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71.
Richard K. Morgan Roger Bowden 《The International journal of environmental studies》2013,70(2-3):161-167
In recent years there has been a move in New Zealand to convert small, uneconomic orchards to other agricultural uses. Overseas research has demonstrated that copper from fungicide sprays often accumulates in the soils of orchards and can cause certain problems for plant growth and livestock. To date, no assessments appear to have been made of the degree of copper accumulation in such older orchards in New Zealand. This study presents the results of an assessment of two well‐established apricot orchards in the Central Otago region of South Island, New Zealand. Two aspects of the results are surprising. The first is the relatively low levels of copper in the soil when compared with results from another orchard in the region. That orchard is 18 years old and mean soil copper has already reached 100.0 μg/g, indicating a much faster rate of accumulation than in the two orchards in the current study. The second unexpected result is that the younger orchard has a significantly higher level of copper than the older orchard. Reasons for these findings are discussed in relation to apparent differences in soil properties. 相似文献
72.
The coastal zone acts as a major interface between the ocean and continents. Harbours located in this zone face grave problems from sedimentation, which is a global issue for most of the harbours of the world. Dredging which counter acts sedimentation, brings about innumerable environmental impacts — both positive and negative. As a case study, this paper reports the impacts of dredging conducted at Cochin harbour which is the second largest port along the west coast of India; this port is a nodal center in trade and commerce connecting south east Asia to European sector. The harbour operation mainly depends on maintenance form of dredging bringing about impacts which have both direct and indirect effects in the long term. The important parameters selected for this study are salinity, current, extinction coefficient, turbidity, nutrients, chlorophyll and bottom fauna. An assessment is made on both positive and negative impacts which indicate rise in turbidity, changes in nutrient content and biota. The current practice on dredging is conducive to harbour operations, regulating the material made available to the near shore areas and highlights the possible venues for utilization of spoil for reclamation of land and wetland development. A flow chart identifies the areas vulnerable to impacts arising out of dredging and its consequential environmental issues. 相似文献
73.
In this paper, we study the energy decay characteristics of the nozzle at supersonic velocity. We have taken three types of configuration: circular, square and elliptical. The results are compared to the circular exit design. The experimental data are compared in relation to the pressure ratio. The throat area assumed to be constant. The supersonic potential core length of the different orientations is calculated. From the results, we have found that the exit geometry plays an important role in mixing promotion. The core length of a non-circular jet is less intense than a circular jet. The core length of the nozzle is the same in both under and overexpanded case. In addition to that, there is no sign of axis switching due to weak shock. The results are obtained in two different categories, total pressure data and numerical simulation. An empirical relation is used to investigate the core length experimentally. 相似文献
74.
Cost significant models have been suggested as one way of overcoming criticisms of the amount of detail contained within the traditional bill of quantities. Recent research into these models reveals a lack of formal rules for the selection of work packages to be used within the models, and a potential to overestimate the cost of projects. This paper presents a methodology for selecting work packages, and recommends a refinement to the technique that reduces the variability in estimates produced using cost significance. Estimates are produced using both the traditional method of producing cost significant models, and a refined global cost methodology. Both techniques are tested against unpriced bills to measure the difference in results, with significant improvements being achieved with the new technique. 相似文献
75.
76.
Globalization today encompasses multinational dialogues on the appropriate role for planning in mediating relationships between individual and community, state and citizen, government and market, and people and property. Yet confusion persists as speakers from one country attempt to convey concepts different from what listeners from another country hear. This paper provides a cross-national contemplation on the sources of that confusion, comparing the USA to Western Continental Europe, primarily Germany. Americans and Europeans engage fundamentally different worldviews in promoting progress while reconciling harms, stemming from different philosophical traditions that can be broadly characterized as a Millian versus a Hegelian liberalism, respectively. 相似文献
77.
78.
Herbert BM Halsall CJ Villa S Fitzpatrick L Jones KC Lee RG Kallenborn R 《The Science of the total environment》2005,342(1-3):145-160
PCNs were measured in air and snow during separate field campaigns at Ny-Alesund (April 2001) and Troms? (February/March 2003) in the Norwegian Arctic. Air concentrations ranged from 27 to 48 and 9 to 47 pg sigmaPCN m(-3) for Ny-Alesund (n=6) and Troms? (n=10), respectively. These concentrations (including the tri-chlorinated naphthalenes) greatly exceeded concentrations previously measured in the Canadian Arctic, but did fall within the upper range of concentrations observed over the eastern Arctic Ocean and regional seas. Local sources appear to be affecting concentrations observed at both sites, with the presence of several hexa-chlorinated naphthalenes at Troms? probably attributed to local/regional sources. Use of air mass back trajectories at Troms? revealed that background air concentrations in the Norwegian Arctic are likely to range between <9 and 20 pg sigmaPCN m(-3) and that contemporary concentrations derived close to potential sources (i.e. arctic towns) may equal or exceed those of PCBs. The mean concentration in surface snow was 350 and 240 pg sigmaPCN L(-1) (meltwater) (or 0.014 and 0.01 pg g(-1) (snow)) at Ny-Alesund and Troms?, respectively. The wide variation in concentrations observed between fresh snowfalls could be explained by different snow densities (as a surrogate of snow surface area), rather than attributed to varying air concentrations. A statistically significant inverse relationship was found between snow density and concentrations of tri- to penta-chlorinated homologues and compliments similar findings for the polychlorinated biphenyls (PCBs). This suggests that the vapour-sorbed quantity changes rapidly with snow ageing/compaction; with implications for the fate of these chemicals in the Arctic. 相似文献
79.
To date, the results of studies which attempted to estimate residential water demand models have varied, but the source of these variations is not evident because the studies have applied different methodologies and data bases to different regions. The purpose of this paper is to develop models of residential water demand for watershed regions and test the null hypothesis that a single model is adequate to explain variations for all of the individual regions. Primary data collected from questionnaires and utility company records is used in a regression analysis to estimate a generalized water demand model for the state as well as one for each of the subregions. The null hypothesis is rejected which indicates that there are other factors which influence the demand for water and the use of a single model could result in biased estimates. 相似文献
80.
Critical swimming velocities of Salmo gairdneri at 12°C were determined in different combinations of copper; pH and hardness. Measurements were made after exposure for 0.5, 5, 10, and 30 days. When copper was not applied, hardness, pH and exposure time had no appreciable effect on critical performance. Copper had the greatest effect on swimming performance at 5 days of exposure. At pH 7.5–8.0, recovery from the initial depression was complete after 10 days of exposure, but critical swimming performance did not return to control levels in pH 6.0 treatments. For any given hardness, copper had a greater effect on critical speed at low than at high pH. A given copper treatment had a more pronounced effect at low than at high hardness.No distinction could be made among total, soluble, or extractable copper but predicted concentrations of 6 specific cupric ions varied with pH and hardness. Of these copper species, only Cu2+ and CuOH+ were found to be related significantly to critical performance.Oxygen consumption of trout was determined in different combinations of copper and pH. In the presence of copper the maximum oxygen consumption decreased and the energy expenditure for a given swimming speed increased.The above observations are discussed in relation to reported toxic actions of copper. 相似文献