What drives the evolution of the sedimentary phosphorus cycle?     

Andreas Kleeberg  Christiane Herzog  Sylvia Jordan  Michael Hupfer 《Limnologica》2010,40(2):102-113

The ‘Chicken Creek’ artificial catchment area, Welzow-South, E Germany, created to study processes and structures of initial ecosystem development, discharges into a small experimental lake (A=3805 m², V=3992 m³, z_max=2.4 m). This lake was man-made in 2005 and filled by natural surface runoff until January 2006. In summer 2006 and 2008, the actual development of sediments and the evolution of the phosphorus (P) cycle were studied. 19.7% of the original lake volume was filled by sediment within the first 3 years. A fine-grained sediment representing silt (6.3-63 μm) accumulated at high accretion rates at the deepest point (200 mm a⁻¹, 0-24 mm week⁻¹) due to massive erosion in the catchment. The sediment is low in organic matter (2.5-5.2%) and total P (TP, 0.31-0.97 mg g⁻¹). Low amounts of P associated with degradable organic matter and surplus of metal hydroxides (Fe:P∼40, Al:P∼20) favor an efficient P binding and low dissolved P concentrations in pore water (1-107 μg l⁻¹). Hence, the mineral sediment quality and the low rates of P release (0.06 mg m⁻² d⁻¹) revealed that a lake at an initial stage of development has essentially no sedimentary P cycle compared to eutrophic shallow lakes. However, the increasing emersed and submersed macrophyte growth will control further lake succession by intensifying the internal nutrient cycling. The macrophytes drive the evolution of a sedimentary P cycle by mobilizing and translocating P, by accumulating carbon and thus by stimulating microbial and redox processes.  相似文献   

准噶尔盆地灰漠土无机磷形态及磷吸附特性研究     

何帅  尹飞虎  谢海霞 《干旱区地理》2017,40(5):1061-1069

选择新疆准噶尔盆地灰漠土作为研究对象,通过测定灰漠土中不同形态的无机磷素含量并进行土壤磷素等温吸附实验,研究灰漠土中各形态无机磷素的有效性和土壤磷吸附特征。结果表明,灰漠土中无机磷形态主要是Ca-P,占全磷含量75%以上,且以Ca₁₀-P形式为主,其次为Ca₈-P和Ca₂-P,无机磷中Al-P、Fe-P和O-P含量较少。全剖面中随着土层深度增加,Ca₂-P、Ca₈-P和Al-P占全磷总量的比例减少,Ca₁₀-P占全磷总量则有所增加,0~20 cm土层全磷和Olsen-P含量最高,分别平均为926 mg·kg^-1和51.54 mg·kg^-1。统计分析表明Ca₂-P、Al-P是最有效的磷源,Ca₈-P和Fe-P是第二有效磷源,O-P和Ca₁₀-P则是作物的潜在磷源。利用Langmuir方程拟合灰漠土的磷等温吸附曲线,得出土壤最大吸磷量（Xm）为957±629 mg·kg^-1,吸附参数（K）为149.285±89.225;灰漠土的粘粒含量对Xm影响最大,其次是有机质,pH值影响最小。  相似文献   

鄂尔多斯盆地砂岩型铀矿深穿透地球化学勘查方法实验   总被引：6，自引：0，他引：6  

姚文生  王学求  张必敏  徐善法  申伍军  杜雪苗 《地学前缘》2012,19(3):167-176

鄂尔多斯盆地尚未开展区域化探扫面工作。文中以东胜砂岩型铀矿区为例,开展深穿透地球化学勘查方法实验。东胜铀矿床产于侏罗系直罗组下段,为隐伏矿床。研究发现,富含细粒级地表结层是半干旱盆地砂岩型铀矿区域地球化学勘查的有效采样介质。在东胜砂岩型铀矿区及周边2 000 km2的方法实验中,每4 km2采集一个样品,过筛后取-200目进行全量分析,在矿化出露区及隐伏矿区圈出了铀及相关元素的地球化学异常。对元素比值R=lnU/(lnCe+lnY+lnZr+lnNb)在不同区域分布特征的研究表明,样品中活动态铀是形成铀异常的主要原因,提取细粒级土壤组分进行全量分析,可作为区域深穿透地球化学的砂岩型铀矿找矿指标。在矿床尺度深化穿透地球化学勘查方法中,因实验区地形特点使得富含细粒级地表结层样品不易普遍取得,地表土壤的全量分析不能满足勘查要求,需要采用铀专属性强的提取试剂进行元素活动态分析。文中采用作者研制的MML-U活动态提取剂,在东胜铀矿区孙家梁矿段剖面实验中,成功探测到矿体上方土壤中的U、Mo、V等元素的活动态异常。  相似文献   

Singularly weighted symplectic forms and applications to asteroid motion     

F. Varadi  C. M. De La Barre  W. M. Kaula  M. Ghil 《Celestial Mechanics and Dynamical Astronomy》1995,62(1):23-41

New techniques to study Hamiltonian systems with Hamiltonian forcing are proposed. They are based on singularly weighted symplectic forms and transformations which preserve these forms. Applications pertaining to asteroid motion are outlined. These involve the presence of both Jupiter and Saturn.  相似文献   

基于遥感数据SOFM网络分类的五种城市增长方式鉴别方法应用研究   总被引：5，自引：0，他引：5  

戴芹  陈雪  马建文  冯春 《武汉大学学报(信息科学版)》2005,30(6):525-529

使用了自主研发的自组织神经网络分类(SOFM)方法，选择了1988、1994、2001和2003年5～6月份TM^ 时间序列多光谱遥感数据，对北京城市增长方式进行了30m分辨率遥感时序数据的鉴别，包括填充式增长方式、扩张式增长方式、独立式增长方式、线状式增长方式和簇状增长方式，并绘制了三个时期的城市增长图。在此基础上，根据北京城市增长环线驱动的特点，分别对四环内、四环至五环、五环至六环1988～1994年、1994～2001年、2001～2003年的5种城市扩展方式面积进行了统计。  相似文献   

