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441.
J.-P. Hettelingh M. Posch J. Slootweg G. J. Reinds T. Spranger L. Tarrason 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):379-384
European critical loads and novel dynamic modelling data have been compiled under the LRTAP Convention by the Coordination
Centre for Effects. In 2000 9.8% of the pan-European and 20.8% of the EU25 ecosystem area were at risk of acidification. For
eutrophication (nutrient N) the areas at risk were 30.1 and 71.2%, respectively. Dynamic modelling results reveal that 95% of the area at risk of acidification
could recover by 2030 provided acid deposition is reduced according to present legislation. Insight into the timing of effects
of exceedances of critical loads for nutrient N necessitates the further development of dynamic models. 相似文献
442.
Steven W. Effler David A. Matthews Josef W. Kaser Anthony R. Prestigiacomo David G. Smith 《Journal of the American Water Resources Association》2006,42(6):1697-1710
Abstract: The impacts of runoff events on external suspended solids loading to Schoharie Reservoir, New York, and patterns of light scattering and sediment deposition in this reservoir are assessed. The assessment is based on monitoring of suspended solids concentrations in the reservoir's primary tributary, detailed vertical profiles of optical backscattering (a surrogate measure of light scattering) in the reservoir water column, and analysis of sediment trap collections, over a seven-month interval of high runoff. These impacts are reported to be tightly temporally coupled and strongly positively related to the magnitude of runoff events. The primary tributary entered the reservoir as a plunging inflow during runoff events, causing conspicuous subsurface peaks in light scattering, with vertical patterns that varied strongly for different events. Deposition quantified by near-bottom trap deployments is reported to be more representative than results from metalimnetic deployments that were generally within, rather than below, the turbid layers. Direct inputs of sediment, transported by density currents, are found to drive deposition, rather than resuspension/redeposition. More than 50 percent of the reported deposition occurred in less than 15 percent of the study period, associated with the four largest runoff events. 相似文献
443.
Ian D. Leith Lucy J. Sheppard David Fowler J. Neil Cape Matt Jones Alan Crossley Ken J. Hargreaves Y. Sim Tang Mark Theobald Mark R. Sutton 《Water, Air, & Soil Pollution: Focus》2004,4(6):207-218
Providing an accurate estimate of the dry component of N deposition to low N background, semi-natural habitats, such as bogs and upland moors dominated by Calluna vulgaris is difficult, but essential to relate nitrogen deposition to effects in these communities. To quantify the effects of NH3 inputs to moorland vegetation growing on a bog at a field scale, a field release NH3 fumigation system was established at Whim Moss (Scottish Borders) in 2002. Gaseous NH3 from a line source was released along of a 60 m transect, when meteorological conditions (wind speed >2.5 m s–1 and wind direction in the sector 180–215°) were met, thereby providing a profile of decreasing NH3 concentration with distance from the source. In a complementary study, using a NH3 flux chamber system, the relationships between NH3 concentrations and cuticular resistances were quantified for a range of NH3 concentrations and micrometeorological conditions for moorland vegetation. Cuticular resistances increased with NH3 concentration from 11 s m–1 at 3.0 g m–3 to 30 s m–1 at 30 g m–3. The NH3 concentration data and the concentration-dependent canopy resistance are used to calculate NH3 deposition taking into account leaf surface wetness. The implications of using an NH3 concentration-dependent cuticular resistance and the importance for refining critical loads are discussed. 相似文献
444.
L. J. Sheppard A. Crossley I. D. Leith K. J. Hargreaves J. A. Carfrae N. van Dijk J. N. Cape D. Sleep D. Fowler J. A. Raven 《Water, Air, & Soil Pollution: Focus》2004,4(6):197-205
Critical N loads for ombrotrophic bogs, which often contain rare and N-sensitive plants (especially those in lower plant groups: lichens, mosses and liverworts), are based on very few experimental data from measured, low background N deposition areas. Additionally the relative effects of reduced versus oxidised N are largely unknown. This paper describes an automated field exposure system (30 km S. of Edinburgh, Scotland) for treating ombrotrophic bog vegetation with fine droplets of oxidised N (NaNO3) and reduced N (NH4Cl). Whim Moss exists in an area of low ambient N deposition (ca. 8 kg N ha–1 y–1), the sources and quantification of which are described. The wet N treatment system is run continuously, and is controlled/activated by wind speed and rainfall to provide a unique simulation of real world treatment patterns (no rain=no treatment). Simulated precipitation is supplied at ionic concentrations below4mMin rainwater collected on site. Treatments provide a replicated dose response to 16, 32 and 64 kg N ha–1 y–1 adjusted for ambient deposition (8 kg N ha–1 y–1). The 16 and 64 kg N ha–1 y–1 are duplicated with a P+K supplement. Baseline soil chemistry and foliar nutrient status was established for all 44 plots for Calluna vulgaris, Sphagnum capillifolium, Hypnum jutlandicum and Cladonia portentosa. 相似文献
445.
