Hydrological management strategies for the control of algal blooms in regulated lowland rivers     

Jian Li  Wei Yin  Haiyan Jia  Xiaokang Xin 《水文研究》2021,35(6):e14171

Reservoirs of lowland floodplain rivers with eutrophic backgrounds cause variations in the hydrological and hydraulic conditions of estuaries and low-dam reservoir areas, which can promote planktonic algae to proliferate and algal bloom outbreaks. Understanding the ecological effects of variations in hydrological and hydraulic processes in lowland rivers is important for algal bloom control. In this study, the middle and lower reaches of the Han River, China, a typical regulated lowland river with a eutrophic background, are selected. Based on the effect of hydrological and hydraulic variability on algal blooms, a hydrological management strategy for river algal bloom control is proposed. The results showed that (a) differences in river morphology and background nutrient levels cause significant differences in the critical threshold flow velocities for algal bloom outbreaks between natural river and low-dam reservoir sections; there is no uniform threshold flow velocity for algal bloom control. (b) There are significant differences in the river hydrological/hydraulic conditions between years with and without algal blooms. The average river flow, water level and velocity in years with algal blooms are significantly lower than those in years without algal blooms. (c) For different river sections where algal blooms occur and to meet the threshold flow velocities, the joint operation of cascade reservoirs and diversion projects is an effective method to prevent and control algal blooms in regulated lowland rivers. This study is expected to deepen our understanding of the ecological significance of special hydrological processes and guide algal bloom management in regulated lowland rivers.  相似文献   

Fluid Inclusion Feature of Gold-Bearing Quartz Veins from the Jinniushan Gold Deposit, Shandong, China     

Shen Ping  Shen Yuanchao  Li Guangming  LIU Tiebing  ZENG Qingdong 《世界地质(英文版)》2002,5(2)

The auriferous veins at Jinniushan occurs within the Jinniushan faulted zone in the Kunyushan Granite. Optical observation reveals that gold ore body formed during the main stage of hydrothermal activity. Detailed geothermometric studies of fluid inclusions from the veins show that the forming temperature ranges between 130℃ and 370℃ and the salinity is from 4.01 to 15.21 wvt percent NaCl. The ore-forming fluid is featured by low to moderate salinity, and low to moderate temperature. According to investigations of the values of vapor/liquid and temperatures of the ore-forming fluids, we propose that the boiling fluid inclusions exist in the main mineralization stages. Fluid boiling is suggested as a mechanism for the precipitation of gold from the hydrothermal fluid in the Jinniushan gold deposit.  相似文献   

彗星等离子体某些特征的讨论     

李中元  李嘉巍  段素平  陈耀  石志东 《紫金山天文台台刊》2003,(1)

本文讨论了彗星中尘埃粒子的充电机制 ,带电特性和平衡电势的变化规律 ,分析了彗星尘埃的破碎特性和临界半径 ,得出了很有意义的结果  相似文献   

滇西动态重力网的分形特征及空间分辨力   总被引：1，自引：1，他引：0  

贾民育 《大地测量与地球动力学》1996,(4)

介绍了用分形学描述地球物理观测网非均匀分布和联合应用分形特征与Ｓｈａｎｎｏｎ定理确定最佳网格距的方法。研究了滇西动态重力网的分形特征，它的分形维Ｄｆ＝１．２７，最佳网格距ｒ０＝２８ｋｍ。讨论了１９８６年至１９９４年间网区发生的８次Ｍｓ＞５．０级地震前重力场变化的可信性，指出这些变化的波长均大于１００ｋｍ，至少２倍于网的最小空间分辨力，因而是可信的  相似文献   

A reinterpretation of the crustal N‐isotope record: evidence for a 15N‐enriched Archean atmosphere?     

Yiefei Jia  Robert Kerrich 《地学学报》2004,16(3):102-108

A new compilation of N‐isotope and abundance data for metasedimentary rocks, and hyrdothermal micas that proxy for bulk crust, show systematic patterns. (1) δ¹⁵N values of kerogen in Precambrian cherts are more negative relative to siliciclastic counterparts, probably due to a mantle hydrothermal component. (2) There is a secular trend from average δ¹⁵N 15.3 ± 1.8‰ in Archean shales, through intermediate values in the Proterozoic, to Phanerozoic counterparts where δ¹⁵N averages +3.5‰. (3) Hydrothermal micas in metamorphic hydrothermal systems of Palaeozoic and Mesozoic age that proxy for crust have δ¹⁵N within the range of contemporaneous sedimentary rocks. (4) Hydrothermal micas track the secular trend of δ¹⁵N for kerogen from 2.7 Ga to the Phanerozoic. (5) Within Precambrian datasets δ¹⁵N does not increase with decreasing N content; accordingly, high δ¹⁵N values cannot stem either from metamorphism or form Rayleigh fractionation. (6) Previous studies show isotopic shifts during metamorphism are only +1 to +3‰ up to amphibolite facies. Values of 10–24‰ are attributed to a high δ¹⁵N Archean atmosphere, a residual signature of CI carbonaceous chondrites where δ¹⁵N is +30‰ to + 42‰.  相似文献   

