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A large scale ecosystem restoration program was initiated in 1997 on the Pecos River in Western Texas. Saltcedar (Tamarix spp.), a non-native invasive tree, had created a near monoculture along the banks of the river by replacing most native vegetation. Local irrigation districts, private landowners, federal and state agencies, and private industry worked together to formulate and implement a restoration plan, with a goal of reducing the effects of saltcedar and restoring the native ecosystem of the river. An initial management phase utilizing state-of-the-art aerial application of herbicide began in 1999 and continued through 2003. Initial mortality of saltcedar averaged about 85–90%. Monitoring efforts were initiated at the onset of the project to include evaluating the effects of saltcedar control on salinity of the river water, efficiency of water delivery down the river as an irrigation water source, and estimates of water salvage. To date, no effect on salinity can be measured and irrigation delivery was suspended in 2002–2003 due to drought conditions. Water salvage estimates show a significant reduction in system water loss after saltcedar treatment. However, a flow increase in the river is not yet evident. Monitoring efforts will continue in subsequent years.  相似文献   

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The authors consider consumption of copper in the UK using data from 1920 to 1970. They draw up an overall balance sheet which, it is hoped, provides a firm foundation on which to base the total availability of copper and against which could be balanced the scrap which was recycled.  相似文献   

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Water is a scarce resource in many parts of the developed world. Two solutions are possible to address water scarcity: conservation of existing resources, or the further production of water from new sources e.g. through recycling of wastewater or desalination of seawater. However, the main hurdle to implementation of many of these solutions is often viewed as a lack of public willingness to adopt these alternative water behaviours. Research in this area is therefore crucial. Yet, and possibly due to the interdisciplinary nature of such research, there is currently no comprehensive overview of what has been done before. This study fills this gap by (1) choosing a general consumer behaviour perspective as a starting point, (2) developing a conceptual model of research required in the area of water-related public acceptance studies, (3) identifying eight key water-related behaviours which require future research attention, and (4) reviewing which areas of the conceptual model have been investigated in the past by conducting an extensive literature review of water-related social science research.The review established that the majority of work which has been conducted is located at the cross-roads of personal characteristics and behavioural intentions. Significant gaps exist in relation to researching the adoption of a wide range of demand-side water behaviours. This indicates a dominance of supply-side solutions in social-research exploration. The review identifies a number of research needs including: the exploration of actual adoption of water-related behaviours (rather than behavioural intentions); and to widen the scope of water behaviour enquiry to include more demand-side solutions. Given the increasing scarcity of water in many areas of the world, addressing these identified gaps will be of significant importance. Thus our model informs the social-research agenda for water policy.  相似文献   

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This paper applies a property rights framework to federal mineral lands in the western United States from the enactment of the Mining Law in 1872 until the enactment of the Mineral Leasing Act for fossil fuels in 1920. There are two principal findings. First, the Mining Law appears to have been an effective means for assigning rights to mineral stocks on public lands (at least through 1920). This conclusion is supported by evidence from claim disputes in the West. Second, the impetus for the Mineral Leasing Act did not derive from the different physical characteristics of hardrock minerals and petroleum. The relevance of these conclusions to contemporary mineral policy is also discussed.  相似文献   

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ABSTRACT. Data from seven vessel cruises from late May to early November permitted definition of the surface water temperature regime of Lake Huron on a monthly basis. Quantitative values are furnished for a portion of the warming, stable, and cooling periods. The lowest temperatures occurred near the center of the lake, southwest of Manitoulin Island, and at De Tour Passage. The highest temperatures occurred at the mouth of Saginaw Bay and in the southernmost portions of the lake. Comparison of the surface water temperatures with temperatures in the 21 - 30 m layer shows the heat storage lag characteristic of large lakes.  相似文献   

