Effects of basin size on low-flow stream chemistry and subsurface contact time in the Neversink River watershed,New York

The effects of basin size on low-flow stream chemistry and subsurface contact time were examined for a part of the Neversink River watershed in southern New York State. Acid neutralizing capacity (ANC), the sum of base cation concentrations (SBC), pH and concentrations of total aluminum (Al), dissolved organic carbon (DOC) and silicon (Si) were measured during low stream flow at the outlets of nested basins ranging in size from 0·2 to 166·3 km². ANC, SBC, pH, Al and DOC showed pronounced changes as basin size increased from 0·2 to 3 km², but relatively small variations were observed as basin size increased beyond 3 km². An index of subsurface contact time computed from basin topography and soil hydraulic conductivity also showed pronounced changes as basin size increased from 0·2 to 3 km² and smaller changes as basin size increased beyond 3 km². These results suggest that basin size affects low-flow stream chemistry because of the effects of basin size on subsurface contact time. © 1997 John Wiley & Sons, Ltd.     

Sr fluxes and isotopic compositions of the eleven rivers originating from the Qinghai-Tibet Plateau and their contributions to <Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr evolution of seawater

To evaluate influence of chemical weathering of the Qinghai-Tibet Plateau (QTP) on seawater ⁸⁷Sr/⁸⁶Sr variation, river water and sediment samples were collected, and their Sr concentrations and isotopic compositions analyzed, from the seven large rivers that originated from the QTP. By combining these with the data of the Ganges, Brahmaputra, Indus and Irrawaddy originated in the southern QTP, the total Sr flux of the eleven rivers reaches 3.47×10⁹ mol·a⁻¹, which accounts for 10.2% of the total Sr flux transported by the global rivers. The weighted mean ⁸⁷Sr/⁸⁶Sr is 0.71694, higher than the average value of the global rivers. The ⁸⁷Sr_ex (⁸⁷Sr flux in excess of the seawater ⁸⁷Sr/⁸⁶Sr ratio) of the Chinese seven rivers is 1.55×10⁶ mol·a⁻¹, only accounting for about 6% of the value of the eleven rivers originated from QTP, and the Ganges-Brahmaputra system accounts for 86%. We assume that the QTP rivers have no strontium contributions to the oceans before ∼40 Ma and the Sr fluxes of the global rivers, except the QTP eleven rivers, are constant, then a maximum linear increase in Sr fluxes of the QTP rivers from zero to the modern value in response to tectonic uplift can explain ∼69% increase of seawater ⁸⁷Sr/⁸⁶Sr over the past ∼40 Ma and the remainder of 31% is perhaps provided from other factors. Supported by National Natural Science Foundation of China (Grant Nos. 40473009, 40331001, 40873001)     

南极碳质球粒陨石中两个富尖晶石球粒状难熔包体的岩石学和矿物化学特征

富尖晶石球粒状CAI(富Ca-Al难熔包体)是球粒陨石中一种特殊类型的CAI,在南极格罗夫山碳质球粒陨石GRV020025和GRV021579中共发现两个富尖晶石球粒状CAI———GRV020025-3RI8和GRV021579-3RI5。GRV020025-3RI8具有占统治地位的尖晶石,在球粒的最外边存在严重蚀变的不规则边,钙钛矿主要分布在靠近边的位置。与GRV020025-3RI8比较,GRV021579-3RI5的尖晶石中的钙钛矿消失,深绿辉石出现,薄薄的蚀变层位于尖晶石核和富钙辉石边之间。两个富尖晶石球粒状CAI的尖晶石均具有低含量FeO和ZnO的特征,而且GRV021579-3RI5具有较GRV020025-3RI8更高的TiO2含量。岩石学和矿物化学特征表明,GRV020025-3RI8和GRV021579-3RI5都经历过熔融结晶过程,它们的蚀变均发生在非氧化的含水或无水的环境中。     

EFFECT OF SNOW AND FIRN HYDROLOGY ON THE PHYSICAL AND CHEMICAL CHARACTERISTICS OF GLACIAL RUNOFF

Near-surface processes on glaciers, including water flow over bare ice and through seasonal snow and firn, have a significant effect on the speed, volume and chemistry of water flow through the glacier. The transient nature of the seasonal snow profoundly affects the water discharge and chemistry. Water flow through snow is fairly slow compared with flow over bare ice and a thinning snowpack on a glacier decreases the delay between peak meltwater input and peak stream discharge. Furthermore, early spring melt flushes the snowpack of solutes and by mid-summer the melt water flowing into the glacier is fairly clean by comparison. The firn, a relatively constant feature of glaciers, attenuates variations in water drainage into the glacier by temporarily storing water in saturated layer. Bare ice exerts opposite influences by accentuating variations in runoff by water flowing over the ice surface. The melt of firn and ice contributes relatively clean (solute-free) water to the glacier water system.     

