北极Svalbard群岛Longyearbyen地区雪坑主要阴、阳离子特征研究

北极Ｓｖａｌｂａｒｄ群岛Ｌｏｎｇｙｅａｒｂｙｅｎ地区３条冰川８个雪坑样品的分析结果表明,该地区冰川表层雪中海盐离子Ｃｌ－和Ｎａ＋占主导地位,其浓度远高于其它离子,而陆源Ｃａ２＋在雪坑秋季污化层中浓度远远高于其它层位,可作为雪坑定年中秋季层位的标志。在季节变化上,海盐离子和ＳＯ２－４、ＮＯ－３在春季和夏季表现为高值,这与冬春季节北大西洋风暴和中纬度人类污染物远距离传输到北极有关,也与夏季局地海洋性气团、大气中氧化作用、光电作用和清除速率有关。同全球的边远地区格陵兰、南极和青藏高原比较,Ｌｏｎｇｙｅａｒｂｙｅｎ地区雪中离子浓度水平较高,特别是海盐离子浓度远高于其它地区。     

巢湖流域非点源污染初步研究

巢肖是我国五大淡品湖中污染最为严重的湖泊之一。对巢湖流域自然、经济、社会系统进行全面分析,运用对应分析技术剖析了不同土地利用方式与营养物地表径流输入之间的关系,为巢湖流域非点源污染的控制提供依据。     

Point source radiation in inhomogeneous anisotropic structures

The ray formulae for the radiation from point sources in unbounded inhomogeneous isotropic as well as anisotropic media consist of two factors. The first one depends fully on the type and orientation of the source and on the parameters of the medium at the source. We call this factor the directivity function. The second factor depends on the parameters of the medium surrounding the source and this factor is the well-known geometrical spreading. The displacement vector and the radiation pattern defined as a modulus of the amplitude of the displacement vector measured on a unit sphere around the source are both proportional to the ratio of the directivity function and the geometrical spreading.For several reasons it is desirable to separate the two mentioned factors. For example, there are methods in exploration seismics, which separate the effects of the geometrical spreading from the observed wave field (so-called true amplitude concept) and thus require the proposed separation. The separation also has an important impact on computer time savings in modeling seismic wave fields generated by point sources by the ray method. For a given position in a given model, it is sufficient to calculate the geometrical spreading only once. A multitude of various types of point sources with a different orientation can then be calculated at negligible additional cost.In numerical examples we show the effects of anisotropy on the geometrical spreading, the directivity and the radiation pattern. Ray synthetic seismograms due to a point source positioned in an anisotropic medium are also presented and compared with seismograms for an isotropic medium.     

Formate and acetate levels compared in monsoon and winter rainwater at Dayalbagh, Agra (India)

A total of 59 rainwater samples were collected during the winter and monsoon (1991–92) at Dayalbagh, Agra. This site is relatively free from the influence of anthropogenic emissions and the volume-weighted average concentrations (VWA) of formate in the winter and monsoon were 22.5±6, 16.1±3 while acetate VWAs were 17.1±5 and 13.8±3 mol l^-1, respectively. Although the VWAs varied between seasons, it was not statistically different. Total deposition (in mmol m^-2) varied between season (winter formate, 1.4; acetate, 1.1; monsoon formate, 7.4; acetate, 6.4). A difference in VWA values may have occurred as a result of the dilution factor; the total rain depth from collected samples in the monsoon was 46 cm while that in winter was 6.3 cm. Sources at this site may be anthropogenic and natural; scavenging from the vapour phase, washout of soil particles and emissions from vegetative sources are probably important sources for formate and acetate.     

Temporal variations in gravity at Mt. Etna (Italy) associated with the 1989 and 1991 eruptions

 Results are presented from 11 microgravity surveys on Mt. Etna between 1987 and 1993, a period including the major 1989 and 1991–1993 flank eruptions and subordinate 1990 activity. Measurements were made with LaCoste and Romberg D-62 and D-157 gravity meters along a network around the volcano between 1000 and 1900 m a.s.l. and, since 1992, a N–S summit profile. Gravity changes of as much as 200 μGal were observed at scales from the size of the summit region to that of the volcano. None was associated with significant changes in ground elevation. The data show an increase in gravity for 2 years before the 1989 eruption. The increase is attributed to the accumulation of magma (0.25–1.7×10⁹m³) in an elongate zone, oriented NNW–SSE, between 2.5 and 6 km below sea level. Part of this magma was injected into the volcanic pile to supply the 1989 and 1990 eruptions. It also probably fed the start of the 1991–1993 eruption, since this event was not preceded by significant gravity changes. A large gravity increase (up to 140 μGal) detected across the volcano between June and September 1992 is consistent with the arrival in the accumulation zone of 0.32–2.2×10⁹m³ of new magma, thus favoring continued flank effusion until 1993. A large gravity decrease (200 μGal) in the summit region marked the closing stages of the 1991–1993 event and is associated with magma drainage from the upper levels of Etna's central feeding system. Received: 15 July 1995 / Accepted: 27 October 1997     

