成都经济区农业生态系统土壤镉通量研究   总被引：5，自引：2，他引：5  

汤奇峰  杨忠芳  张本仁  金立新  刘爱华 《地质通报》2007,26(7):69-877

以四川成都经济区农业生态系统中的重金属Cd为对象,对其在土壤中的输入输出通量进行初步探索。综合各方面的因素,确定以大气干湿沉降、灌溉水、化肥为输入途径和农作物为输出途径进行研究。经过计算,经济区大气干湿沉降通量平均值为17.76g/hm2·a,灌溉水和化肥通量明显较低,三者对土壤Cd污染的贡献率分别为86%、10%和4%。对于6个不同的地区,三者比例略有差别,大气干湿沉降所占比例最高达94%,最低也达到了77%。Cd通过农作物收割输出的量相对较小。土壤Cd年净增量主要受大气干湿沉降的制约,因此大气环境质量应是重点监控的对象。以耕作土体为研究介质,经估算,当前的Cd年平均通量可引起土壤Cd的质量分数升高0.006mg/kg。  相似文献   

青藏高原羌塘中部果干加年山上三叠统望湖岭组的建立及意义   总被引：7，自引：3，他引：7  

李才  翟庆国  董永胜  于介江  黄小鹏 《地质通报》2007,26(8):1003-1008

在果干加年山的主脊及其以北识别出一套稳定的沉积岩系,角度不整合于蛇绿混杂岩之上,以细砂岩、硅质粉砂岩为主,其中夹有大小不等的古生代外来岩块,底砾岩成分因地而异并具有快速堆积的特点,底部夹有流纹岩。厚度大于1633m。流纹岩夹层获得的锆石SHRIMPU-Pb谐和年龄为214Ma±4Ma,时代为晚三叠世诺利期。在剖面测制和区域对比的基础上建立了上三叠统望湖岭组,代表龙木错-双湖缝合带闭合以后接受的最早的沉积盖层。望湖岭组之下的蛇绿混杂岩获得阳起石Ar-Ar年龄219.7Ma±6.5Ma。同位素定年确定构造转化事件发生在214～220Ma之间,为龙木错-双湖缝合带的闭合时间提供了确切的时间约束,望湖岭组是这一事件的沉积记录,是龙木错-双湖缝合带蛇绿混杂岩之上首次发现的沉积盖层。  相似文献   

RESERVOIR SEDIMENTATION AND LAND USE IN TAIWAN WUSHEH WATERSHED     

Su Chin CHEN 《国际泥沙研究》1998,(3)

ＲＥＳＥＲＶＯＩＲＳＥＤＩＭＥＮＴＡＴＩＯＮＡＮＤＬＡＮＤＵＳＥＩＮＴＡＩＷＡＮＷＵＳＨＥＨＷＡＴＥＲＳＨＥＤＳｕＣｈｉｎＣＨＥＮ１ＡＢＳＴＲＡＣＴＷｕｓｈｅｈＲｅｓｅｒｖｏｉｒｉｓａｇｏｒｇｅｔｙｐｅｈｙｄｒｏｐｏｗｅｒＲｅｓｅｒｖｏｉｒｏｎＷ...  相似文献   

The Characteristics of Spinels in Mantle-derivedXenoliths in Cenozoic Basalts from Eastern Chinaand Their Thermal States     

DONG Zhenxin Geological Museum of Chin  Xisi  Beijing 《《地质学报》英文版》1998,72(3):271-281

The colours and chemical composition variations of 160 spinels in peridotite and pyroxenite xenoliths from Cenozoic basalts in eastern China and their petrogeneses have been studied in detail. The relationships between major elements of spinels are discussed. The equilibrium temperatures, pressures and oxygen fugacities of spinels and their coexisting olivines, orthopyroxenes and clinopyroxenes have been determined using the Brey-kohler' s T-P calculation methods (1990) and Ballhaus' fo2 calculation method (1991). The relationships betweenthe composition and the equilibrium temperatures, pressures or oxygen fugacities of spinels in peridotite xenoliths from the basalts and the stable field of the spinels in the upper mantle have been shown.  相似文献   

Mechanism of the reservoir impounding earthquakes at Hsinfengkiang and a preliminary endeavour to discuss their cause     

Wang Miao-yueh  Yang Mao-yuan  Hu Yu-liang  Li Tzu-chiang  Chen Yun-tai  Chin Yen  Feng Jui 《Engineering Geology》1976,10(2-4):331-351

After the filling up of the Hsinfengkiang Reservoir Kwangtung Province, seismicity was greatly increased. The majority of earthquakes occurred in the deep water gorge close to the dam, concentrated within a northwest belt. They are usually of shallow focal depths. A strong earthquake with magnitude 6.1 took place on March 19, 1962, about two and a half years since the impounding of the reservoir.

According to the results of analysis of data from geodetic leveling and the spectra of seismic waves, the fault parameters of the main shock were determined. The fault plane solutions of 150 small earthquakes, occurring within a period of 18 months before and after the main shock were determined from the amplitudes of the first motion of P wave. The directions of the earthquake generating stress of about 2000 small earthquakes were obtained by smoothing the first motion patterns. Displacement field and stress field in the rock bodies underneath the reservoir caused by the loading of the reservoir water were calculated. Variations of the velocity ratio of the P and S waves prior to the main shock and several strong aftershocks were analysed.

