香港一富营养河港内的底泥耗氧和营养盐释放

Tolo Harbour has received massive discharges of municipal sewage, agricultural wastes and cottage industrial effluents, via three river systems, in the past two decades before the mid Eighties. The Harbour is almost land locked and poorly flushed. The soft sediment acted as a sink for nutrients and organic pollutants. After a decade of efforts in establishing and enforcing water pollution control legislations and upgrading wastewater treatment facilities, the sediments have turned into sources of nutrients and exert a measurable oxygen demand upon the overlying waters. In vitro measurements showed that the sediments oxygen demand (SOD) was between 17.6 and 54.3 mgo₂ · m^-2 · h^-1. The maximum rates of release of ortho-phosphate phosphorus and ammonia nitrogen were 15.0 and 206.0 mg · m^-2 · h^-1, respectively.     

Seismotectonic deformations related to the 2010 Maule earthquake at different stages of the seismic cycle from satellite geodetic observations

Doklady Earth Sciences - The interpretation of multiannual satellite geodetic observations after the 2010 Maule earthquake is given on the basis of the keyboard concept of the subduction region...     

Conceptual models for carbonate aquifers. 1969

The very diverse types of ground‐water behavior in carbonate terrains can be classified by relating the flow type to a particular hydrogeologic environment each exhibiting a characteristic cave morphology. The ground water may move by diffuse flow, by retarded flow, or by free flow. Diffuse flow occurs in less soluble rocks such as extremely shaley limestones or crystalline dolomites. Integrated conduits are rare. Caves tend to be small, irregular, and often little more than solutionally widened joints. Retarded flows occur in artesian environments and in situations where unfavorable stratigraphy forces ground water to be confined to relatively thin beds. Network cave patterns are characteristic since hydrodynamic forces are damped by the external controls. Solution occurs along many available joints. Free flowing aquifers are those in which solution has developed a subsurface drainage system logically regarded as an underground extension of surface streams. These streams may have fully developed surface tributaries as well as recharge from sinkholes and general infiltration. Characteristic cave patterns are those of integrated conduit systems which are often truncated into linear, angulate, and branchwork caves. Free Flow aquifers may be further subdivided into Open aquifers lying beneath karst plains and Capped aquifers in which significant parts of the drainage net lie beneath an insoluble cap rock. Other geologic factors such as structure, detailed lithology, relief, and locations of major streams, control the details of cave morphology and orientation of the drainage network.     

Intermittent chaos in nonlinear wave–wave interactions in space plasmas

There is increasing observational evidence of nonlinear wave–wave interactions in space and astrophysical plasmas. We first review a number of theoretical models of nonlinear wave–wave interactions which our group has developed in the past years. We next describe a nonlinear three-mode truncated model of Alfvén waves, involving resonant interactions of one linearly unstable mode and two linearly damped modes. We construct a bifurcation diagram for this three-wave model and investigate the phenomenon of intermittent chaos. The theoretical results presented in this paper can improve our understanding of intermittent time series frequently observed in space and astrophysical plasmas.     

U-Pb age and genetic significance of heterogeneous zircon populations in rocks from the Favourable Lake area,Northwestern Ontario

The study evaluates the relationships between measured U-Pb ages and zircon characteristics of five morphologically, texturally, and isotopically complex zircon populations and compares the zircon development stages to the orogenic evolution of the Favourable Lake area. Two distinct zircon types from a hornblendite xenolith in a granitoid batholith of the Sachigo subprovince of the Superior Province yield U-Pb ages of 2729.0±6.8 Ma and 2714.8 _–6.4 ^+7.4 Ma, which date specific metamorphic phases coinciding with major plutonic pulses in the batholith. Zircons from a metamorphosed felsic dike, crosscutting the hornblendite, consist of an old zircon component with a minimum age of 2788 Ma possibly reflecting igneous crystallization 2950 Ma ago, and a younger component with an inferred age of 2725±15 Ma, probably reflecting metamorphism during batholith emplacement.In the Berens River subprovince to the south, granodiorite forms both a late tectonic phase in a large batholith and a post-tectonic pluton intruded into the batholith, yet zircons from these granodiorites have identical ages of 2697.3±1.7 Ma and 2696.2±1.2 Ma, respectively. The late tectonic granodiorite also contains inherited zircons with a minimum age of 2767 Ma which are indirect evidence for the presence of old sialic crust in this subprovince. Zircons from a sheared monzonite near the boundary fault between the two subprovinces yield an upper intercept age of 2769 _–26 ⁺⁶³ Ma, which we interpret as the intrusion age of the monzonite. This rock is older than most dated units in the surrounding batholiths and suggests that the boundary is a long-lived Archean structure.A lower intercept age of about 1750 Ma for zircons of the hornblendite is the result of chemical alteration of the zircons. This, and a similar lower intercept age shown by the sheared monzonite zircons, are thought to reflect increased fluid activity and possibly shearing during the Early Proterozoic Hudsonian orogeny which occurred in the Churchill Province to the northwest. A later Pb-loss mainly from near-surface domains of the zircons is indicated by lower intercept ages of about 500–100 Ma.Publication approved by the Director, Ontario Geological Survey     

