南京江北地区全新世沉积与古洪水研究*

根据区域调查和对南京江北剖面沉积物及埋藏古树和炭化木的年代测定,以及对孢粉、粒度、石英砂表面特征鉴定分析,发现本区存在晚北方期至亚北方气候期(8200±126aBP、7822±250aBP～7670±160aBP、7562±90aBP、4085±95aBP～4090±100aBP以及3730±90aBP)具有洪积特征的天然剖面地层,该剖面位于长江北岸二级阶地上,其洪积层系由古洪水期长江摆动时沉积所致。剖面上部厚0.53m的灰黄色土层系在亚北方期大约3000aBP～2850aBP的寒冷期中主要由风尘搬运堆积所致。     

东北夏季极端低温天气事件的定义及其冷空气路径分析

采用东北三省150 个测站1961~2010 年的逐日温度资料和同期美国环境预报中心（NCEP）以及国家大气研究中心（NCAR）2.5°×2.5°分辨率的全球再分析资料,定义了东北夏季极端低温天气事件（extreme low-temperatureevent 以下简称ELTE事件）,统计给出了ELTE事件的发生、峰值和持续时间的日历表。根据该日历分析,发现了影响东北地区夏季ELTE事件的最主要的2 条冷空气路径（西北路径和东北路径）,1961~2010 年期间,影响东北地区的ELTE事件最主要是受西北路径的冷空气的影响,其次是东北路径。同时也发现,ELTE事件20 世纪80 年代发生频率最高,90 年代后开始减少,但是东北路径的ELTE事件在90 年代以后开始明显的增加。还发现,ELTE事件发生的前4 d,贝加尔湖地区若是被低压槽覆盖,易发生西北路径的ELTE事件,若该区域被一个东北-西南走向的高压斜脊控制,同时鄂霍次克海区域存在一个低压中心,形成西北“+”东南“-”的跷跷板形态,易发生东北路径的ELTE事件。     

Chemical composition of waters and the phytoplankton of the lakes within the delta of the Selenga river

Field observations showed that the characteristics of chemical composition of waters and the development of plankton algae in the lakes within the delta of the Selenga river are determined by their flowage. The most open Lake Nekipelovskoe communicates with the Selenga outlets throughout a year, and Lake Zavernyaikha only at the period of an open channel. Lake Semenovskoe and Lake Khlystov Zaton are located in the islands and are isolated from the outlets. According to composition of main ions, the lakes under investigation refer to the hydrocarbonate class, the calcium group. The sum of ions in the water of Lake Nekipelovskoe approaches the one in the Selenga (86?221 mg/dm³), and the highest sums of ions were recorded in the wintertime in the lakes isolated from the outlets (446?743 mg/dm³). The lakes of the delta are characterized by a high trophicity. The maximum concentrations of total phosphorus in Lake Nekipelovskoe and Lake Zavernyaikha were 68 and 122 μg mg/dm³, and in Lake Semenovskoe and Lake Khlystov Zaton ?0.8 and ?0.63 μg mg/dm³, respectively. The most intense development of algae is observed in Lake Zavernyaikha, which is due to the high population of Baikal endemics. Lake Zavernyaikha showed a close negative correlation between the concentration of NO ₃ ^? , mineral phosphorus and phytoplankton biomass; the correlation coefficient was ?0.8 and ?0.63, respectively. The lakes exhibited increased contents readily hydrolysable organic matter, and a decrease in dissolved oxygen concentration in winter; hydrogen sulfide was repeatedly recorded in Lake Khlystov Zaton. The water quality in the lakes during the springtime varies from “quite clean” to “weakly polluted”; at low-water periods, especially in winters, it can drop to the category of “exceedingly dirty”. The water quality of the Selenga can be influenced by the lakes during spring floods when material accumulated during the wintertime is transported to the river outlets and further to Lake Baikal.     

