青藏高原东缘川西云杉林皆伐后灌木生长、繁殖与更新的研究

植物群落及其环境在干扰后的演替格局和过程的研究，是群落和生态系统动态研究的一个热点。选取青藏高原东缘山原区川西云杉林皆伐后，从草地过渡到灌丛的关键阶段的4 个皆伐迹地（恢复时间为8 a、10 a、16 a 和21 a），研究皆伐及自然恢复过程对林下典型灌木银露梅（Potentilla glabra）和唐古特忍冬（Lonicera tangutica）的生长与繁殖能力的影响以及灌木植物在迹地上的更新情况，分析灌木在不同生境中的适应对策和适应能力的差异,为揭示青藏高原东缘山原区迹地植被从草甸到灌丛演替的过程和特点及促进迹地演替与植被恢复进程提供理论依据和技术支撑。研究主要结论如下：1）皆伐后银露梅生长和繁殖能力显著提高，但对唐古特忍冬的影响不明显。皆伐后银露梅丛基径、高度和各部分生物量都显著增加（P < 0.05），但唐古特忍冬只有叶生物量和地下生物量增加，总生物量和其余构件生物量无显著变化。皆伐后，银露梅的结实数量、结实株数、不结实株数和结实株/不结实株比例显著增加（P < 0.05）。自然恢复过程中，银露梅和唐古特忍冬生长能力以及银露梅的结实量都表现出降低的趋势。随着迹地自然恢复时间的增加，银露梅和唐古特忍冬的基径、高度、丛叶片数和各部分生物量有减少的趋势。银露梅的结实株数增加, 但结实数量减少。2）皆伐对银露梅和唐古特忍冬生物量分配模式影响不一致。原始林和迹地中（除CT85）银露梅的生物量大小关系皆为：地下>茎>侧枝>叶。唐古特忍冬在原始林中的生物量大小关系为：茎＞地下部分＞侧枝＞叶,而皆伐后生物量的分配情况改变，生物量大小关系变为：地下部分＞茎＞侧枝＞叶。随着自然恢复时间的增加，银露梅减少了地下生物量的分配，而唐古特忍冬增加了地下生物量的分配。3）皆伐和恢复时间的增加改变了迹地物种组成，促使阳性乔、灌木在迹地上定居。4 个迹地上共出现了灌木15 种，乔木3 种，没有出现天然云杉和冷杉幼苗。随着恢复时间的增加，迹地上的灌木物种由原始林下的耐阴物种逐步发展为以针刺悬钩子（Rubus pungens）为主的阳性灌木。4）影响灌木幼苗密度和幼树密度的因子不一致。灌木幼苗密度与灌木层盖度显著负相关，与苔藓层盖度显著正相关。幼树密度与草本层盖度正相关，与苔藓层盖度、灌木层盖度和高度负相关。5）研究发现在青藏高原东缘山原区皆伐15～20 a 后，迹地仍以草本植物为主，推测皆伐后至少20 a 以上迹地才可能向灌丛阶段过渡，比高山峡谷地区的演替进程至少推迟了20 a。银露梅和唐古特忍冬在皆伐后自然恢复过程中表现出不同的生长与繁殖策略是由两个物种的生物学特性的差异引起的。银露梅比唐古特忍冬更适应迹地退化环境。促进青藏高原东缘山原林区迹地森林恢复一方面是尽量减少人为活动的破坏，另一方面，可以通过在迹地中播种适当的乡土乔、灌木种子（如白桦、银露梅）等人工措施，以加快演替进程。The succession pattern and process of plant community and their environments is a hot spotin community and ecosystem dynamic study. Four clearcuts were chosen in Rangtang(recovery time of 8 a、10 a、16 a and 21 a), which represented the key stage of thecommunity evolved from grass stage to shrub stage in the eastern margin of theQinghai-Tibetan Plateau. The growth and reproduction of the Potentilla glabra andLonicera tangutica and the natural regeneration of shrub plants in the primary Piceabalfouriana forest and 4 clearcuts were studied to explore how clear cutting andnatural recovery process affected the understory shrub species during the 21 years inthe eastern margin of the Qinghai-Tibetan Plateau. The main results were below.1) The growth and reproduction of P. glabra significantly increased after forestclear cutting.. But it was not so significant as to the L. tangutica. The organismbiomass and total biomass of P. glabra were increased obviously after clear cutting（P< 0.05）. But only leaves and underground biomass of L. tangutica increasedsignificantly after clear cutting（P < 0.05）. The number of fruit