The dry deposition of ozone to aconiferous forest in northeastern Bavaria(southern Germany) was quantified during 1999with both the eddy correlation method and a bigleaf model. The model included parameterizationsof the atmospheric transfer resistances fromdirect measurements, stomatal resistance from aplant ecological model, and an estimation of thecuticle resistance as function of leaf wetness.Early in the season, the measured and themodelled deposition fluxes were in goodagreement, although the modelled fluxes tended tounderestimate the measured ones. Thisunderestimation was more pronounced in the latesummer, when high nocturnal fluxes werefrequently measured. The model parameterizationof the cuticle and the stomatal resistances didnot allow for such high fluxes. In these cases,the 24 hour average of the measured fluxes wereup to 4.5 times higher than the modelled ones.The reasons for these large discrepancies remainunknown. However, assigning the unaccounted partof the deposition to a nonstomatal surfacedeposition pathway, a new parameterization of therespective resistance yielded an average value of300 s m-1. It exhibited a decreasing trendthrough the vegetation period. 相似文献
446.
Radioactive contamination of agricultural land may necessitate long-term changes in food production systems, through application
of selected countermeasures, in order to reduce the accumulation of radionuclides in food. We quantified the impact of selected
countermeasures on habitat diversity, using the hypothetical case of two agricultural areas in Finland. The management scenarios
studied were conversions from grassland to cereal production and from grassland and crop production to afforestation. The
two study sites differed with respect to present agricultural production: one being predominantly cereal production and seminatural
grasslands, while the other was dominated by intensive grass and dairy production. Some of the management scenarios are expected
to affect landscape structures and habitat diversity. These potential changes were assessed using a spatial pattern analysis
program in connection with geographic information systems. The studied landscape changes resulted in a more monotonous landscape
structure compared to the present management, by increasing the mean habitat patch size, reducing the total habitat edge length
and reducing the overall habitat diversity calculated by the Shannon diversity index. The degree of change was dependent on
the present agricultural management practice in the case study sites. Where dairy production was predominant, the landscape
structure changes were mostly due to conversion of intensive pastures and grasslands to cereal production. In the area dominated
by cereal production and seminatural grasslands, the greatest predicted impacts resulted from afforestation of meadows and
pastures. The studied management changes are predicted to reduce biodiversity at the species level as well as diminishing
species-rich habitats. This study has predicted prominent side effects in habitat diversity resulting from application of
management scenarios. These potential long-term impacts should be considered by decision-makers when planning future strategies
in the event of radionuclide deposition. 相似文献
447.
钛合金ZrN耐磨抗冲蚀防护涂层 总被引:3,自引:0,他引:3
采用真空多弧镀设备在TC11钛舍金表面沉积超硬耐磨ZrN防护涂层,通过增压气流固体颗粒冲蚀实验评价ZrN涂层的耐磨抗冲蚀性能,划痕仪测试涂层与基体的结合力,SEM、X射线分析涂层组成及观察涂层冲蚀前后表面形貌,盐雾及电化学实验测试涂层耐腐蚀性能。结果表明,ZrN涂层成分主要为(111)择优取向的ZrN相;ZrN涂层不影响钛合金的耐腐蚀性能及疲劳性能;ZrN涂层与基体结合牢固.涂层大大提高了基体的耐磨抗冲蚀性能。 相似文献
448.
449.
以韶山蔡家塘森林小流域2001年实地监测的大气降水、穿透水和地表水数据为基础,对酸沉降作用下韶山森林N的输入、输出的月均通量及变化特征进行了研究.结果表明:2001年N输入通量为53.81 kg/hm2,主要以NH4+ 形式(占总输入的64%)输入该森林生态系统;2001年N输出通量为3.57 kg/hm2,主要以NO3-形式(占总输出的64%)输出该森林生态系统.韶山森林2001年N净滞留量达到50.24 kg/hm2.月均输出通量极大值出现在降雨量较多的5-7月,其N输出通量占全年N总输出通量的59%.从N的总输入通量、总输出通量的变化来看,N输出并不随输入的增加而增加,N的输出主要受到降水量的影响. 相似文献
450.
Zhang Leiming Brook Jeffrey R. Vet Robert Shaw Mike Finkelstein Peter L. 《Water, Air, & Soil Pollution: Focus》2001,1(5-6):67-78
A dry deposition model (RDM) for operational application has beenevaluated and modified in the present study. Field measurements of friction velocity and dry deposition velocity of SO2 andO3 over a mixed forest have been used to evaluate RDM. It was found that RDM predicts friction velocities very close to measurements and thus it can predict reasonable aerodynamic resistance. RDM overestimated O3 deposition during dry nighttime conditions and underestimated both O3 andSO2deposition for early morning hours. It could not predict the mean diurnal variation in deposition velocity for either O3 or SO2 deposition under wet surface conditions. Modifications have been made for O3 and SO2 dry deposition based on the comparison of results and based upon additional published data. Compared to an earlier version of RDM, the modified versionpredicts better results for O3 and SO2 dry deposition,especially under rain and dew conditions. 相似文献