毛乌素沙地北缘泊江海子剖面粒度特征及环境意义

通过毛乌素沙地现代风成沙的粒度与泊江海子剖面沉积物粒度特征对比分析,确定了剖面中4个层位（290—210 cm、190—160 cm 、153.5—123.5 cm、50—40 cm）基本属于风成砂沉积,并且这些风成砂中间夹杂着三次湖相沉积,结合14C年代测定,我们认为此区域在4 000—5 000 a BP存在以下沉积（气候）旋回:至(4 958±84)a BP,沉积风成砂,反映该时期风沙活动强烈,气候干燥,冬季风强盛;(4 958±84)a BP前后,沉积物为灰绿色湖相层,表明这一时期存在短暂的湖面扩展,沙漠退缩;(4 958±84)—(4 793±74)a BP,沉积风成砂,反映了湖泊的退缩和沙漠的扩展;(4 793±74)—(4 536±70)a BP,湖相沉积物,反映了流域降水量的增多;(4 536±70)—(4 085±67)a BP沉积风成砂后,(4 085±67)a BP前后又出现了短暂的湖相沉积,之后又是风成砂沙沉积。     

东亚夏季风的变化特征及其对甘肃夏季暴雨日数的影响

采用NCEP/NCAR再分析资料,计算了1974—2013年乔云亭等定义的东亚季风指数,研究了东亚夏季风的变化特征,利用甘肃省80个站逐日降水资料,分析了东亚夏季风对夏季甘肃暴雨日数的影响。结果表明：（1）夏季,西南季风、东南季风和偏北季风存在明显的年际变化且有所差异。（2）夏季,西南季风、东南季风对甘肃省暴雨日数的影响存在很大差异：当西南季风盛行时,西太平洋副热带高压位置偏西,东亚大槽位于贝加尔湖至中国西北部,冷空气与西太平洋副热带高压输送的暖湿气流在陇东南一带交汇,贝加尔湖至张掖为西南暖湿和西北干冷气流,孟加拉湾水汽输送在陇东南地区辐合,造成河东陇南南部、天水东部、平凉、庆阳西部一带和河西张掖地区暴雨日数偏多;当东南季风盛行时,西太平洋副热带高压西伸北抬,冷暖空气主要交汇于甘肃中西部,孟加拉湾西南水汽输送在河东西南部辐合,造成甘南高原、甘肃中部、河西武威一带和酒泉地区暴雨日数偏多。     

The cooling effect of crushed rock structures on permafrost under an embankment

Based on the analysis and comparison of soil temperature, thermal regime and permafrost table under the experimental embankment of crushed rock structures in Beiluhe, results show that crushed rock structures provide an extensive cooling effect, which produces a rising permafrost table and decreasing soil temperatures. The rise of the permafrost table under the embankment ranges from an increase of 1.08 m to 1.67 m, with an average of 1.27 m from 2004 to 2007. Mean annual soil temperatures under the crushed rock layer embankment decreased significantly from 2005 to 2007, with average decreases of ?1.03 °C at the depth of 0.5 m, ?1.14 °C at the depth of 1.5 m, and ?0.5 °C at the depth of 5 m. During this period, mean annual soil temperatures under the crushed rock cover embankment showed a slight decrease at shallow depths, with an average decrease of ?0.2 °C at the depth of 0.5 m and 1.5 m, but a slight rise at the depth of 5 m. After the crushed rock structures were closed or crammed with sand, the cooling effect of the crushed rock layer embankment was greatly reduced and that of the crushed rock cover embankment was just slightly reduced.     

The natural-climatic events on the coast of Middle Baikal in the Early Holocene

Presented are the results from pedolithological investigations and reconstructions of the naturalclimatic events in the Early Holocene (radiocarbon age 10.3?8 ka; calendar age 11.7?8.8 ka) on the coast of Middle Baikal, based on data obtained by studying the structure, composition and properties of subaerial deposits and soils in terrestrial sections. A study was made of the numerous soil profiles and sections of geoarchaeological sites. The investigation revealed common features in the layered structure of the Early-Holocene portion of the terrestrial sections and evidence of climate warming represented by buried soils, signals of a cooling in the form of cryogenic fissures, and signals of drying in the form of aeolian drifts and evidence of deflation. It is shown that the Early Holocene was the time of cardinal changes in the nature of subaerial sedimentation (calcareous deposits were replaced by noncalcareous deposits) and the pedogenesis. Considerable cold storage from inherited permafrost and humidification of soils and earth materials with moisture from the thawing of permafrost were responsible for the specific character of soil formation, and for the spread of forest vegetation under a rather low atmospheric humidity. The phases of climate warming were accompanied by an intensification of soil formation with the production of soils of two types: early boreal, and boreal. Deluvial, colluvial and sometimes (in Priol’khonie) aeolian deposits accumulated during the cooling phases (Late Preboreal and Late Boreal). Small cryogenic fissures were generated. The issues of man’s adaptation to the cardinally changed natural conditions at the turn of the Pleistocene and Holocene and over the course of the Early Holocene are associated with the problem of Baikal’s water level and human settlement on its shores. The Lake Baikal stage at the end of the Late Neopleistocene was lower than at present; during the Early Holocene it was rising to reach at the late-boreal period the present-day level (or even exceeded it). The rises of Baikal’s stage at the Mid- and Late-Holocene period were causing scouring and destruction of the Early-Holocene sites that were located at lower elevations.     

