共查询到20条相似文献，搜索用时 46 毫秒
1.
We analyze ground level ozone pollution in Illinois. We find that during elevated ground level ozone conditions, Illinois is located to the south-west of a high pressure system centered over south-eastern Canada. This state causes weakening of the climatological westerlies, near-surface southerlies and upper troposphere northerlies. This results in corresponding weakening of both lower troposphere heating and upper troposphere cooling by lateral advective heat flux divergence. Heat balance is restored primarily by enhanced subsidence, most notably between the surface and ～400 mb. The strengthened subsidence suppresses boundary layer deepening by upward surface heat fluxes, resulting in a shallower than normal boundary layer during times of elevated ground level ozone. We argue that subsidence induced boundary layer suppression, aided by elevated temperatures, is the primary cause of the elevated ground level ozone events. The enhanced subsidence during those times also dries the lower troposphere, reducing the probability of moist convection, and thus slowing boundary layer ventilation. 相似文献
2.
Modelling and Mapping Ozone Deposition in Europe 总被引：1，自引：0，他引：1
L. D. Emberson M.R. Ashmore D. Simpson J.-P. Tuovinen H.M. Cambridge 《Water, air, and soil pollution》2001,130(1-4):577-582
A new dry deposition module has been developed for European-scale mapping and modelling of ozone deposition fluxes (Emberson et al., 2000a,b). The module is being implemented in the photochemical long-range transport model of EMEP that is currently used to estimate exceedance of the existing critical levels for ozone within the UN ECE LRTAP programme. The deposition model evaluates the atmospheric, boundary layer and surface resistances to ozone transfer with the calculation of the dry deposition velocity performed according to a standard resistance formulation. The approach differs from other existing methods through the use of a detailed stomatal uptake model that describes stomatal conductance as a function of plant species, phenology and four environmental variables (air temperature, solar radiation, water vapour pressure deficit and soil moisture deficit). Comparison of preliminary model outputs for selected land-cover types indicate that the model is capable of predicting the seasonal and diurnal range in deposition velocities that have been reported previously in the literature. The application of this deposition scheme enables calculations of ambient ozone concentrations to be made using a biologically based method that can distinguish stomatal and non-stomatal components of total ozone deposition. The ability to estimate stomatal ozone fluxes (according to vegetation type, phenology and spatial location) that are consistent with evaluations of atmospheric ozone concentrations will be helpful in future assessments of ozone impacts to vegetation. 相似文献
3.
Pirovano G. Simoni P. Ballarin Denti A. Angelino E. Calori G. Finardi S. 《Water, air, and soil pollution》2001,132(3-4):233-249
Mountain rural sites can be subject to high ozone concentrations (Puxbaum et al., 1991; Gay, 1991; Sandroni,1994) that can lead to plant injuries. Very often, unfortunately,such sites do not have a sufficient number of monitoring stations to accurately capture the spatial patterns and temporal evolution of ozone concentrations. The present studyaims at the reproduction of ozone patterns in a forest site onthe southern slopes of the Alps. The calculation of ozone concentrations has been carried out for a three days episode,by using the CALGRID model. Meteorological fields have been obtained by the application of the CALMET model. Emissions have been calculated for the main sources categories in the area (biogenic and road transport), with a bottom up techniqueand derived from a regional inventory for minor sources. Finally, boundary conditions have been derived from a simulation performed over a larger area (240 × 232 km2). The CALGRID model application has provided realistic ground-level concentrations. However, some differences have been spotted between estimated and observedconcentrations, particularly at nighttime, when concentrationsare more influenced by local effects. The methodology used andresults obtained are presented, the comparison with measurements and the temporal evolution of ozone vertical profile in different locations of the domain is discussed. 相似文献
4.
