3种石生苔藓植物碳酸酐酶对石灰岩的溶蚀作用

以普定严重石漠化区域石生细叶小羽藓Haplocladium microphyllum Hedw.、银叶真藓Bryum argenteum Hedw. 和美灰藓Eurohypnum leptothollum(C. Muell. ) Ando.为研究材料,运用模拟土柱实验装置收集植物淋出液并测定其电导率、pH值、CA活性、钙镁元素含量并对石灰岩试片溶蚀进行估算。结果表明：岩溶生态系统中不同植物的碳酸酐酶活性差异较大,其中细叶小羽藓的溶蚀效果最为显著,产生的碳汇量最大;CA活性最高为美灰藓,为272.99 U·g-1·FW;最小的为细叶小羽藓的CA活性较低,为38.31 U·g-1·FW。淋出液均检测到CA的存在,银叶真藓淋溶6 d的CA活性最高,随着时间的推移,3种植物CA总体表现出先略降,然后升高,最后趋于平稳的趋势;pH值呈上升趋势;电导率呈下降趋势;淋出液中Ca2+和Mg2+浓度随淋溶时间的延长浓度逐渐降低,一定时间后趋于动态的平衡;说明石生植物对石灰岩有明显的酶促溶蚀驱动作用,且溶蚀率与CA活性成正相关。     

1961-2019年新疆暴雨山洪灾害损失的时空变化特征

利用1961—2019年新疆86县(市)暴雨山洪灾害的5个灾情要素数据(死亡人数、倒塌房屋数、倒塌棚圈数、牲畜死亡数量、农作物受灾面积),采用比值权重法和无量纲化线性求和方法构建暴雨山洪灾害灾损指数,根据灾损指数的不同阈值范围将暴雨山洪灾害定量划分等级,并分析其时空分布特征。结果表明:(1)新疆暴雨山洪灾害主要出现在伊犁州、阿克苏地区和喀什地区,其中伊犁州伊宁县、巩留县、霍城县和尼勒克县最重,伊犁州暴雨山洪的致灾危险性与其暴雨日数分布有很好的一致性。(2)新疆暴雨山洪灾害发生具有很强的季节性,在夏季6—8月危害性最大,其中灾害出现次数和死亡人数均在7月最多(与降水相关性最大)。(3)近59 a来新疆暴雨山洪灾害的强度呈上升趋势,年灾损指数随时间呈线性增长趋势,暴雨山洪灾害的强度在20世纪80年代中期明显增加,其年际变化与3—10月降水量、大雨日数、暴雨日数密切相关。     

Nonlinear consolidation of vertical drains with coupled radial-vertical flow considering time and depth dependent vacuum pressure

The system of vacuum pressure combined with vertical drains to accelerate soil consolidation is one of the most effective ground improvement methods. The consolidation theories of soft soil improved by vertical drains including void ratio–dependent compressibility and permeability have been widely applied in practice to predict the consolidation behavior. In this paper, analytical solutions of the consolidation of vertical drains are derived incorporating the loss and propagating stage of vacuum pressure. In addition, special solutions are obtained for the cases of instantaneous surcharge loading and staged surcharge loading, based on the general solution. The solution is verified by ignoring the propagating stage of vacuum pressure formation and comparing it with an existing solution. The effects of vacuum pressure loss and propagating stage combined with other parameters are investigated through the ratio between excess pore water pressure and surcharge loading.     

Sediment particle selectivity and its response to overland flow hydraulics within grass strips

Particle selectivity plays an important role in clarifying sediment transport processes in vegetative filter strips (VFS). 10-m long grass strips at slopes of 5° and 15° were subjected to a series of sediment-laden inflows experiments with different particle sizes to investigate the sediment transport and its response to overland flow hydraulics. The inflow sediments came from local soil, river-bed sand, and mixed, with median particle size d₅₀ of 39.9, 207.9 and 77.4 μm, respectively. Three independent repeated experiments were carried for each treatment. The results show that when the sediment trapping lasted for a certain length of time, the re-entrainment of some small-sized particles was greater than the deposition; that is, net loss occurred, which was not erosion of the original soil. Net loss of particles is mainly determined by the particle diameter. The coarser the inflow sediment particles and/or the steeper the slope, the coarser the particles can be net lost. Deposited sediment causes the VFS bed surface to become smooth and hydraulic resistance decrease exponentially. Unit stream power P is more suitable than shear stress τ of overland flow to be used to describe the process of sediment particle transport in VFS. The relationship between P and d₅₀ of outflow sediment is very consistent with the form of power function with a constant term. These results are helpful to understand the physical process of sediment transport on vegetation hillslopes.     