浙江嵊县—新昌盆地新生代玄武岩中橄榄石、辉石、斜长石矿物化学及演化的研究

浙江嵊县—新昌盆地新生代玄武岩为橄榄拉斑玄武岩—碱性橄榄玄武岩—碧玄岩组合。根据124个矿物电子探针分析资料研究了橄榄石、单斜辉石和斜长石的种属、成分相关性及演化。根据矿物组合、单斜辉石化学成分和演化趋势以及岩石化学特征,认为本区玄武岩属于碱性玄武岩系列。     

新疆尾亚地区石英二长闪长岩的岩浆混合成因

新疆东天山的尾亚钒钛磁铁矿矿区,在花岗岩中含有大量闪长岩包体,而且花岗岩与闪长岩相互包裹、渗透,并在花岗岩与闪长岩接触带形成二者混合的产物--岩浆混合岩.通过野外特征、岩相学和矿物成分对比,发现矿区中部的石英二长闪长（斑）岩体与岩浆混合岩完全相同,表明该岩体系岩浆混合成因.各类参与岩浆混合作用岩石的岩相学和矿物学表现出典型的岩浆混合作用特征.矿物不平衡组构主要有：钾长石的更长环斑结构、斑晶的环边结构、针状磷灰石发育、暗色矿物的聚晶团块、岩浆混合岩中出现钾长石“变晶”等等.各类岩石中斜长石和角闪石的主要氧化物成分对SiO2（%）表现出类似全岩哈克图解的线性关系.主要造岩矿物的化学成分以及钾长石巨晶的化学成分剖面,反映出本区岩浆混合作用有化学混合的参与.黑云母的化学成分表明,本区岩浆混合为以壳慢混源为基础的混合作用.     

Mantle diapir-induced arc volcanism: The Ueno Basalts, Nomugi-Toge and Hida volcanic suites, central Japan

Stratigraphic and geochronological data show that the late Cenozoic Ueno Basalts and related Nomugi-Toge and Hida volcanic suites of the Norikura Volcanic Chain, Japan, were active for ~ 1 million years. Temporal and spatial variations of the volcanic activity and chemistry of the volcanic products suggest that it was induced by a common mantle diapir. The Ueno Basalts are small monogenetic volcanoes scattered over an area 50 km in diameter, and comprise a small volcanic province. The Ueno Basalts are almost all subalkalic basalt to basaltic andesite, erupted through the late Pliocene to the earliest Pleistocene (2.7–1.5 Ma). Andesite to dacite of the Nomugi-Toge volcanic rocks were concurrently active in the back arc side, and two eruption stages (2.6–2.2 and 2.1–1.7 Ma) are recognizable. Two voluminous dacite and rhyolite ignimbrites, the Hida Volcanic Rocks, were erupted deeper in the back-arc region, at ca 1.75 and 1.7 Ma. Both the Nomugi-Toge and Hida suites are also subalkalic, except for the last ignimbrite. In the Ueno Basalts, alkali olivine basalt was erupted in the earliest stage, and was followed by subalkalic basalt, showing that the magma segregation depth ascended with time. This coincided with uplift of the volcanic province and with quasi-concentric expansion of the eruption centers, suggesting that an upwelling mantle diapir was the cause of the volcanism. The Nomugi-Toge andesite–dacite lavas and the Hida dacite and rhyolite ignimbrites are considered to have originated from the same mantle diapir, because of their close proximity to the Ueno Basalts and their near-contemporaneous activity. Mantle diapirs have a significant role in the origin of subalkalic volcanic rocks in the island arcs.     

Occurrence of polar stratospheric clouds at Kiruna

Polar stratospheric clouds (PSCs) are often observed in the Kiruna region in northern Sweden, east of the Scandinavian mountain range, during wintertime. PSC occurrence can be detected by ground-based optical instruments. Most of these require clear tropospheric weather. By applying the zenith-sky colour index technique, which works under most weather conditions, the data availability can be extended. The observations suggest that PSC events, especially of type II (water PSCs) may indeed more common than predicted by synoptic models, which is expected because of the frequent presence of mountain-induced leewaves. However, it will be of importance to increase the density of independent observations.     