基于边际模型的中国城镇化演进对耕地影响极限研究 总被引：2，自引：1，他引：1
城镇化建设是支撑社会经济持续发展的国家战略,城镇化快速演进对耕地影响如何,关系到耕地保护红线目标能否实现及粮食安全,探索城镇化演进对耕地影响的极限规律具有重要现实意义。运用扩展Kaya恒等式及LMDI分解模型,测算了1997—2011年中国城镇化引致的耕地减少份额;借鉴经济学边际理论及边际效应模型,采用回归分析及高数求导方法,构建了边际耕地影响及边际耕地变化率测度模型;以边际耕地变化率时序数据为基础,借助EXCEL软件,通过作散点图并添加趋势线,构建了边际耕地变化率曲线,据此测算了城镇化演进对耕地影响最小的极限时刻。结果表明:①城镇化演进占用耕地面积由1997年的59.59万hm2下降至2011年的31.73万hm2,整体呈降幅态势,年均占用43.49万hm2;②边际耕地变化率指数由1997年的0.183 3下降至2011年的0.037 8,年均下降11%;③边际耕地变化率拟合曲线为开口向上的"U"形抛物线,其最低极值点大约出现在2010年。研究结果可为管理层科学编制土地利用规划及制定协调城镇化演进与耕地保护政策提供参考,也可为省域尺度的同类研究提供方法借鉴。 相似文献
5.
Jae-Cheol Nam Deb J. Fish Alan J. Thorpe Soon-Ung Park 《Water, air, and soil pollution》2001,130(1-4):361-366
A quantitative study of the amount of air transported between the boundary layer and the free atmosphere is important for understanding air quality and upper tropospheric ozone, which is a greenhouse gas. Frontal systems are known to be an effective mechanism for the vertical transport of pollutants. Numerical experiments have been performed with a simple two-dimensional front model to simulate vertical transport of trace gases within developing cold fronts. Three different trace gases experiments have been done numerically according to the different initial fields of trace gases such as aerosol, ozone and H2O2. Trace gas field tilts to the east while the front tilts to the west. Aerosol simulation shows that pollutants can be transported out of the boundary to altitudes of about 10 km. The stratospheric ozone is brought downwards in a tropopause fold behind of the frontal surface. The meridional gradient in trace gas (H2O2) can cause a complicate structure in the trace field by the meridional advection. 相似文献
6.
Fowler David Flechard Chris Cape J. Neil Storeton-West Robert L. Coyle Mhairi 《Water, air, and soil pollution》2001,130(1-4):63-74
Water, Air, &; Soil Pollution - Ozone deposition to vegetation represents the major sink for boundary layer ozone and yet the underlying mechanism of reaction and uptake at the surface is poorly... 相似文献
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8.
U. Platt 《Water, air, and soil pollution》2000,123(1-4):229-244
While the role of reactive halogen species (e.g., Cl, Br) in the destruction of the stratospheric ozone layer is well known, up to now it was assumed that these tropospheric halogen events were confined to the polar regions during springtime. However, during the last few years, significant amounts of BrO and Cl-atoms were also found in the Arctic and Antarctic boundary layer. Recently, even higher BrO mixing ratios (up to 90 ppt) were detected by optical absorption spectroscopy (DOAS) in the Dead Sea basin during summer. In addition, evidence is accumulating that BrO (at levels around 1–2 ppt) is also occurring in the free troposphere (in polar regions as well as at mid- latitudes). In contrast to the strategosphere, where halogens are released from species which are very long lived in the troposphere, likely sources of boundary layer Br and Cl are oxidation of sea-salt halides, while precursors of free tropospheric BrO probably are short-lived organo-halogen species. In addition, it is well possible that boundary layer halogens, in particular bromine, may 'leak out' to the free troposphere and thus could have a regional or even more widespread effect. At the levels suggested by the available measurements, reactive halogen species have a profound effect on tropospheric chemistry: In the boundary layer during 'halogen events' ozone is usually completely lost within hours or days — the 'Polar Tropospheric Ozone Hole'. In the free troposphere the effective O3- losses due to halogens could be comparable to the known photochemical O3 destruction. Further interesting consequences include the increase of OH levels and (at low NOX) the decrease of the HO2/OH ratio in the free troposphere. 相似文献
9.