and growth of P. glabraincreased significantly after clear cutting too（P < 0.05）. The ramet height, basaldiameter , organism biomass and friut number of P. glabra and L. tangutica reducedas the increase of recovery time.2) The biomass allocation patterns varied between P. glabra and L. tangutica inthe primary forest and clearcuts. The biomass allocation of P. glabra both in primary forest and clearcuts was followed as: underground part > stem > branch > leaves.However, the biomass allocation of L. tangutica had changed after the clear cutting.The biomass allocation of L. tangutica in the primary forest was followed as: stem >underground part > branch > leaves and it was underground part > stem > branch >leave in clearcuts. The biomass allocation of P. glabra and L. tangutica varied amongclearcuts. Aboveground biomass was increased while underground biomass decreasedfor P. glabra with the increase of recovery period. However, the L. tangutica showedthe reverse changing pattern.3) Clear cutting and recovery time had changed the species composition of theclearcuts. There were 15.shruby species and 3 tree species in the four clearcuts. Nospruce and fir seedlings were found. In the early stage after clear cutting, there wereonly understory shrub species from the primary Picea balfouriana forest. The sunnyspecies, especieally Rubus pungens invaded intensly as the increase of recovery time.4) There was a significant negative relationship between density of seedlingswith shrub layer coverage and positive correlation with moss coverage. The saplingshad significantly positive correlation with herb layer coverage and negativecorrelation with moss coverage, shrub layer coverage and height.5）Comparing to studies in Miyalou, a nearby high mountain and canyon area,the secondary sucession in this subalpine plateau areas lagged at least 20 years.P. glabra and L. tangutica showed different growth and reproduction strategies toclear cutting and natural recovery , which may associated with the difference of theirbiological characters. P. glabra was more adaptive to the clear cutting than the L.tangutica. Two suggestions were probably recommended to promote the recoveryprogress in the subalpine plateau areas based on the results of this study. Limitanthropogenic disturbance, and meanwhile sow native tree and shrub seeds inclearcuts.

