NO3-中15N和18O同位素新技术在岩溶地区地下水氮污染研究中的应用——以河南林州食管癌高发区研究为例   总被引：13，自引：1，他引：12  

杨琰  蔡鹤生  刘存富  周爱国 《中国岩溶》2004,23(3):206-212

介绍了在野外用阴离子交换树脂收集地下水中的NO-3的新技术,以及用AgNO3 和氧化铜丝及铜颗粒燃烧反应测定氮同位素比值;用AgNO3+ C(石墨)生成CO2 测定NO-3 中氧同位素比值的密封石英管燃烧法。安阳和林州岩溶区饮用水中广泛的NO-3 - N污染大大超过饮用标准,食管癌的死亡率与饮用水中NO-3 、NO-2 、NH+4 和亚硝胺过剩的含量成正比。δ18O和δ15N资料证实,饮用水中的NO-3主要来自农家肥和化肥,这个地区没有发生有意义的反硝化作用,而以硝化作用为主。在食管癌低发区(东部)存在反硝化作用而使该区地下水中硝酸盐含量降低。δ18O和δ15N资料还表明氧化环境中可能出现局部反硝化作用。   相似文献   

华东地区稻麦轮作农田生态系统N2O排放的模拟研究   总被引：7，自引：0，他引：7  

勾继  郑循华  王明星  李长生 《大气科学》2000,24(6):835-842

利用DNDC（DeNitrification and DeComposition）模式,对华东地区典型稻麦轮作农田生态系统的N2O排放特征进行了模拟研究。结果表明：该模式能模拟出轮作周期中N2O的主要排放峰值和排放趋势,但与实测值相比,模拟结果普遍有些偏小。相对而言,该模式对旱地阶段的模拟结果比较理想,尤其是对春季小麦返青至成熟期的模拟最好。因此,我们就该阶段影响N2O排放的主要因子进行了敏感性研究。结果指出,对这一阶段N2O排放影响最大的是化肥的施用,其他比较重要的影响因子还包括犁地方式、有机肥、降水量、降水中的N含量以及温度等。  相似文献   

多项式拟合技术在煤田地震勘探中的应用   总被引：6，自引：3，他引：3  

崔若飞  王辉 《地球物理学进展》2000,15(2):47-54

本文讨论了三种多项式拟合方法在煤田地震勘探中的应用情况 .它们可以消除动校拉伸对波形的影响以及普通叠加的低通滤波效应 ,保持了振幅的真实形态和较高的频率信息 ,能得到较高分辨率的零炮检距剖面 ,有利于地震资料的构造解释和岩性研究 .  相似文献   

青藏高原高寒草原生态系统CO2,CH4和N2O排放通量研究   总被引：4，自引：1，他引：3  

裴志永  欧阳华  周才平  XU Xingliang 《地理学报(英文版)》2003,13(1):27-34

Using static chamber technique, fluxes of CO2, CHh and N2O were measured in the alpinegrassland area from July 2000 to July 2001, determinations of mean fluxes showed that CO2 and N2Owere generally released from the soil, while the alpine grassland accounted for a weak CH4 sink.Fluxes of CO2, CH4 and N2O ranged widely. The highest CO2 emission occurred in August, whereasalmost 90% of the whole year emission occurred in the growing season. But the variations of CH4and N2O fluxes did not show any clear patterns over the one-year-experiment. During a dailyvariation, the maximum CO2 emission occurred at 16:00, and then decreased to the minimumemission in the early morning. Daily pattern analyses indicated that the variation in CO2 fluxes waspositively related to air temperatures (R2=0.73) and soil temperatures at a depth of 5 cm (R2=4).86),whereas daily variations in CH4 and N2O fluxes were poorly explained by soil temperatures andclimatic variables. CO2 emissions in this area were much lower than other grasslands in plain areas.  相似文献   

Carbonate removal by acidification causes loss of nitrogenous compounds in continental margin sediments   总被引：1，自引：0，他引：1  

Lutz Lohse  Rikus T. Kloosterhuis  Henko C. de Stigter  Willem Helder  Wim van Raaphorst  Tjeerd C. E. van Weering 《Marine Chemistry》2000,69(3-4)

This study reports on measurements of organic carbon (C_org) and total nitrogen (N_tot) in surface sediments originating from 6 transects along the northwest European continental margin. After elimination of carbonates by an acidification technique using sulphurous acid, both elements were analysed in the same sediment sample using an elemental analyser. C_org and N_tot in the sample were comparatively low, ranging between 1 and 10 mg C and 0.2 to 1 mg N g⁻¹ dry sediment. In a second analysis, the samples were analysed without acid addition, resulting in N_tot concentrations of 0–50% higher compared to their acidified counterparts. As a consequence, molar C/N ratios derived from the analysis of C_org and N_tot in the acidified sample ranged between 6 to 11, while the N_tot separate analysis reduced C/N ratios to 6 to 8. It is suggested that the addition of sulphurous acid to eliminate inorganic carbon volatilises nitrogenous organic matter.  相似文献   

