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831.
Is there a common metals demand curve? 总被引:1,自引:0,他引:1
Previous studies have identified a single, stable and strong correlation between the price of metals and their consumption, such that low priced metals are always used in large amounts and visa versa. Some have interpreted this as evidence that metals share a common demand curve so that a single price elasticity of demand exists. This paper reviews and tests this hypothesis against a number of other possible explanations, including the idea that the relationship is an empirical curiosity. Modifications to the demand curve were tested by allowing metals to have different intercepts and price elasticities. The results from this analysis suggest that metals do not share a common demand curve and that the correlation identified between the price of metals and their level of consumption is an empirical curiosity. As such, the singular price elasticities published in past papers should not be used for assessing future rates of metals substitution. 相似文献
832.
833.
Various features of a landscape contribute to the regulating ecosystem service of reducing waterborne pollutant loading to downstream environments. At local scales, wetlands have been shown to be effective in retaining pollutants. Here, we investigate the landscape-scale contribution to pollutant retention provided by multiple wetlands. We develop a general analytical model which shows that the retention contribution of wetlands and other landscape features is only significant if a large fraction of the total waterborne pollutant transport passes through them. Next, by means of a statistical analysis of official data, we quantify the nutrient retention contribution of wetlands for multiple sub-catchments in two Swedish Water Management Districts. We compare this with the retention contribution of two other landscape features: the waterborne transport distance and major lakes. The landscape-scale retention contribution of wetlands is undetectable; rather, the other two landscape features account for much of the total nutrient retention. 相似文献
834.
Julien Sialelli Graham J. Urquhart Christine M. Davidson Andrew S. Hursthouse 《Environmental geochemistry and health》2010,32(6):517-527
A simple, two-stage, physiologically based extraction has been applied to assess the human bioaccessibility of potentially
toxic elements (PTE) in 20 urban soils from a major UK city. Chromium and iron bioaccessibilities were found to be markedly
higher in the intestinal phase, whilst lead and zinc bioaccessibilities were higher in the stomach. Copper and manganese bioaccessibilities
were generally similar under both extraction conditions. Principal component analysis was used to study relationships amongst
bioaccessible element concentrations and land use. Distinctions could be observed between the distributions of the urban metals—copper,
lead and zinc—and metals predominantly of geogenic origin, such as iron. There was no clear delineation between roadside soils
and soils obtained from public parks. Bioaccessible analyte concentrations were found to be correlated with pseudototal (aqua
regia soluble) analyte concentrations for all elements except iron. Results of the BCR sequential extraction did not, in general,
provide a good indication of human bioaccessibility. Comparison of bioaccessible PTE concentrations with toxicological data
indicated that lead is the element of greatest concern in these soils but that levels are unlikely to pose a health risk to
children with average soil intake. 相似文献
835.
Manuelle Cottin Ben Raymond Akiko Kato Fran?oise Amélineau Yvon Le Maho Thierry Raclot Ben Galton-Fenzi Andrew Meijers Yan Ropert-Coudert 《Marine Biology》2012,159(8):1843-1852
Knowledge of habitat use by top marine predators in response to environmental conditions is crucial in the current context of global changes occurring in the Southern Ocean. We examined the at-sea locations of male Adélie penguins (Pygoscelis adeliae) breeding at Dumont d’Urville during their first, long incubation trip. Compared with the chick-rearing period, penguins performed longer trips, going to oceanic waters as far as 320 km from the colony. We observed 3 strategies: (1) five individuals covered large distances to the north, targeting open-ocean areas and following the currents of two persistent eddies; (2) five individuals foraged to the north-west, close to the Antarctic shelf slope at the limit of the pack ice; and (3) three individuals covered much shorter distances (northwards or eastwards). The foraging range also seemed to be limited by the body condition of the penguins before their departure to sea. 相似文献
836.
本文主要概述了提高工业用水效率的各种途径(例如:定价方法、财政激励、自愿协议、采用环境管理标准、清洁生产、"工业生态学")水工业中预期的变化将是经济、环境和社会发展的反映.供水、废水的产生及良好的商业行为被认为是推动这种变革的动力.本文强调了需要将城区及工业设施放在其所处的水环境中进行考虑. 相似文献
837.