Age of the Vishnyakovskoe deposit of rare-metal pegmatites (East Sayan): U-Pb geochronological study of manganotantalite

The U-Pb age of the manganotantalite from rare-metal pegmatites of the Vishnyakovskoe deposit (East Sayan Belt) has been assessed at 1838 ± 3 Ma. The acquired data indicate the pegmatites of this deposit and associated granites of the Sayan complex belong to the postcollision South Siberian igneous belt (1.88–1.84 Ga), which stretches along the southwestern frame of the Siberian Craton by more than 2500 km, from the Yenisei Ridge to the Aldan Shield. Formation of this igneous belt is related to joining (starting from about 1.9 Ga BP) of the series of continental microplates and island arcs to the Siberian Craton; this led to final stabilization of the craton at about 1.8 Ga BP.     

Biogenic silica from the BDP93 drill site and adjacent areas of the Selenga Delta, Lake Baikal, Siberia

Biogenic silica contents of sediments on the lower Selenga Delta and Buguldeika saddle in Lake Baikal show distinct fluctuations that reflect changes in diatom productivity, and ultimately, climate. The pattern of the upper 50 m of the section, dating from about 334 ka, is similar to that of the marine oxygen-isotope record, increasingly so as the younger sediments become progressively finer grained and less locally derived with time. The last two interglaciations are marked by biogenic silica abundances similar to those of the Holocene. The equivalent of marine oxygen-isotope stage 3 is distinctly intermediate in character between full glacial and full interglacial biogenic silica values. Following near-zero values during the last glacial maximum, biogenic silica began to increase at about 13 ka. The rise in biogenic silica to Holocene values was interrupted by an abrupt decrease during Younger Dryas time, about 11 to 10 14C ka.     

热带西太平洋海温距平与Rossby波传播对1993和1994年东亚夏季风异常影响的差异

利用NCEP/NCAR再分析资料、Hadley中心海温资料与降水资料,分析了1993和1994年东亚夏季风异常的天气气候特征以及大气环流的差异.分析结果表明: 1993年东亚夏季风弱,副热带西风急流和副热带高压位置偏南,来自于孟加拉湾和南海的水汽仅输送到35°N以南地区.东亚地区出现低温凉夏天气.1994年东亚夏季风强,副热带西风急流和副热带高压位置偏北,7～8月副高持续偏强并控制日本,水汽可以输送到45°N以北的较高纬度,东亚发生破纪录的热浪干旱.对1993和1994年东亚夏季风异常物理过程差异的研究发现,副热带西风急流中静止Rossby波的传播和热带西太平洋暖池海温距平激发出来的PJ型遥相关波列作用的叠加引起1994和1993年东亚夏季风异常差异.     

Performance assessment of three convective parameterization schemes in WRF for downscaling summer rainfall over South Africa

Austral summer rainfall over the period 1991/1992 to 2010/2011 was dynamically downscaled by the weather research and forecasting (WRF) model at 9 km resolution for South Africa. Lateral boundary conditions for WRF were provided from the European Centre for medium-range weather (ECMWF) reanalysis (ERA) interim data. The model biases for the rainfall were evaluated over the South Africa as a whole and its nine provinces separately by employing three different convective parameterization schemes, namely the (1) Kain–Fritsch (KF), (2) Betts–Miller–Janjic (BMJ) and (3) Grell–Devenyi ensemble (GDE) schemes. All three schemes have generated positive rainfall biases over South Africa, with the KF scheme producing the largest biases and mean absolute errors. Only the BMJ scheme could reproduce the intensity of rainfall anomalies, and also exhibited the highest correlation with observed interannual summer rainfall variability. In the KF scheme, a significantly high amount of moisture was transported from the tropics into South Africa. The vertical thermodynamic profiles show that the KF scheme has caused low level moisture convergence, due to the highly unstable atmosphere, and hence contributed to the widespread positive biases of rainfall. The negative bias in moisture, along with a stable atmosphere and negative biases of vertical velocity simulated by the GDE scheme resulted in negative rainfall biases, especially over the Limpopo Province. In terms of rain rate, the KF scheme generated the lowest number of low rain rates and the maximum number of moderate to high rain rates associated with more convective unstable environment. KF and GDE schemes overestimated the convective rain and underestimated the stratiform rain. However, the simulated convective and stratiform rain with BMJ scheme is in more agreement with the observations. This study also documents the performance of regional model in downscaling the large scale climate mode such as El Niño Southern Oscillation (ENSO) and subtropical dipole modes. The correlations between the simulated area averaged rainfalls over South Africa and Nino3.4 index were ?0.66, ?0.69 and ?0.49 with KF, BMJ and GDE scheme respectively as compared to the observed correlation of ?0.57. The model could reproduce the observed ENSO-South Africa rainfall relationship and could successfully simulate three wet (dry) years that are associated with La Niña (El Niño) and the BMJ scheme is closest to the observed variability. Also, the model showed good skill in simulating the excess rainfall over South Africa that is associated with positive subtropical Indian Ocean Dipole for the DJF season 2005/2006.