岷江柏种子的形态和发芽特征与贮藏生理动态研究

岷江柏(Cupressus chenggiana S. Y. Hu)是我国川甘地区特有的珍稀濒危乔木，一般生长在干旱的河谷区，在涵养水源和保护水 土等方面起着重要的作用。本文选择4个岷江柏种群，采用了野外调查和室内实验相结合的研究方法，调查岷江柏种群结实状况， 分析种子和球果形态特征，阐明种子发芽的基本特征，研究岷江柏种子贮藏过程中几个生理指标的动态变化特点，目的是为岷江柏 种苗繁育、自然更新能力评估以及珍稀濒危机制分析提供理论依据。研究得出如下结论：1.岷江柏球果呈椭球形，长为1.5～ 2.2cm,宽为1.5～1.9cm，质量为1.7～4.2g，球果鳞片数量为8～11片，球果内种子数量一般在40～70粒。岷江柏种子为椭圆形，长 为3.58～4.02mm，宽为3.10～3.15mm，厚为0.96～1.11mm，千粒重为3.1～3.5g。岷江柏的结实率很低，并且有显著的地理差异和 大小年差异。2. 岷江柏种子发芽温度范围是5℃～30℃,其中种子的适宜发芽温度范围是10℃～25℃。种子最适发芽温度随着贮藏 时间的增加而变化。在适宜温度范围内，种子发芽周期为20d。温度对种子的发芽势和T50有显著影响，对种子发芽率没有显著影响 ；光照有利于种子发芽；岷江柏种子的发芽特征是岷江柏保护种子资源、防止物种濒危的一种环境适应，有助于岷江柏种子提高发 芽率和幼苗的存活率。岷江柏种子是一种耐贮藏的正常性种子，在短期贮藏过程中，贮藏温度和种子含水量对于种子生理指标和种 子发芽没有显著影响。3. 岷江柏种子在短期贮藏过程中，千粒重没有显著变化；含水量都经历了先下降，再稳定的过程；粗脂肪 含量和可溶性糖含量逐渐降低；可溶性蛋白含量和丙二醛含量逐渐增加；脯氨酸含量在贮藏1～7个月时变化差异不明显，但是贮藏 7～10个月后显著增加。岷江柏种子的各个生理指标之间的相关性差异不显著。4. 岷江柏球果和种子的形态特征存在显著的地理差 异。岷江柏种子的发芽能力的地理性差异不大，种群间差异不大。岷江柏种群的地理差异由种群特征、生境特征和气候特征共同决 定。5. 在岷江柏的人工繁育中，对于刚刚采集的种子，发芽温度在15℃～25℃比较适合，其中以25℃最佳；而对于短期贮藏(4～ 10个月)后的种子，发芽温度在10℃～25℃均可，以15℃～20℃为最佳。野外播种的最适时间为4～6月，6～9月的间歇性干旱和降 水波动可能是限制岷江柏自然更新的因素之一。在短期贮藏过程中，种子可以采用常规室温贮藏，可以节约成本。Cupressus chenggiana is a specific and endangered plant in Sichuan and Gansu provinces of China, and it usually grows in dry valley and plays an important role in water supply and soil and water conservation in the dry valley of alpine and canyon region of southwest China. The research selected four Cupressus chenggiana populations and used the methods of the field investigation and the lab experiments. The fruiting characters of Cupressus chenggiana populations, the morphological characters of seeds and cones, the germination characters of seeds and the store physiological dymatics of several factors of seeds have been studied in order to give some theoretical advices on the artificial propagation and the ability of natural regeneration and the endangered principle of Cupressus chenggiana in the paper. The main results may be clarified as follows: 1. The cones of Cupressus chenggiana are ellipsoidal, length ranged from 1.5 to 2.2cm, with ranged from 1.5 to 1.9 cm, weight ranged from 1.7 to 4.2g, the number of cone squama ranged from 8 to 11, and the seed number of per cone ranged from 40 to 70. The seeds of Cupressus chenggiana are elliptical, length ranged from 3.58 to 4.02 mm, width ranged from 3.10 to 3.15 mm, thickness ranged from 0.96 to 1.11 mm, and the weight of 1000 seeds ranged from 3.1 to 3.5g. The fruiting rate of Cupressus chenggiana is very low, and the fruiting period of Cupressus chenggiana has the geographical differences and the big or small year differences. 2. Seed germination temperature is between 5℃ and 30℃, while the suited temperature is between 10℃ and 25℃. The optimum temperature of seed germination will change as the store time of seeds changes logner. The cycle of seed germination can persist 20 days in the range of the suited temperature. The germination temperatures have significant influences on the germination potential and T50, but have no significant infuluences on the germination rate. The photoperiod is in favor of seed germination. The characters of Cupressus chenggiana seed germination represent a kind of environmental adaptability to protect the seed sources and endangered species, and it can give help to increase the germination rate of seeds and the livability of seedings. The seeds of Cupressus chenggiana are a kind of orthodox seeds that can endure the long time storage. In the short time storage, the store temperatures and the moisture contents of seeds have no significant infuluences on the physiological factors and the germination of seeds, but the store time has significant influences on the physiological factors of seeds. 3. In the short store course of Cupressus chenggianna seeds, the 1000 seed weight has no significant variation; The moisture content descends at the beginning of the storage, but has no significant variation later; The crude fat content and the soluble sugar content descend gradually; The soluble protein content and MDA content increase gradually; The praline content has no significant variation after 1～7 months storage, but increase significantly after 7～10 months storage. The correlations of different physiological factors are not significant. 4. The morphological characters of cones and seeds of four populations exist significant differences. The germination of Cupressus chenggiana seeds has no significant geographical variation. The geographical variation of Cupressus chenggiana populations can be ascribed to the population characters, climate and environment. 5. In the course of artificial propagation of Cupressus chenggiana, it is favored that the germination temperature of newly collected seeds is between 15℃ and 25℃, while the optimum temperature is 25℃. After the short storage ranged from 4 months to 10 months, it is favored that the germination temperature is between 10℃ and 25℃, while the optimum temperature is ranged from 15℃ to 20℃. The field sowing optimum time is between April and June, and the interval drought and fallrain fluctuation between July and September may be one of the reasons that restrict natural regeneration of Cupressus chenggiana. In the short storage, seeds can be stored in the condition of room temperature.

