Mountain wave motions determined by the Esrange MST radar

A European campaign of ground-based radar, lidar and optical measurements was carried out during the winter of 1996/1997 (28 December–2 February) to study lee waves in the northern part of Scandinavia. The participants operated ozone lidars, backscatter lidars and MST radars at ALOMAR/Andoya and Esrange/Kiruna, and an ALIS imaging system in Kiruna. The Andoya site was generally windward of the Scandinavian mountains, the Kiruna site on the leeward side. The goal of the experiment was to examine the influence of lee waves on the formation of Polar Stratospheric Clouds (PSCs). This paper studies the radar data from MST-radar ESRAD located at Esrange [68.°N, 21.°E], i.e. in the lee of the mountains. We present three cases where strong lee waves were observed: in one case they propagated upwards to the lower stratosphere and in the other two cases they were trapped or absorbed in the troposphere. We examine the local waves and the direction and strength of the local wind using the radar, the synoptic meteorological situation using weather maps (European Meteorological Bulletin) and the synoptic stratospheric temperatures using ECMWF data. We observed that waves propagate up to the stratosphere during frontal passages. When anticyclonic ridges are present, the propagation to the stratosphere is very weak. This is due to trapping of the waves at or below the tropopause. We also show that the radar data alone can be used to characterise the different weather conditions for the three cases studied (through the variation of the height of the tropopause). The synoptic stratospheric temperatures in the three cases were similar, and were above the expected threshold for PSC formation. Lidar and visual observation of PSCs and nacreous clouds, respectively, showed that these were present only in the case when the lee waves propagated up to the lower stratosphere.     

The role of dynamics in total ozone deviations from their long-term mean over the Northern Hemisphere

Total ozone anomalies (deviation from the long-term mean) are created by anomalous circulation patterns. The dynamically produced ozone anomalies can be estimated from known circulation parameters in the layer between the tropopause and the middle stratosphere by means of statistics. Satellite observations of ozone anomalies can be compared with those expected from dynamics. Residual negative anomalies may be due to chemical ozone destruction. The statistics are derived from a 14 year data set of TOMS (Total Ozone Mapping Spectrometer January 1979-Dec. 1992) and corresponding 300 hPa geopotential (for the tropopause height) together with 30 hPa temperature (for stratospheric waves) at 60°N. The correlation coefficient for the linear multiple regression between total ozone (dependent variable) and the dynamical parameters (independent variables) is 0.88 for the zonal deviations in the winter of the Northern Hemisphere. Zonal means are also significantly dependent on circulation parameters, besides showing the known negative trend function of total ozone observed by TOMS. The significant linear trend for 60°N is 3 DU/year in the winter months taking into account the dependence on the dynamics between the tropopause region and the mid-stratosphere. The highest correlation coefficient for the monthly mean total ozone anomalies is reached in November with 0.94.     

热带水库消落区植物群落物种组成与结构特征——以海南松涛水库为例

消落区是河流、湖泊和水库因阶段性或长期性的水位涨落而反复淹没或出露而形成的一种特殊的季节性湿地.消落区植被在维持水陆生态系统的动态平衡、生物多样性、生态安全及生态服务功能等方面发挥着重要作用.通过样方法调查分析了海南松涛水库消落区植物组成、区系特点以及群落分布特征.结果显示：松涛水库消落区共有维管植物40科101属115种,其中被子植物36科97属111种,蕨类植物4科4属4种.植物区系以热带性为主,外来入侵种较多,且既耐水淹又耐干旱植物众多;群落以草本、灌木植物为主,乔木较少且大多以幼苗形式存在.主要群落类型为以铺地黍（Panicum repens）为优势种的复合群落,个别区域零散分布有美洲蟛蜞菊（Wedelia trilobata）、光荚含羞草（Mimosa sepiaria）、猪屎豆（Crotalaria pallida）、马松子（Melochia corchorifolia）、假臭草（Praxelis clematidea）和铺地黍等单优群落.消落区不同海拔区间群落分布存在明显差异,物种多样性从高到低呈显著递减趋势.研究结果可为松涛水库消落区植被恢复工作提供科学指导.     

蓝藻水华暴发和衰亡对太湖有色可溶性有机物的影响

利用平行因子分析(PARAFAC)技术对藻华暴发季节太湖梅梁湾和开敞区水样中有色可溶性有机物(CDOM)的三维荧光光谱进行分析,获得代表类酪氨酸、类色氨酸和类腐殖酸等3种荧光组分,这3个组分的荧光得分值均与叶绿素a浓度呈极显著正相关,其中类腐殖酸物质荧光得分值占总分值的比例也与叶绿素a浓度极显著正相关,由此可以推测,蓝藻水华可能是太湖CDOM的一个重要来源,并极大地影响了湖泊CDOM的组成结构.为进一步探索蓝藻水华对湖泊CDOM的影响,于太湖梅梁湾湖岸进行藻华暴发和衰亡模拟试验.PARAFAC结果显示,模拟试验水样CDOM的三维荧光图谱同样含有3个组分,其中类酪氨酸和类色氨酸荧光峰位置与湖泊水样基本相同,而类腐殖酸物质荧光峰则有一定程度的蓝移,表明培养试验中有新的内源类腐殖酸物质产生.利用PARAFAC模型中的得分值计算后发现,初始叶绿素a浓度越高,类腐殖酸物质所占比例越大,而实验结束时添加了高浓度和中等浓度藻的2个处理中类腐殖酸物质对荧光的贡献率也有显著提高.因此,藻华的长期暴发可以显著改变湖泊CDOM的组成,导致类腐殖酸物质比例提高.     