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ABSTRACT: As a part of a water quality survey of the Spoon River, Illinois, algal genera were identified and their densities were enumerated. Weekly samples were collected at five stations starting on June 1, 1971. This report presents the first year's results. Algal densities for each station were found to be distributed geometrically normal. Total algal densities increased as water progressed downstream. Although water temperature has been observed to be an important factor affecting the density and the composition of algae in streams, attempts to correlate algal densities with temperatures for the Spoon River were not fruitful. Correlations of algal densities with dissolved oxygen, flow, and coliform densities also could not be made. The dominant genera observed were Cyclotella, Navicula, Scenedesmus, and Euglena. On the average diatoms accounted for 87% of all algae counts. The average diversity indices varied about 1.0 to 1.5 for five stations. There did not appear to be any advantage in the use of diversity index over that of algal density and genera richness in characterizing algae in the Spoon River.  相似文献   

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In this article, we analyzed the mass concentrations of particulate matter 2.5 micrometers (µm) or less in size (PM2.5), particulate matter 10 µm or less in size (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3) in Lanzhou, the capital of Gansu province, China. We analyzed monitoring data collected from five air quality monitoring stations during the spring–summer period from 2014 to 2016. Our comparison of contaminant concentrations and average diurnal, daily, monthly, and annual concentrations revealed that the average concentrations of PM2.5 and PM10 amounted to 128.57 and 46.4 micrograms per cubic meters (µg/m3), respectively, exceeding the Chinese National Ambient Air Quality Standard (NAAQS). We used the Pearson correlation coefficient to establish connections between particulate matter and gaseous pollutants. The results show significant differences in the concentration levels of airborne pollutants. The Pearson correlation coefficient between PM2.5 and PM10 had the highest coefficient of r = 0.842. A correlation between the two particulate matter sizes (PM2.5 and PM10) and SO2 was PM2.5 and SO2 r = 0.313; PM10 and SO2 r = 0.279; and CO and the two particulate matter sizes, PM2.5 and CO r = 0.304; and PM10 and CO r = 0.203. The average monthly ratio for the study months of PM2.5 to PM10 was 0.361. In addition, we used the hybrid single particle Lagrangian integrated trajectory model for tracking sources and pathways of the air pollutants in Lanzhou.  相似文献   

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An analysis of 179 junior exploration floats, listed on the Australian Securities Exchange (ASX) between July 2001 and June 2006, helped to build a basic understanding of the strategy and business structure of these companies. The “typical” junior explorer raised A$4 million at initial public offering (IPO) to finance a 2-year, mainly greenfields exploration program. The capital raised at IPO entitled its investors to approximately half of the company, with the balance in the hands of the promoters, vendors and/or seed capital investors. Of the A$4 million raised at IPO, it intended to spend approximately two-thirds on exploration, while the remainder was absorbed in corporate overheads and the costs of the IPO. Once these were paid, ongoing corporate overheads averaged approximately 28% of its total operational expenditure. However, given an average total annual expenditure of approximately A$2.6 million, most juniors held insufficient capital reserves to meet operational costs beyond a time frame of 2 years. As at October 2006, 9% of the companies were in the process of mine construction, whereas 6% had made it to producer status. The lead time from listing to production ranged from 1.5 to 53 months, giving a median of 28 months.  相似文献   

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ABSTRACT: Recent occurrences of heavy rainfall in New Orleans, Louisiana, have led to speculation that the local heavy rainfall regime has changed. To objectively determine the validity of these speculations, changing magnitudes of storm rainfall were investigated through an examination of the annual maximum storm series from 1871 to 1991 at the New Federal site. Although a long-term trend was not found, the Wilcoxon test indicated that magnitudes during the last 14 years (from 1978–1991) differed significantly from the rest of the series.  相似文献   

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In the present study, the multivariate statistical technique cluster analysis (CA) is used to evaluate the spatial and temporal variations in the water quality data for the Karun River, which was gathered during 46 years of monitoring (from 1968 to 2014). The data recorded electrical conductivity (EC) in the river at six water monitoring stations along its course. The mean of EC was 972.05 ± 365.466 micromhos per centimeter (μmhos/cm) at the most upstream station and showed an increase to 1458.41 ± 675.048 μmhos/cm at the most downstream of the stations. By using hierarchical CA, the six sampling stations were grouped into three clusters of similar characteristics, which may be a result of different land uses in proximity to the stations. Furthermore, two‐way analysis of variance showed that EC had a significant correlation (p < 0.001) with the season, and the mean of the pollution depended on the level of the cluster and the season (spring, summer, autumn, and winter).  相似文献   

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