Utiyama Masahiro Fukuyama Tsutomu Yamada Maruo Yasuko Ichino Toshihiro Izumi Katsuyuki Hara Hiroshi Takano Kenichi Suzuki Haruko Aoki Masatoshi 《Water, air, and soil pollution》2004,151(1-4):53-70
Concentrations of ozone and nitrogen oxides, together with air temperature and solar radiation intensity, were measured at several heights on a tower standing through the canopy of a red pine forest in summer and in autumn. In the summer observation, the diurnal variation patterns of ozone concentration both above and below the canopy were all similar and parallel to the solar radiation intensity. Using the data collected immediately above the canopy, deviation from the Leighton relationship and variations of concentration sums [O3] + [NO] and [NO2] + [NO] were examined, and as a result, it was supposedthat ozone was photochemically formed there in the daytime, probably because hydrocarbons emitted from pine trees broke the photostationary state among ozone and nitrogen oxides. The vertical temperature profile exhibited an inversion at the leaf-layer, which must have hindered vertical mixing of the air and made the trunk space more or less isolated from the upper atmosphere. These observations led to an idea that the similarity of the ozone variation pattern at every height was caused by the photochemical formation that proceeded simultaneously above and below the canopy rather than by vertical transport. Such situations of ozone formation were supported by observation of two maximums in the ozone vertical profile, one immediately above the canopy and another in the trunk space. Another feature of the ozone profile was a deep minimum in the leaf layer, which indicated ozone deposition onto leaf surfaces. This study thus revealed concurrence of ozone formation and deposition, and left two potentially important implications worthy of further investigation: (1) a forest is not always a sink but can be a source of ozone in sunlit conditions, and (2) deposition of ozone to trees can take place not only from outside but also from inside of a forest. In the autumn observation, however, the ozone formation was barely recognizable above the canopy and no longer found in the trunk space; in addition, the ozone concentration minimum in the leaf layer disappeared, suggesting that the deposition or removal was dependent on temperature. 相似文献
10.
乡镇规划调控下的农村居民点空间布局优化 总被引：5，自引：3，他引：2
为科学确定农村居民点空间布局优化类型,有效指导农村居民点空间布局优化及新农村建设实践。该文以武川县可可以力更镇为例,在乡镇规划调控的前提下,按农村居民点不同演化方向,将位于城镇建设用地扩展边界范围内的农村居民点确定为城镇化型,位于扩展边界范围外的农村居民点确定为非城镇化型。针对城镇化型农村居民点,因其未来演化方向而将其空间布局优化类型确定为社区化管理型;针对非城镇化型农村居民点,从乡镇总规协调度、生产生活便利度、居民点活跃度3大方面构建农村居民点斑块综合影响力评价指标体系,评价其综合影响力,并据此将其空间布局优化类型划分为综合发展潜力型、原地整治保持型、迁村并点扶持型3类。结果表明,可可以力更镇确定为社区化管理型的农村居民点6个,面积15.29 hm2;综合发展潜力型46个,面积178.28 hm2;原地整治保持型53个,面积189.20 hm2;迁村并点扶持型40个,面积141.22 hm2,并针对4种农村居民点空间布局优化类型提出较为具体的优化方案。研究结果符合可可以力更镇实际情况,能为农村居民点空间布局优化与整治提供新的思路。 相似文献
11.
