夏季红枫湖地区农田土壤-大气界面汞交换通量的初步研究

采用动力学通量箱法(Dynamic Flux Chamber)与高时间分辨率大气测汞仪联用技术对贵州红枫湖地区土壤-大气界面间汞交换通量进行了初步研究.结果显示,红枫湖地区土壤-大气界面间汞交换通量变化范围为-8.6 ng～215.3 ng@m-2@h-1,平均27.4士40.1 ng/m2@h(n=255);且土壤与大气界面间的汞交换是双向的既有土壤汞的释放,又有大气汞的沉降,主要以土壤汞的释放为主(n释放=253,n沉降=2n).土壤汞的释放通量与土壤温度、气温、光照强度有强相关关系,相关系数分别为0.80、0.83、0.74.     

四川雅安地质灾害时空预警试验区初步研究

借鉴美国旧金山湾和香港地区的经验,提出了地质灾害监测预警试验区建设和研究思路。经过近两年的工作,初步建成了四川雅安地质灾害监测预警试验区。取得的阶段性成果主要有:(1)根据现场考察和试验区地质灾害数据库,统计研究了降雨型滑坡的几何特征;(2)建成了由20台遥测雨量计构成的降雨观测网,取得了2002年4月～2003年8月的降雨观测数据;(3)结合历史降雨资料分析,初步研究了雅安试验区的年、日、小时和十分钟最大降雨特征;(4)研制了斜坡岩土体含水量野外监测仪,取得了桑树坡试验点2003年4月～8月的实时监测数据;(5)自上而下分4层研究了斜坡岩土层含水量变化,发现了岩土层含水量变化对降雨过程的滞后性;(6)基于区域地质灾害评价预警的递进分析理论与方法(AMFP),利用地质灾害因子分析结果,分别计算了雅安试验区地质灾害"发育度"和"潜势度";(7)利用2003年8月23～25日的过程降雨观测资料,对雅安试验区在该降雨过程中发生的地质灾害事件进行了时空预警反演模拟研究,计算出的地质灾害"危险度"分布比较符合实际,"危险度"可以作为预警指数使用。     

Hydro-thermal performance of multilayer capillary barriers in arid lands

In this study, a capillary barrier system was designed and tested for an arid land environment. To simulate arid land conditions of high temperature and sub-irrigation systems, the barrier was subjected to thermal and hydraulic gradients in opposite directions; to test the barrier system under these severe conditions, an experimental apparatus was designed and fabricated. The multilayer capillary barrier consisted of three layers made of silica sand, a mixture of sand and bentonite in equal portions, and a mixture of clay (25%) and aggregate (75%). Several one dimensional coupled heat and moisture tests were performed. Temperature variations along the thickness of the barrier were recorded as a function of time, and at the end of each test, the barrier was sliced into small sections, for the determination of volumetric water content as a function of distance from the heat source. The experimental results were discussed in view of the barrier's intended purpose of its ability to store moisture for long time durations. Coupled heat and moisture flow equations were developed and solved numerically via a finite difference method. Diffusivity parameters were calculated by using experimental results, a numerical model, and Powell's conjugate directions method of nonlinear optimization. The model was calibrated and the results were discussed. Good agreement between calculated and experimental results was obtained. This revised version was published online in July 2006 with corrections to the Cover Date.     

Soil moisture potential and water content in the unsaturated zone within the arid Ejina Oasis in Northwest China

Three soil profiles were selected in the Ejina Oasis, northwest China, to determine water content profiles and evolution of soil moisture potentials in the unsaturated zone within the arid area. The total soil moisture potentials have been monitored for about 3 months in 2001 at different depths in the soil profiles. The occurrence and movement of water in the unsaturated zone was analyzed using the zero flux plane (ZFP) method. It is shown that convergent ZFPs and divergent ZFPs may occur at depths between 0.5 and 3.0 m, and that the depth of the ZFPs was controlled by the root zone of plants growing on the land surface. Profiles of the total soil moisture potentials were observed to be coincident with those of the water contents at the three experimental sites. The total soil moisture potential showed a slight increasing trend and the ZFPs tend to vanish from summer to winter as the water extraction by roots decreased. Evapotranspiration through vegetation has an important bearing on the water content and the total potential in the unsaturated zone.     

Optimisation de la quantification des flux de matière en suspension d'un cours d'eau alpin : l'Isère à Grenoble (France)

This study seeks to determine suspended-matter flux of the Isère at Grenoble, one of the most important rivers of the northern French Alps. Since 1994, and especially 1996, systematic samplings of the left bank make it possible to follow in one point the variations of suspended particles and matter (SPM) of this river. But from a single measurement, sometimes not very representative of the whole observable concentrations within the section, it remains still difficult to estimate precisely the SPM flux. The results of this study show in particular the successive appearance of several turbidity gradients, whose occurrence is explained mainly by the hydrological and hydro-sedimentary dynamics of this river. The estimate of these gradients thus makes it possible to extrapolate specific measurements more easily and consequently to daily define the quantities of suspended matter exported by the Isère. Since 1996, the results show a very high flow, specific of the Isère at Grenoble, variable between 124 and more than 460 t km^?2 yr^?1. To cite this article: D. Dumas, C. R. Geoscience 336 (2004).     