Geological Storage Forms of Injected CO2 and Variation with Time: A Case Study for Ordos Deep Saline Formation     

YUE Gaofan  XU Tianfu  WANG Fugang 《《地质学报》英文版》2013,87(Z1):980-981

  相似文献   

长江口海域表层沉积物重金属元素赋存形态特征     

何中发  方正  温晓华  张琢  王张华  赵宝成  谢建磊  李晓 《上海国土资源》2012,33(2):69-73

通过长江河口地区水下表层沉积物样品多种化学元素的赋存形态分析测试数据,综合分析重金属元素的赋存形态特征。研究结果显示：镉、汞、铅残渣态所占比例均小于50%,锌、砷、铬、铜、镍残渣态占比均大于50%;8个元素的残渣态与全量呈显著正相关关系。沉积环境和沉积物粒径对重金属元素赋存形态具有重要影响。沉积物的物质来源、矿物组成特征、水动力作用与沉积物粒度和物理化学条件等是长江口地区表层沉积物重金属元素赋存形态的主要控制因素。  相似文献   

Enrichment of Platinum-group Elements (PGE) and Re-Os Isotopic Tracing for Porphyry Copper (Gold) Deposits     

HE Xiaohu  ZHONG Hong  ZHU Weiguang  BAI Zhongjie  HU Wenjun 《《地质学报》英文版》2014,88(4):1288-1309

Platinum-group elements （PGE） in PGE-rich porphyry copper （gold） deposits are mainly Pt and Pd, whereas the concentrations of other PGE （Ru, Rh, Os, Ir） are significantly low. Moreover, Pt and Pd mainly exist in sulfides in the forms of crystal lattice or tiny platinum-group mineral （PGM） inclusions. The present data show that there is a positive relationship between Pt and Pd concentrations and Cu （Au） in porphyry copper （gold） deposits. The comparison of chondrite-normalized PGE distribution patterns between the ore-bearing porphyry intrusions and ore-barren porphyry intrusions in arc setting, 187^Os/188^Os, 87^Sr/86^Sr and S isotopes for porphyry copper （gold） deposits shows that PGEs were mainly derived from the mantle, and fluids from subduction zones devoted trivial PGE to the magma. The porphyry copper （gold） deposits associated with subducted events are most probably enriched in PGE, whereas those related to crustal thickening, lithospheric delamination or underplating rarely concentrate PGE. The osmium isotopic compositions in porphyry copper （gold） deposits reveal that （187^Os/188^Os）i values are highly variable and not lower than those of primitive upper mantle （PUM） and mantle peridotite, however, osmium concentrations are commonly lower than mantle peridotite, suggesting that parental magmas of some porphyry intrusions had experienced crustal contamination during magma evolution. Experimental investigations have proved that PGE exist in the forms of Cl^- and HS^- complexes during transportation and migration of the oreforming fluids. This paper summarizes previous studies including crucial controlling factors and mechanisms for PGE enrichment, and points out that the mantle-derived magmas parental to porphyry intrusions are the prerequisite for PGE enrichment in porphyry copper （gold） deposits. Favorable physical and chemical conditions （including salinity, temperature, pressure, pH, and oxygen fugacity） in hydrothermal fluids crucially control the  相似文献   

Within-reach spatial variability of snails and molluscivory by brown trout     

Joseph R Holomuzki 《新西兰海洋与淡水研究杂志》2013,47(3):189-197

Linking habitat distributions of prey to the probability of predation is important to understanding consumptive effects of predators on prey populations. This study reports how within-reach spatial variability of two snails, the hydrobiid Potamopyrgus antipodarum and the physid Physella acuta, was linked to habitat-based predation risk by young brown trout (Salmo trutta) of different age classes. Potamopyrgus is endemic to New Zealand streams and lakes, where it commonly co-exists with the invader P. acuta, but both snails are worldwide invaders to many freshwater systems. Examination of egested snails revealed Potamopyrgus and Physella were consumed in similar numbers within age classes. However, 10-month-old trout consumed, on average, fewer snails than 20-month-old trout, and 8-month-old trout ate essentially no snails, suggesting snails were a more important prey item for larger age-1 fish than smaller age-0 fish. No Physella were egested alive by any trout age class. However, 38% and 16% of the Potamopyrgus consumed were egested alive by 10- and 20-month-old trout, respectively, with some passing live after ~70 h in digestive tracts. Physella and the spiny-shell form of Potamopyrgus were significantly denser on macrophytes than on stony sediments in midchannel, and these habitat distributions affected their odds of consumption. Risk of consumption by trout was ~10 times greater for Physella than Potamopyrgus on stones, but their risk was similar in protective macrophytes. Odds of consumption were similar for spiny and smooth shell forms of Potamopyrgus on stones, suggesting spines do not provide protection from large predators like trout. My results suggest that brown trout can potentially exert stronger population regulatory effects on Physella than on Potamopyrgus and that these effects are partly mediated by macrophyte cover.  相似文献   

中国中元古代同位素地质年代学研究进展述评   总被引：5，自引：1，他引：4       下载免费PDF全文

陆松年  李怀坤  相振群 《中国地质》2010,37(4)

本文较全面地总结了自2000年第三届全国地层大会以来,中国中元古代地层和热-构造事件同位素地质年代学研究工作所取得的主要进展,讨论了这些进展所具有的重要意义,指出确立中国中元古代上部地层标准剖面,重新厘定中元古界地质年表,是当前最迫切需要解决的课题。  相似文献