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11.
太湖流域水库型水源地硅藻水华发生特征及对策分析 总被引:13,自引:2,他引:11
基于溧阳市天目湖沙河水库2009—2014年的硅藻群落结构及水质调查,以及宜兴横山水库等硅藻水华期藻类和水质调查数据,分析了太湖流域水库中硅藻水华群落结构特征及受气温、水位、营养盐等环境条件的影响.结果表明,太湖流域硅藻水华的主要发生期为5—7月,快速生长期发生在气温为16~26℃期间,当气温超过26℃时,硅藻的生物量开始下降.硅藻的优势属包括针杆藻、曲壳藻、小环藻和颗粒直链藻.其中沙河水库和横山水库中针杆藻是主要危害,其生物量主导了硅藻总生物量.大溪水库有时以针杆藻为主,有时以颗粒直链藻为主.当总氮浓度低于1.0 mg/L的Ⅲ类水上限时,水体氮浓度能大大限制硅藻生物量,当总磷浓度低于0.025 mg/L的Ⅱ类水上限时,也可能对硅藻生物量产生限制.高于此营养水平,硅藻水华的严重程度主要受气温、降雨等因素影响.研究表明,对于处于中营养水平的太湖流域水库而言,硅藻生物量既受气温、降雨、水位等气象水文条件的控制,又受氮、磷、硅等营养盐供给的影响.硅藻水华的防控既要关注气候和气象条件,也要尽量削减氮、磷营养盐入湖通量,维持较低营养盐水平是确保硅藻水华不形成危害的关键. 相似文献
12.
早期的理论分析认为大气中临界纬度的存在使得热带-热带外的大气活动互不影响。然而,大量的观测事实表明中低纬度大气运动存在着明显的动力联系。为了帮助人们更好地理解大气中的遥相关现象,在大量文献的基础上,综述了几种波能量传播理论:(1) 大圆理论指出了罗斯贝波在球形大气中的传播特征;(2) 西风通道理论发现了中纬度瞬变扰动越赤道传播的“走廊”;(3) 能量堆积-波列发射理论揭示了热带扰动影响到更高纬度大气活动的可能过程;(4) 赤道波侧向膨胀理论则利用转折纬度的概念更进一步解释了这种中低纬度大气相互作用的物理机制;(5) 经向基本流理论则认为在一定的条件下定常波可以穿过热带东风带传播到另一半球。此外,文中还回顾了在波-流相互作用诊断方面的研究进展,尤其是关于罗斯贝波、惯性重力波和赤道开尔文波。大气能量的经向传播具有显著的年变化和年际变化,这与ENSO、西风急流、大洋中部槽等的变化密切相关。 相似文献
13.
Early theoretical analyses indicated that the tropics and extratropics are relatively independent due to the existence of critical latitudes. However, considerable observational evidence has shown that a clear dynamical link exists between the tropics and midlatitudes. To better understand such atmospheric teleconnection, several theories of wave energy propagation are reviewed in this paper: (1) great circle theory, which reveals the characteristics of Rossby waves propagating in the spherical atmosphere; (2) westerly duct theory, which suggests a “corridor” through which the midlatitude disturbances in one hemisphere can propagate into the other hemisphere; (3) energy accumulation-wave emanation theory, which proposes processes through which tropical disturbances can affect the atmospheric motion in higher latitudes; (4) equatorial wave expansion theory, which further explains the physical mechanisms involved in the interaction between the tropics and extratropics; and (5) meridional basic flow theory, which argues that stationary waves can propagate across the tropical easterlies under certain conditions. In addition, the progress made in diagnosing wave-flow interaction, particularly for Rossby waves, inertial-gravity waves, and Kelvin waves, is also reviewed. The meridional propagation of atmospheric energy exhibits significant annual and interannual variations, closely related to ENSO and variation in the westerly jets and tropical upper-tropospheric troughs, amongst others. 相似文献
14.
