Seasonal connections between meteoric water and streamflow generation along a mountain headwater stream

In snowmelt-driven mountain watersheds, the hydrologic connectivity between meteoric waters and stream flow generation varies strongly with the season, reflecting variable connection to soil and groundwater storage within the watershed. This variable connectivity regulates how streamflow generation mechanisms transform the seasonal and elevational variation in oxygen and hydrogen isotopic composition (δ¹⁸O and δD) of meteoric precipitation. Thus, water isotopes in stream flow can signal immediate connectivity or more prolonged mixing, especially in high-relief mountainous catchments. We characterized δ¹⁸O and δD values in stream water along an elevational gradient in a mountain headwater catchment in southwestern Montana. Stream water isotopic compositions related most strongly to elevation between February and March, exhibiting higher δ¹⁸O and δD values with decreasing elevation. These elevational isotopic lapse rates likely reflect increased connection between stream flow and proximal snow-derived water sources heavily subject to elevational isotopic effects. These patterns disappeared during summer sampling, when consistently lower δ¹⁸O and δD values of stream water reflected contributions from snowmelt or colder rainfall, despite much higher δ¹⁸O and δD values expected in warmer seasonal rainfall. The consistently low isotopic values and absence of a trend with elevation during summer suggest lower connectivity between summer precipitation and stream flow generation as a consequence of drier soils and greater transpiration. As further evidence of intermittent seasonal connectivity between the stream and adjacent groundwaters, we observed a late-winter flush of nitrate into the stream at higher elevations, consistent with increased connection to accumulating mineralized nitrogen in riparian wetlands. This pattern was distinct from mid-summer patterns of nitrate loading at lower elevations that suggested heightened human recreational activity along the stream corridor. These observations provide insights linking stream flow generation and seasonal water storage in high elevation mountainous watersheds. Greater understanding of the connections between surface water, soil water and groundwater in these environments will help predict how the quality and quantity of mountain runoff will respond to changing climate and allow better informed water management decisions.     

A modified numerical model for moisture-salt transport in unsaturated sandy soil under evaporation

Soil salinization, caused by salt migration and accumulation underneath the soil surface, will corrode structures. To analyze the moisture-salt migration and salt precipitation in soil under evaporation conditions, a mathematical model consisting of a series of theoretical equations is briefly presented. The filling effect of precipitated salts on tortuosity factor and evaporation rate are taken into account in relevant equations. Besides, a transition equation to link the solute transport equation before and after salt precipitation is proposed. Meanwhile, a new relative humidity equation deduced from Pitzer ions model is used to modify the vapor transport flux equation. The results show that the calculated values are in good agreement with the published experimental data, especially for the simulation of volume water content and evaporation rate of Toyoura sand, which confirm the reliability and applicability of the proposed model.     

地震前后垂直形变场动态演化的量化指标

提出一种表达垂直形变场动态演化过程的量化指标——区域应变率、应变集中度。在此基础上，对南北地震带各水准监测区近30年的垂直形变资料进行了实际计算．并结合具体震例进行了对比研究。结果表明：量化指标在一定程度上能够反映地震前后形变场的动态演化过程和地壳运动状态，对地震的中长期预报有一定的积极意义。     

我国个人所得税制度完善的法律思考

个人所得税是与每个人联系都很紧密的税种,它的完善与否,直接体现了我国法制建设的完善程度及居民素质的高低。但现行税制由于内外原因,存在各种缺陷。因此有必要在理论中找到对策,并在实践中寻求答案逐步完善个人所得税制度。     

板翅式换热器综合性能优化的设计方法

应用给定换热器结构材料而使换热量最大的两侧换热表面的最佳匹配准则和使可用能损失率最小的最佳运行参数准则。利用两个准则间的关系 ,采用迭代的方式完成换热器的优化设计 ,使换热器的设计达到材料省、换热效果好及运行费用低的目的 ,且能在设计阶段实现。     

测绘科技进步的研究与测算

科技进步是测绘事业发展的动力 ,讨论运用科技进步的评价指标 ,对测绘单位的科技进步速度和对经济增长的贡献等进行测算和分析 ,可以为测绘规划管理及决策提供参考。     

Observational Test of an Accretion Model of Star Formation in Galactic Clusters

Theoretical predictions of an accretion model of star formation in galactic clusters, published quite long ago, which is found to have some relevance with the current picture of star formation have been tested with observation of seven clusters of young and intermediate ages. It is found that the agreement between the theory and observation is very good.     