Sedimentary Steryl Chlorin Esters (SCEs) and Other Photosynthetic Pigments as Indicators of Paleolimnological Change Over the Last 28,000 Years from the Buguldeika Saddle of Lake Baikal

Detailed depth profiles of photosynthetic pigments in a sediment core (G-12) collected at the BDP93 site, the Buguldeika saddle, of south Lake Baikal, along with depth profiles of total organic carbon (TOC) and biogenic silica, were studied to elucidate the temporal changes of phytoplankton assemblages in the lake during the past 28 kyr. In addition to the quantification of carotenoids by high-performance liquid chromatography with photodiode-array detection (HPLC-PDA), steryl chlorin esters (SCEs) were analyzed by HPLC-PDA, HPLC-mass spectrometry (LC-MS) and sterols in SCEs by gas chromatography–mass spectrometry (GC–MS) to enrich the taxonomical information on the phytoplankton composition. Allochthonous input of organic matter from the Selenga River resulted in the higher TOC contents in core G-12 than in a previously reported core (G-6) collected at another site from the southern basin. The poorer correlation in core G-12 than in G-6 between TOC and chlorophyll-a-originating pigments, which are indicative of autochthonous production, also indicated a significant allochthonous input at the site. The abundance of lutein among the carotenoids detected, and the good correlation of total chlorophyll a and b shows that green algae represented a significant portion of the phytoplankton, accompanying the diatoms at the G-12 site, after the last glacial period. The presence of cryptomonads and cyanobacteria were confirmed from marker carotenoids in the sediment core. GC–MS analysis of sterols in SCEs detected marker sterols of diatoms, green algae, chrysophytes and dinoflagellates. The depth profiles of the measured indicators gave consistent features for temporal changes in phytoplankton assemblage at the G-12 site of Lake Baikal after the last glacial maximum. Notably, the profile of a chrysophyte-specific sterol in SCEs was consistent with the reported distribution of chrysophyte cysts during the Holocene. The presence of phytoplankton, such as green algae, diatoms and chrysophytes, in Lake Baikal during the late last glacial period was indicated by the analysis of sterols in SCEs. Sedimentary carotenoids and sterols in SCEs were found to give complementary information about phytoplankton composition. These molecular indicators allow us to reconstruct past lake phytoplankton assemblages responding to environmental changes with a time resolution as high as age–depth relationship in sediments attainable at present.     

塔里木盆地一次东灌型沙尘暴环流动力结构分析

利用NCEP再分析资料和常规地面观测资料,对2006年4月10日塔里木盆地发生的一次东灌型沙尘暴,从气候背景、环流形势、螺旋度场、锋生次级环流、温度平流等方面进行分析,揭示了此类沙尘暴强盛期的环流动力结构。结果表明：①里咸海脊、乌拉尔脊、新地岛脊同位向叠加,西西伯利亚横槽转竖南下,引导泰米尔半岛强冷空气爆发直插新疆,东灌进入南疆盆地,造成大范围沙尘暴天气;②西西伯利亚地面冷高压爆发性南下并强烈发展是造成此次沙尘天气的根本原因;③盆地前期的干暖形势为沙尘暴的产生提供了有利的热力条件;④沙尘暴区上空螺旋度垂直分布为低层正值、高层负值,构成低空强辐合、高空强辐散的上升运动区,揭示强旋转上升运动是大范围沙尘暴发生的动力条件;⑤高空急流入口区次级环流下沉支导致高层动量下传 ,促使对流层中低层风力加大,冷锋南压,驱动沙尘天气的发生。     

Contribution of waters of Atlantic and Pacific origin in the Northeast Water Polynya

Measurements of nitrate and phosphate taken in the Northeast Water Polynya (NEWP) during the summer of 1993 have been used to identify the contribution of waters of Atlantic and Pacific origin in the polynya. Since waters from the northern Pacific exhibit a deficit in nitrate relative to phosphate due to denitrification in low oxygen waters, the relationship between nitrate and phosphate can be used to distinguish between oceanic waters of Pacific and Atlantic origin. The Pacific Water enters the Arctic Ocean through Bering Strait and flows along the northern coasts of Alaska and Canada. Some of this water exits through Fram Strait and may therefore enter the polynya which is situated above the continental shelf off the north-eastern coast of Greenland. Compared to data from the Greenland Sea, which only show a N–P relationship of typical Atlantic Water, the data from the Northeast Water Polynya show that the upper waters of the polynya bear a clear signal of waters of Pacific origin. In the surface mixed layer an average of about 90% is found to have Pacific N–P characteristics. Below the surface mixed layer the amount of Pacific derived water decreases through the halocline and from about 150 m to the bottom only typical Atlantic Water is found.     