Marion Garçon Catherine Chauvel Emmanuel Chapron Xavier Faïn Mingfang Lin Sylvain Campillo Sarah Bureau Marc Desmet Marie-Christine Bailly-Maître Laurent Charlet 《Applied Geochemistry》2012
High-altitude lake sediments are often used as archives for environmental changes and their chemical and isotopic compositions provide significant constraints on natural and anthropogenic long-term changes that have occurred in their catchment area. Here, trace-element concentrations and Pb isotopes are presented for two sedimentary cores from Lake Blanc Huez in the French Alps, to trace the impact of climate changes and human activities over the Holocene. Lead and Ag contents are very high and clearly dominated by input from a Pb–Ag vein located a few meters from the lakeshore, a vein that also buffers the Pb isotopes. Mining of this vein in medieval times is recorded in the corresponding lake sediments with high Ag content coupled with high Pb/U ratio. These chemical characteristics can be used to constrain the major Holocene climate changes. Significant advances of glaciers next to the lake produced sediments with Ag and Pb concentration peaks and high Pb/U ratios due to accelerated erosion of the Pb–Ag vein, similar to the effects of the medieval mining. In contrast, reduced glacier activity led to the formation of organic-rich sediments with high U and As contents and low Pb/U ratios. More generally, the observed combination of chemical changes could be used elsewhere to decipher environmental changes over long periods of time. 相似文献
15.
通过基于COM组件的VB与Matlab混合编程途径,实现已知区域P波速度条件下利用多台P波到时估测震中位置算法程序化,使用发现,该程序具有运行界面友好、速度快及对网内和网缘地震定位精度较好的优点. 相似文献
16.
17.
Yin-Sung HSU Chi-ma WEI Yuan-Chi TING Shih-Yi YUAN Chia-Ling CHANG Kao-Chung CHANG 《国际泥沙研究》2010,25(2):175-184
Automated, real-time, and continuous techniques for monitoring suspended sediment concentration in rivers and reservoirs can play an important role in the improvement of the quantity and quality of sediment data, and are valuable to the management of water environment, water conservancy, hazard prevention, and water resources. Research in the monitoring techniques has examined the possibility of using the characteristics of dielectric constants for detecting soil moisture and concentration of air-water two-phase flow, based on the fact that dielectric constants of sediment, air and water are different. A capacitance sensor was developed to monitor the silt suspended sediment concentration (SSSC) in a recent study, following the principle that as SSSC increases in the sediment-water mixture, the apparent dielectric constant of the water sample also increases and therefore the capacitance detected by the sensing system also increases. It is demonstrated that the variations in the concentration of silt sediment correlates positively with the variations in observed capacitance in a linear fashion, and correlates negatively with voltage outputs but also in a linear fashion. The correlation coefficients reached above 0.98. The overall errors in estimated concentrations range between 0.26% and 2.91%. Elements in the capacitance sensor system such as the frequencies of the signal generating system, areas of the electrode plates, and effects of sample temperature have also been evaluated. The results illustrated that the capacitance sensor techniques can be applied to monitoring SSSC automatically and continuously. Also, the range of SSSC in the experiment reached 200 kg/m3; therefore, the application of this technique in practical SSSC monitoring is worthy of further research. 相似文献
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19.
The corals described by Mr. Yü in the preceding paper came mainly from southern Kueichou, in the districts of Tushan (獨山) and Tat'ang (大塘). The first fossiliferous section met with in the field (Pl. Ⅰ, Section ra) is that between the village of Kolaoho ((?)狫河). Ⅱ kilometers south of the city 相似文献
20.
工程场地地震安全性评价、特别是在地震小区划工作中,对地震滑坡的评价通常采用定性分析方法,因此,对其影响范围未给出定量的评价结果。本文以吕梁新城地震小区划滑坡评价为例,通过对该区的地质条件、地貌特征的研究,针对具有典型特征的剖面,选取地震力、内聚力、摩擦角作为影响因子,采用离散单元法(DEM)对潜在滑坡体的稳定性进行了数值模拟计算,得到了可能失稳的滑坡体潜在滑动的影响范围。并在此基础上通过对已知滑坡与潜在滑坡剖面结构特征的类比,对整个研究区内滑坡体的影响范围进行了评价。研究结果可为吕梁新城的规划提供依据,也可为同类工程中地震滑坡灾害的定量评价提供参考。 相似文献