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排序方式: 共有257条查询结果,搜索用时 15 毫秒
31.
32.
Germination and seedling development of switchgrass and smooth bromegrass exposed to 2,4,6-trinitrotoluene 总被引:2,自引:0,他引:2
Peterson MM Horst GL Shea PJ Comfort SD 《Environmental pollution (Barking, Essex : 1987)》1998,99(1):53-59
It is estimated that explosives contaminate approximately 0.82 million cubic metres of soil at former military installations throughout the US; major contaminants often include 2,4,6-trinitrotoluene (TNT) and its degradation products. At some sites, phytoremediation may be a viable option to incineration or other costly remediation treatments. Grasses may be particularly suited for remediation because of their growth habit and adaptability to a wide range of soil and climate conditions. We characterized the effects of TNT on germination and early seedling development of switchgrass and smooth bromegrass to evaluate their potential use on contaminated sites. Switchgrass and smooth bromegrass seeds were germinated in nutrient-free agar containing 0 to 60 mg TNT litre(-1). Smooth bromegrass germination decreased as TNT concentration increased, while switchgrass germination was unaffected by TNT. Concentrations up to 15 mg TNT litre(-1) did not affect switchgrass root growth rate, but bromegrass root growth was reduced at TNT concentrations above 7.5 mg litre(-1). At 7.5 mg TNT litre(-1), however, shoot growth rate was reduced in both species. Examination at 20-fold magnification revealed switchgrass radicles were unaffected by TNT, while smooth bromegrass radicles appeared slightly swollen. Results indicate switchgrass is more tolerant of TNT than smooth bromegrass, but the establishment of both species may be limited to soil containing less than 50 mg kg(-1) of extractable TNT. 相似文献
33.
Del Grosso S Ojima D Parton W Mosier A Peterson G Schimel D 《Environmental pollution (Barking, Essex : 1987)》2002,116(Z1):S75-S83
We present evidence to show that DAYCENT can reliably simulate soil C levels, crop yields, and annual trace gas fluxes for various soils. DAYCENT was applied to compare the net greenhouse gas fluxes for soils under different land uses. To calculate net greenhouse gas flux we accounted for changes in soil organic C, the C equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Model results and data show that dryland soils that are depleted of C due to conventional till winter wheat fallow cropping can store C upon conversion to no till, by reducing the fallow period, or by reversion to native vegetation. However, model results suggest that dryland agricultural soils will still be net sources of greenhouse gases although the magnitude of the source can be significantly reduced and yields can be increased upon conversion to no till annual cropping. 相似文献
34.
We quantified the distribution of tropospheric ozone in topographically complex western Washington state, USA (total area approximately 6000 km(2)), using passive ozone samplers along nine river drainages to measure ozone exposure from near sea level to high-elevation mountain sites. Weekly average ozone concentrations were higher with increasing distance from the urban core and at higher elevations, increasing a mean of 1.3 ppbv per 100 m elevation gain for all mountain transects. Weekly average ozone concentrations were generally highest in Cascade Mountains drainages east and southeast of Seattle (maximum=55-67 pbv) and in the Columbia River Gorge east of Portland (maximum=59 ppbv), and lowest in the western Olympic Peninsula (maximum=34 ppbv). Higher ozone concentrations in the Cascade Mountains and Columbia River locations downwind of large cities indicate that significant quantities of ozone and ozone precursors are being transported eastward toward rural wildland areas by prevailing westerly winds. In addition, temporal (week to week) variation in ozone distribution is synchronous within and between all drainages sampled, which indicates that there is regional coherence in air pollution detectable with weekly averages. These data provide insight on large-scale spatial variation of ozone distribution in western Washington, and will help regulatory agencies optimize future monitoring networks and identify locations where human health and natural resources could be at risk. 相似文献
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Making index insurance attractive to farmers 总被引:1,自引:0,他引:1
Anthony Patt Nicole Peterson Michael Carter Maria Velez Ulrich Hess Pablo Suarez 《Mitigation and Adaptation Strategies for Global Change》2009,14(8):737-753
There are several factors that influence whether people will want to participate in index insurance programs. A number of
these influence their attractiveness on economic grounds, including both the size and timing of the premium and potential
payouts, and the degree of risk aversion of the potential customers. Other factors make programs attractive for reasons that
are not economic, but no less valid. These have to do with the trust that people have in the insurance product and the organizations
involved in selling and managing it. Indeed, data from India, Africa, and South America show that these factors may be more
important than the economic ones in influencing demand. Index insurance pilot projects, in order to estimate demand for alternative
products, have typically involved a great deal of interaction with potential customers. It is important to recognize that
such interaction is crucial not just as a research tool, but also as a means to build understanding and trust in the products.
