Rock-weathering by lichens in Antarctic: patterns and mechanisms

Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns, mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore, it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out in Antarctica.     

1998年上半年全世界地震灾害综述

１９９８年上半年全世界共发生ＭＳ≥６地震３６次。全世界地震造成的死亡人数总计为９７９４人,伤１５１７３人;经济损失为５．３亿～８．１亿美元。１９９８年上半年全世界地震活动总水平与去年同期相同,但灾情较重于去年同期。主要灾害地震发生在阿富汗、土耳其、玻利维亚和中国张北－尚义地区。在南极海域地区发生８级大地震。     

南极长城站地区环境演变的生物地球化学研究——古降水的复原与末次冰盖消退时间的推断

作者在南极地区近代环境的研究中提出了一种新的研究方法——利用生物地球化学指示元素来研究古环境的变迁。通过研究南极长城站地区西湖底沉积物丛其所含的植物残体、复原了约4000年来的年平均降水量的变化,推断了末次冰盖从本区消退的时间为3500年前。研究南极地区近代环境的演变对解决全球性环境演变是不可缺少的内容。     

南极极夜期间臭氧含量变化及其与平流层风温关系

本文利用昭和基地 (6 9°0 0′ S,3 9°3 5′ E) 1 982～ 1 987年的臭氧总量的探空资料 ,着重分析了1 987年南极昭和站极夜期间臭氧含量变化与 5 0 h Pa风速、气温及变温的关系。发现在极夜期间 ,臭氧含量与 5 0 h Pa风速存在较好的相关性。根据热成风原理 ,计算了极夜期间的温度平流项 ,发现臭氧含量与 5 0 h Pa温度平流也存在一定的相关性 ,变温 ΔT的变化主要是由温度平流引起的。平流层臭氧只具有微弱的加热效应     

南极半岛西北海域表层沉积物中硅藻的初步研究

本文对南极半岛西北海域22个表层沉积物中的硅藻进行了初步研究,鉴定出硅藻82种.根据硅藻的数量分布和生态特征,将本区硅藻分为三个组合;1.Yhalassiosiraantarctica—Charcatia actionchilus—Eucampia balautium组合.2.Th.antarctica——Nitzschiakerguelensis—Coscinodiscus lentignosus组合.3.Coscinodiscus lentiginosus——Eucampiabalaustium—Nitzschia kerguelesis—Schimperiella antarctica组合.文章还通过沉积物中和水体中硅藻的对比,水动力状况,以及海水对硅藻壳体的溶解作用等特征.讨论了区内硅藻壳体的沉积作用.     

南极南奥克尼群岛西部水域南极电灯鱼生物学

根据2010—2012年南半球夏季南极南奥克尼群岛西部水域开展的资源调查期间收集的数据,本研究对南极电灯鱼的基础生物学,包括体长（SL）、纯重（DW）、体长-体重关系、性成熟度和性腺指数及摄食强度进行了分析。结果表明：（1）南极电灯鱼体长范围为6.3—8.8cm,平均体长为7.51±0.03cm（平均值±95%置信区间）;体重范围为3.46—10.13g,平均体重为5.96±0.08g;纯重范围为3.11—8.69g,平均纯重为5.17±0.07g。（2）体重与纯重关系为DW=0.8497TW+0.1623（R2=0.9502）,体长与纯重关系为FL=0.0238DW2.6695。（3）调查期间,南极电灯鱼性成熟度处于Ⅰ—Ⅳ级,未发现有Ⅴ和Ⅵ级的个体出现。（4）摄食强度随体长的增加而有所加强,空胃与1级所占比例随体长增加而下降。     

