林草复合经营模式养分动态关系   总被引：2，自引：0，他引：2  

王海明  李贤伟  陈治谏  王海娥 《山地学报》2006,24(2):156-160

林草复合经营模式在目前的退耕还林工程中起着重要的作用，研究林草复合模式的林与草之间的营养元素关系，通过对不同林草养分的研究得出林木、草、土壤之间的养分动态关系，对矿质养分相互关系的研究为合理搭配林草提供重要依据，为退化山地生态系统的恢复和重建提供重要的模式。模式Ⅰ在退耕还林初期，土壤养分供给氮素虽未亏缺，但从三者问的消长关系看出：氮磷素供应并不富足，特别是水解性氮。土壤交换性钙供应不足，引起杉木与黑麦草对钙质竞争。而土壤全钙含量很高，钙质向交换性钙转化的速度缓慢。模式Ⅱ与模式Ⅰ得到相似结果，所以在这两种模式中应加强人为管理，在退耕初期应适当增施氮磷钙肥，辅以土壤结构改良，加速土壤养分向植物可利用态转化。模式Ⅲ牛鞭草的生物量极高，磷、钙索相对缺乏。由于牛鞭草被不断的采割用于牲畜的饲料，对该模式中必须进行一定养分的输入，以保持杂交竹与牛鞭草这一林草生态系统的养分平衡。  相似文献   

长白山锦北雨养泥炭剖面元素富集规律分析   总被引：3，自引：2，他引：3  

贾琳  王国平  刘景双 《湿地科学》2006,4(3):187-192

为了揭示长白山锦北泥炭沼泽区泥炭沉积环境和重金属元素的历史变化及其对环境的指示意义,利用荷兰W ardenaar泥炭采样器采取泥炭样品并对样品进行高分辨率切割。用原子吸收分光光度计和等离子体发射光谱仪测定不同深度剖面Ca,Mg,Na,K,A l,Ti,Cu,Zn,Fe,Mn,Pb,Cr,N i和Co的浓度。研究分析了Ca,Mg,Na,K,A l,Ti,Mn,Zn,Cu,Pb,Cr,N i和Co在泥炭剖面的分布趋势并对其进行了相关分析和富集分析,得出Mn,Zn,Cu,Pb,Cr,N i和Co呈显著相关且在泥炭表层明显累积,揭示出泥炭表层重金属元素的大气沉降来源,表明近年来人类重金属消耗量及排放量的增加是大气沉降重金属元素的主要释放源,而且环境中重金属污染有加重的趋势。  相似文献   

Improved reliability in the interpretation of geochemical measurements by the quantification of uncertainty from sampling     

Michael H. Ramsey Paul D. Taylor Katy A. Boon 《中国地球化学学报》2006,25(B08):209-210

All geochemical measurements require the taking of field samples, but the uncertainty that this process causes is often ignored when assessing the reliability of the interpretation, of the geochemistry or the health implications. Recently devised methods for the estimation, optimisation and reduction of this uncertainty have been evaluated by their application to the investigation of contaminated land. Uncertainty of measurement caused by primary sampling has been estimated for a range of six different contaminated land site investigations, using an increasingly recognized procedure. These site investigations were selected to reflect a wide range of different sizes, contaminants （organic and metals）, previous land uses （e.g. tin mining, railway sidings and gas works）, intended future use （housing to nature reserves） and routinely applied sampling methods. The results showed that the uncertainty on measurements was substantial, ranging from 25% to 186% of the concentration values at the different sites. Sampling was identified as the dominant source of the uncertainty （〉70% of measurement uncertainty） in most cases. The fitness-for-purpose of the measurements was judged using the optimized contaminated land investigation （OCLI） method. This identifies the optimal level of uncertainty that reduces to overall financial loss caused by the measurement procedures and the misclassification of the contamination, caused by the uncertainty. Generally the uncertainty of the actual measurements made in these different site investigations was found to be sub-optimal, and too large by a factor of approximately two. The uncertainty is usually limited by the sampling, but this can be reduced by increasing the sample mass by a factor of 4 （predicted by sampling theory）. It is concluded that knowing the value of the uncertainty enables the interpretation to be made more reliable, and that sampling is the main factor limiting most investigations. This new approach quantifies this problem for the first time, and allows sampling procedures to be critically evaluated, and modified, to improve the reliability of the geochemical assessment.  相似文献   

The distribution of radiogenic heat production as a function of depth in the Sierra Nevada Batholith, California   总被引：4，自引：0，他引：4  

Robert J. Brady  Mihai N. Ducea  Steven B. Kidder  Jason B. Saleeby 《Lithos》2006,86(3-4):229-244