内蒙古温带半干旱羊草草原N2O通量及其影响因素

利用静态箱 -气相色谱法于 2 0 0 1～ 2 0 0 3年对内蒙古锡林河流域羊草草原进行了连续 2年的野外定位试验 ,获得羊草草原原状群落与土壤N2 O年排放通量分别在 3 91～ 4 71μgm- 2h- 1以及 5 5 0～ 10 0 3μgm- 2 h- 1范围内变动 ,证明内蒙古温带半干旱羊草草原生态系统是大气中N2 O的源 ;系统分析了羊草草原N2 O通量的季节变化、源汇特征以及关键的环境因子对草地N2 O通量的影响等 ,建立了N2 O通量与环境因子间的回归方程 ;并利用两年连续完整的观测数据对羊草草原N2 O年排放量进行了估算     

应用高光谱遥感数据估算土壤表层水分的研究

土壤水分是土壤的重要组成部分，它在陆地表层和大气之间的物质和能量交换方面扮演着重要角色，寻求快速而准确的方法估算土壤水分具有重要意义。通常，从可见光一近红外对土壤表层水分的估计多是建立在土壤水分与反射率的关系之上的。而在土壤水分含量不高时，土壤水分的增加使土壤光谱反射率在整个波长范围内降低，尤其在760nm，970nm，1190nm，1450nm，1940nm和2950nm等水分吸收波段，而在土壤水分含量较高时，土壤水分的增加会使土壤光谱反射率在某些光谱波段升高。而土壤水分的估计往往是基于土壤水分与土壤水分吸收波段的吸收强度之间的线性关系上，虽然这些经验的方法对于估算某些土壤的表层水分含量是有效的，但这些关系应用于其它条件(如不同种类土壤、土壤湿度变化范围很大的情况)时却面临很多困难，这与土壤的光谱反射率是由土壤的组成成分(土壤水分、有机质、氧化铁和粘土矿物等)的含量和它们在土壤中的分布密切相关。微分技术处理“连续”的光谱是遥感中常用的数学方法，微分技术能部分消除低频光谱成分的影响。现在微分光谱已广泛地应用于研究植被的生物物理参数、矿物和有机质等。然而利用微分光谱对土壤水分反演的研究却鲜见报道。本文通过对实验室中多种不同类型的土壤进行光谱与土壤表层水分含量进行观测，探讨了通过土壤反射率与微分光谱对土壤表层水分的反演方法。4种类型的土壤光谱数据(反射率(R)，反射率倒数的对数(log(1／R))，反射率的一阶微分光谱(dR／dλ)，反射率倒数的对数的一阶微分光谱(d(log(1／R))／dλ))与土壤表层水分之间的关系在本文中得到分析，R与log(1／R)对于不同土壤类型与土壤表层水分都很敏感，说明通过R与log(1／R)反演土壤表层水分受土壤类型的影响很大，而dR／dλ，d(log(1／R))／dλ)对土壤类型却不敏感，对土壤表层水分较为敏感，说明dR／dλ和d(log(1／R))／dλ)对于反演不同类型土壤具有很大的潜力，微分光谱与土壤水分在某些波段具有显著的相关性。通过随机对9种土壤(各具有4个土壤水分)的数据建立反演土壤水分的模型，并其他9种土壤(各具有4个土壤水分)的数据进行验证模型，结果表明，dR／dλ和d(log(1／R))／dλ)能够显著提高R与log(1／R)对于不同土壤类型土壤表层水分的反演精度，由于吸收过程是非线性的，在四种类型的土壤光谱数据中，总体来说，d(log(1／R))／dλ)具有最好的能力预测不同类型土壤的表层水分含量。     

基于通量均衡基准的地壳垂直形变场分析模型

根据全球通量均衡假说建立了地壳垂直形变场的分析模型，在球面近似下求得了该模型的球谐函数级数解并拟合了两个不同区域的地壳垂直形变场，编绘了等值线图，继而在密切平面坐标系下导出了该模型的Fourier级数解。结果表明，该方法不仅具有几何意义，而且具有一定的地球动力学意义。     

Slow mass movement in the Kangchenjunga area, eastern Nepal Himalaya

Abstract   The rates of the accumulated and continuous displacement of solifluction lobes in the Kangchenjunga area, eastern Nepal Himalaya, were determined using glass fiber tubes and a strain probe. Ground temperature, precipitation and soil moisture were monitored at two sites, whose altitude differed by approximately 100 m, to understand the solifluction process. The average movement rate of the glass fiber tubes on a 31° slope at altitudes of 5412–5414 m a.s.l. was approximately 11 mm/year, being almost threefold greater than that observed on a 22° slope at 5322–5325 ma.s.l. There was no significant difference in the depth of displacement at these sites. The continuous displacement measurement near the ground surface at 5414 m showed permanent downslope movement from early July. Such movement may be attributed to additional moisture supply during the monsoon season. The amplitude of the displacement cycle was highest at the ground surface, and decreased to virtually zero at and below 20 cm in depth. Probable factors leading to the relatively slow rates of downslope displacement at the surface and depth at the studied altitudes are the lack of concurrence of the freeze–thaw cycles and the high moisture condition in the soil, and the low moisture retention capacity of the soil because of steep slopes and superficial desiccation. The rate of displacement may be more pronounced at altitudes above 5600 m because of the freeze–thaw cycles during the summer season.     

内蒙古中西部地区土壤水分对沙尘暴的贡献

以2001年4月至2002年6月内蒙中部地区逐时观测的土壤水分资料为基础，论证了该区日土壤水分和日平均风速的变化规律，统计分析了日平均风速与土壤水分对沙尘暴的成生综合贡献。得出的主要结论是：①该地区沙尘暴发生时日平均风速的最小值是3．5m／s。如果日平均风速大于8．0m／s，预示着有沙尘暴的发生。②在平均风速大于3.5m／s的条件下，观测样本中18．4％日数发生沙尘暴，而81．6％日数没有发生。说明大风的天气条件不应当被视其为沙尘暴的唯一重要的因子。③在同一地点、同样的风力条件下，在沙尘暴发生时，日平均风速与日平均土壤水分呈明显的反相关变化；而它们的反相关关系不明显时，沙尘暴就很少发生。