Modelling the composition of melts formed during continental breakup of the Southeast Greenland margin

We have developed a generic dynamic model of extension of the lithosphere, which predicts major element composition and volume of melt generated from initial extension to steady state seafloor spreading. Stokes equations for non-Newtonian flow are solved and the mantle melts by decompression. Strengthening of the mantle due to dehydration as melting progresses is included. The composition is then empirically related to depletion. Using a crystallisation algorithm, the predicted primary melt composition was compared with mean North Atlantic mid-ocean ridge basalt (MORB). At steady state, using half spreading rates from 10 to 20 mm yr^− 1 and mantle potential temperatures of 1300 to 1325 °C we predict a major element composition that is within the variation in the mean of North Atlantic MORB.

This model is applied to the Southeast Greenland margin, which has extensive coverage of seismic and ODP core data. These data have been interpreted to indicate an initial pulse of magmatism on rifting that rapidly decayed to leave oceanic crustal thickness of 8 to 11 km. This pattern of melt production can be recreated by introducing an initial hot layer of asthenosphere beneath the continental lithosphere and by having a period of fast spreading during early opening. The hot layer was convected through the melt region giving a pulse of high magnesian and low silica melt during the early rifting process. The predicted major element composition of primary melts generated are in close agreement with primary melts from the Southeast Greenland margin. The observed variations in major element composition are reproduced without a mantle source composition anomaly.     

Short-term effects of changes in water management on the limnological characteristics and zooplankton of a eutrophic Mediterranean coastal lagoon (NE Iberian Peninsula)

The Ter Vell (NE Iberian Peninsula) is a eutrophic coastal lagoon which has been flooded by the excess irrigation water and the agricultural runoff during the last decades. Between 1999 and 2003, restoration measures were applied to improve its water quality. At the same time, but independently, agricultural water management drastically reduced the freshwater inflow. The short-term effects of these management actions on the limnological characteristics of the lagoon were analysed by comparing two hydrological cycles, one before (1999/2000) and the other one after (2002/2003) the actions. The two cycles are illustrative of opposite situations in the hydrological functioning of coastal wetlands. In the first, the lagoon was exorheic, with prolonged flooding periods and a low residence time; in the second, it had a more endorheic character, with scarce water inputs and prolonged periods of confinement. Consequently, nitrogen inputs diminished and organic load and salinity increased as the internal loading and the accumulation effects became more relevant. These effects were actually caused by the drastic reduction in the freshwater inflow which prevented, in turn, the success of the restoration measures. The zooplankton community of the Ter Vell lagoon was not significantly altered by the hydrological change, at least in the short-term, and rotifers and cladocerans, mainly those species indicative of eutrophy, dominated the community.     

Controls on the chemical and isotopic compositions of urban stormwater in a semiarid zone

The temporal variations in the chemical and isotopic compositions of urban stormwater under different land uses, and their dependence on physical parameters such as precipitation intensity, stormwater discharge, cumulative stormwater volumes and the size of the drainage area, were investigated in the coastal city of Ashdod, Israel. During 2000/2001 and 2001/2002, 46 stormwater events were intensively monitored for precipitation distribution and intensity at three stations across the city, and for stormwater discharge at seven stations draining 85% of the city area. Sixty-eight and 202 precipitation samples were collected and analyzed for chemical and isotopic compositions, respectively, as were 186 stormwater samples, collected from the drains during 15 of the 46 events. Land use had only a minor effect on the concentrations of major ions and trace elements. Conversely, the concentrations and variety of volatile and semi-volatile organic compounds were significantly higher in stormwater generated in the industrial area than in that draining from residential areas. Ion and trace-metal concentrations were very low (below drinking-water standards) in 97% of the stormwater samples collected from all drains. Stormwater concentrations were higher at stations draining a larger area, thereby linking concentrations to the length of the stormwater flow paths. A first-flush effect was documented on both a seasonal and event basis for both ions and trace elements. The high concentrations of fecal coliform bacteria exceeded the drinking-water standards and displayed a random pattern. The isotopic ratios of oxygen and hydrogen in the stormwater suggest very little exposure to the atmosphere, resulting in very limited fractionation. The presence of fecal coliforms, ammonium in some samples, and specific ratios of oxygen and nitrogen isotopes, suggest that although the sewer and stormwater-collection systems are separated, wastewater, possibly from overflowing sewers, contributed to the drained stormwater.     