Lee D. S. Dollard G. J. Derwent R. G. Pepler S. 《Water, air, and soil pollution》1999,113(1-4):175-202
Measurements of sulphur dioxide, ozone, ammonia, and soluble inorganic components of the atmospheric aerosol were made at a site in central southern England. Ammonia, ozone, and nitrate aerosol in winter were shown to exhibit significant diurnal variation. Ozone showed a typical diurnal variability, the magnitude of which was dependent upon wind speed. The lower night-time ozone concentrations at lower wind speeds were attributed to depletion inside nocturnal boundary layers by dry deposition. Ammonia, in contrast, showed a different behaviour, whereby the diurnal cycle was more pronounced at higher wind speeds, indicating that the cycle was unlikely to be the result of dry deposition at night. Ammonia concentrations showed a temperature dependence and the diurnal cycle of ammonia at this site appears to be the result of a temperature-driven emission signal. Of the total reduced nitrogen, NHx (NHx = NH3 + NH4 + aerosol), the phase was dominant and it is likely that more than 60% of the boundary layer NHx is in this phase. The loss term of ammonia by reaction with acid sulphate aerosol is likely to be greater than that by dry deposition on a UK scale. Nitrate aerosol showed a positive correlation with sodium aerosol, once the effect of mutual correlations with sulphate and ammonium were removed. This correlation effect, in combination with evidence of a marine-oriented directional dependence of nitrate aerosol, and negative non sea-salt chloride aerosol from the same ‘marine’ sector, shows the potential importance of the formation of sodium nitrate aerosol from reaction of dinitrogen pentoxide, or possibly nitric acid or nitrogen dioxide with sodium chloride aerosol. It is likely that this provides the major route of nitrate into rain, not the scavenging of nitric acid vapour. Aerosol sulphate, nitrate, and ammonium have been measured at Harwell since 1954. Sulphate aerosol increased up until 1976 and has declined subsequently. Nitrate aerosol has increased over the whole period, whereas ammonium aerosol follows a similar pattern to that of sulphate, but with an equivocal direction of trend after 1976. Sulphate, nitrate and ammonium aerosol all show a similar statistically significant seasonality. A historical inventory of ammonia emissions shows a clear correlation with ammonium aerosol. 相似文献
12.
以安徽省为例,选取城镇常住人口占总人口比例等18项指标,从人口、空间、经济、社会生活四维度构建了城镇化综合水平评价体系,采用熵值赋权法对其综合指数进行了测算;运用对数平均迪氏分解模型（Logarithmic Mean Divisia Index,LMDI）,对城镇化进程引致的耕地减少份额进行了计算;基于经济学边际理论,采用最小二乘回归分析方法,构建了城镇化边际耕地变化率测度模型;借助EXCEL软件,通过作散点图并添加趋势线,采用最佳拟合优度获取曲线及高数极值求导判别方法,测算了城镇化演进对耕地影响最小的极限时刻,结果表明：安徽省城镇化综合指数由1996年的0.0319上升至2012年的0.9945;城镇化进程引致耕地面积减少量2002年后呈降幅态势,契合经济学边际效应递减规律;城镇化边际耕地变化率指数由2002－2003年的1292517.63下降至2011－2012年的7430.35,整体呈下降态势;边际耕地变化率拟合曲线为开口向上U形抛物线,当城镇化综合指数为7.325时,即2022－2023年间,城镇化对耕地影响处极小状态,2023年前,安徽省推进城镇化与耕地保护矛盾较突出。基于研究结果,从依靠产业结构优化升级促进城镇土地集约利用等方面提出了政策建议。该研究成果可为安徽省科学编制土地利用规划及制定协调城镇化演进与耕地保护政策提供参考,也可为同类研究提供借鉴。 相似文献
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14.
金坛市土地生态质量的城乡梯度规律研究 总被引：2，自引：0，他引：2
金坛市作为长三角经济发达地区的典型地区,快速城镇化背景下其土地生态状况具有代表性。从基础、胁迫、结构、效益4个角度构建土地生态指数指标体系,以行政村为评价单元计算4个准则层分值和土地生态指数综合分值,在此基础上假设金坛市土地生态质量分布具有城乡梯度的规律。通过热点和梯度分析验证表明:（1）土地生态指数热点空间分异特征符合城乡梯度规律,城镇化是导致该规律的重要原因;（2）土地生态指数沿着金坛市“城镇—城乡结合部—近郊—远郊”环形梯度分布,总体上土地生态指数不断升高,沿城镇中心向外每增加2 400 m,土地生态指数提高1.6%;（3）城镇中心土地生态质量状况处于最低值,且城镇所在地土地生态质量比正常状态差,更精细地表明城镇化对土地生态质量的不良影响;区域土地生态结构是影响金坛市土地生态综合指数波动的最大因素。（4）该文对土地生态指数空间分异规律作了深入探究,对土地生态指数空间分异的驱动力分析和主控因子识别将在进一步研究中进行探索。该研究可引导政府在城镇化进程中实施改善土地生态质量的政策。 相似文献
15.