Short-lived nuclides in the early solar system

Isotopic records in meteorites provide evidence for the presence of several short-lived nuclides in the early solar system with half-lives varying from 10⁵ to ∼8x10⁷ years. Most of the nuclides with longer half-life (> 10⁷ years) are considered to be products of stellar nucleosynthesis taking place over long time scales in our galaxy. However, for the relatively shorter-lived nuclides, two possibilities exist; they could be products of energetic particle interactions taking place in a presolar or early solar environment, or, they could have been produced in a stellar source and injected into the protosolar molecular cloud just prior to its collapse. The presently available data appear to support the latter case and put a stringent constraint of less than a million years for the time scale for the collapse of the protosolar molecular cloud to form the Sun and some of the first solar system solids. This short time scale also suggests the possibility of a triggered origin for the solar system with the very process of injection of the short-lived nuclides acting as the trigger for the collapse of the protosolar molecular cloud. Fossil records of the short-lived nuclides in meteorites also provide very useful chronological information on the early solar system processes like the time scale for nebular processing, the time scales for differentiation and for metal/silicate fractionation within planetesimals. The currently available data suggest a time scale of a few million years for nebular processing and a relatively short time scale of about ten million years within which differentiation, melting and recrystallization in some of the planetesimals took place.     

A Two-Dimensional Zonally Averaged Ocean Carbon Cycle Model

ＡＴｗｏ－ＤｉｍｅｎｓｉｏｎａｌＺｏｎａｌｙＡｖｅｒａｇｅｄＯｃｅａｎＣａｒｂｏｎＣｙｃｌｅＭｏｄｅｌＸｕＹｏｎｇｆｕ（徐永福）ａｎｄＷａｎｇＭｉｎｇｘｉｎｇ（王明星）ＬＡＰＣ,ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ,Ｃｈｉｎｅｓ...     

1979年5月东南亚夏季风的建立和青藏高原的作用

东南亚夏季风开始于5月,它是大气环流向夏季环流过渡的一个重要阶段。本文用FGGE-IIIb全球网格点资料,分析1979年4月26日到5月25日,大范围（40°S～50°N,30～160°E）温度、湿度和风场变化特征,计算了垂直速度、辐散风场、热源和水汽汇收支,研究了东南亚夏季风的性质和来源,其中着重分析了青藏高原的热力和动力作用与东南亚夏季风建立的关系。东南亚夏季风建立的主要因素是中纬度的环流形势,来自热带海洋的西南气流和青藏高原的作用。东南亚夏季风开始时,高空大气环流发生调整,青藏高原上空为波脊,两侧为波槽。低空东南亚夏季风区的辐合气流有四个来源:1）同经度范围的偏南辐散风,2）高原南侧的偏西辐散风,3）高原东侧的偏北辐散风,4）西太平洋上的偏东辐散风。分析表明,东南亚夏季风降水受高原西南侧的中纬度西风带波动影响。低空西南气流来源于80～120°E的南半球热带地区,西南气流输送水汽并且加强低空辐合。主要的热源位于东南亚,主要是潜热释放形成的,它是驱动东南亚夏季风环流的主要机制。整个分析期,青藏高原是一热源,抬升的感热加热和动力作用形成和维持了高原上空的高压脊和两侧的波槽,从而有助于东南亚夏季风的建立。     

典型纳污坑塘周边地下水污染来源识别及其健康风险评估

以典型纳污坑塘(污水库)周边地下水水质监测数据为基础,在对区内地下水污染源进行分析的基础上,采用水环境健康风险评估模型,对区内地下水污染健康风险进行了系统评价研究.污染来源识别结果表明:纳污坑塘周边第Ⅰ、第Ⅱ含水层地下水污染严重,其污染源主要为坑塘内堆放的工业污水以及工业废渣.污染健康风险评估结果表明:8号坑附近第Ⅰ含水层中砷浓度以及北库南侧第Ⅱ含水层中1,2-二氯乙烷总致癌风险分别为10-2、10-3数量级,远超可接受风险水平10-6.不同含水层中污染物平均致癌风险大小关系为,第Ⅰ含水层:砷>1,2-二氯乙烷;第Ⅱ含水层:1,2-二氯乙烷>砷>1,1,2-三氯乙烷>四氯化碳.1,2-二氯乙烷等挥发性有机污染物4种潜在暴露途径的平均致癌风险大小关系表现为:饮用地下水>皮肤接触地下水>经室外吸入空气中气态污染物>经室内吸入空气气态污染物.相对于敏感用地,非敏感用地污染物的总致癌风险以及危害商较低.     

SOIL FINGERPRINTING IN THE PALOUSE BASIN, USA USING STABLE CARBON AND NITROGEN ISOTOPES

1 INTRODUCTION Watershed restoration efforts have been accelerated in recent years by mandates in the Clean Water Act, the Endangered Species Act, and increasing pressure from environmental groups (Wagner and Roberts, 1998). To address these mandates, water-quality management plans and Total Maximum Daily Loads (TMDLs) have been developed for surface waters, such as streams placed on the 303(d) list because of beneficial use impairment. Commonly, much of the degradation of surface…