When scaling up from isolated pilots to operational programs, it is vital to recognize this trust building function by replicating
participation efforts in every community. In this paper, we examine the role of field games in establishing and building trust
in three important aspects of these projects for participants: trust in the insurance product, trust in the participating
organizations, and trust in their own ability to make good decisions. While games have previously been used as a way to gauge
interest in the product and to identify design features, we argue that these games are also valuable tools for constructing
these kinds of trust. 相似文献
38.
Peter J. Peterson W. Peter Williams 《Environmental science and pollution research international》1999,6(4):225-232
Measurements of urban air quality at monitoring stations in developed countries have frequently involved the criteria gaseous
pollutants, particulates, hazardous air pollutants, perceived air quality and relevant meteorological conditions. Large numbers
of indicators have therefore been established to quantify emissions, concentrations and environmental and human health impacts
of each of these groups of substances. To simplify the data for management, several indicators have been grouped together
to form urban air quality indices but the weightings of individual variables is contentious.
In industrialising and developing countries, data may be limited and traditional air pollutant indicators cannot often be
constructed. The emphasis therefore has to be placed on the development of policy-relevant indicators, such as Response Indicators
that reflect different policy principles for regulating air pollutant emissions. Indices that quantify the air quality management
capabilities and capacities at the city level provide further useful decision-relevant tools. Four sets of indices, namely,
1. air quality measurement capacity, 2. data assessment and availability, 3. emissions estimates, and 4. management enabling
capabilities, and a composite index to evaluate air quality management capability, were constructed and applied to 80 cities.
The indices revealed that management capability varied widely between the cities. In some of the cities, existing national
knowledge on urban air quality could have been more effectively used for management.
It was concluded that for effective urban air quality management, a greater emphasis should be given, not just to monitoring
and data capture programmes, but to the development of indicators and indices that empower decision-makers to initiate management
response strategies. Over-reliance on restricted, predetermined sets of traditional air quality indicators should be avoided. 相似文献
39.
Rising dissolved pCO2 is a mounting threat to coral reef ecosystems. While the biological and physiological impacts of increased pCO2 are well documented for many hermatypic corals, the potential effects on bioerosion processes remain largely unknown. Increases in pCO2 are likely to modify the direct interactions between corals and bioeroders, such as excavating sponges, with broad implications for the balance between biologically mediated deposition and erosion of carbonate in reef communities. This study investigated the effects of three levels of CO2 (present-day, mid-century and end-of-century projections) on the direct interaction between a bioeroding sponge, Cliona varians, and a Caribbean coral, Porites furcata. Increased pCO2 concentrations had no effect on the attachment rates of C. varians to the corals, and we observed no significant impact of pCO2 on the survival of either the coral or sponges. However, exposure to end-of-century levels of CO2-dosing (~750 μatm) reduced calcification in P. furcata and led to a significant increase in sponge-mediated erosion of P. furcata. These findings demonstrate that pCO2 can enhance erosional efficiency without impacting survival or competitive vigor in these two species. While few studies have considered the influence of pCO2 on the competitive outcomes of interactions between corals and other reef organisms, our study suggests that assessing the impacts of changing pCO2 on species interactions is crucial to adequately predict ecosystem-level responses in the future. 相似文献
40.
Holly Fearnbach John W. Durban David K. Ellifrit Janice M. Waite Craig O. Matkin Chris R. Lunsford Megan J. Peterson Jay Barlow Paul R. Wade 《Marine Biology》2014,161(2):459-472
The productive North Pacific waters of the Gulf of Alaska, Aleutian Islands and Bering Sea support a high density of fish-eating “Resident” type killer whales (Orcinus orca), which overlap in distribution with commercial fisheries, producing both direct and indirect interactions. To provide a spatial context for these interactions, we analyzed a 10-year dataset of 3,058 whale photo-identifications from 331 encounters within a large (linear ~4,000 km) coastal study area to investigate the ranging and social patterns of 532 individually identifiable whales photographed in more than one encounter. Although capable of large-scale movements (maximum 1,443 km), we documented ranges generally <200 km, with high site fidelity across summer sampling intervals and also re-sightings during a winter survey. Bayesian analysis of pair-wise associations identified four defined clusters, likely representing groupings of stable matrilines, with distinct ranging patterns, that combined to form a large network of associated whales that ranged across most of the study area. This provides evidence of structure within the Alaska stock of Resident killer whales, important for evaluating ecosystem and fisheries impacts. This network included whales known to depredate groundfish from longline fisheries, and we suggest that such large-scale connectivity has facilitated the spread of depredation. 相似文献