基于地形指数的流域非点源磷素输出关键源区识别   总被引：2，自引：1，他引：1       下载免费PDF全文

王妞  陆海明  邹鹰  陈晓燕  朱乾德 《水文》2016,36(2):12-16

以非点源污染形式输出的磷素是导致水体富营养化的主要原因,识别流域磷素输出的关键源区并进行重点整治是控制流域非点源磷素污染的重要手段。以修正的磷指数法为基础,引入地形指数因子,建立了流域非点源磷素输出风险评价方法,并以位于江淮丘陵区的西源流域为例开展了磷素输出风险评价,识别了该流域磷素输出的关键源区。结果表明,西源流域磷素输出关键源区主要集中在下游河道、沟渠两侧农田区域,占流域总面积的8%。  相似文献   

西藏错那洞淡色花岗岩地球化学特征、成岩时代及岩石成因     

林彬  唐菊兴  郑文宝  冷秋锋  林鑫  王艺云  孟展  唐攀  丁帅  徐云峰  袁梅 《岩石矿物学杂志》2016,35(3):391-406

错那洞淡色花岗岩是西藏北喜马拉雅淡色花岗岩带的重要组成部分。通过地球化学分析揭示其具有富硅(SiO_2含量为74.20%~74.52%)、贫铁(Fe_2O_3含量为0.04%~0.20%,FeO含量为0.40%~0.58%)、贫镁(MgO含量为0.06%~0.14%)、钙碱性(σ为2.15~2.32)、强过铝质(A/CNK为1.11~1.15)的地球化学特征。稀土元素总量较低(∑REE为47.24×10~(-6)~57.59×10~(-6)),轻稀土元素富集(LREE为39.85×10~(-6)~49.23×10~(-6)),重稀土元素亏损(HREE为6.91×10~(-6)~8.68×10~(-6)),有明显负Eu异常(0.49~0.80);富集Rb、Th、U、K等大离子亲石元素,亏损Nb、Ta、Zr、Ti等高场强元素。锆石U-Pb测年结果显示,错那洞淡色花岗岩形成中新世(21 Ma),属北喜马拉雅淡色花岗岩晚阶段峰值期(24~12 Ma)产物。锆石εHf(t)值为负值,且变化较大(-3.92~-17.64),说明其岩浆源区为壳源,以变泥质岩为主,可能存在多种物质组分的混合。初始岩浆结晶温度应不超过675~702℃,构造背景为后碰撞环境,是高喜马拉雅结晶岩系在板片快速折返过程中发生减压熔融而形成的产物。  相似文献   

Contribution of soil fauna respiration to CO<Subscript>2</Subscript> flux in subtropical Moso bamboo (<Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>) forests: a comparison of different soil treatment methods     

Yan Jiang  Bing Wang  Xiang Niu  Zhixin Dong  Peng Wang 《Environmental Earth Sciences》2016,75(13):1047

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A novel hybrid KPCA and SVM with PSO model for identifying debris flow hazard degree: a case study in Southwest China     

Xin Qian  Jian-Ping Chen  Liang-Jun Xiang  Wen Zhang  Cen-cen Niu 《Environmental Earth Sciences》2016,75(11):991

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Evaluation of sediment amendment with zirconium-reacted bentonite to control phosphorus release   总被引：1，自引：0，他引：1  

Jianwei Lin  Hong Wang  Yanhui Zhan  Zhe Zhang 《Environmental Earth Sciences》2016,75(11):942

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鄂尔多斯盆地陇东地区延长组长8₂优质储集层成因机理研究^*          下载免费PDF全文

徐黎明  李志成  梁晓伟  纪友亮  牛小兵  叶博  郝炳英  马继业  尤源 《古地理学报》2016,18(2):237-250

鄂尔多斯盆地陇东地区长8₂储集层平均孔隙度为8.8%,平均渗透率为0.64×10^-3μm²,属于低孔低渗储集层。强烈的压实作用是储集层物性变差主要原因,碳酸盐胶结作用促使储集层物性进一步变差。尽管储集层物性整体较差,但在普遍低孔低渗背景下仍发育相对高孔渗的优质储集层。对优质储集层进行了分析,总结了优质储集层的典型特征,统计表明:优质储集层的塑性组分含量较低,孔隙类型以绿泥石胶结残余粒间孔和溶孔为主,孔隙结构以中小孔—中细喉为主。在此基础上,分析了优质储集层成因机理。研究认为:分流河道、河口坝等微相高能厚层砂体有利于优质储集层发育,相对低的塑性组分含量和绿泥石环边胶结有利于粒间孔隙的保存,溶蚀作用是次生孔隙形成的最主要成岩作用。  相似文献   

Effect of earth–air breathing on evaporation of deeply buried phreatic water in extremely arid regions     

Hongshou Li  Hongtao Zhan  Xiaowei Wang  Qinglin Guo  Wenjun Liu  Yanfei Li  Yipu Gong 《水文研究》2021,35(4):e14078