Geochemical analyses and geobarometric determinations have been combined to create a depth vs. radiogenic heat production database for the Sierra Nevada batholith, California. This database shows that mean heat production values first increase, then decrease, with increasing depth. Heat production is 2 μW/m³ within the 3-km-thick volcanic pile at the top of the batholith, below which it increases to an average value of 3.5 μW/m³ at 5.5 km depth, then decreases to 0.5–1 μW/m³ at 15 km depth and remains at these values through the entire crust below 15 km. Below the crust, from depths of 40–125 km, the batholith's root and mantle wedge that coevolved beneath the batholith appears to have an average radiogenic heat production rate of 0.14 μW/m³. This is higher than the rates from most published xenolith studies, but reasonable given the presence of crustal components in the arc root assemblages. The pattern of radiogenic heat production interpreted from the depth vs. heat production database is not consistent with the downward-decreasing exponential distribution predicted from modeling of surface heat flow data. The interpreted distribution predicts a reasonable range of geothermal gradients and shows that essentially all of the present day surface heat flow from the Sierra Nevada could be generated within the 35 km thick crust. This requires a very low heat flux from the mantle, which is consistent with a model of cessation of Sierran magmatism during Laramide flat-slab subduction, followed by conductive cooling of the upper mantle for 70 m.y. The heat production variation with depth is principally due to large variations in uranium and thorium concentration; potassium is less variable in concentration within the Sierran crust, and produces relatively little of the heat in high heat production rocks. Because silica content is relatively constant through the upper 30 km of the Sierran batholith, while U, Th, and K concentrations are highly variable, radiogenic heat production does not vary directly with silica content.  相似文献   

Monazite behaviour and age significance in poly-metamorphic high-grade terrains: A case study from the western Musgrave Block, central Australia     

Nigel M. Kelly  Geoffrey L. Clarke  Simon L. Harley 《Lithos》2006,88(1-4):100-134

Integrated, in situ textural, chemical and electron microprobe age analysis of monazite grains in a migmatitic metapelitic gneiss from the western Musgrave Block, central Australia has identified evidence for multiple events of growth and recrystallisation during poly-metamorphism in the Mesoproterozoic. Garnet + sillimanite-bearing metapelite underwent partial melting and segregation to palaeosome and leucosome during metamorphism between 1330 and 1296 Ma, with monazite grains in leucosome recording crystallisation at 1300 Ma. Monazite breakdown during melting is inferred to have occurred in the palaeosome. During a subsequent granulite facies event at 1200 Ma, deformation and metamorphism of leucosome and palaeosome resulted in partial disturbance of ages and potential minor growth on 1300 Ma monazite in leucosome. Growth of new, high-Y (+HREE) monazite in palaeosome domains occurred during garnet breakdown in the presence of sillimanite to cordierite and spinel, as a result of post-peak isothermal decompression. Diffusive enrichment of resorbed garnet rims in Y + HREE suggests garnet breakdown occurred slower than volume diffusion of REE. Monazite in both palaeosome and leucosome were subsequently partially to penetratively recrystallised during a retrogression event that is suggested to have occurred at 1150–1130 Ma. The intensity of recrystallisation and disturbance of ages appears linked to proximity to retrogressed garnet porphyroblasts and their occurrence in the relatively reactive or ‘fertile’ local environments provided by the palaeosome/mesosome volumes, which caused localised changes in retrogressive fluids towards compositions more aggressive to monazite. Like reaction textures, it is apparent that domainal equilibrium and reaction may control or at least strongly influence monazite REE and U–Th–Pb chemistry and hence ages.  相似文献   

Towards Formulation of a Space-borne System for Early Warning of Floods: Can Cost-Effectiveness Outweigh Prediction Uncertainty?     

Faisal Hossain 《Natural Hazards》2006,37(3):263-276

The three most important components necessary for functioning of an operational flood warning system are: (1) a rainfall measuring system; (2) a soil moisture updating system; and, (3) a surface discharge measuring system. Although surface based networks for these systems can be largely inadequate in many parts of the world, this inadequacy particularly affects the tropics, which are most vulnerable to flooding hazards. Furthermore, the tropical regions comprise developing countries lacking the financial resources for such surface-based monitoring. The heritage of research conducted on evaluating the potential for measuring discharge from space has now morphed into an agenda for a mission dedicated to space-based surface discharge measurements. This mission juxtaposed with two other upcoming space-based missions: (1) for rainfall measurement (Global Precipitation Measurement, GPM), and (2) soil moisture measurement (Hydrosphere State, HYDROS), bears promise for designing a fully space-borne system for early warning of floods. Such a system, if operational, stands to offer tremendous socio-economic benefit to many flood-prone developing nations of the tropical world. However, there are two competing aspects that need careful assessment to justify the viability of such a system: (1) cost-effectiveness due to surface data scarcity; and (2) flood prediction uncertainty due to uncertainty in the remote sensing measurements. This paper presents the flood hazard mitigation opportunities offered by the assimilation of the three proposed space missions within the context of these two competing aspects. The discussion is cast from the perspective of current understanding of the prediction uncertainties associated with space-based flood prediction. A conceptual framework for a fully space-borne system for early-warning of floods is proposed. The need for retrospective validation of such a system on historical data comprising floods and its associated socio-economic impact is stressed. This proposal for a fully space-borne system, if pursued through wide interdisciplinary effort as recommended herein, promises to enhance the utility of the three space missions more than what their individual agenda can be expected to offer.  相似文献   

