Spatiotemporal distribution of caddis fly larvae <Emphasis Type="Italic">Aethaloptera evanescens</Emphasis> MacLachlan, 1880 (Trichoptera: Hydropsychidae) in the Selenga River

Data on the occurrence, abundance, and biomass of caddis fly larvae Aethaloptera evanescens in the Selenga during the ice periods of 1987–2005 are presented. These insect larvae prefer river stretches with a gravel-sand ground, flow rate of 0.3–0.4 m/s, and depth of 2–3 m. Probable factors determining their distribution in the Selenga in recent years are a considerable drop of water level in the river (1995–2005), the improvement of hydrochemical conditions, and the presence of suspended and drifting erosion materials entering the river as a consequence of sand-gravel mixture excavation between 1980 and 1990.     

锰细菌在加拿大海盆、楚科奇海沉积物中的分布

用平板法分别在4℃和25℃时对北极加拿大海盆和楚科奇海10个沉积物岩芯中的锰细菌进行培养,并测定了检出率和含量.分析结果表明,4℃与25cc温度下培养的锰细菌含量范围均为(-)～3.3×108个g-1,锰细菌平均检出率分别为77.78%、86.03%.平均含量分别为5.60×106、7.91×106个g-1;该结果高于太平洋深海沉积物中的锰细菌含量,比北极阿拉斯加淡水湖湖水中的锰细菌含量高1个数量级,比印度洋海岭Carlsberg Ridge区热水区海水样品中的锰细菌含量高3个数量级,证实寒冷北极海同样广布锰细菌.对锰细菌在不同水深、经纬度以及沉积物深度中的分布进行了讨论;结果表明,锰细菌检出率随沉积物深度的增加而增大.含量变化呈现浅层少、下层多之势;纬度分布范围较大,并显出有扩大的趋势.水深对沉积物中锰细菌也有一定影响.尽管锰细菌对温度有较强的适应能力,环境温度的升降对本研究区锰细菌具有双重作用.     

THE EFFECT OF ICE COVER ON VERTICAL TRANSFER IN STREAM CHANNELS1

ABSTRACT: The effect of ice cover on vertical transfer is examined based on the Reynolds' analogy and composite logarithmic velocity distributions. A finite difference scheme is used to predict concentration profiles in a two-dimensional channel. Comparisons made between the ice-covered condition and the ice-free condition show that considerable reduction in mixing capacity of the channel is caused by the ice cover.     

Historical trends of PCBs and PBDEs as reconstructed in a lake sediment from southern Tibetan Plateau

High-altitude lake sediment can be used as a natural archive to reconstruct the history of pollutants. In this work, the temporal distribution of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were determined using a high-resolution gas chromatography coupled with high-resolution mass spectrometer (HRGC/HRMS) in an alpine lake sediment core collected from the southern Tibetan Plateau (TP) to examine whether the expected decreasing trends due to the implementation of the international Conventions could be observed. The concentrations of PCBs and PBDEs in the sediment core were in the range of 11.8–142 pg/g dw and ND-457 pg/g dw, and their fluxes were in the range of 2.51–31.7 ng/(m²·yr) and ND-43.2 ng/(m²·yr), respectively. The prevalence of low-chlorinated (tri-CB) PCBs and low-brominated (tri- to tetra-) PBDEs in most sections of the sediment profiles was observed, suggesting that the light molecular weight PCBs and PBDEs have most likely reached lake sediments by long-range atmospheric transport from distant sources. Despite the restrictions on their applications, the sediment records for the concentrations and fluxes showed no corresponding decreasing trend with restrictions for PCBs, which suggested that these POPs (e.g., PCBs) were still emitted to the environment owing to the influence of primary or secondary emissions. To our knowledge, this is the first report on input history of atmospheric PCBs and PBDEs recorded in TP Lake sediment.     

南极拉森北部冰架表面物质损失机制探讨

基于解密航片、光学遥感影像以及卫星雷达测高数据,完成一个较长时间序列的拉森A和B冰架的范围及表面高程变化监测.在此基础上,结合NCEP/NCAR夏季逐月平均气温数据和GPCP全球降水数据这两种气象数据来探讨拉森北部冰架表面物质平衡机制.结果表明：随着气温的升高,拉森A和B冰架自1968年以来总共消失了14 000km²的浮冰.当前,拉森A冰架已经完全消失,拉森B冰架仅存2 000km².伴随着冰架的持续崩塌与退缩,拉森北部冰架展现出高程持续降低的趋势,而且拉森A冰架的降低速度（-0.45m/a）明显高于拉森B冰架（-0.09m/a）.作为冰架表面物质平衡估算的两个主要参数,拉森A冰架的夏季平均气温从1968年的0.16℃升高到近期的0.84℃;拉森B冰架的夏季平均气温从1968年的0.04℃升高到近期的0.66℃.过去几十年的降水量变化对拉森北部冰架表面物质累积产生的影响很小,反倒是夏季温暖的降雨进一步加剧该地区的表面物质负平衡.对于持续崩塌与退缩型的拉森北部冰架来说,其高程降低除了受到冰架表面冰雪融化与再凝结导致的积雪致密化驱动外,还受到冰架后退导致的背向应力减少,进而导致的冰架物质输送加快的深刻影响.总之,在全球气候变暖的背景下,拉森A和B冰架的表面物质体现出越来越明显的负平衡趋势.     