梳状聚合物电解质的力学松弛时间

以苯乙烯 /马来酸酐共聚物为骨架 ,聚乙二醇单甲醚为侧链合成了 3种不同侧链长度的梳状高分子聚合物 ,制成了锂盐络合物薄膜 .动态力学性能研究结果表明 ,本体系是主链刚性、侧链较柔软的梳状接枝聚合物 .应用时间温度等效原理 ,选择Tα 作为参考温度 ,建立了主曲线 ,得到了移动因子图和等自由体积图 .Williams、Landel和Ferry(WLF)经验方程的两个参数C1、C2 随着盐浓度增加而增大 .若T0 =50℃作为参考温度 ,平均松弛时间lgτc 与锂盐浓度C呈线性关系 .随着侧链分子量增加 ,主曲线向高频率移动 ;平均松弛时间lgτn 与侧链分子量的关系也是线性的 ;另外随着盐的不同 ,主曲线也会产生移动 ,表明盐种类对松弛时间产生影响.

Study of the conductivity and side chain mobility of a comb-like polymer electrolyte using the dynamic mechanical method

Using poly(styrene-co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether (PEGME) with different molecular weights as side chains, three comb-like polymers and their Li salt complexes were synthesized. The dynamic mechanical properties and conductivities were investigated. Results showed that the polymer electrolytes possess two glass transitions: alpha -transition and beta -transition, and the temperature dependence of the ionic conductivity shows WLF (Williams-Landel-Ferry) behavior. Based on the time-temperature equivalence principle, a master curve was constructed by selecting T-beta as reference temperature. The values of the WLF parameters (C-1 and C-2) were obtained and were found to be almost independent of the length of the PEGME side chain and the content of Li salt. By reference to T-0 = 50 degreesC. the relation between log tau (c) and c was found to be linear. The master curves are displaced progressively to higher frequencies as the molecular weight of the side chain is increased. The relation between log tau (n) and the molecular weight of the side chain is also linear. (C) 2001 Elsevier Science B.V. All rights reserved.

Rheological properties of phenophthalein poly(ether ether ketone)

The rheological properties of the novel engineering thermoplastic phenophthalein poly(ether ether ketone) (PEK-C) have been investigated using both a rotational and a capillary rheometer. The dependence of the viscosity on the shear rate and temperature was obtained. The activation energy was evaluated both from the Arrhenius and the Williams-Landel-Ferry (WLF) equation. An estimate for the proper E(eta) (dependent only on the chemical structure of the polymer) has been found from the WLF equation at temperatures about T-g + 200 degrees C. Measurements of the die swell have been performed. The first normal stress differences were evaluated from the die swell results and compared with the values obtained from the rotational rheometer at low shear rates.