Time scale of an early to mid-Paleozoic orogenic cycle of the long-lived Central Asian Orogenic Belt, Inner Mongolia of China: Implications for continental growth

We present a detailed, new time scale for an orogenic cycle (oceanic accretion–subduction–collision) that provides significant insights into Paleozoic continental growth processes in the southeastern segment of the long-lived Central Asian Orogenic Belt (CAOB). The most prominent tectonic feature in Inner Mongolia is the association of paired orogens. A southern orogen forms a typical arc-trench complex, in which a supra-subduction zone ophiolite records successive phases during its life cycle: birth (ca. 497–477 Ma), when the ocean floor of the ophiolite was formed; (2) youth (ca. 473–470 Ma), characterized by mantle wedge magmatism; (3) shortly after maturity (ca. 461–450 Ma), high-Mg adakite and adakite were produced by slab melting and subsequent interaction of the melt with the mantle wedge; (4) death, caused by subduction of a ridge crest (ca. 451–434 Ma) and by ridge collision with the ophiolite (ca. 428–423 Ma). The evolution of the magmatic arc exhibits three major coherent phases: arc volcanism (ca. 488–444 Ma); adakite plutonism (ca. 448–438 Ma) and collision (ca. 419–415 Ma) of the arc with a passive continental margin. The northern orogen, a product of ridge-trench interaction, evolved progressively from coeval generation of near-trench plutons (ca. 498–461 Ma) and juvenile arc crust (ca. 484–469 Ma), to ridge subduction (ca. 440–434 Ma), microcontinent accretion (ca. 430–420 Ma), and finally to forearc formation. The paired orogens followed a consistent progression from ocean floor subduction/arc formation (ca. 500–438 Ma), ridge subduction (ca. 451–434 Ma) to microcontinent accretion/collision (ca. 430–415 Ma); ridge subduction records the turning point that transformed oceanic lithosphere into continental crust. The recognition of this orogenic cycle followed by Permian–early Triassic terminal collision of the CAOB provides compelling evidence for episodic continental growth.     

Thin-section analysis as a tool to aid identification of palaeoearthquakes on the “slow”, active Geleen Fault, Roer Valley Graben

We analyzed thin sections from two palaeoseismic trenches across the low-slip-rate Geleen Fault in the Belgian Maas River valley to help identifying the most recent large palaeoearthquake on this fault segment. In the first trench we sampled silty sediment below and above a prehistoric stone pavement that was supposedly at or near the surface at the time of the event, and subsequently thrown down. The samples below show a well-developed in situ argillic Bt soil horizon in parent sediment containing remnants of stratification, whereas the sediment above is a structureless colluvium reworked at least partly from Bt-horizon material. Below the stone pavement, we also found evidence of contorted stratification, which is in agreement with macroscopic observations of both the sediment and the stone pavement itself, and which is attributed to co-seismic soft-sediment deformation. In the second trench, we sampled a sequence of vaguely discernible soil horizons in the hanging-wall, interpreted as a buried soil profile (Bt, E, and possibly A horizons), overlain by a featureless deposit. Thin-section analysis supports the colluvial nature of the latter, and also provides evidence that both the base of this layer and the top of the poorly developed A horizon below have occupied a shallow position in a soil profile. A sample from the same depth in the footwall is composed of very different material. Instead of colluvium, we find patches of Bt soil, most likely representing the same pedogenic level as the in situ Bt horizon at larger depth in the hanging-wall, but displaced and subsequently degraded. Furthermore, thin sections confirm that vertical structures cutting this Bt horizon are sand dykes. These dykes could be traced macroscopically upward to the base of the colluvium. In both trenches, we have thus identified a stratigraphic boundary in the hanging-wall, close to the surface, separating an in situ soil below from colluvium above. We interpret this limit and the overlying colluvium as the event horizon and the colluvial wedge, respectively, of a surface-rupturing palaeoearthquake. In addition, in both cases we found evidence of soft-sediment deformation (related to liquefaction) contemporaneous with the event within the stratigraphic resolution.