农田土壤水分和盐分的空间变异性及其协同克立格估值   总被引：46，自引：3，他引：46       下载免费PDF全文

胡克林  李保国  陈德立  R.E.White 《水科学进展》2001,12(4):460-466

通过对一块面积为1hm2麦田内的98个观测点取样分析,测定了两个时期的土壤水分和盐分含量。结果表明两个时期的土壤含水量均服从正态分布,底层盐分均服从对数正态分布,而表层的盐分分布具有不确定性。两个时期土壤水分和盐分的变异系数分别属于弱变异和中等变异强度。通过结构分析,发现两个时期的水分和盐分均在一定范围内存在空间相关性。对两个时期土壤水分和盐分空间分布的动态变化进行了比较,同时采用CoKriging方法进行估值,与Kriging法相比,其估计方差减少百分数最大达到了136.3%。  相似文献   

A—型花岗岩的成因:实验的控制因素     

J. D. Clemens  J. R. Houowag  A. J. R. White  毕立君 《世界地质》1987,(4)

关于具有特征化学成分的A-型花岗岩或非造山花岗岩的成因,人们已经提出了许多岩石成因的理论模式。对澳大利亚东南部A-型花岗岩伴生流纹岩和玄武岩双峰态组合的Watengums偏铝质花岗岩进行了实验研究,以便探讨其成因。Watergums岩浆浸入于地壳很浅的部位。且几乎处于全熔状态。因此在~-1kb时,晶-液相关系可以同岩相学上已确定的结晶顺序进行对比。资料表明,这种岩浆的最低温度为830℃,可能超过900℃推断熔体中水的含量为2.4—4.3％。这种岩浆的温度高,暗示在成因上与稍晚的I-型花岗岩是有区别的。岩石学、地球化学以及实验资料直接证明了A-型花岗岩是下部地壳中亏损熔体的I-型花岗岩源岩高温部分熔融形成,幔源岩浆(玄武岩)为产分熔融提供了热源。熔融作用很可能伴随缺少流体相而略富卤族元素的云母和闪石类矿物的分解。这些矿物是早期形成I—型岩浆后的熔融残余。由于A-型岩浆温度高、中等水分以及高F,特别当它分馏时显示出低粘度,这与A-型流纹岩、黑(?)岩流体的正常产出是一致的。相反,S-型和I-型火山岩通常为火山灰流的凝灰岩。  相似文献   

森林生态服务市场的开发     

Ian Powell  Andy White  Natasha Landell-Mills  刘硕  王学全 《湿地科学与管理》2002,(4):39-43

<正> 森林提供许多有价值的生态服务,诸如保护流域和生物多样性以及贮存碳素等,现已引起企业、政府乃至个人越来越多的关注,同时人们也意识到随着森林这些功能的退化甚至丧失所带来的危险和代价。这种退化既能引起洪水、山崩之类的局部灾难,也会导致全球气候变化之类的广泛影响。  相似文献   

南海夏季风爆发与大气对流低频振荡的年际变化   总被引：8，自引：0，他引：8  

何有海  彭楚明  关翠华  林锡贵  王东晓 《大气科学》2000,24(6):785-794

根据1980～1991年云顶黑体温度（TBB）相位和强度的变化确定了南海夏季风爆发的时间,分析研究了夏季风爆发期间TBB场和850hPa风场的变化过程及其与海温的关系。结果表明:南海夏季风爆发平均时间是5月第4候,它爆发的时间和强度有显著的年际变化,并与大气的低频振荡及前期海洋的热力状况有密切关系。南海夏季风爆发早年（4月第6候）,副热带高压较弱,撤离南海较快,从赤道东印度洋到赤道西太平洋,大气对流活动较强,夏季风爆发南海早于孟加拉湾,季风爆发时90～100°E区域过赤道气流显著加强。夏季风爆发晚年（6月第1候）情况相反。南海夏季风爆发早晚与大气30～60天振荡到达南海的位相有关,前冬和早春南海海温的高低和4月中旬至5月中南半岛强对流区的出现时间,是南海夏季风爆发年际变化的前期征兆。根据前冬南海海温预测1998年南海夏季风爆发的时间和强度与实际相符。  相似文献   

Testing the Validity of Ar/Ar Single-Crystal White Mica Ages for Erosion, Exhumation and Provenance Stud ies: Recent Sediments From the Ganga River, North India     

Nikki White  Malcolm Pringle  Yani Najman  Mike Bickle  Peter Friend  Judith Bunbury WT  ”BX 《地学前缘》2000,(Z1)

TESTING THE VALIDITY OF Ar/Ar SINGLE-CRYSTAL WHITE MICA AGES FOR EROSION, EXHUMATION AND PROVENANCE STUDIES:RECENT SEDIMENTS FROM THE GANGA RIVER, NORTH INDIA1　CopelandP ,HarrisonTM .EpisodicrapidupliftintheHimalaya[J].Geology ,1990 ,18:35 4～ 35 7. 2　FrankW ,MillerCh ,GrassemannB .Ar/AragesofdetritalmicasandpalaeogeographicprovenanceofProterozoicclasticsedimentsintheHimalayas[J].10thHimalayan Karakorum TibetWorkshop[C],As…  相似文献   

Biota: sediment partitioning of aluminium smelter related PAHs and pulp mill related diterpenes by intertidal clams at Kitimat, British Columbia     

Yunker MB  Lachmuth CL  Cretney WJ  Fowler BR  Dangerfield N  White L  Ross PS 《Marine environmental research》2011,72(3):105-126