Assessment of transmission loss in a Mediterranean karstic watershed (Wadi Natuf,West Bank)

Run‐off transmission loss into karstified consolidated aquifer bedrock below ephemeral streams (wadis) has rarely been described nor quantified. This study presents unique data of long‐term high‐resolution field measurements and field observations in a semiarid to subhumid Mediterranean carbonatic mountainshed. The catchment with a 103 km² surface area is subdivided into 5 subcatchments. Coupled run‐off measurements were made in the different stream sections (reaches), and transmission loss calculated from differences in discharge. Rainfall and run‐off observations from 9 automated precipitation gauging stations and 5 pressure transducers for automatic water level recording are complemented by manual measurements during 34 run‐off events covering a total measurement period of 8 consecutive years. Run‐off generation is strongly event based depending on rainfall intensities and depths. Both, run‐off generation and transmission losses are related to spatial patterns of bedrock lithologies (and hydrostratigraphy). Transmission losses range between 62% and 80% of generated run‐off, with most of the smaller events showing 100% transmission loss. Therefore, although event run‐off coefficients in the mountains can reach up to 22%, only 0.11% of total annual precipitation leaves the catchment as run‐off. Most run‐off infiltrates directly into the regional karst aquifers (Upper Cretaceous carbonate series), with transmission loss intensities of up to 40 mm/h below the stream channels. The factors determining run‐off—such as geology, pedology, vegetation cover and land use, relief and morphology, the semiarid to subhumid Mediterranean climate with a strong elevation gradient, and the patchiness of individual storm events distributed over the winter seasons—as well as the lithology and epikarst features of the bedrock are all characteristic for larger areas in the Mediterranean region. Therefore, we expect that our findings can be generalized to a large extent.     

A simple approach to estimating freshwater discharge in branched estuarine systems

In tidal estuaries, quantifying freshwater discharge is still a difficult problem that has not yet been overcome due to the inherent difficulty in measuring and analysing the tidal discharge, especially during periods of low river flow. Because observations are often made in the stations further upstream, where the ratio of river to tidal discharge is large, it remains difficult to determine the discharge rate in the saline region. Freshwater discharge estimation is even more difficult in a branched estuary system having multiple diversion channels that connect with each other at a junction. To date, several methods have been developed for estimating freshwater discharge in estuaries. The most widely used are analytical and conceptual models that employ salinity as the principal trace and numerical simulations. However, these methods are very time consuming and costly as they require large sets of observations before the computations can take place. This paper presents a simple approach to investigating the discharge distribution over branched channels by considering the energy loss due to friction. We develop an analytical model that can obtain the discharge rate quantitatively at a junction where the main flow bifurcates into two branches. The model uses the bed roughness, tidal water level, and cross‐sectional profile under tidally averaged conditions as input data. Two selected estuarine systems in the Hiroshima delta in Japan and the Mekong delta in Vietnam have been investigated. Computations of the newly developed model show good agreement with earlier published results computed by sophisticated analytical and numerical models.     

Mineral equilibria constraints on open‐system melting in metamafic compositions

The recent development of activity–composition relations for mineral and melt phases in high‐grade metamafic rocks allows mineral equilibria tools to be used to further aid our understanding of partial melting and the mineralogical consequences of melt segregation in these rocks. We show that bulk compositional data from natural amphibolites cover a wide compositional range, with particular variability in the content and ratios of Ca, Na and K indicating that low‐grade metasomatic alteration can substantially alter the igneous protolith chemistry and potentially affect the volume and composition of melt generated. Mineral equilibria calculations for five samples that span the compositional variability in our data set indicate that melting occurs primarily via the fluid‐absent breakdown of amphibole+quartz to produce a pressure‐sensitive peritectic assemblage of augite, orthopyroxene and/or garnet. The introduction of orthopyroxene at the onset of the amphibolite‐to‐granulite‐facies transition at lower pressure results in an increased rate of melt production until quartz is typically exhausted, and this is similarly seen for the introduction of garnet at higher pressure. Calculated melt compositions are dependent on the protolith composition, but initial solidus melting and biotite breakdown produce 1–3 mol.% of K‐rich granitic melts. As hornblende melting proceeds, 15–20 vol.% of either more granodioritic‐to‐tonalitic or granodioritic‐to‐trondhjemitic melt is produced. Once quartz is exhausted, intermediate to mafic melt compositions are produced at ultrahigh‐temperature conditions. Quartz‐rich lithologies with high Ca coupled to low Na and K are the most fertile under orogenic conditions, yielding up to 25 mol.% of sub‐alkalic granitic melt by 850°C. Such rocks did not experience significant subsolidus alteration. Altered compositions with low Ca and elevated Na and K are not as fertile, yielding less than 15 mol.% of alkalic granitic melt by 850°C. These melt volumes are enough to be segregated, and can make a contribution to granite magmatism and intracrustal differentiation that should not be overlooked.     