The Fault Block''s Framework in Boli Basin and its Control Over the Deposition     

Cao Chengrun  SHAN Xuanlong  Wang Dongpo  WANG Xianmin  Yao Ping 《世界地质(英文版)》2001,4(1)

Boli basin, between Yishu fracture belt and Dunmi fracture belt, is the biggest Mesozoic coal basin in the east of Heilongjiang Province. Now it is a fault - fold remnant basin. The basin' s shape is generally consistent with the whole distribution of the cover folds, an arc protruding southwards. The basement of the basin can be divided into three fault blocks or structural units. The formation and evoluation of the basin in Mesozoic was determined by the basement fault blocks' displacement features rusulted from by the movement of the edge faults and the main basement faults.  相似文献   

An algorithm for detecting and estimating cycle slips in single-frequency GPS   总被引：1，自引：0，他引：1  

Jia Pei-zhang  Wu Lian-da 《Chinese Astronomy and Astrophysics》2001,25(4):1089-521

An algorithm for detecting outliers and cycle slips in single-frequency GPS using a 3rd order polynomial model of the Kalman filter and for estimating the ambiguity by using optimal wavelet is presented in this paper. It is applicable to the carrier phase measurement with sample rate of one per second. The results of calculation with the GPS data aboard satellite Topex on 1995 June 22 show that the algorithm is so efficient that it can accurately estimate the ambiguity even for signals interrupted by a few seconds.  相似文献   

测绘科技进步的研究与测算     

卢萍 《地理信息世界》2001,(3)

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。  相似文献   

Study on Application of Polyenzyme Method to Offal of Harengula zunasi     

邓尚贵  杨萍  夏杏洲 《中国海洋湖沼学报》2003,21(4):312-318

The new polyenzyme method for making gravy from Harengula zunasi offal involves protein enzymolysis with flavorase after proper alkaline and neutral protease levels were established by orthogonal trials to select the best hydrolytic conditions for processing offal with alkaline and neutral protease. The conditions for the polyenzyme method were pH of 7.0, temperature of 50℃ , alkaline and neutral protease concentration of 1.5% respectively, hydrolysis time of 120 min, andflavorase concentration of 2.0% , for 60 min. The new gravy-making technology yields a nutritious and delicious gravy containing 40.3 % of total essential amino acids, with delicious amino acids Glu, Asp, Gly, Ala, Pro and Ser comprising 49.5% , total and amino nitrogen being respectively1.9 and 1.1 g/100 g (amino acid nitrogen being 61.0% of total nitrogen), The polyenzyme method was used to make 14.8% protein gravy from Harengula zunasi offal. In addition, in inorganic elements, the phosphorus content is the highest.  相似文献   

Automated Separation of Stars and Normal Galaxies Based on Statistical Mixture Modeling with RBF Neural Networks     

Dong-Mei Qin  Ping Guo  Zhan-Yi Hu  Yong-Heng ZhaoNational Laboratory of Pattern Recognition Laboratory  Institute of Automation  Chinese Academy of Sciences  Beijing  dmqin@nlpr.ia.ac.cnDepartment of Computer Sciences  Beijing Normal University  Beijing National Astronomical Observatories  Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2003,3(3)

For LAMOST, the largest sky survey program in China, the solution of the problem of automatic discrimination of stars from galaxies by spectra has shown that the results of the PSF test can be significantly refined. However, the problem is made worse when the redshifts of galaxies are not available. We present a new automatic method of star/(normal) galaxy separation, which is based on Statistical Mixture Modeling with Radial Basis Function Neural Networks (SMM-RBFNN). This work is a continuation of our previous one, where active and non-active celestial objects were successfully segregated. By combining the method in this paper and the previous one, stars can now be effectively separated from galaxies and AGNs by their spectra-a major goal of LAMOST, and an indispensable step in any automatic spectrum classification system. In our work, the training set includes standard stellar spectra from Jacoby's spectrum library and simulated galaxy spectra of EO, SO, Sa, Sb types with redshift ranging from 0 to 1  相似文献