A study of the dependence of ferrocene diffusion on chain length in polymer electrolytes

The diffusion rates of ferrocene have been estimated in five kinds of poly(ethylene glycol) solution, containing the electrolyte LiClO4, by using non-steady-state chronoamperometry. The D-app of ferrocene increases with increasing temperature, and the dependency of D-app on temperature obeys the Williams-Landel-Ferry equation. The D-app of ferrocene decreases with increasing polymer chain length. Both the chain length and temperature dependence conform to a simple free volume model. A relation between current and polymer chain length is suggested at room and high temperatures.

VISCOELASTIC PROPERTIES OF PHENOLPHTHALEIN POLY(ETHER KETONE)

Stress relaxation and dynamic mechanical behavior of phenolphthalein poly(ether ketone) (PEK-C) have been investigated. Using Ferry's reduction method, the master curve was obtained. From the experimental results, we found that the WLF equation is not appropriate in the lower-temperature range (T < T-g). The relaxation spectrum was calculated according to the first approximation method proposed by Schwarzl and Staverman. In addition to the alpha-transition region, a second transition zone is revealed at low temperature. This transition is probably due to a restricted motion of its main chain. (C) 1995 John Wiley and Sons, Inc.

EFFECT OF REPTATION ON FRACTURE-MECHANICS OF RUBBER NETWORKS

End-linked hydroxyl-terminated polybutadiene containing unattached linear polybutadiene was used to study the effect of reptating species on the fracture mechanics of rubber networks. The concentration of reptating species in the networks ranged from 0 to 100%. The fracture mechanics of the networks was described using the critical strain energy release rate in mode III testing, i.e. the tearing energy. The tearing energy was measured at room temperature using a 'trouser' specimen at a strain rate spanning five logarithmic decades. When the strain rate was as low as 10(-4) s-1, the tearing energy of the networks increased with reduction in reptating species. In this case the reptating species did not contribute to the tearing energy of the networks due to relaxation. Hence, the tearing energy increased with the number of crosslinked chains per unit volume in the networks. At a strain rate ranging from 10(-3) to 10(-1) s-1, the tearing energy of the networks was governed by local viscosity. The tearing energies of the networks containing various amounts of reptating species were superimposed to give a master curve based on the Williams-Landel-Ferry equation.

Geomorphology, sedimentary processes and development of the Zenisu deep-sea channel, northern Philippine Sea

The Zenisu deep-sea channel originates on the Izu-Ogasawara island arc, and disappears in the Shikoku Basin of the Philippine Sea. The geomorphology, sedimentary processes, and the development of the Zenisu deep-sea channel were investigated on the basis of swath bathymetry, side-scan sonar imagery, submersible observations, and seismic data. The deep-sea channel can be divided into three segments according to the downslope gradient and channel orientation. They are the Zenisu Canyon, the E-W fan channel, and the trough-axis channel. The sediment fill is characterized by turbidite and debrite deposition and blocky-hummocky avalanche deposits on the flanks of the Zenisu Ridge. In the Zenisu Canyon and the Zenisu deep-sea channel, sediment transport by turbidity currents generates sediment waves (dunes) observed during the Shinkai 6500 dive 371. The development of the Zenisu Canyon is controlled by a N-S shear fault, whereas the trough-axis channel is controlled by basin subsidence associated with the Zenisu Ridge. The E-W fan channel was probably affected by the E-W fault and the basement morphology.

