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971.
Environmental Fluid Mechanics - The influence time distribution in Santa María La Reforma coastal lagoon, which is one of the most productive ecosystems in Mexico, has been numerically... 相似文献
972.
Subrata Mondal Paul Memmott Darren Martin 《Journal of Polymers and the Environment》2012,20(2):326-334
In this paper we explore the preparation of polyurethanes from spinifex resin biopolymer. Polyurethanes were prepared by both one-shot and pre-polymer (two step) processes. Attenuated total reflection??Fourier transform infrared analysis revealed urethane bond formation in both processes, and the peak intensity for N?CH stretching was more sharp when the network was prepared by the pre-polymer method. Gel permeation chromatography revealed that the molecular weight of synthesized polyurethane increased with respect to the resin starting material, and the molecular weight was further increased when polyurethane was synthesized by the pre-polymer method. The glass transition temperature was also increased for the polyurethanes as compared with the starting resin. Thermo-gravimetric analysis revealed that the thermal stability of the PU-spinifex resin was reduced at intermediate temperatures due to the urethane bond formation. However, thermal degradation properties were superior at higher temperatures due to the cyclization degradation reaction of spinifex-polyurethane. 相似文献
973.
974.
Jody N. Connor Michael R. Martin 《Journal of the American Water Resources Association》1989,25(4):845-853
ABSTRACT: Aluminum sulfate and sodium aluminate were utilized as sediment phosphorus inactivants to improve the water quality of a northeastern eutrophic lake. A four-year monitoring program has provided an extensive lake-database utilized to evaluate the short-and long-term effectiveness of sediment phosphorus inactivation as a lake restoration technique. An immediate impact of treatment was marked by a reduction in hypolimnetic BOD and dissolved oxygen deficit, lower chlorophyll-a and phosphorus concentrations, improved transparency, and the elimination of obnoxious blue-green phyto-plankton blooms. For two to three years after treatment, these pa-rameters continued to exhibit both less variability and improved values over the pre-treatment conditions. The improved water quality conditions warranted an upgrade of the lake trophic status from eutrophic to mesotrophic. Four years after the treatment, the mean hypolimnetic total phosphoru.s and chlorophyll-a have increased and transparency has decreased from initial post-treatment levels. Although long-term trends show water quality decreasing since the treatment, the water quality has stabilized at a level suitable for recreation. A major benefit is an increase in the average attendance at the lake by almost 2,000 people per summer. 相似文献
975.
976.
977.
Monitoring and modelling walking track impacts in the Tasmanian Wilderness World Heritage Area, Australia 总被引:1,自引:0,他引:1
A program has been developed for monitoring the condition of unimproved walking tracks on a 1000-km track system in Western Tasmania, and it has been used as the basis of an eight-year study of track-impact development. The monitoring technique involves measuring track depth and two track-width indicators at permanently marked and widely dispersed sites, each site comprising ten transects located at 2-m intervals. Sites have been 'typed' on the basis of track slope, drainage and substrate characteristics, and the typing scheme has been tested and refined by assessing the relationship between type-usage groups and observed impacts. Analysis reveals that track depth and rates of erosion are strongly influenced by track type and to a lesser extent by usage, while track width is influenced mainly by usage and track bogginess. The time-invariant variable 'usage gradient' was introduced to compensate for the fact that usage levels on most walking tracks in Western Tasmania have varied over time. Data derived from multiple inspections at 2-3 year intervals since 1994 from over 250 sites have been used to derive impact/time curves for different type-'usage gradient' groups. Each of the impact variables can be approximated by the formula m = alphatBeta, where m is the expected value of the impact variable, t is chronological time, and alpha and Beta are constants characteristic of the impact variable and type-'usage gradient' group in question. The typing scheme and impact-development model have the potential to be used for systematically describing and predicting impacts over extensive systems of 'typed' tracks. The implications of these findings for the ongoing monitoring, sitting and management of walking tracks are discussed. 相似文献
978.
979.
Martin B. Hocking 《Environmental management》1991,15(6):731-747
An analysis of the overall relative merits of the use of uncoated paper vs molded polystyrene bead foam in single-use 8-oz
cups is described here as a manageable example of the use of paper vs plastics in packaging. In raw material requirements
the paper cup required about 2.5 times its finished weight of raw wood and about the same hydrocarbon fueling requirement
as is needed for the polystyrene foam cup. To process the raw materials about six times as much steam, 13 times as much electric
power, and twice as much cooling water are consumed to produce the paper cup as compared to the polystyrene foam cup. Emission
rates to air are similar and to water are generally higher for the paper cup.
Virtually all primary use factors favor polystyrene foam over paper. Once used both cup types may be recycled. Landfill disposal
of the two items under dry conditions will occupy similar landfill volumes after compaction and will confer similarly slow
to nonexistent decomposition to either option. Under wet conditions polystyrene foam will not readily degrade, but may help
other materials to do so. Paper under wet conditions will biodegrade to produce methane, a significant greenhouse gas, biochemical
oxygen demand to any leachate, and instability to the land surface during the process. Both materials can be incinerated cleanly
in a municipal waste stream with the option of energy recovery, to yield an ash volume of 2%–5% of the incoming waste volume.
Overall this analysis would suggest that polystyrene foam, with an extension to plastics in general, should be given more
evenhanded consideration relative to paper in packaging applications than is currently the case. 相似文献
980.
Adrian H. Griffin James C. Wade William E. Martin 《Journal of the American Water Resources Association》1980,16(5):849-855
ABSTRACT: The ground water in the Tucson basin is being drawn faster than it is replenished by nature. The water table is falling, giving rise to several conflicts between water users in the basin. At present, several lawsuits are in progress, including an action by the Papago Tribe against some of the major water users in the basin. Largely because of these difficulties, the State Legislature has established a commission to make proposals for the reform of Arizona's ground water law. The pattern of water use in the basin will undoubtedly be changed by the outcome of the present litigation and the coming reform of Arizona's ground water law. This paper describes how water use in the basin might be affected by changes in the availability of water and gives an account of the effects that these changes in water use could have on the region's economy. The paper concludes that the water problems of the Tucson basin will have little effect on the region at large and that these problems are simply a matter for the Indians and the other water users in the basin to sort out amongst themselves. 相似文献