云南稻核心种质苗期耐冷性及其地理生态差异

采用Nagamine等(1991)法研究了598份云南稻核心种质在稻作区划间、地州间苗期耐冷性强弱、变异程度及其地理生态差异。结果表明,稻作区划间苗期耐冷强弱差异较大,平均耐冷级别为:I(4.70)>II(4.78)>V(4.79)>III(5.34)>IV(5.36),40份强耐冷种质频率为II(45%)>I(25%)>III(22.5%)>V(5.0%)>IV(2.5%),其变异系数为II(32.22%)>I(31.28%)>V(29.65%)>III(19.66%)>IV(19.59%);揭示了苗期耐冷性与低温胁迫下水稻冬春育秧、冷泉水密切相关,其耐冷基因源是云南南部地区冬季育秧和滇中一带苗期倒春寒长期协同进化的结果;苗期耐冷种质广泛存在于热带、亚热带和温带地区,品种间苗期耐冷差异也明显。云南稻核心种质16个地州平均苗期耐冷强弱差异较大。根据气候、生态、云南稻种多样性及其苗期耐冷性等将云南稻作区划分为重冷害多样性贫乏区、冷害多样性中区和轻冷害区三部分。其中,曲靖、大理、楚雄、昆明和丽江5个地州平均耐冷级别3.65~4.32,0—2级苗期强耐冷种质占27.5%(2.5%~10%)和高海拔冷泉水苗期灌溉,属于重冷害多样性贫乏区;文山、红河、思茅、保山、德宏和临沧6个地州平均耐冷级别4.45~5.40,0—2级苗期耐冷种质占70%(5%~30%)和冬春育秧,属于冷害多样性中区;怒江、玉溪、昭通、迪庆和西双版纳5个地州平均耐冷级别5.05~5.87,0—2级苗期耐冷种质占2.5%(0~2.5%),属于轻冷害多样性扩散区。水稻冬春育秧和高海拔冷泉水灌溉在云南稻核心种质苗期耐冷基因源演化中起了重要作用。     

环渤海海冰弯曲强度影响因素分析

本文根据多年环渤海海冰弯曲强度试验结果，分析了诸单因子对海冰弯曲强度的影响，并给出了各海区海冰弯曲强度设计值，海冰的弯曲强度随着应力速度的增加，经过延性，过渡和脆性三个阶段，在过渡区，海冰的弯曲强度达到最大值。随冰温的降低和冰中盐水体积减少，海冰的湾曲强度增大。     

Use of Water Clarity to Monitor the Effects of Climate Change and other Stressors on Oligotrophic Lakes

We present evidence from studies oflakes in Killarney Park, Ontario, Canada that waterclarity is a key variable for monitoring theeffects of climate change, high UV exposure andacidification. In small oligotrophic lakes, thesestressors affect water clarity primarily byaltering the concentration of DOC in lake water. Clear lakes (<2 mg L^-1 DOC) proved to be highlysensitive indicators of stressors, exhibiting largethermal and optical responses to small changes inDOC. Extremely clear (<0.5 mg L^-1 DOC) acidic lakesshowed the effects of climate change and solarbleaching in recent decades. These lakes becamemuch clearer even though they were slowlyrecovering from acidification.     

Ice Storm Damage and Early Recovery in an Old-Growth Forest

We quantified the damage causedby a major ice storm to individual trees in two1-ha permanent plots located at Mont St. Hilairein southwestern Québec, Canada. The storm, whichoccurred in January 1998, is the worst on recordin eastern North America; glaze ice on the orderof 80–100 mm accumulated at our study site. Allbut 3% of the trees (DBH 10 cm) lost at leastsome crown branches, and 35% lost more than halftheir crown. Damage to trees increased in the order: Tsuga canadensis, Betula alleghaniensis, Ostrya virginiana, Acer saccharum, Fagus grandifolia, Quercus rubra, Betula papyrifera, Acer rubrum, Tilia americana, and Fraxinus americana. Only 22% of the saplings and small trees (4 cm < DBH < 10 cm)escaped being broken or pinned to the ground byfalling material. Levels of damage generally weregreater in an exposed ridge top forest than in acove protected from wind. By August 1999 only53% of the trees had new shoots developing fromthe trunk or broken branches; among the moredominant canopy trees, Fagus grandifoliahad the least sprouting and Acer saccharumand Quercus rubra the most. We anticipateand will monitor both significant turnover in thetree community and some shift in composition ofthe canopy dominants.     

中国边缘海柱样沉积物中239+240Pu的分布与时标价值

根据中国边缘海已研究的77根^239+240Pu柱样沉积物,分析了柱样沉积物中^239+240Pu的来源、分布和时标特征.结果表明理论上给出的利用²¹⁰Pb、¹³⁷Cs和^239+240Pu 3种核素进行定年可能出现的26种情况,与实际情况完全吻合.中国边缘海海陆交汇,柱样沉积物中不同来源的^239+240Pu沉积叠加使得近岸海域（尤其是河口区）柱样沉积物中^239+240Pu的峰型轮廓明显.从近岸到远海,受到沉积物来源方式、海水深度、黑潮混合、扩散效应和边界清除效应等综合因素的影响,柱样沉积物中^239+240Pu的分布可能出现双峰（多峰）、单峰和无峰的情况.其中,柱样中^239+240Pu呈现单峰分布时,与全球大气沉降的高峰年1963年相对应,时标价值可靠.不同海洋环境条件下²¹⁰Pb、¹³⁷Cs和^239+240Pu定年的可靠性,应根据具体海洋沉积环境进行分析;海水中¹³⁷Cs和^239+240Pu核素沉积性质的差异,可能导致沉积峰不一致而影响定年的判断.