Sedimentary processes and development of the Zenisu deep-sea channel, Philippine Sea

Zenisu deep-sea channel originated from a volcanic arc region, Izu-Ogasawara Island Arc, and vanished in the Shikoku Basin of the Philippine Sea. According to the swath bathymetry, the deep-sea channel can be divided into three,segments. They are Zenisu canyon, E-W fan channel and trough-axis channel. A lot of volcanic detritus were deposited in the Zenisu Trough via the deep-sea channel because it originated from volcanic arc settings. On the basis of the swath bathymetry, submersible and seismic reflection data, the deposits are characterized by turbidite and debrite deposits as those in the other major deep-sea channels. Erosion or few sediments were observed in the Zenisu canyon, whereas a lot of turbidites and debrites occurred in the E-W channel and trough axis channel. Cold seep communities, active fault and fluid flow were discovered along the lower slope of the Zenisu Ridge. Vertical sedimentary sequences in the Zenisu Trough consist of the four post-rift sequence units of the Shikoku Basin, among which Units A and B are two turbidite units. The development of Zenisu canyon is controlled by the N-S shear fault, the E-W fan channel is related to the E-W shear fault, and the trough-axis channel is related to the subsidence of central basin.

藏北措勤盆地白垩纪碳酸盐岩沉积相及缺氧事件响应研究

As a part of Gangdisi-Nianqingtanggula plate, Cuoqin basin (N 29°3O'～33°20'; E 80°～90°) is situated in the west of the Tibet autonomous Region, with an area of 100000 square kilometers. Cretaceous shallow-water carbonate is widely distributed in this basin. Its accumulative thickness is more than 1000 meters. Sedimentary facies of cretaceous shallow-water carbonate and carbon isotope feature are studied in details here. On basis of two main sections researched comprehensively, five facies marks are found. With the combination of Wilson's model and ramp model, a platform-mild slope model are put forward, which is thought to be a comprehensive model for this area. There are three sedimentary circles which are comprised of terrestrial clastic tidal flat and carbonate platform facies in Duoba Member of Duoni Formation. Langshan Formation is mainly comprised of carbonate platform facies. We also studied the carbon isotope features influenced by Cretaceous Aptian-Albian's oceanic anoxic events (OAE). After correlating the δ~(13)C curves of the studied section with that of Peregrina Canyon section in Mexico, we find that there are similar δ~(13)C curves fluctuation styles, namely there is also a δ~(13)C positive excursion in shallow-water carbonate in the studied area, and the degree of δ~(13)C positive excursion in shallow-water carbonate is much higher. There are two main causes which should interpret above δ~(13)C positive excursion feature: on the one hand ,much organic carbon take much 12C off when they are buried with a higher speed during the OAE, which lead to the ~(12)C rise of oceanic total dissolved carbon (TDC),on the other hand, during the OAE there are stratification structures in pale-ocean, in the upper mixed layer with high carbon fixation (HCML). There are so much plankton organisms which absorb much ~(12)C as the ~(13)C of shallow-water carbonate in this layer rise higher. Furthermore, on the basis of the theories of carbonate isotope strata, we suggest that the currently used boundary between Aptian and Albian in the studied area is possibly above the international one, which means the main parts of Duoba Member of Duoni Foramatiom in this area should be belong to Albian in stead of Aptian.