P. Stella B. LoubetE. Lamaud P. LavilleP. Cellier 《Agricultural and Forest Meteorology》2011,151(6):669-681
The variables controlling ozone deposition onto bare soil are still unknown and it is necessary to understand this pathway well, as it represents a significant sink for ozone. Eddy-covariance measurements of ozone (O3) fluxes were performed over bare soils in agricultural land. Three datasets with contrasted meteorological conditions and soil nitric oxide (NO) emissions were used to study the factors controlling soil deposition. It is considered that ozone deposition can be represented with an aerodynamic resistance (Ra), a quasi-laminar boundary layer resistance (Rb O3), and an additional resistance, named soil resistance (Rsoil). Although it is assumed in previous studies that soil resistance is a function of soil water content (SWC) and could be considered constant as variation of SWC at monthly scale are generally weak, the results of this study indicate that SWC is not the main factor controlling Rsoil which shows daily and hourly variations. The main factor controlling soil resistance is the surface relative humidity which is positively correlated with Rsoil, contrary to non stomatal resistance onto canopies which show a negative correlation with relative humidity. The relationship between Rsoil and the surface relative humidity is probably due to a decrease in the surface available for ozone deposition, due to an increasing adsorption of water molecules onto the ground with relative humidity. A new parameterisation of Rsoil was established, where Rsoil is a function of the surface relative humidity only (Rsoil = Rsoil min × e(k×RHsurf), and Rsoil min = 21 ± 1.01 s m−1 and k = 0.024 ± 0.001, mean ± SD). The measured and parameterised ozone deposition velocities agree well when soil NO emissions are negligible. However, when there are large soil NO emissions, the parameterised ozone deposition strongly underestimates the measured deposition velocity even if the chemical destruction of ozone by reaction with NO in the air column was evaluated to be negligible. This suggests that soil NO emissions enhance soil ozone deposition by chemical reaction at or near the soil surface. The new parameterisation allows a better estimation of soil deposition, especially during daytime when Rsoil is overestimated using previously published parameterisations. It is an important step towards a better parameterisation of the non-stomatal uptake of ozone. 相似文献
16.
边界层方法是描述土壤溶质迁移的简单方法,通过边界层距离与时间的关系可以估计溶质迁移参数。基于边界层方法,研究了土壤溶质迁移的数学模拟及相应参数估计问题。假定土壤溶质浓度剖面为指数函数,得到了描述溶质浓度分布的指数函数模型。各参数对边界层距离的影响分析表明,应选取较小的孔隙水流速度、短历时推求土壤溶质迁移参数;对不同模型预测土壤溶质分布进行比较,结果表明,在短距离处指数型解与精确解的误差比其它都要小。误差分析表明了指数函数模型的有效性和实用性。 相似文献
17.
安徽省城镇化演进边际生态环境效应的测度与分析 总被引：1，自引：0，他引：1
以安徽省为例,构建了由32个指标组成的城镇化与生态环境质量评价体系。采用主成分分析综合评价方法,对城镇化与生态环境质量进行了综合评价;并借鉴随机回归影响模型(STIRPAT模型),采用偏最小二乘回归方法,对城镇化演进的边际生态环境效应进行了测度。研究结果表明:(1) 安徽省城镇化综合评价指数由1996年的43.83上升至2011年的83.83,呈波动递增态势。(2) 安徽省生态环境综合评价指数由1996年的40.95上升至2011年的80.95,整体呈上升态势,反映了该区生态环境质量良好。(3) 安徽省城镇化演进与生态环境质量呈正向关联关系,城镇化演进对生态环境具有弱正向效应,其边际弹性系数为0.010 2。 相似文献
18.