近普里兹湾大陆架外水域水文物理特征

通过１９９０年１２月～１９９１年１月中国＂极地＂号南印度调查资料分析得出如下一些重要结论：（１）８３°Ｅ以西、６４°Ｓ以北海域，南极夏季表层水厚度约２０ｍ，冬季残留水厚度３０～７０ｍ，７０ｍ以下的水层逐渐过渡到南极深层水。南极深层水中心温度最高，为１．８５～２．００℃；８３°Ｅ以东、６４°Ｓ以北海域，０～３０ｍ为南极夏季表层水，５０～１００ｍ层为南极冬季残留水，１００ｍ以下为南极深层水。深层水中心温度普遍降低，最低为１．０４℃，最高为１．４９℃。它表明８３°Ｅ以东区域受陆架水影响更明显。（２）８３°Ｅ以西，６４°Ｓ以南海域，为深水大洋向陆架浅海过渡区域，温度由北向南迅速降低，普里兹湾基本为陆架低温水所盘据；８３°Ｅ以东、６４°Ｓ以南海域主要为西冰架、谢克尔顿冰架低温水，６４°Ｓ附近形成东西方延伸的温、盐锋面。（３）由动力计算知，在８３°Ｅ以西主要为反时针方向环流；８３°～９８°Ｅ中间，６３°Ｓ南北各有一个顺时针环流；９８°Ｅ以东基本为南向流控制。但是，近岸有一顺时针涡旋。（４）８３°Ｅ以西水文锋面主要有夏季表层水锋面；８３°Ｅ以东主要为陆坡区温度锋，是陆架外高温水与陆架低温水之间过渡带。（５）８３°Ｅ是水文     

A Sr,Nd, Hf,and Pb isotope perspective on the genesis and long-term evolution of alkaline magmas from Erebus volcano,Antarctica

We report new Nd, Hf, Sr, and high-precision Pb isotopic data for 44 lava and tephra samples from Erebus volcano. The samples cover the entire compositional range from basanite to phonolite and trachyte, and represent all three phases of the volcanic evolution from 1.3 Ma to the present. Isotopic analyses of 7 samples from Mt. Morning and the Dry Valley Drilling Project (DVDP) are given for comparison. The Erebus volcano samples have radiogenic ²⁰⁶Pb/²⁰⁴Pb, unradiogenic ⁸⁷Sr/⁸⁶Sr, and intermediate ¹⁴³Nd/¹⁴⁴Nd and ¹⁷⁶Hf/¹⁷⁷Hf, and lie along a mixing trajectory between the two end-member mantle components DMM and HIMU. The Erebus time series data show a marked distinction between the early-phase basanites and phonotephrites, whose Nd, Hf, Sr, and Pb isotope compositions are variable (particularly Pb), and the current ‘phase-three’ evolved phonolitic lavas and bombs, whose Nd, Hf, Sr, and Pb isotope compositions are essentially invariant. Magma mixing is inferred to play a fundamental role in establishing the isotopic and compositional uniformity in the evolved phase-three phonolites. In-situ analyses of Pb isotopes in melt inclusions hosted in an anorthoclase crystal from a 1984 Erebus phonolite bomb and in an olivine from a DVDP basanite are uniform and identical to the host lavas within analytical uncertainties. We suggest that, in both cases, the magma was well mixed at the time melt inclusions were incorporated into the different mineral phases.     

Heavy metal enrichment in Antarctic precipitation and near surface snow

Ion exchange and flameless atomic absorption spectrophotometry methods were used to measure the concentrations of sodium, manganese, iron and silver in snow accumulating at several sites on the Antarctic continent. The results show that the ratio of Mn/Fe is consistently close to the crustal value at all sites. The silver concentrations observed suggest a different origin, probably oceanic. When referenced to sodium, the degrees of enrichment of silver, manganese and iron increase by factors of 8, 2 and 2 respectively over a distance of 500 km from the ocean, after changes in sodium are accounted for.Investigation of the heavy metal content of fresh falling precipitation occorring on the Ross Ice Shelf, has shown that more enhanced enrichments of silver, manganese and iron occur in this fresh precipitation by factors up to 100, than in samples of snow and firn collected from shallow (up to 2 meters depth) pits at the same locations. Because the occurrences of these precipitation types vary temporally and geographically, it seems apparent that the shear stress conditions in the near surface boundary layer need to be considered in studies of snow and ice chemistry, particularly in polar regions where the chemical composition of permanent snow and ice fields are often investigated for evidence of climatic change, of glaciological behavior and of origins of chemical constituents.