西北太平洋风场和海浪场特点分析   总被引：6，自引：1，他引：5  

刘金芳  孙立尹 《海洋预报》2000,17(3):54-62

本文根据1950～1995年共46a的西北太平洋气象船舶报资料,按5°×5°网格统计的风、浪要素进行分析研究,阐明了西北太平洋风、浪、涌的特点及其变化规律。该区是世界最典型的季风气候区,季风时期的风向、浪向、涌向基本一致,赤道地区常年盛行东北浪。冬季季风比夏季季风强盛,相应的平均波高、大浪大涌频率也较大。该海域与北印度洋同属季风气候区,但其特点正好相反。本文为船舶在西北太平洋航行、作业和科学试验以及军事活动,提供了较翔实的风场和浪场资料及变化规律。  相似文献   

青藏高原东北部末次间冰期以来的古气候──以若尔盖盆地RM孔分析为例   总被引：8，自引：1，他引：7  

薛滨  王苏民  吴敬禄  钱君龙 《海洋与湖沼》1999,30(3):327-332

于１９９３年在青藏高原东北部若尔盖盆地沉积中心钻取一长３１０ｍ的湖泊岩芯,对其上部３１ｍ的湖泊沉积物进行了年代测定以及自生碳酸盐氧同位素,有机碳氮分析,重建了１４万ａ来的古气候演化过程,基本上可以区分出５个阶段。结果表明,５阶段（１４０－８０ｋａＢ．Ｐ）气候温暖湿润,内部又可区分出５ａ－５ｅ,４阶段（８０－６０ｋａＢ．Ｐ）气候以冷干为主;３阶段为相对湿湿期,降水丰富,流域径流量较大;３０ｋａＢ．Ｐ  相似文献   

Dehydration melting and devolatilization during exhumation of high-grade metapelites: the Tatra Mountains, Western Carpathians   总被引：1，自引：0，他引：1  

Janák  Hurai  Ludhová  O'Brien  & Horn 《Journal of Metamorphic Geology》1999,17(4):379-395

Partial melting and retrogression related to Variscan tectonic exhumation have been recognized in the high-grade metapelites of the Tatra Mountains, Western Carpathians. Staurolite and kyanite relics document an early stage of the prograde metamorphism at c. 600 °C and 9–10 kbar. An increase in temperature to >730 °C at 11–12 kbar resulted in partial melting and incipient migmatization in the stability field of kyanite. Further heating at decreasing pressure during the earliest stage of exhumation led to the dehydration-melting of muscovite and biotite at >750–800 °C and 6–10 kbar, producing garnet-bearing granite as leucosomes in migmatite. Subsequent cooling is documented by garnet resorption by biotite and sillimanite (a reversal of the prograde biotite dehydration-melting reaction). This was followed by nearly isothermal decompression to c. 4–5 kbar producing cordierite and some melt due to biotite decomposition. Later nearly isobaric cooling led to cordierite pinitization and formation of orthoamphibole, chlorite and carbonates. Densities of primary, monophase CO₂–N₂ inclusions (0.69–1.06 g cm^?3) from the migmatite leucosome are consistent with the near-peak and retrograde conditions. Highly varying N₂ contents (5–30 mol%) are thought to result from the nitrogen uptake in retrograde K-bearing minerals, or dilution by CO₂ liberated during interaction of melt-derived water with metapelite graphite. The relatively high nitrogen content, not observed until now in migmatites, could have been inherited from the high-pressure metamorphism stage. It is assumed that the water-absent composition of fluid inclusions is not representative of the bulk water content (X_H2O≤0.7), which was masked by mechanical separation of the CO₂- and H₂O-dominated immiscible phases, and/or by post-entrapment modifications of the fluid inclusions. Decompression and the final stage of exhumation were accomplished by top-to-the-south thrusting as well as west–east (orogen-parallel) extension. They were most probably related to regional uplift and gravitational collapse of thermally weakened Variscan crust.  相似文献   

Nitrogen and Oxygen Isotope Balance in Tropospheric N2O—An Improved Budget     

徐文彬  洪业汤等 《中国地球化学学报》1999,18(2):187-192

In steady state the stable isotopic composition of nitrogen and oxygen in tropospheric N2O is balanced by isotopically light N2O emitted from soils and oceans and isotopically heavy N2O as a return flux from the stratosphere.However,no such balance was reached in calculations given by Kim and Caig(1993).Modifications have been made on their calculations based on the most recent reports on annual global emission of N2O.It is considered that the nitrogen and oxygen isotope budget in tropospheric N2O are approximately in balance if isotopic fractionation effects during the production of N2O in soils and furthermore this paper puts forward further evidence for validating the above results.  相似文献   

廉州湾富营养化与赤潮形成的研究     

韦蔓新  何本茂 《热带海洋学报》1998,(4)

根据1995年的调查资料,概述了廉州湾沿岸海域营养盐的分布特征及与水化因子之间的关系。以化学耗氧量（COD）、无机磷（P）、无机氮（N）为评价指标,分析评价了该湾的富营养化程度,指出该湾赤潮形成的主要因素是陆源营养物质的排人,通过N／P值,表明了N是该湾初级生产力的主要限制因子。  相似文献