Record of Late Pleistocene Glaciation and Deglaciation in the Southern Cascade Range. I. Petrological Evidence from Lacustrine Sediment in Upper Klamath Lake, Southern Oregon

Petrological and textural properties of lacustrine sediments from Upper Klamath Lake, Oregon, reflect changing input volumes of glacial flour and thus reveal a detailed glacial history for the southern Cascade Range between about 37 and 15 ka. Magnetic properties vary as a result of mixing different amounts of the highly magnetic, glacially generated detritus with less magnetic, more weathered detritus derived from unglaciated parts of the large catchment. Evidence that the magnetic properties record glacial flour input is based mainly on the strong correlation between bulk sediment particle size and parameters that measure the magnetite content and magnetic mineral freshness. High magnetization corresponds to relatively fine particle size and lower magnetization to coarser particle size. This relation is not found in the Buck Lake core in a nearby, unglaciated catchment. Angular silt-sized volcanic rock fragments containing unaltered magnetite dominate the magnetic fraction in the late Pleistocene sediments but are absent in younger, low magnetization sediments. The finer grained, highly magnetic sediments contain high proportions of planktic diatoms indicative of cold, oligotrophic limnic conditions. Sediment with lower magnetite content contains populations of diatoms indicative of warmer, eutrophic limnic conditions. During the latter part of oxygen isotope stage 3 (about 37–25 ka), the magnetic properties record millennial-scale variations in glacial-flour content. The input of glacial flour was uniformly high during the Last Glacial Maximum, between about 21 and 16 ka. At about 16 ka, magnetite input, both absolute and relative to hematite, decreased abruptly, reflecting a rapid decline in glacially derived detritus. The decrease in magnetite transport into the lake preceded declines in pollen from both grass and sagebrush. A more gradual decrease in heavy mineral content over this interval records sediment starvation with the growth of marshes at the margins of the lake and dilution of detrital material by biogenic silica and other organic matter.     

北极涛动异常对西北地区东部沙尘暴频次的影响

利用西北地区东部沙尘暴日数资料、北极涛动指数资料、东亚高低空大气环流形势场资料,分析了沙尘暴日数与北极涛动的关系,进而研究了北极涛动异常年东亚大气环流分布特征,探讨了北极涛动影响西北地区东部沙尘暴的可能途径。结果表明：西北地区东部沙尘暴频次呈波动减少之势,20世纪80年代中期发生气候突变;北极涛动指数与西北地区东部沙尘暴频次显著负相关,二者年际、年代际变化都有较好的应关系,北极涛动正位相年,西北地区东部沙尘暴偏少,反之亦然。究其原因：北极涛动异常对东亚冬季风强度、东亚高低空气压场、风场分布形势有重要影响：北极涛动正位相年,东亚冬季风、蒙古高压均偏弱;500 hPa高度场上,春季西风带纬向环流占优势,极涡面积偏小,强度偏弱,贝加尔湖阻塞高压异常强盛,蒙古国及我国华北和西北地区位于贝加尔湖阻塞高压底部的暖区里,地面至高空西北风偏弱;在这种形势下,整个中高纬度冷空气势力较弱,活动次数偏少,不利于大风、寒潮天气的发生,因此沙尘暴频次也偏少。而北极涛动负位相年基本相反。     

Structural analysis and design of frost resistance function for subgrade of high-speed railway ballasted track in cold regions

