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121.
C. di Marco U. Skiba K. Weston K. Hargreaves D. Fowler 《Water, Air, & Soil Pollution: Focus》2004,4(6):143-149
In order to assess nitrous oxide (N2O) emissions from typical intensively managed grassland in northern Britain fluxes were measured by eddy covariance using tuneable diode laser absorption spectroscopy from June 2002 to June 2003 for a total period of 4000 h. With micrometeorological techniques it is possible to obtain a very detailed picture of the fluxes of N2O at field scale (103–104 m2), which are valuable for extrapolation to regional scales. In this paper three of the four fertilizer applications were investigated in detail. N2O emissions did not always show a clear response. Hourly fluxes were very large immediately after the June 2002 nitrogen fertilizer application, peaking at 2.5 mg N2O–N m–2 s–1. Daily fluxes were averaging about 300 ng N2O m–2 s–1 over the 4 days following fertilizer application. The response of N2O emissions was less evident after the August fertilization, although 2 days after fertilizer application an hourly maximum flux of 554 ng N2O–N m–2 s–1 was registered. For the rest of August the flux was undetectable. The differences between fertilization events can be explained by different environmental conditions, such as soil temperature and rainfall. A fertiliser-induced N2O emission was not observed after fertilizer application in March 2003, due to lack of rainfall. The total N2O flux from June 2002 to June 2003 was 5.5 kg N2O–N ha–1y–1, which is 2.8% of the total annual N fertilizer input. 相似文献
122.
D. Famulari D. Fowler K. Hargreaves C. Milford E. Nemitz M. A. Sutton K. Weston 《Water, Air, & Soil Pollution: Focus》2004,4(6):151-158
Field measurements of NH3 fluxes using an eddy covariance technique were made for a total of 60 days between July and September 2002 at an intensively managed grassland in Southern Scotland. The collected data demonstrate the suitability of a tuneable diode laser absorption spectroscopy (TDLAS) system coupled with a sonic anemometer for eddy covariance measurements. The novelty of these measurements is the application to ammonia, which has only become measurable using TDLAS techniques recently, because of its small ambient concentration. Data presented in this paper show typical features of the fluxes and concentration for the summer season. NH3 concentration and flux values are in a similar range to previous studies using flux gradient methods at the same field site, although the particularly wet season reduced the concentration of NH3 in the air. For an example day, measured NH3 fluxes ranged between –11 and 44 ng m–2 s–1 with an average value of 3.78 ng m–2 s–1 indicating a small net emission from the vegetation. Spectral analysis executed on the data shows the percentage of flux carried by the small eddies (from 0.2 to 2 m) suggesting that high detection frequency instruments are particularly suitable for estimating NH3 fluxes between atmosphere and vegetation. 相似文献
123.
M. Yamada Y. Iwasaka A. Matsuki D. Trochkine Y. S. Kim D. Zhang T. Nagatani G.-Y. Shi M. Nagatani H. Nakata Z. Shen B. Chen G. Li 《Water, Air, & Soil Pollution: Focus》2005,5(3-6):231-250
Free tropospheric aerosol particles were collected using a balloon-borne particle impactor in August of 2002 and March of
2003 at Dunhuang in northwestern China (40°00′N, 94°30′E), and the morphology and elemental composition of the aerosol particles
were analyzed in order to understand the mixing state of coarse dust particles (diameter >1 μm) over the desert areas in the
Asian continent in spring. Electron microscopic experiments on the particles revealed that dust particles were major constituents
of coarse mode particles in the free troposphere over the Taklamakan Desert in spring and summer.
Si-rich or Ca-rich particles are major components of dust particles collected in the free troposphere over dunhuang and the
values of [number of Ca-rich particles]/[number of Si-rich particles] differs markedly between spring and summer, being about
0.3 in the spring of 2003 and about 1.0 in the summer of 2002 at heights 3–5 km above sea level. It is likely that the condition
of the ground surface and the strength of vertical mixing in source areas of Asian dust are potential factors causing the
difference in the chemical types of dust particles.
Comparison of the elemental compositions of these particles with those of particles collected over Japan strongly suggests
that these particles were chemically modified during their long-range transport in the free troposphere. Analysis of wind
systems shows that both the predominating westerly wind in the free troposphere and the surface wind strongly controlled by
the geographical structure of the Tarim Basin are important in the long-range transport of KOSA particles originating in the
Taklamakan Desert. 相似文献
124.
K. Schäfer G. Fömmel H. Hoffmann S. Briz W. Junkermann S. Emeis C. Jahn S. Leipold A. Sedlmaier S. Dinev G. Reishofer L. Windholz N. Soulakellis N. Sifakis D. Sarigiannis 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):91-102
Urban air quality and meteorological measurements were carried out in the region of Brescia (Italy) simultaneously to the acquisition of satellite data during winter and summer smog conditions in 1999. The main objectives of the campaigns were: delivery of data for the validation of air pollution interpretations based on satellite imagery, and determination of the aerosol optical thickness in spectral ranges similar to those used by satellites. During the winter campaign the ground-based network was complemented by local stations and by SODAR, DOAS, and FTIR remote sensing measurements. Size distributions of aerosol particles up to 4,000 m a.s.l. were measured by means of an ultra-light aircraft, which was also equipped with meteorological sensors and an ozone sensor. During the summer campaign an interference filter actinometer, an integrating nephelometer and an ozone LIDAR were operated additionally. The satellite images acquired and processed were taken from SPOT. Optical thickness retrieved from interference filter actinometer measurements were compared with the retrievals from the satellite imagery in the same spectral intervals. It is concluded that remaining aerosols in the reference image yield an off-set in the satellite retrieval data and that information about the vertical structure of the boundary layer is very important. 相似文献
125.