碳、氧稳定同位素分析在古环境研究中的应用

A number of proxy records of paleoenvironment using stable isotopes could show the history of past environmental changes. These archives include peat and lake sediments, loess-paleosot sequence, fossil mammals and stalagmite, and so on. The stable isotopic composition of carbonate and organic matter and frequency magnetic susceptibility from Tianshuigou and Yuanlei loess-palesol sequence can be used to give estimates of the paleoenvironmental history of Dali, and even of the whole Chinese Loess Plateau during the last 250ka. Features of the High Temperature and Large Precipitation Event in the Tibet Plateau and its adjacent area during 40~30kaBP had been studied by Professor Shi Y. In this dissertation, its impact on Chinese Loess Plateau has been discussed again. Carbon and oxygen isotopic ratios, magnetic susceptibility and frequency magnetic susceptibility in Tianshuigou and Yuanlei profiles show that the Event in this area is not so stronger as the Tibet Plateau. The carbon isotopic composition of organic matter in Tianshuigou, Yuanlei, dingcun and Jingcun loess-palesol sequences are indicative of major changes in the paleovagetation between terrace and plain of the Chinese Loess Plateau. Water is one of the most important factors adjusting the relative biomass of C4 plant in terrestrial ecosystems. Stable carbon isotope ratio of vertebrate tooth enamel is used increasingly to reconstruct environmental and ecological information modern and ancient ecosystems. The SI3C value of tooth enamel bioapatites can distinguish between browsers and grazers. Data from typical grassland of Inter Mongolia, the Alpine meadow of Qinghai-Tibet Plateau and the Yaluzangbu Great Canyon indicate that diets of mammals could record the relative biomass of C4 plant only in the C4 dominated ecosystem. In a C3 dominated ecosystem, diet of mammals would include more C3 plants than vegetation. According to Professor Cerling, proxy records from North and South America, Africa and Pakistan show that at the end of the Miocene (between 8Ma to 6 Ma) there was a global expansion of CA biomass, probably when atmospheric CO2 levels declined. Thus, "C4 world" and "CO2 starvation" are put forward. In this dissertation, carbon isotopes of fossil tooth such as Equus sanmeniensis and Hipparion chiai from Linxia, China reveal that there is a C3 dominated ecosystem in the late Miocene. Diets of ancient mammals in Linxia are not evidence of global expansion of C4 biomass.

Maritime policy in Scotland.

This paper begins by defining the meaning of the term `maritime policy'. Since devolution in the UK, the opening of the new Scottish parliament in 1998 and the creation of the Scottish Executive, little effort has been made to establish a distinct maritime policy for Scotland. As was evident prior to devolution, the primary emphasis from any maritime policy perspective has continued to be a focus on lifeline island ferry services. This ignores significant developments in several other key maritime transport sectors, and this paper provides examples of areas that require some form of policy response, including intra-European short sea shipping, UK coastal shipping, urban/river transport and global container shipping. Long-standing institutional bias against maritime transport coupled with subsidy devoted almost entirely to land transport systems has resulted in a quite distorted marketplace. This suggests that a maritime policy is now imperative if maritime transport is to play a more significant role in the overall transport system. Further discussion centres on the need to consider, from a Scottish policy perspective, the role of various state-sponsored maritime service providers and how these bodies might fit better within evolving policy. The conclusion is that formulation of a maritime policy by the Scottish Executive is overdue and that a degree of restructuring of transport responsibilities within the Executive, combined with adequate resource allocation towards the maritime industry, will be necessary in order that market distortions can be overcome, so enabling Scotland to fully exploit the competitive and environmental advantages that maritime transport can provide.

Jesus, the Resurrection: A Sermon

Memorial Sermon

Modelling air quality in street canyons: a review

High pollution levels have been often observed in urban street canyons due to the increased traffic emissions and reduced natural ventilation. Microscale dispersion models with different levels of complexity may be used to assess urban air qualityand support decision-making for pollution control strategies and traffic planning. Mathematical models calculate pollutant concentrations by solving either analytically a simplified set of parametric equations or numerically a set of differential equations that describe in detail wind flow and pollutant dispersion. Street canyon models, which might also include simplified photochemistry and particle deposition–resuspension algorithms, are often nested within larger-scale urban dispersion codes. Reduced-scale physical models in wind tunnels may also be used for investigating atmospheric processes within urban canyons and validating mathematical models. A range of monitoring techniques is used to measure pollutant concentrations in urban streets. Point measurement methods (continuous monitoring, passive and active pre-concentration sampling, grab sampling) are available for gaseous pollutants. A number of sampling techniques (mainlybased on filtration and impaction) can be used to obtain mass concentration, size distribution and chemical composition of particles. A combination of different sampling/monitoring techniques is often adopted in experimental studies. Relativelysimple mathematical models have usually been used in association with field measurements to obtain and interpret time series of pollutant concentrations at a limited number of receptor locations in street canyons. On the other hand, advanced numerical codes have often been applied in combination with wind tunnel and/or field data to simulate small-scale dispersion within the urban canopy.