Sediment yield and transport process assessment from reservoir monitoring in a semi‐arid mountainous river

Soil loss, fluvial erosion, and sedimentation are major problems in semi‐arid environments due to the high associated costs of decreasing services such as provisioning and regulating water resources. The objective of this research is to analyse sediment yield in a mountainous semi‐arid basin, paying special attention to the sources of sediment, the associated uncertainties, and the transport processes involved. The segregation hypothesis along a reservoir of the sediment coming from hillslopes or fluvial systems is also evaluated. For this purpose, bottom‐set and deltaic deposits of a reservoir (110 hm³ ) in southern Spain have been measured and compared with basin erosion and fluvial transport monitoring over a 12‐year period. The volume of sediment stored at the bottomset of the reservoir shows a relative match with parametric predictions based on the Revised Universal Soil Loss Equation/Modified Universal Soil Loss Equation hillslope models and rating curves, estimated as being between 7 and 13 t·ha^?1·year^?1. Similarly, the measured volume of deltaic deposit fits the average value of stochastic simulations from different bedload transport equations. These contributions represent 50–65% of the total volume measured regarding suspended sediment inputs, way above that described in previous works. This highlights the importance of considering bedload when estimating the useful life of reservoirs in semi‐arid environments. The major differences in sediment grain size between hillslopes and river systems, and the size fractions measured along the reservoir, support the assertion of segregation hypothesis. Nonetheless, based on the processes observed and the uncertainty related to modelling, that assertion has to be taken with caution. At basin scale, a specific sediment yield of between 19 and 24 t·ha^?1·year^?1 has been estimated, which includes hillslopes and fluvial contributions. This rate is in the range of sediment yield reported for Mediterranean mountain areas of a torrential character. The pulse‐like nature of the system and the spatial heterogeneity of fluvial and hillslope erosion rates points out the importance of considering mid to long‐term and process‐based approaches and emphasizes the limitations of annual estimations for management purposes.     

西和县大桥一带金矿区复杂地层钻探施工技术

本文针对西和县大桥一带金矿区钻探施工中地层破碎、裂隙发育,漏失,坍塌,卡钻,埋钻等复杂地层钻进难点,采用金刚石单动双管钻进工艺和聚丙烯酰胺不分散低固相钻井液护孔技术,并采用多种堵漏措施,取得了较好的技术效果。     

冀中坳陷前第三系岩溶发育规律及其控制因素

冀中坳陷自蓟县纪杨庄运动以来经历了七次较大规模的构造运动,伴随发育有七期岩溶,但只有最晚的发生于印支—燕山运动的第Ⅶ期岩溶被较多保存下来,它可划分出三个次级岩溶期。从中元古界长城系高于庄组到下古生界奥陶系峰峰组,潜山碳酸盐岩的溶蚀作用发生在多个层位,尤其是蓟县系白云岩和奥陶系灰岩岩溶现象普遍。纵向上可统计出第Ⅶ期岩溶中的全部三期次级岩溶,岩溶层位主要为蓟县系雾迷山组、寒武系及奥陶系。钻井中泥浆漏失现象普遍,其中单井泥浆漏失量最大的层位是雾迷山组,其次是奥陶系,寒武系相对最小。冀中坳陷岩溶的总体展布特征表现为水平岩溶带距古地表的深度由凹陷向凸起变大,而水平岩溶带的厚度总体呈现由凹陷向凸起减小的趋势。构造运动、多层系碳酸盐岩的发育以及多套烃源岩的生烃演化,是影响冀中坳陷岩溶发育的三个主要控制因素。