换水率和营养水平对太湖流域横山水库硅藻水华的影响

为探讨水文过程对水库硅藻异常增殖的影响,对江苏宜兴横山水库的硅藻生消过程中浮游植物、水质、降水、水位、气温等指标进行观测研究.结果表明,横山水库硅藻年际生物量波动很大,9月出现明显的异常增殖,总生物量达到14.27 mg/L,硅藻的优势属为针杆藻(Synedra)、小环藻(Cyclotella)、曲壳藻(Achnanthes)和直链藻(Melosira),以针杆藻的优势度最高;浮游植物生物量与营养盐浓度关系不明显,与总氮浓度甚至呈负相关,但小环藻生物量与水体溶解性磷浓度呈正相关;水库的换水率与浮游植物生物量、硅藻的异常增殖过程和营养盐浓度水平均密切关联,总氮、溶解性磷浓度与水库换水率呈正相关,而硅藻生物量与水库换水率呈指数负相关.数值拟合分析显示硅藻生物量可以用换水率和磷浓度推算而得.研究表明,对于中营养水平的水库,硅藻生物量变化可能受水文过程与水质条件共同控制,在水库的硅藻水华防控中,既要加强营养盐水平的严格控制,也需考虑水文过程的调控手段.     

菹草(Potamogeton crispus)附着物对水体氮、磷负荷的响应

通过实验模拟了10组氮、磷负荷对菹草(Potamogeton crispus)生长期和衰亡期茎叶附着物的影响.结果显示:随着水体氮、磷浓度的升高,菹草附着物的叶绿素a(Chl.a)含量、附着有机物量、附着无机物量和附着物总量均增加,在氮、磷浓度最高的T10组(总氮12.0 mg/L,总磷1.0 mg/L),附着物的总量达到高峰,附着物的Chl.a含量为2.005~4.765mg/g(DW),附着有机物的量为29.027~94.886 mg/g(DW),附着无机物的量为176.881~397.750 mg/g(DW),附着物总量为205.909~492.636 mg/g(DW).在菹草的快速生长期、稳定期和衰亡期,附着物的Chl.a含量、附着有机物量、附着无机物量和附着物总量均存在显著差异,均表现为衰亡期 >稳定期 >快速生长期,且在各营养盐浓度下均存在这一趋势.菹草衰亡期附着物的Chl.a含量、附着有机物量、附着无机物量和附着物总量分别为稳定期的1.046~1.826、1.046~1.638、1.029~1.858和1.106~1.717倍,为快速生长期的2.324~4.059、2.323~3.640、2.101~3.792和2.280~3.584倍.结果表明水体氮、磷负荷的增加促进了菹草茎叶附着物的生长和积累,加速了沉水植物衰亡.     

Chinese stalagmite paleoclimate researches: A review and perspective

Stalagmite is one kind of secondary carbonates formed in limestone caves(speleothem). After cave water droplets containing Ca~(2+)and HCO_3 drip onto floor, carbonate in the water might become supersaturated due to CO_2 degassing under certain conditions, resulting in the formation of stalagmite in a process year after year. Stalagmite is one of important geological archives for paleoclimate research. The advantages include wide spatial distribution, suitable for U-Th and U-Pb dating, enriched in climate proxies, continuity, long time span, comparability and lower sampling cost etc. These factors have propelled stalagmite paleoclimate research to the forefront of global paleoclimatology with an irreplaceable role. The stalagmite paleoclimate study started in the western countries, mainly in Europe and America in 1960 s–1970 s, while the relevant research in China was progressively developed in the 1980 s–1990 s after the Reform and Opening up. Although there was a huge gap between the overall research level in China and western countries, a solid research foundation, as well as a number of talent teams were established during the period. In the 21 st century, starting from the publication of stalagmite records from Hulu Cave in Nanjing in 2001, the stalagmite paleoclimate research in China has ushered in a flourishing development and a real leap on the basis of international cooperation, resulting in significant international impacts. The landmark achievements, including establishment of the world's longest(640000 years) East Asian monsoon stalagmite record, as well as the longest Indian monsoon(280000 years),South American monsoon(250000 years), North American westerly climate(330000 years), Central Asian westerly climate(135000 years), and northwestern China westerly climate(500000 years), have laid a milestone in the paleoclimate study in these climate domains. Importantly, these stalagmite records have revealed the relationship of Asian monsoon variations with solar insolation climate change in polar regions, and the South American monsoon changes on orbital-suborbital timescales, which have provided new geological observations for the development of orbital-suborbital climate theory; elaborated coupling and differentiation relationships between the Asian monsoon and the westerly climate; reconstructed the history of Asian monsoon changes in the Holocene in detail, and thus the hydrological and climate variances behind Chinese and Indian civilizationcultural evolutions. Furthermore, a large number of high-resolution stalagmite records over the past 2000 years have been reconstructed, which are important for understanding short-term climate variability and magnitude, events, cycles, and thus the future climate projection. The achievements have also involved the improvements of a number of important techniques, such as U-Th dating method, the establishments of various hydroclimatic proxies, as well as the contributions to the reconstruction of the atmosphere~(14)C variation history over the past ～54000 years. On the perspective of the future, the Chinese stalagmite community should continue to develop key techniques, further clarify the hydroclimatic significance of stalagmite proxies, impel the integration of related disciplines, and concentrate on key scientific issues in global climate change and major social demands.     