126.
The impact of wake wash from high-speed ferries on the coastal environment in non-tidal seas is analysed in terms of wave
energy and power, and properties of the largest waves. Shown is that hydrodynamic loads caused by heavy high-speed traffic
may play a decisive role not only in low-energy coasts but also in certain areas with high wind wave activity. For example,
ship-generated waves form, at least, about 5–8% from the total wave energy and about 18–35% from the wave power in the coastal
areas of Tallinn Bay exposed to dominating winds. The periods of wake waves from high-speed ships frequently are much larger
than dominating periods of wind waves. The leading waves typically have a height of about 1 m and a period of 10–15 s. Such
waves extremely seldom occur in natural conditions in many regions of semi-enclosed seas. They cause unusually high hydrodynamic
loads in the deeper part of the nearshore. The fast ferry traffic thus is a qualitatively new forcing component of vital impact
on the local ecosystem. It is demonstrated that wakes from high-speed ferries may trigger considerable changes of the existing
balance of coastal processes. Owing to their low decay rates combined with their exceptional compactness after crossing many
kilometres of the sea surface, such wakes may cause considerable remote impact of the ship traffic. This feature has to be
addressed in the analysis of the impact of harbours and associated ship traffic in the neighbourhood of vulnerable areas. 相似文献
127.
This paper presents a mathematical model of local pollutant dispersion designed to compute the concentration field above and
around the Marcoule nuclear site. The model is based on integrating the classical turbulent diffusion equation, corrected
(prior to integration) by experimental wind tunnel data obtained for a scaled-down model of the site. The computed results
are compared with full-scale experimental observations at Marcoule in the case of neutral atmosphere. A comparison with the
standard Gaussian model is also made. Finally, a critical analysis of the model is presented.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
128.
Edwards G. C. Dias G. M. Thurtell G. W. Kidd G. E. Roulet N. T. Kelly C. A. Rudd J. W. M. Moore A. Halfpenny-Mitchell L. 《Water, Air, & Soil Pollution: Focus》2001,1(5-6):447-454
Methane emissions were measured from a bog andlake in the Experimental Lakes Area in Northern Ontario in 1992and 1993, prior to and following flooding. Bog fluxes were smallin 1992 (0.27 mg m-2 d-1) but increased 5-fold in 1993 afterflooding. Over the bog, there was a diel cycle of nighttimeemission and daytime uptake in 1992 in contrast to constantemission in 1993. Lake emissions decreased after flooding butwere much greater than bog emissions in both years (average = 7.3 mg m-2 d-1). Seasonally, the bog flux was correlated withground temperatures after flooding. In 1992, lake fluxes werecorrelated with air temperature on a daily basis. In contrast,seasonal lake fluxes were correlated with water and sedimenttemperatures in 1992, but only with sediment temperatures in1993. These results are explained with respect to the effects offlooding on lake and bog dynamics. 相似文献
129.
Tuovinen J.-P. Simpson D. Mikkelsen T. N. Emberson L. D. Ashmore M. R. Aurela M. Cambridge H. M. Hovmand M. F. Jensen N. O. Laurila T. Pilegaard K. Ro-Poulsen H. 《Water, Air, & Soil Pollution: Focus》2001,1(5-6):263-274
The performance of a new dry deposition module, developedfor the European-scale mapping and modelling of ozone flux to vegetation, was tested against micrometeorological ozone and water vapour flux measurements. The measurement data are for twoconiferous (Scots pine in Finland, Norway spruce in Denmark) and one deciduous forest (mountain birch in Finland). On average, themodel performs well for the Scots pine forest, if local inputdata are used. The daytime deposition rates are somewhat over-predicted at the Danish site, especially in the afternoon. The mountain birch data indicate that the generic parameterisationof stomatal responses is not very representative of this northernspecies. The module was also tested by using modelled meteorological data that constitute the input for a photochemical transport model. 相似文献
130.
中国生态环境的新特点及其对策 总被引:25,自引:0,他引:25
在分析我国生态环境现状的基础上 ,提出了生态环境发展的 3个新特点 :①由单纯的工业污染过渡到工业和大众消费形成的污染并存阶段 ,而且乡镇企业污染问题越来越突出 ;②水体污染由工业污染发展到工业污染加农业污染的复合污染 ;③生态恶化问题正在由局部扩展到更大范围 ,从流域的一部分扩到全流域 .针对目前生态环境目前出现的新特点 ,在对策上提出了应实现 3个方面的转变 :①在环境污染控制上 ,应从末端治理发展到清洁生产 ;②在生态保护上 ,应从生态赤字到生态建设 ;③在污染治理上 ,从“谁污染、谁治理”转变到“谁污染、谁付费”、“谁治理、谁收益”. 相似文献