New Generation of Probabilistic Seismic Hazard Assessment for the Area Cologne/Aachen Considering the Uncertainties of the Input Data     

G. Grünthal  R. Wahlström 《Natural Hazards》2006,38(1-2):159-176

A new earthquake catalogue for central, northern and northwestern Europe with unified M_w magnitudes, in part derived from chi-square maximum likelihood regressions, forms the basis for seismic hazard calculations for the Lower Rhine Embayment. Uncertainties in the various input parameters are introduced, a detailed seismic zonation is performed and a recently developed technique for maximum expected magnitude estimation is adopted and quantified. Applying the logic tree algorithm, resulting hazard values with error estimates are obtained as fractile curves (median, 16% and 84% fractiles and mean) plotted for pga (peak ground acceleration; median values for Cologne 0.7 and 1.2 m/s² for probabilities of exceedence of 10% and 2%, respectively, in 50 years), 0.4 s (0.8 and 1.5 m/s²) and 1.0 s (0.3 and 0.5 m/s²) pseudoacclerations, and intensity (I₀ = 6.5 and 7.2). For the ground motion parameters, rock foundation is assumed. For the area near Cologne and Aachen, maps show the median and 84% fractile hazard for 2% probability of exceedence in 50 years based on pga (maximum median value about 1.5 m/s²), and 0.4 s (>2 m/s²) and 1.0 s (about 0.8 m/s²) pseudoaccelerations, all for rock. The pga 84% fractile map also has a maximum value above 2 m/s² and shows similarities with the median map for 0.4 s. In all maps, the maximum values fall within the area 6.2–6.3° E and 50.8–50.9° N, i.e., east of Aachen.  相似文献   

Estimating the minimum in-stream flow requirements via wetted perimeter method based on curvature and slope techniques     

LIU Suxia  MO Xingguo  XIA Jun  LIU Changming  LIN Zhonghui  MEN Baohui  JI Lina 《地理学报》2006,16(2):242-250

Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement (MEIFR) is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique (corresponding to the maximum curvature) and slope technique (slope being 1) are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.  相似文献   

Optimization of SAGD Well Elevation     

Jason A. McLennan  Weishan Ren  Oy Leuangthong  C. V. Deutsch 《Natural Resources Research》2006,15(2):119-127

The application of steam-assisted gravity drainage (SAGD) to recover heavy oil sands is becoming increasingly important in the northern Alberta McMurray Formation because of the vast resources/reserves accessible with this mechanism. Selecting the stratigraphic elevations of SAGD well pairs is a vital decision for reservoir evaluation and planning. The inherent uncertainty in the distribution of geological variables significantly influences this decision. Geostatistical simulation is used to capture geological uncertainty, which is used can be transformed into a distribution of the best possible well pair elevations. A simple exhaustive calculation scheme is used to determine the optimum stratigraphic location of a SAGD well pair where the recovery R is maximized. There are three basic steps to the methodology: (1) model the uncertainty in the top continuous bitumen (TCB) and bottom continuous bitumen (BCB) surfaces, (2) calculate the recovery at all possible elevation increments within the TCB and BCB interval, and (3) identify the elevation that maximizes R. This is repeated for multiple TCB/BCB pairs of surfaces to assess uncertainty. The methodology is described and implemented on a subset of data from the Athabasca Oilsands in Fort McMurray, Alberta.  相似文献   

Biological and Geochemical Record of Anthropogenic Impacts in Recent Sediments from Lake Pupuke, Auckland City, New Zealand     

Paul Augustinus  Michael Reid  Sofia Andersson  Yanbin Deng  Mark Horrocks 《Journal of Paleolimnology》2006,35(4):789-805

Frozen sediment cores from Lake Pupuke in Auckland City, New Zealand, contain a high resolution decadal to annual scale record of changing lake paleoenvironments and geochemistry that reflects changing landuse and hydrology in the catchment over the past c. 190 years. A reliable chronology is available from AMS ¹⁴C and ²¹⁰Pb dating of the sediments, with the timing of the older part of the record supported by the first appearance of pollen of introduced Pinus and Plantago lanceolata associated with European settlement of Auckland in the early 1840s. Diatom stratigraphy, sediment elemental and carbon isotope geochemistry reflect changes in sediment sources and lake conditions commensurate with European development of the Lake Pupuke catchment, in particular enhanced algal productivity controlled by the influx of nutrients after c. 1920 AD. Attempts to prevent nuisance algal blooms in 1933, 1934 and 1939 using CuSO₄ addition produced Cu spikes in the sediment that allowed confirmation of the accuracy of the ²¹⁰Pb chronology. Hence, the elemental and isotopic composition of the Lake Pupuke sediments reflect the timing of significant anthropogenic activities, rather than climatic variations, that have occurred within the watershed over the past c. 190 years. The comparison of records of land use change in the catchment with the multi-proxy record of changes in the sediments usually allowed unambiguous identification of the signatures of change and their causes.  相似文献