Response of soil detachment rate to the hydraulic parameters of concentrated flow on steep loessial slopes on the Loess Plateau of China

Using hydraulic parameters is essential for describing soil detachment and developing physically based erosion prediction models. Many hydraulic parameters have been used, but the one that performs the best for describing soil detachment on steep slopes when the lateral expansion (widening) of rills is not limited has not been identified. An indoor concentrated flow scouring experiment was performed on steep loessial slopes to investigate soil detachment rates for different flow rates and slope gradients. The experiments were conducted on a slope‐adjustable plot (5 m length, 1 m width, 0.5 m depth). Sixteen combinations of 4 flow rates (10, 15, 20, and 25 L/min) and 4 slope gradients (17.6%, 26.8%, 36.4%, and 46.6%) were investigated. The individual and combined effects of slope gradient and flow hydraulic parameters on soil detachment rate were analysed. The results indicated that soil detachment rate increased with flow rate and slope gradient. Soil detachment rate varied linearly and exponentially with flow rate and slope gradient, respectively. Multivariate, nonlinear regression analysis indicated that flow depth exerted the greatest influence on the soil detachment rate, followed by unit discharge per unit width, slope gradient, and flow rate in this study. Shear stress and stream power could efficiently describe the soil detachment rate using a power equation. However, the unit stream power and unit energy of the water‐carrying section changed linearly with soil detachment rate. Stream power was an optimal hydraulic parameter for describing soil detachment. These findings improve our understanding of concentrated flow erosion on steep loessial slopes.     

澜沧江流域重大水电工程地区地震层析成像

根据云南区域地震台网记录的地震观测资料,使用澜沧江流域周边40个地震台记录到的3600多个地震的近25000条P波和S波波形数据,采用层析成像理论,反演了云南澜沧江流域地区的三维速度结构图,结果表明,上地壳速度异常分布与地表地质断裂构造有关。以澜沧江断裂为界,西侧大部分地区表现为速度负异常,扰动值在-2．0％～-4．0％;东侧大部地区为速度正异常。在30km深的剖面上,澜沧江流域西南出现一条近北东走向的负速度异常带,这可能与南汀河深大断裂有关;在45km和65km深度以下的剖面上,同样出现与澜沧江断裂和红河断裂有关的速度负异常带,并且澜沧江断裂北段与南段速度异常不同,北段总体表现为负异常,南段则表现为正异常。腾冲火山地热区从地表至地幔均出现低速异常,表明地幔热物质参与了腾冲火山的活动。研究区域层析成像三维速度异常分布揭示了谰沧江流域地球内部状态的某些特征,为澜沧江流域重大梯级电站的水库诱发地震机理研究与地震预测提供了地球内部介质结构的深部背景。     

云南气候特征与主要经济作物种植适宜性的关系

基于云南省、贵州省和广西壮族自治区共163个站点气候资料和主要经济作物产地分布数据,应用作物生态学和农业气象学原理,分析云南气候特征与经济作物种植的气候适宜性关系.结果表明,受季风气候、高原山地气候、低纬气候的影响,云南干湿季节分明、夏季气温偏低、春秋季长、气温日较差大、干季日照较多,具有气候区域性和层次性差异特点,由...     