In consideration of the seismicity as well as the geological background, we endeavour to discuss the cause of reservoir impounding earthquakes at Hsinfengkiang. We have the opinion that the penetration of water along fissures becomes the most important cause of the main shock of March 19, 1962 at Hsinfengkiang.  相似文献   

Delineation of spatial redox zones using discriminant analysis and geochemical modelling in arsenic‐affected alluvial aquifers     

Jin‐Jing Lee  Cheng‐Shin Jang  Sheng‐Wei Wang  Chin‐Ping Liang  Chen‐Wuing Liu 《水文研究》2008,22(16):3029-3041

This study characterized the redox conditions in arsenic‐affected groundwater aquifers of the Lanyang plain, Taiwan. Discriminant analysis was adopted to delineate three redox zones (oxidative, transitional and reductive zones) in different aquifers and yielded 92·3% correctness on groundwater quality data. Arsenic is mainly distributed in the reductive zone, and arsenic distribution in the shallow aquifer is mainly affected by surface activities. According to PHREEQC modelling results, possible mechanisms for arsenic release to groundwater in Lanyang plain are explored. Arsenic released to groundwater in the oxidative zone (zone 1) is primarily caused by the oxidations of arsenic‐bearing pyrite minerals, and arsenate is the predominant species. While the reductive dissolution of Fe‐oxides are responsible for the high arsenic concentration found in the transitional and reductive zones (zones 2 and 3), arsenite is the predominant species. The reduction potential of groundwater rises as the depths and zones increase. Some sulphates may be reduced to form sulphide ions, which then react with arsenic to form arseno‐sulphide deposits (such as realgar, orpiment) and then slightly lower groundwater arsenic concentrations. A conceptual diagram which summarized the possible release processes of arsenic in different redox zones along groundwater flow in Lanyang plain is postulated. Arsenic‐bearing pyrite and arsenopyrite (FeAsS) are oxidized as they are exposed to the infiltrated oxygenated rainwater, releasing soluble arsenate Fe(II) and SO₄^2? into zone 1. The dissolution of arsenic‐rich Fe‐oxides due to the onset of reducing conditions in zones 2 and 3 is responsible for the mobility of arsenic and likely to be the primary mechanism of arsenic release to groundwater in the Lanyang plain Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Analysis of geomorphologic and hydrological characteristics in watershed saturated areas using topographic‐index threshold and geomorphology‐based runoff model     

Chin‐Hsin Chang  Kwan Tun Lee 《水文研究》2008,22(6):802-812

The objective of this paper is to investigate the variation of geomorphology and runoff characteristics in saturated areas under different partial contributing area (PCA) conditions. Geomorphologic information and hydrologic records from two mid‐size watersheds in northern Taiwan were selected for analysis. The PCA ratio in the watershed during a storm was assumed equal to the ratio of the surface‐flow volume to the direct runoff volume from measured hydrologic data. The extents of PCA regions were then determined by using a topographic‐index threshold. Consequently, the geomorphologic factors in saturated and unsaturated areas could be calculated using a digital elevation model, and these factors could then be linked to a geomorphology‐based IUH model for runoff simulation, which can consider both the surface‐ and subsurface‐flow processes in saturated and unsaturated areas, respectively. The results show that geomorphologic characteristics in the saturated areas vary significantly with different PCA ratios especially for higher order streams. A large PCA ratio results in a sharp hydrograph because the quick surface flow dominates the runoff process, whereas the hydrologic response in a low PCA case is dominated by the delayed subsurface flow. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

The structure of ocean-surface currents measured by Doppler radar     

Chin  D.A. Chinthamreddy  S. Shay  L.K. Graber  H.C. 《Oceanic Engineering, IEEE Journal of》1997,22(1):156-167

The spatial structure of surface currents collected using a Doppler Radar system off the Florida Keys has been investigated. Surface current vectors were acquired within a rectilinear grid containing 700 nodes, where each node was spaced 1 km apart. Principal component analyses indicate that at least 63% of the variance of the surface currents at the 700 nodal locations can be accounted for by only three principal components. The principal modes of circulation during two separate experiments were extracted and found to be basically the same, although the first two modes were reversed between the two experiments. Coherence spectra were determined for nodal spacings between 1.76 km and 10.48 km, and the results of these analyses indicate that over most of the experimental area, approximately 60% of the variance is coherent over separations of 10.48 km. Application of a synoptic time-series model indicates that accurate prediction of the mean currents over each of the 65-h subrecord lengths was the dominant factor in controlling model performance, and that on the order of 10% error could be expected in using the time-series model to predict the low-frequency fluctuations. This indicates that time-series modeling of surface currents may be feasible and useful in estimating the long-term mixing characteristics of contaminants transported in the surface layer  相似文献   

Matrix methods in synthetic seismograms     

R. C. Y. Chin  G. W. Hedstrom  L. Thigpen 《Geophysical Journal International》1984,77(2):483-502

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太行山前平原非河道条件下地下调蓄功能实验研究--以滹沱河冲洪积平原为例   总被引：5，自引：0，他引：5  

张光辉费宇红  邢开刘克岩  王金哲申建梅 聂振龙 《水文》2004,24(2):15-19

摘要：通过实验研究探讨了太行山前平原地下调蓄能力,实验研究表明,在汇水坑渗、井灌和引水渠渗条件下,太行山前冲洪积平原地下调蓄功能不仅与地表积水深度、入渗时间有关,而且还与汇水总量的多少有关。单位时间渗漏量的大小与地表蓄水深度呈正相关关系。地表蓄水深度愈大,单位时间渗漏量愈大;累计渗漏量随着入渗时间的延长而增加,渗漏速率随着累计渗漏量的增加而减小。采用井灌方式进行地下调蓄的关键,是选择具有强渗透性的层位。  相似文献