近地层臭氧浓度增高对稻米品质的影响: FACE研究 总被引：1，自引：0，他引：1
利用稻田开放式空气中臭氧浓度增加(FACE,Free Air gas Concentration Enrichment)平台,以常规粳稻‘武粳15’和杂交粳稻‘陵风优18’为供试材料,设置大气背景臭氧浓度(Ambient)和高臭氧浓度(比Ambient增高21%,模拟21世纪中叶臭氧浓度)两个水平,研究臭氧胁迫对大田生长水稻成熟期稻米加工、外观、蒸煮/食味和营养品质的影响及其种间差异。结果表明,近地层臭氧浓度增高使稻米糙米率、精米率和整精米率均不同程度下降,其中精米率降幅达显著水平。与Ambient相比,臭氧胁迫使两品种稻米垩白米率、垩白大小和垩白度平均分别增加15.0%(P=0.10)、42.0%(P0.05)和60.5%(P0.05)。臭氧胁迫使稻米胶稠度平均降低7.1%(P0.05),但对两品种稻米直链淀粉和糊化温度均无显著影响。稻米RVA谱测定结果显示,臭氧胁迫对稻米最高黏度值、崩解值、冷胶黏度值、消减值和回复值均无显著影响。臭氧胁迫使两品种稻米蛋白质浓度呈增加趋势,但均未达显著水平。方差分析表明,多数情况下,两品种间稻米诸品质性状存在显著差异,但品种与臭氧的互作对所有测定指标均无显著影响,说明两品种稻米品质对臭氧胁迫的响应无明显差异。本试验在开放稻田条件下运行,适度臭氧胁迫使稻米垩白明显增加,胶稠度显著下降,但对其他米质指标影响较小,两品种趋势一致。 相似文献
19.
科学辨识乡村聚落用地空间演化过程是乡村振兴进程中优化乡村生产生活生态空间的重要依据。该研究选取厦门市集美区作为典型案例区,以1986—2017年4个时间点的遥感影像解译数据为基础,利用标准差椭圆、核密度和空间自相关等分析方法,定量识别了近30年集美区乡村聚落用地空间演化过程及其机理。结果表明:集美区乡村聚落密度分布存在空间异质性,中、高密度区域集中分布于农业区位条件良好的中部地区;聚落演化过程以关联扩张方式为主导,乡村聚落用地收缩斑块空间分布呈现随机性,扩张斑块存在空间自相关性;地形地势因素和演化特点的共同作用,聚落用地基本空间格局保持稳定;聚落用地核密度分析和局部自相关分析,揭示了聚落演化与地理环境、产业演进和城乡关系变化紧密的关系,反映了集美区各发展阶段,城乡互动过程对乡村聚落空间演化的驱动特点及其内在机理。研究结果可为优化乡村聚落发展布局以及统筹乡村振兴规划与土地整治规划提供理论支撑和方法指导。 相似文献
20.
We present a dry deposition modeling approach that includesvegetation-atmosphere interactions through photosynthesis/carbonassimilation relationships. Gas deposition velocity (V d) is calculated using an electrical resistance-analogapproach in a coupled soil-vegetation-atmosphere transfer (SVAT)model. For this, a photosynthesis-based surface evapotranspirationand gas exchange model is dynamically coupled to an atmospheric model with prognostic soil hydrology andsurface energy balance. The effective surface resistance(composed of aerodynamic, boundary layer, and canopy-basedresistances) is calculated for a realistic and fully interactiveestimation of gaseous deposition velocity over natural surfaces.Based on this coupled framework, the photosynthesis-based gasdeposition approach is evaluated using observed depositionvelocity estimates for ozone over a soybean field (C3photosynthesis pathway) and a corn field (C4 photosynthesispathway). Overall, observed V d and modeled V d show good qualitative and quantitative agreement.Results suggest that photosynthesis-based physiologicalapproaches can be adopted to efficiently develop depositionvelocity estimates over natural surfaces. Such a physiologicalapproach can also be used for generalizing results from fieldmeasurements and for investigating the controlling relationshipsamong various atmospheric and surface variables in estimatingdeposition velocity. 相似文献