According to the technical characteristics of short fixed wheelbase of a high-speed carriage, a subgrade-track integrated space mechanical response analysis model is proposed for trains under the action of biaxial load after the comparison of the stress distribution characteristics of the ballast track subgrade bed structures for high-speed railway under the action of uniaxial load and biaxial load. The loading threshold value (high-cycle long-term dynamic strength) under the circumstance where the cumulative deformation of subgrade structure gradually develops and finally reaches the convergent state, and its relationship with the foundation coefficient K₃₀ were deduced, based on the characteristics of cumulative deformation evolution obtained from the unit structure filling model test under the action of cyclic loading. In view of structure stability and frost resistance requirements of the railway subgrade in cold regions, technical conditions to maintain good service performance of subgrade structure of high-speed railway ballasted track are discussed and analyzed. Study results show that the additive effect manifests itself obviously for railway train bogies under the action of biaxial load than uniaxial load, which has a significant dynamic effect on the subgrade bed bottom and a slight effect on the surface layer. Thus, the adoption of a biaxial load model in the design of a high-speed railway subgrade accurately reflects the vehicle load. Pursuant to the structure design principle, the design method of the subgrade structure of high-speed railway ballasted track is proposed to meet the technical requirements such as structural strength, bearing stiffness and high-cyclic and long-term stability. Technical indicators are obtained for the variation of thickness of the surface layer of reinforced subgrade bed in the double-layer subgrade mode along with the change of K₃₀ at the subgrade bed bottom. The double-layer structure mode of "closure on the upper layer and drainage on the lower layer" was proposed in order to meet the waterproofing and drainage requirements of the upper layer of the subgrade bed in cold regions. A dense-framework graded gravel filler with weak water permeability at a coefficient of 10^-4 cm/s is used on the upper layer and the void-framework graded gravel filler at the water permeability coefficient of 10^-2 cm/s is adopted on the lower layer.     

宁夏一次春季突发寒潮极值暴雪过程的等熵位涡分析

利用常规观测、地面加密站逐时观测和欧洲中期数值预报中心0.125 °×0.125 °逐6 h再分析资料,从天气系统演变、冷空气路径、灾害性天气预报指标等方面,利用315K等熵位涡对2016年4月2～3日宁夏突发寒潮极值暴雪过程进行了诊断分析。结果表明：（1）此次过程属于高空小槽东移合并型,地面有冷高压分裂且主体快速南下,并有锋面相配合,导致强冷空气入侵和锋后降雪。（2）前期环流形势稳定,后期天气系统突变,常规气象资料难以预报,315K等熵位涡图可作为短时、局地的春季寒潮降雪过程的有效分析和预报工具。（3）等熵位涡清楚地示踪冷空气的来源和传播路径：咸海区域对流层顶冷空气东移南扩与青藏高原对流层中层冷空气合并加强,且新地岛平流层下部的冷空气在前期缓慢东移后,自贝加尔湖加速南下对其补充引发寒潮。（4）等熵位涡异常大值可定量、清晰地表述关键影响系统西风带小槽的演变,具有更好的指示意义。（5）等熵位涡高值区随时间变化与寒潮演变一致,可提前6 h指示冷空气活动,且等熵位涡大于1.0 PVU区域与寒潮及降雪落区一致,大于0.8 PVU区域与强降温区域一致,可作为精细定量预报的重要指标。     

Changes in the mullet fishery of Lake Manzala,Egypt

Growth rates of the main mullet species (Liza ramada andMugil cephalus) in Lake Manzala are low compared to those in other Egyptian lakes. But average growth rates during the period 1989–1993 were relatively faster than in the 1960's. Spawning and migration seasons have been determined for every species, and their distribution in the lake, in terms of certain ecological parameters (salinity, turbidity and dissolved oxygen) have been investigated. Changes in the mullet fishery in the lake during the past 70 years have been studied. Due to an increase in nutrient loading and a decrease in salinity, mullet declined from 65 per cent of the total catch during the 1920's to only 2.2 per cent during the early 1980's. As a result of fisheries management and development programmes from 1989 to 1993, mullet production increased to 9.2 per cent of the total catch.     

2012-2013年中国西南地区秋、冬、春季持续干旱的成因

利用多种资料从大尺度大气环流、水汽输送、热带海表温度、北极涛动、平流层极涡等方面分析了2012-2013年中国西南地区秋、冬、春季持续干旱的成因。结果表明, 西南水汽输送偏弱、高纬度地区南下冷空气路径偏东、冷暖空气难以在西南地区上空交汇, 是此次持续干旱的直接原因。这段时间西南地区大都受平直西风气流控制, 孟加拉湾和中南半岛地区位势高度较常年偏高, 不利于这些地区气旋性环流的发展;热带海表温度异常变化,特别是冬春季印度洋海表温度的持续偏高, 使得菲律宾地区上空低层反气旋异常环流增强。这些都导致了西南向水汽输送偏弱。此外, 北极涛动异常变化对西南地区的干旱也有重要影响, 北极涛动持续处于负位相, 不仅使南支槽减弱变浅, 西南水汽输送减少, 还导致贝加尔湖高压脊偏弱, 使北方南下冷空气主体偏东。冬季平流层极涡强度的变化在各个高度的位势高度场和位势涡度场上都有体现, 其变化对冷空气的强度及路径有明显影响。     