安徽升金湖越冬白头鹤（Grus monacha）肠道菌群组成的时间变化

肠道微生物对于维持动物消化道内环境的稳定具有重要意义,而肠道微生物菌群结构也受寄主食物成份等外界环境因素的影响.研究动物肠道微生物菌群结构可以更好地了解动物生活状况.以升金湖越冬白头鹤的粪便作为研究对象,以微生物16S rRNA的V3~V4区作为标记基因,进行高通量测序,分析升金湖越冬不同时期白头鹤肠道菌群结构的差异性.研究结果表明:升金湖越冬期不同时期白头鹤粪便样品中微生物多样性指数如香农威纳多样性指数和辛普森指数无显著性差异.但是越冬期不同阶段的粪便样品中菌群组成存在差异,主要包括:在门分类水平,越冬前期拟杆菌门含量较高,厚壁菌门含量较中后期低;越冬中期放线菌门含量较高;越冬后期变形菌门含量较高.在属分类水平,相对于其他两个时期,越冬前期普氏菌属(Prevotella)含量较高,越冬中期杆菌属(Lysinibacillus)含量较高,越冬后期梭菌属(Clostridium)含量较高,并且普氏菌属含量从越冬前期到中期、再到后期有明显的下降趋势,而梭菌属含量从越冬前期到中期、再到后期有明显的升高趋势.这些结果表明不同越冬时期白头鹤肠道菌群组成不同,越冬期不同阶段的食物变化可能作为一个影响因素.     

Fluvial organic carbon composition and concentration variability within a peatland catchment—Implications for carbon cycling and water treatment

Fluvial organic carbon (OC) transformations are an important component of carbon cycling and greenhouse gas production in inland waters resulting in considerable recent interest in the fate of fluvial OC exported from carbon rich soils such as peatlands. Additionally, peatland catchments are important drinking water collection areas, where high OC concentrations in runoff have water treatment implications. This analysis presents the results from a year‐round intensive study within a water treatment catchment draining an area of peatland, considering carbon transformations along a continuum from headwater river, through a storage reservoir and pipe, to a water treatment works. The study uses a unique combination of methods (colourmetric, ultrafiltration, and ¹⁴C radiocarbon dating) to assess catchment wide changes in fluvial carbon composition (colour, size, and age) alongside concentration measures. The results indicate clear patterns of carbon transformations in the river and reservoir and dissolved low molecular weight coloured carbon to be most subject to change, with both loss and replacement within the catchment residence time. Although the evidence suggests dissolved OC (DOC) gains are from particulate OC breakdown, the mechanisms of DOC loss are less certain and may represent greenhouse gas losses or conversions to particulate OC. The transformations presented here appear to have minimal impact on the amount of harder to treat (<10 kDa) dissolved carbon, although they do have implications for total DOC loading to water treatment works. This paper shows that peatland fluvial systems are not passive receptors of particulate and dissolved organic carbon but locations where carbon is actively cycled, with implications for the understanding of carbon cycling and water treatment in peatland catchments.     

应用扫描电镜与X射线能谱仪研究黔北黑色页岩储层孔隙及矿物特征

页岩储层研究已经成为页岩气研究的重点,页岩组构特征的特殊性使得页岩储层发育纳米/微米级孔隙。岩石及矿物中的纳米/微米级空隙是黔北黑色页岩的结构组分之一,传统的光学显微镜方法由于分辨率及放大倍数的限制无法对页岩储层的孔隙类型进行观察;核磁共振等仪器虽能准确测试页岩储层的孔隙度,但是无法获得孔隙的形貌及分布特征等信息。本文整合扫描电镜微区分析与X射线谱学分析的优点,运用Hitachi S-4800型场发射扫描电镜与IE250X-Max50牛津能谱仪组合,对黔北黑色页岩储层中矿物的分布、形态特征及矿物的组成元素进行分析测试。分析结果表明,利用场发射扫描电镜发现黑色页岩中发育微裂缝、纳米/微米级粒内溶孔;通过X射线能谱发现黑色页岩矿物主要有伊利石、石英、钠长石,其次为绿泥石、白云母、白云石等。黔北黑色页岩中裂隙直径为0.1~20μm,其中主要分布在1~5μm,均大于甲烷分子直径(0.414 nm),因此可作为天然气的运移通道与储集空间。此外通过X射线能谱仪对黔北黑色页岩中的石英、方解石、白云石、伊利石等脆性矿物进行分析,发现石英的含量(9.1%~78%)较高,伊利石(17.6%~25.5%)等黏土矿物含量较低,所以该页岩具有很高的脆性,易产生裂缝,可为游离气提供运移通道及储集空间,提高页岩气的产能及储量,进而为黔北地区储层评价及预测等提供依据。