Chemical composition of Russian Arctic precipitation in 2007-2015     

P. F. Svistov  N. A. Pershina  M. T. Pavlova  A. I. Polishchuk  E. S. Semenets 《Russian Meteorology and Hydrology》2017,42(5):314-318

The results of observations of the chemical composition of precipitation in the Russian Arctic in 2007-2015 are summarized including the data from NP-35 drifting ice station obtained in 2007-2008 in the framework of the joint program of Arctic and Antarctic Research Institute and Voeikov Main Geophysical Observatory. The qualitative and quantitative difference in the chemical composition of precipitation in the Atlantic, Siberian, and Pacific sectors of the Russian Arctic is revealed. It is found that the concentration of microelements (heavy metals) in precipitation at NP-35 ice station did not exceed 12% of total ions at the lowest mineralization. The comparative analysis is presented of the concentration of sulfate ions in precipitation in Norilsk and at NP-35 ice stations.  相似文献   

Formation Mechanisms of the Spring–Autumn Asymmetry of the Midlatitudinal <Emphasis Type="Italic">NmF</Emphasis>2 under Daytime Quiet Geomagnetic Conditions at Low Solar Activity     

A. V. Pavlov  N. M. Pavlova 《Geomagnetism and Aeronomy》2018,58(3):383-393

Formation mechanism of the spring–autumn asymmetry of the F2-layer peak electron number density of the midlatitudinal ionosphere, NmF2, under daytime quiet geomagnetic conditions at low solar activity are studied. We used the ionospheric parameters measured by the ionosonde and incoherent scatter radar at Millstone Hill on March 3, 2007, March 29, 2007, September 12, 2007, and September 18, 1984. The altitudinal profiles of the electron density and temperature were calculated for the studied conditions using a one-dimensional, nonstationary, ionosphere–plasmasphere theoretical model for middle geomagnetic latitudes. The study has shown that there are two main factors contributing to the formation of the observed spring–autumn asymmetry of NmF2: first, the spring–autumn variations of the plasma drift along the geomagnetic field due to the corresponding variations in the components of the neutral wind velocity, and, second, the difference between the composition of the neutral atmosphere under the spring and autumn conditions at the same values of the universal time and the ionospheric F2-layer peak altitude. The seasonal variations of the rate of O⁺(⁴S) ion production, which are associated with chemical reactions with the participation of the electronically excited ions of atomic oxygen, does not significantly affect the studied NmF2 asymmetry. The difference in the degree of influence of O⁺(⁴S) ion reactions with vibrationally excited N₂ and O₂ on NmF2 under spring and autumn conditions does not significantly change the spring–autumn asymmetry of NmF2.  相似文献   

IRI model in the problem of predicting ionospheric radio-wave propagation under conditions of high solar activity     

I.?V.?KrasheninnikovEmail author  N.?M.?Pavlova  Yu.?S.?Sitnov 《Geomagnetism and Aeronomy》2017,57(6):719-726

The paper presents the results of an analysis of the correspondence between model representations the monthly mean diurnal dependences of critical frequency and vertical profiles of plasma frequency at local noon at IZMIRAN station for the middle months of the four seasons of 2014, the year of the maximum solar activity in the current 24th cycle. It is shown that in general the IRI model reliably describes the daily variation of foF2, and the smallest discrepancy is achieved when its basic input parameter is given by the ionospheric index of solar activity IG12. An exception is April, for which there is a fundamental discrepancy with the model both in the daily variation of the critical frequency foF2 and in the N _e (h)-profile for local noon time. For this month, the inadequacy in the model representation of the vertical distribution of the electron density turned out to be very significant in the calculation of the MUF: the relative error can reach 20%. The simulation results are confirmed by data from oblique-incidence ionospheric radio sounding.  相似文献   

Zinc-rich and copper-bearing amphiboles from sulfide-free ore occurrences of the Pelagonian Massif,Republic of North Macedonia     

Chukanov  Nikita V.  Zubkova  Natalia V.  Jančev  Simeon  Pekov  Igor V.  Ermolaeva  Vera N.  Varlamov  Dmitry A.  Belakovskiy  Dmitriy I.  Britvin  Sergey N. 《Mineralogy and Petrology》2020,114(2):129-140

Mineralogy and Petrology - This paper describes specific features of isomorphism of unusual amphiboles containing up to 23&nbsp;wt% ZnO and up to 1.3&nbsp;wt% CuO from sulfide-free...  相似文献   

Groundwater Hydrochemistry of Suprapermafrost–Intrapermafrost Flow in Their Discharge Areas in Central Yakutia     