烟台芝罘黄土剖面末次间冰期沉积物色度特征及其古环境意义

以烟台市的芝罘岛风砂沉积剖面为研究对象,分析色度特征,并结合光释光测年探讨末次间冰期该地区的气候。结果表明：1）色度参数L^*均值为52.13,在整个剖面表现为黄土层L^*高于古土壤层,指示寒冷干燥的气候条件。a^*、b^*、C^*、h^*均值依次为11.18、25.03、27.43和0.421,其值均表现为古土壤层高于黄土层,指示温暖湿润的气候条件。2）各色度参数在剖面垂直方向上呈现峰谷交替的3个旋回,反映该地区末次间冰期的气候变化经历由夏季风占主导,气候暖湿,降水较多（MIS5e：118.5—124.9 ka）→夏季风势力减弱,冬季风增强,气温下降（MIS5d：105.2—118.5 ka）→夏季风影响明显,气候湿热（MIS5c：94.7—105.2 ka）→冬季风增强,气温下降（MIS5b：83.4—94.7 ka）→开始转向暖湿（MIS5a：70.18—83.4 ka）→再转向干冷（MIS4：62.85—70.18 ka）的冷暖震荡。     

The hydrological response and nutrient loss of certain horticultural ecosystems

Surface runoff, sediment output, and input and output of precipitation nutrients were studied in ber (Zizyphus mauritiana) and pomegranate plantations in the Indian arid zone of Rajasthan during 1993–96. Over 77% of rainfall events were small with low intensity and prolonged duration. High magnitude rainfall (>50 mm) accounted for less than 2% of the rainfall events. Surface runoff was significantly different across the plantations and size of micro-watersheds. Average surface runoff was less than 10% of incidental rainfall, indicating the prominence of deep percolation. Sediment output was positively related to surface runoff. Rainfall added a significant amount of nutrients to the orchards. The extra-system of input was greater than loss through surface runoff plus sediment output. Nutrient loss as particulate matter was more than in solution.     

Oxygen isotope variability in calcite shells of the ostracod Cyprideis torosa in Akyatan Lagoon,Turkey

The euryhaline ostracod Cyprideis torosa lives in Akyatan Lagoon, Turkey, which is exposed to large spatial and seasonal variations in water salinity, δ¹⁸O, and temperature. Hydrogen and oxygen isotope measurements of waters reveal that the large range of salinity (15–80 g L^?1) in the lagoon results from a combination of evaporation and mixing between Mediterranean seawater and Seyhan River input. Round sieve-pore relative abundance in C. torosa provides a robust proxy for water salinity (S) from 15 to 80 g L^?1, according to the equation: S = 161.41 (±4.52) * log₁₀(% rounded pores) ? 94.04 (±3.44) (R² = 0.937; p = 10^?31). Seasonal sampling and isotope analysis of C. torosa in waters of known δ¹⁸O values (?4.7 to +6.9 ‰ V-PDB) and temperatures (15–35 °C) yielded a weak positive correlation (r = 0.71) between 1000 lnα_{(calcite–water)} ‰ V-SMOW) and 10³ * T^?1. Specimens of C. torosa collected during the mild and warm seasons have oxygen isotope compositions close to those of inorganic calcite precipitated in equilibrium with ambient water. The large oxygen-isotope variability observed during any season of the year most likely results from shell calcification in water bodies of highly variable salinity, alkalinity, Mg/Ca and water saturation relative to calcite. Indeed, distinct water bodies in the Akyatan Lagoon are generated by mixing of fresh and marine waters, which are exposed to different evaporation rates at the seasonal scale.     

Distribution of minor gas pollutants in the atmosphere over Lake Baikal

An analysis is made of the data obtained by means of the gas analyzer in comparison with meteorological conditions. The values of sulfur and nitrogen dioxide concentrations in the layer above water of Lake Baikal varied from 1 to 10 micrograms. The largest values of SO₂ concentration were observed in the area of the Baikalsk Pulp and Paper Mill (Southern Baikal) under the plume. The calculated and measured values of sulfur dioxide and nitrogen oxide concentrations were compared to provide a good qualitative agreement.