Kyle G. Horton Benjamin M. Van Doren Heidi J. Albers Andrew Farnsworth Daniel Sheldon 《Conservation biology》2021,35(6):1777-1786
Near-term ecological forecasting has the potential to mitigate negative impacts of human modifications on wildlife by directing efficient action through relevant and timely predictions. We used the U.S. avian migration system to highlight ecological forecasting applications for aeroconservation. We used millions of observations from 143 weather surveillance radars to construct and evaluate a migration forecasting system for nocturnal bird migration over the contiguous United States. We identified the number of nights of mitigation required to reduce the risk of aerial hazards to 50% of avian migrants passing a given area in spring and autumn based on dynamic forecasts of migration activity. We also investigated an alternative approach, that is, employing a fixed conservation strategy based on time windows that historically capture 50% of migratory passage. In practice, during both spring and autumn, dynamic forecasts required fewer action nights compared with fixed window selection at all locations (spring: mean of 7.3 more alert days; fall: mean of 12.8 more alert days). This pattern resulted in part from the pulsed nature of bird migration captured in the radar data, where the majority (54.3%) of birds move on 10% of a migration season's nights. Our results highlight the benefits of near-term ecological forecasting and the potential advantages of dynamic mitigation strategies over static ones, especially in the face of increasing risks to migrating birds from light pollution, wind energy infrastructure, and collisions with structures. 相似文献
838.
Andrew Smith 《Resources Policy》1989,15(4)
By comparing the 1964–1973 period of exceptional strength in the copper price with current market conditions, a more informed judgement can be made about the longevity of the current boom in the copper price. Preconditions for an extended period of strong real prices appear to be in place, while there are few signs of an imminent price collapse. 相似文献
839.
As far as the impact of air pollutants on human health being is concerned, ozone (O3) is one of the most pollutant sources, and, in particular, the ground level ozone is responsible for a variety of adverse effects on both human being and plant life. To protect the population from such adverse health effects, early information and precautions about the high ozone level need to be ascertained. In this study, statistical characteristics of ground level ozone is analyzed according to field monitoring data in mixed residential, commercial and industrial areas, e.g., Tsuen Wan area in Hong Kong. The study deals with the characteristics of hourly and daily mean ozone levels under different climatic conditions such as temperature, solar radiation (SR), wind speed (WS), and other pollutant concentration levels. The study aims to investigate the importance of meteorological factors and their impact on relevant pollutant concentration levels from a chemical aspect. Further, reasons for the spatial and temporal variation of ozone levels are discussed. All these results will provide a physical basis for accurately predicting ozone concentration in similar research. 相似文献
840.
Zvomuya F Larney FJ Nichol CK Olson AF Miller JJ Demaere PR 《Journal of environmental quality》2005,34(6):2318-2327
Nitrogen (N) loss during beef cattle (Bos taurus) feedlot manure composting may contribute to greenhouse gas emissions and increase ammonia (NH(3)) in the atmosphere while decreasing the fertilizer value of the final compost. Phosphogypsum (PG) is an acidic by-product of phosphorus (P) fertilizer manufacture and large stockpiles currently exist in Alberta. This experiment examined co-composting of PG (at rates of 0, 40, 70, and 140 kg PG Mg(-1) manure plus PG dry weight) with manure from feedlot pens bedded with straw or wood chips. During the 99-d composting period, PG addition reduced total nitrogen (TN) loss by 0.11% for each 1 kg Mg(-1) increment in PG rate. Available N at the end of composting was significantly higher for wood chip-bedded (2180 mg kg(-1)) than straw-bedded manure treatments (1820 mg kg(-1)). Total sulfur (TS) concentration in the final compost increased by 0.19 g kg(-1) for each 1 kg Mg(-1) increment in PG rate from 5.2 g TS kg(-1) without PG addition. Phosphogypsum (1.6 g kg(-1) P) addition had no significant effect on total phosphorus (TP) concentration of the final composts. Results from this study demonstrate the potential of PG addition to reduce overall N losses during composting. The accompanying increase in TS content has implications for use of the end-product on sulfur-deficient soils. Co-composting feedlot manure with PG may provide an inexpensive and technologically straightforward solution for managing and improving the nutrient composition of composted cattle manure. 相似文献