In extremely arid regions, deeply buried phreatic water evaporates during the daytime from March to November in the northern hemisphere. It has been found that the earth–air undergoes ‘autonomous breathing’ and ‘passive breathing’, respectively caused by the changes of temperature and atmospheric pressure. In this paper, the effects of these breathing modes on phreatic evaporation (PhE) were investigated as well as the responsible mechanisms. Quantitative estimates suggest that the direct contribution from autonomous breathing is only 0.55 g·m⁻²·yr⁻¹. Passive breathing pumps water vapour upwards from the deeply buried phreatic water table. Film water on the soil continuously migrates in pulsation from deep layers to the upper layer. Na₂SO₄ in the shallow soil absorbs moisture from the earth–air at night and decomposes during the day, forming water vapour, which is critical to the occurrence of PhE. The diurnal PhE process can be elucidated in detail by the bimodal variation in the atmospheric pressure. PhE occurs mainly from 10:00 to 17:00 during daytime from March to November, which correlates with passive breathing of the earth–air. The amplitude of atmospheric fluctuation determines the amount of earth–air that outflows, while temperature determines the water vapour concentration. In calculation, PhE is equal to the net absolute humidity (AH) times the amount of earth–air. There is 1.55 mm·year⁻¹ of PhE caused by daily peak→valley differences, and about 2.97 mm·year⁻¹ in estimation caused by numerous atmospheric fluctuations smaller than 2.84 hPa. The results coincide with the actual amount of PhE monitored of 4.52 mm·year⁻¹. Therefore, the amount of PhE is proportional to the range and frequency of fluctuation in external atmospheric pressure, and is also positively related to soil temperature, salt content, water content, porosity, and vadose zone thickness.  相似文献   

Field of tectonic stresses from focal mechanisms of earthquakes and recent crustal movements from GPS measurements in China     

V. A. Petrov  Niu Anfu  V. B. Smirnov  A. O. Mostryukov  Li Zhixiong  A. V. Ponomarev  Jiang Zaisen  Shen Xuhui 《Izvestiya Physics of the Solid Earth》2008,44(10):846-855

Orientations of the principal axes of the tectonic stress field reconstructed from seismological data on focal mechanisms of earthquakes and strain fields determined from GPS measurements in China are compared. The data of GPS measurements used in the paper were obtained by the Crustal Movement Observation Network of China (about 1000 stations) in the period of 1998–2004. On the basis of information on the recent horizontal crustal motions, the strain field is calculated for the study territory by the finite element method. Calculations of the strain tensor using GPS data were carried out with a step of 1° in latitude and longitude. A catalog of earthquake focal mechanisms was used for the reconstruction of tectonic stress field components. Focal mechanisms of earthquakes were calculated with the use of seismological data on signs of first arrivals from the bulletin of the International Seismological Center. To estimate characteristics of the regional stress field, an approach based on the kinematic method proposed by O.I. Gushchenko was applied. The tectonic stress field was reconstructed in depth intervals of 0 < H < 35 km and 35 km < H < 70 km from data on focal mechanisms of earthquakes over the periods of 1998–2004 and 1985–2004. Comparison of directions of the principal strain axes at the surface (according to GPS measurements) and directions of the principal stress axes (reconstructed from focal mechanisms of earthquakes) showed their good convergence. Seismotectonic strains and GPS measurements coincide within a larger part of the territory. The coincidence is best in a depth interval of 0 < H < 35 km. Maximum misfit values are confined to areas of high 3-D gradients of strain axis directions and are possibly related to the structural heterogeneity of the region, zones with strains of the same type along both horizontal axes (compression or extension along all directions), or areas of small absolute values of recent horizontal movements. Areas with invariable directions of the stress axes are recognizable regardless of the depth of initial data. Good reproducibility of results obtained by two different methods made it possible to check the method of stress field reconstruction using data on focal mechanisms of earthquakes.  相似文献   

琼州海峡水沙输运特征研究   总被引：5，自引：0，他引：5  

李占海  柯贤坤  王倩  高建华 《地理研究》2003,22(2):151-159

根据1995年2～3月在琼州海峡两岸12个站点的同步观测资料,本文集中分析研究了海峡的水沙输运特征。琼州海峡潮流作用活跃,流速平均在015～074ms^-1(大潮)和012～051ms^-1(小潮)之间。海峡悬沙浓度大小潮十分接近(分别为0028kgm^-3、0026kgm^-3),并具有明显的时间性和地域性。周日单宽悬沙输运量在30～11000kg之间。潮流和波浪产生的泥沙再悬浮对海峡含沙量有较大影响,潮流作用还造成底质沉积物的运动,海峡周日单宽推移质输运率最大可达16400kg。受潮波系统和地形地貌影响,海峡北岸输水、输沙方向以西向为主,南岸以东北、东南向为主,流速、余流、悬沙输运通量皆具有大潮强于小潮,北岸强于南岸的特点  相似文献   

雪峰山西侧重点白云岩储层成岩、储集特征 及质量影响因素     

李嵘  张娣  赵瞻  朱丽霞 《地质通报》2012,31(11):1852-1861

雪峰山西侧地区下古生界中—上寒武统和震旦系灯影组白云岩是潜在的重要油气储集层。作为主要目的层段,本区的白云岩类型主要包括结晶白云岩、残余颗粒白云岩、灰质白云岩和藻白云岩四大类。白云岩储层总体上均属于低—特低孔、低—特低渗储层。影响储层发育的成岩事件包括重结晶作用、白云岩化作用、溶蚀作用、破裂作用等。研究表明,白云岩结晶程度可以影响其初始孔隙的发育程度,具粉晶—细晶结晶程度的白云岩具有最好的孔渗性。白云岩化作用的强弱对储层物性具有较为直接的影响。最佳白云岩储层中主要储集空间包括晶间孔隙(包括剩余晶间孔和晶间溶蚀孔)、次生溶孔、洞和裂缝。总体上,较强的白云岩化作用、一定程度的重结晶、较发育的微裂缝、较好的区域渗透性、晚期压溶缝合线发育和晚期较大构造缝不发育等因素有利于白云岩储层的发育。  相似文献