宁夏固原炭山地区中侏罗统延安组油页岩特征及其沉积环境

宁夏固原炭山地区存在大量与煤伴生的油页岩资源,油页岩主要赋存于中侏罗统延安组中下部各含煤层系中。本文采集钻孔所获延安组油页岩岩心样品,通过低温干馏、主量元素测定以及钻井录井等方法对炭山地区油页岩特征进行了研究,明确了油页岩测井识别依据,恢复了油页岩沉积环境。研究表明：炭山地区油页岩主要以黑色、灰黑色、深灰色为主,质地较轻,密度小,硬度小,断口参差状、贝壳状,具油脂光泽、沥青光泽,块状层理发育;油页岩含油率为3.60%~9.00%,灰分质量分数为42.50%~79.05%,全硫质量分数为0.07%~1.37%,发热量为11.01 kJ/g（平均值）,属中品质、硅质灰分、低硫且与煤伴生的油页岩;油页岩中w（SiO₂）变化较大,为53.89%~65.55%,w（Al₂O₃）为17.45%~23.29%,w（K₂O）明显高于w（Na₂O）,w（Fe₂O₃+MgO）为12.75%~21.98%,表明油页岩中含有较多的含钾矿物和镁铁成分;另外,Al₂O₃/（CaO+Na₂O）值为3.09~21.12,揭示油页岩稳定组分含量较高。炭山地区油页岩测井曲线特征明显区别于煤层和泥岩,油页岩长距伽马、声波时差和密度介于煤层与泥岩之间,而电阻率明显低于煤层和泥岩。炭山地区油页岩化学蚀变指数为74.87~84.35,Sr/Ba值为0.33~0.83,平均为0.61,Th/U值为1.00~3.50,表明本地区油页岩沉积环境为温暖、温润的缺氧、贫氧的陆相淡水湖泊环境和沼泽环境。     

淮南煤田刘庄煤矿深部煤层气地质特征

为了查明刘庄煤矿深部煤层气赋存及开发地质条件,在井田内实施了两口煤层气探井,并开展了系统的分析测试工作。结果表明:刘庄深部勘查区主要煤层孔隙度一般为4.14%~4.77%,比表面积集中在2.184~5.228m 2/g,13-1煤层、11-2煤层和8煤层试井渗透率分别为0.12mD、0.09mD和0.08mD,孔裂隙系统发育一般,属于渗透性差的储集层;储层压力梯度大于静水压力梯度,属高异常压力范畴;主要煤层兰氏压力平均为2.61MPa,兰氏体积平均为6.74m 3/t,吸附能力较低;LT-1井气测录井过程中共出现14层气测异常,异常层段全烃含量均较低,最大为3.701%(16-1煤);主要煤层的含气量分布在0.21~1.47m 3/t,平均0.65m 3/t,主要煤层含气饱和度均很低,最大值仅为18.0%。综合分析认为,刘庄煤矿深部主要煤层埋深大,孔裂隙系统发育差,渗透率低,而且具有低含气量和低饱和度的特征,煤层气勘探风险较高。     

3D bearing capacity probabilistic analyses of footings on spatially variable c–φ soil

Acta Geotechnica - The paper examines three-dimensional (3D) analyses of the load bearing capacity of square and strip footings on a spatially variable cohesive–frictional (c–φ)...     

Effect of the pressurized duration on improving dredged slurry with air booster vacuum preloading

Abstract

Compared with traditional vacuum preloading, air booster vacuum preloading is more effective at strengthening dredged slurry and improving the consolidation process. Although many engineering practices have shown that the pressurized duration has a significant effect on the reinforcement effect, there is no standard available for determining the pressurized duration. In this study, five dredged slurry samples were tested to examine the effect of different pressurized durations on the consolidation. An extensive monitoring system was used to measure the vacuum pressure, pore water pressure, settlement, and water discharge during the test, while the water content and shear strength were measured after the test. The collected monitoring data were comprehensively analyzed to evaluate the reinforcement effect. The results revealed that the pressurization system can be used to reinforce deep dredged slurry and make the whole soil layer more homogeneous. If the pressurized duration is too short, the dissipation of pore water pressure is too little to achieve the pressurization effect. If the pressurized duration is too long, too much gas will be in the soil and enter the vacuum system, which will significantly reduce the vacuum pressure and thus the reinforcement effect. Based on these findings, the optimal pressurized duration was obtained.