An anomalous subauroral red arc on 4 August, 1972: comparison of ISIS-2 satellite data with numerical calculations

This study compares the Isis II satellite measurements of the electron density and temperature, the integral airglow intensity and volume emission rate at 630 nm in the SAR arc region, observed at dusk on 4 August, 1972, in the Southern Hemisphere, during the main phase of the geomagnetic storm. The model results were obtained using the time dependent one-dimensional mathematical model of the Earth’s ionosphere and plasmasphere (the IZMIRAN model). The major enhancement to the IZMIRAN model developed in this study to explain the two component 630 nm emission observed is the analytical yield spectrum approach to calculate the fluxes of precipitating electrons and the additional production rates of N⁺₂, O⁺₂, O⁺(⁴S), O⁺(²D), O⁻(²P), and O⁺(²P) ions, and O(¹D) in the SAR arc regions in the Northern and Southern Hemispheres. In order to bring the measured and modelled electron temperatures into agreement, the additional heating electron rate of 1.05 eV cm⁻³ s⁻¹ was added in the energy balance equation of electrons at altitudes above 5000 km during the main phase of the geomagnetic storm. This additional heating electron rate determines the thermally excited 630 nm emission observed. The IZMIRAN model calculates a 630 nm integral intensity above 350 km of 4.1 kR and a total 630 nm integral intensity of 8.1 kR, values which are slightly lower compared to the observed 4.7 kR and 10.6 kR. We conclude that the 630 nm emission observed can be explained considering both the soft energy electron excited component and the thermally excited component. It is found that the inclusion of N₂(v > 0) and O₂(v > 0) in the calculations of the O⁺(⁴S) loss rate improves the agreement between the calculated N_e and the data on 4 August, 1972. The N₂(v > 0) and O₂(v > 0) effects are enough to explain the electron density depression in the SAR arc F-region and above F2 peak altitude. Our calculations show that the increase in the O⁺ + N₂ rate factor due to the vibrationally excited nitrogen produces the 5–19% reductions in the calculated quiet daytime peak density and the 16–24% decrease in NmF2 in the SAR arc region. The increase in the O⁺ + N₂ loss rate due to vibrationally excited O₂ produces the 7–26% decrease in the calculated quiet daytime peak density and the 12–26% decrease in NmF2 in the SAR arc region. We evaluated the role of the electron cooling rates by low-lying electronic excitation of O₂(a¹δ_g) and O₂(b¹σ_g⁺), and rotational excitation of O₂, and found that the effect of these cooling rates on T_e can be considered negligible during the quiet and geomagnetic storm period 3–4 August, 1972. The energy exchange between electron and ion gases, the cooling rate in collisions of O(³P) with thermal electrons with excitation of O(¹D), and the electron cooling rates by vibrational excitation of O₂ and N₂ are the largest cooling rates above 200 km in the SAR arc region on 4 August, 1972. The enhanced IZMIRAN model calculates also number densities of N₂(B³π_g⁺), N₂(C³π_u), and N₂(A³σ_u⁺) at several vibrational levels, O(¹S), and the volume emission rate and integral intensity at 557.7 nm in the region between 120 and 1000 km. We found from the model that the integral integral intensity at 557.7 nm is much less than the integral intensity at 630 nm.     

A distribution law for relative humidity in the upper troposphere and lower stratosphere derived from three years of MOZAIC measurements

Data from three years of MOZAIC measurements made it possible to determine a distribution law for the relative humidity in the upper troposphere and lower stratosphere. Data amounting to 13.5% of the total were obtained in regions with ice supersaturation. Troposphere and stratosphere are distinguished by an ozone concentration of 130 ppbv as threshold. The probability of measuring a certain amount of ice supersaturation in the troposphere decreases exponentially with the degree of ice supersaturation. The probability of measuring a certain relative humidity in the stratosphere (both with respect to water and ice) decreases exponentially with the relative humidity. A stochastic model that naturally leads to the exponential distribution is provided. Mean supersaturation in the troposphere is about 15%, whereas ice nucleation requires 30% supersaturation on the average. This explains the frequency of regions in which aircraft induce persistent contrails but which are otherwise free of clouds. Ice supersaturated regions are 3-4 K colder and contain more than 50% more vapour than other regions in the upper troposphere. The stratospheric air masses sampled are dry, as expected, having mean relative humidity over water of 12% and over ice of 23%, respectively. However, 2% of the stratospheric data indicate ice supersaturation. As the MOZAIC measurements have been obtained on commercial flights mainly between Europe and North America, the data do not provide a complete global picture, but the exponential character of the distribution laws found is probably valid globally. Since water vapour is the most important greenhouse gas and since it might enhance the anthropogenic greenhouse effects via positive feedback mechanisms, it is important to represent its distribution correctly in climate models. The discovery of the distribution law of the relative humidity makes possible simple tests to show whether the hydrological cycle in climate models is represented in an adequate way or not.