water harvesting techniques (treatments). The study was conducted at three sites, representing environmental
condition gradients, located in the southern part of the West Bank. For each treatment, the study evaluated soil chemical
and physical properties, soil moisture at 30 cm depth, surface runoff and sedimentation at each site. Results showed that
runoff is reduced by 65–85% and sedimentation by 58–69% in stone terraces and semi-circle bunds compared to the control at
the semi-humid site. In addition, stone terraces and contour ridges significantly reduced the amount of total runoff by 80%
and 73%, respectively, at the arid site. Soil moisture content was significantly increased by water harvesting techniques
compared to the control in all treatments at the three study sites. In addition, the difference between the control and the
water harvesting structures were higher in the arid and semi-arid areas than in the semi-humid area. Soil and water conservation,
via utilization of water harvesting structures, is an effective principle for reducing the negative impact of high runoff
intensity and subsequently increasing soil moisture storage from rainfall. Jessour systems in the valley and stone terraces
were effective in increasing soil moisture storage, prolonging the growing season for natural vegetation, and decreasing the
amount of supplemental irrigation required for growing fruit trees. 相似文献
499.
Diversity of Soil Nematodes in Areas Polluted with Heavy Metals and Polycyclic Aromatic Hydrocarbons (PAHs) in Lanzhou,China 总被引:1,自引:0,他引:1
This study investigated the soil nematode community structure along the Yellow River in the Lanzhou area of China, and analyzed
the impact of heavy metals (Cd, Pb, Cr, Cu, and Zn) and polycyclic aromatic hydrocarbons (PAHs) on the nematode community.
Soil samples from five locations (named A–E), which were chosen for soil analysis, showed significant differences in their
heavy metal content (p < 0.01), as well as in the variety of nematodes (up to 41 genera) and families (up to 20) that were present. The different
samples also differed significantly in the total PAH content (p < 0.05), as well as the six types of PAH present. Sites A–C showed the most severe contamination with heavy metals and PAHs;
these sites had the lowest abundance of fungivores and omnivore/predators, but the proportion of bacteriovores was the highest
(p < 0.05). Site E, in contrast, showed only minor pollution with heavy metals and PAHs, and it contained the highest abundance
of plant parasites (p < 0.05). Several nematode ecological indicators were found to correlate with concentration of soil pollutants at all the
sites tested: the maturity index (MI, in addition to plant parasites), plant parasite index (PPI), ΣMI (including all the
soil nematodes), Shannon-Wiener diversity index (H′′), and Wasilewska index (WI). Disturbance to the soil environment was more severe when MI, ΣMI, and H′ values were lower. The results of the study show that the abundance and structure of the soil nematode communities in the
sampling locations were strongly influenced by levels of heavy metals and PAHs in the soil. They also show that the diversity
index H′ and the maturity index can be valuable tools for assessing the impact of pollutants on nematodes. 相似文献
500.
Frank Merry Britaldo Soares-Filho Daniel Nepstad Gregory Amacher Hermann Rodrigues 《Environmental management》2009,44(3):395-407
Logging has been a much maligned feature of frontier development in the Amazon. Most discussions ignore the fact that logging
can be part of a renewable, environmentally benign, and broadly equitable economic activity in these remote places. We estimate
there to be some 4.5 ± 1.35 billion m3 of commercial timber volume in the Brazilian Amazon today, of which 1.2 billion m3 is currently profitable to harvest, with a total potential stumpage value of $15.4 billion. A successful forest sector in
the Brazilian Amazon will integrate timber harvesting on private lands and on unprotected and unsettled government lands with
timber concessions on public lands. If a legal, productive, timber industry can be established outside of protected areas,
it will deliver environmental benefits in synergy with those provided by the region’s network of protected areas, the latter
of which we estimate to have an opportunity cost from lost timber revenues of $2.3 billion over 30 years. Indeed, on all land
accessible to harvesting, the timber industry could produce an average of more than 16 million m3 per year over a 30-year harvest cycle—entirely outside of current protected areas—providing $4.8 billion in returns to landowners
and generating $1.8 billion in sawnwood sales tax revenue. This level of harvest could be profitably complemented with an
additional 10% from logging concessions on National Forests. This advance, however, should be realized only through widespread
adoption of reduced impact logging techniques. 相似文献