The question of polycyclic aromatic hydrocarbon (PAH) bioavailability and its relationship to specific PAH sources with different PAH binding characteristics is an important one, because bioavailability drives PAH accumulation in biota and ultimately the biochemical responses to the PAH contaminants. The industrial harbour at Kitimat (British Columbia, Canada) provides an ideal location to study the bioavailability and bioaccumulation of sediment hydrocarbons to low trophic level biota. Samples of soft shell clams (Mya arenaria) and intertidal sediment collected from multiple sites over six years at various distances from an aluminium smelter and a pulp and paper mill were analysed for 106 PAHs, plant diterpenes and other aromatic fraction hydrocarbons. Interpretation using PAH source ratios and multivariate data analysis reveals six principal hydrocarbon sources: PAHs in coke, pitch and emissions from anode combustion from the aluminium smelter, vascular plant terpenes and aromatised terpenes from the pulp and paper mill, petroleum PAHs from shipping and other anthropogenic activities and PAHs from natural plant detritus. Harbour sediments predominantly contain either pitch or pyrogenic PAHs from the smelter, while clams predominantly contain plant derived PAHs and diterpenes from the adjacent pulp mill. PAHs from the smelter have low bioavailability to clams (Biota-Sediment Accumulation Factors; BSAFs <1 for pitch and coke; <10 for anode combustion, decreasing to ∼0.1 for the mass 300 and 302 PAHs), possibly due to binding to pitch or soot carbon matrices. Decreases in PAH isomer ratios between sediments and clams likely reflect a combination of variation in uptake kinetics of petroleum PAHs and compound specific metabolism, with the importance of petroleum PAHs decreasing with increasing molecular weight. Plant derived compounds exhibit little natural bioaccumulation at reference sites, but unsaturated and aromatised diterpenes released from resins by industrial pulping processes are readily accumulated by the clams (BSAFs >500). Thus while most of the smelter associated PAHs in sediments may not be bioavailable to benthic organisms, the plant terpenes (including retene, totarol, ferruginol, manool, dehydroabietane and other plant terpenes that form the chemical defence mechanism of conifers) released by pulp mills are bioavailable and possess demonstrated toxic properties. The large scale release of plant terpenes by some of the many pulp mills located in British Columbia and elsewhere represents a largely undocumented risk to aquatic biota.  相似文献   

Multilevel samplers as microcosms to assess microbial response to biostimulation     

Baldwin BR  Peacock AD  Park M  Ogles DM  Istok JD  McKinley JP  Resch CT  White DC 《Ground water》2008,46(2):295-304

Passive multilevel samplers (MLS) containing a solid matrix for microbial colonization were used as in situ microcosms in conjunction with a push-pull biostimulation experiment designed to promote biological U(VI) and Tc(VII) reduction. MLS were deployed at 24 elevations in the injection well and two downgradient wells to investigate the spatial variability in microbial community composition and growth prior to and following biostimulation. The microbial community was characterized by real-time quantitative polymerase chain reaction (Q-PCR) quantification of bacteria, NO(3)(-)-reducing bacteria (nirS and nirK), delta-proteobacteria, Geobacter sp., and methanogens (mcrA). Pretest cell densities were low overall but varied substantially with significantly greater bacterial populations detected at circumneutral pH (t-test, alpha= 0.05), suggesting carbon substrate and low pH limitations of microbial activity. Although pretest cell densities were low, denitrifying bacteria were dominant members of the microbial community. Biostimulation with an ethanol-amended ground water resulted in concurrent NO(3)(-) and Tc(VII) reduction, followed by U(VI) reduction. Q-PCR analysis of MLS revealed significant (1 to 2 orders of magnitude, Mann-Whitney U-test, alpha= 0.05) increases in cell densities of bacteria, denitrifiers, delta-proteobacteria, Geobacter sp., and methanogens in response to biostimulation. Traditionally, characterization of sediment samples has been used to investigate the microbial community response to biostimulation; however, collection of sediment samples is expensive and not conducive to deep aquifers or temporal studies. The results presented demonstrate that push-pull tests with passive MLS provide an inexpensive approach to determine the effect of biostimulation on contaminant concentrations, geochemical conditions, and the microbial community composition and function.  相似文献   

预测农田水分渗漏和氮素淋失的两种模型比较   总被引：8，自引：1，他引：8       下载免费PDF全文

胡克林  李保国  陈德立  R.E.White 《水科学进展》2004,15(1):87-93

以田间试验为基础,分别用平衡模型和动力学模型计算了3个小区农田水分渗漏量和氮素淋失量,并对其结果进行了比较,平衡模型计算的水分渗漏量为191～202mm,氮素淋失量为38～63kg·N/hm2;而用动力学模型计算的水分渗漏量为168～234mm,氮素淋失量为27～53kg·N/hm2。造成结果差异的主要原因是:平衡模型没有考虑向上的水流和非饱和流;而动力学模型同时考虑了二者。动力学模型需要大量的田间实测资料,主要应用于农田氮素循环、定量评价水氮资源利用率、优化水肥管理措施等方面。平衡模型仅需要非常少的资料,就能够得到农田水分渗漏量和氮素淋失量,这对精度要求不太高的农田水肥管理来说,不失为一种好方法。  相似文献   

南海上层海洋热含量的年际和年代际变化   总被引：15，自引：0，他引：15  

何有海  关翠华 《热带海洋》1997,16(1):23-29

分析了１９５９－１９８８年南海表面至１００ｍ垂直平均温度资料，结果表明，南海上层海洋热含量存在明显的准两年，４－５年和年代际振动，在Ｅ１ Ｎｉｎｏ年，南海上层热含量显著增加，５０年代末至７０年代初，南海ＴＡＶ为负距平，此后转为正距平，南海ＴＡＶ的变化与ＥＮＳＯ事件，东亚冬季风和热带大气环流的变异密切相关。  相似文献   

北海中岩石圈扩张的性质     

White  N. 沈政威 《海洋地质译丛》1989,(5):74-77

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