Pavlova  N. A.  Shepelev  V. V.  Galanin  A. A.  Efremov  V. S. 《Water Resources》2020,47(4):581-590

Water Resources - The results of long-term studies of a group of aufeis-forming Buluus groundwater sources are given. A stow, which has been formed by the spring, contains the drainage area of the...  相似文献   

Use of incipient motion data for backward erosion piping models     

Vera M. van Beek  Bryant A. Robbins  Gijs J.C.M. Hoffmans  Adam Bezuijen  Leo C. van Rijn 《国际泥沙研究》2019,34(5):401-408

Backward erosion piping involves the gradual removal of granular material under the action of water flow from the foundation of a dam or levee, whereby shallow pipes are formed that grow in the direction opposite to the flow. This pipe-forming process can ultimately lead to failure of a water-retaining structure and is considered one of the most important failure mechanisms for dikes and levees in the Netherlands and the United States. Modeling of this mechanism requires the assessment of hydraulic conditions in the pipe, which are controlled by the particle equilibrium at the pipe wall. Since the pipe's dimensions are controlled by the inflow to the pipe from the porous medium, the flow through the pipe is thought to be laminar for fine- to medium-grained sands. The literature provides data for incipient motion in laminar flow, which is reviewed here and complemented with data from backward erosion experiments. The experiments illustrate the applicability of the laminar incipient motion data to determine the erosion pipe dimensions and corresponding pipe hydraulics for fine- to medium-grained sands, for the purpose of backward erosion piping modeling.  相似文献   

Zoning of Groundwater Quality for Plain Garmsar in Iran     

Abouzar Nasiri  Shirocova  Vera A.  Zareie  Sajad 《Water Resources》2019,46(4):624-629

Water Resources - Groundwater performs an important role in the territory of the plains Garmsar. In this study, on the basis of water samples, which were obtained from the wells of the region,...  相似文献   

Diurnal Variations in the Statistical Characteristics of the Variability of the Midlatitude NmF2 during Quiet Geomagnetic Conditions at Low Solar Activity     

Pavlov  A. V.  Pavlova  N. M. 《Geomagnetism and Aeronomy》2019,59(5):593-605

Geomagnetism and Aeronomy - The work examines diurnal variations in the statistical characteristics of the variability of the electron number density NmF2 of the maximum of the ionspheric F2 layer...  相似文献   

Efficacy of Coagulants and Ballast Compounds in Removal of Cyanobacteria (<Emphasis Type="Italic">Microcystis</Emphasis>) from Water of the Tropical Lagoon Jacarepaguá (Rio de Janeiro,Brazil)     

Leonardo de Magalhães  Natália Pessoa Noyma  Luciana Lima Furtado  Maíra Mucci  Frank van Oosterhout  Vera L. M. Huszar  Marcelo Manzi Marinho  Miquel Lürling 《Estuaries and Coasts》2017,40(1):121-133

Eutrophication is considered the most important water quality problem in freshwaters and coastal waters worldwide promoting frequent occurrence of blooms of potentially toxic cyanobacteria. Removal of cyanobacteria from the water column using a combination of coagulant and ballast is a promising technique for mitigation and an alternative to the use of algaecides. In laboratory, we tested experimentally the efficiency of two coagulants, polyaluminium chloride (PAC) and chitosan (made of shrimp shells), alone and combined with two ballasts: red soil (RS) and the own lagoon sediment, to remove natural populations of cyanobacteria, from an urban brackish coastal lagoon. PAC was a very effective coagulant when applied at low doses (≤8 mg Al L^?1) and settled the cyanobacteria, while at high doses (≥16 mg Al L^?1) large flocks aggregated in the top of test tubes. In contrast, chitosan was not able to form flocks, even in high doses (>16 mg L^?1) and did not efficiently settle down cyanobacteria when combined with ballast. The RS itself removed 33–47 % of the cyanobacteria. This removal was strongly enhanced when combined with PAC in a dose-dependent matter; 8 mg Al L^?1 was considered the best dose to be applied. The lagoon sediment alone did not promote any settling of cyanobacteria but removal was high when combined with PAC. Combined coagulant and ballast seems a very efficient, cheap, fast and safe curative measure to lessen the harmful cyanobacteria bloom nuisance in periods when particularly needed, such as around the 2016 Olympics in Jacarepaguá Lagoon.  相似文献   

Dependences of statistical characteristics of <Emphasis Type="Italic">NmE</Emphasis> on the month of the year at middle and low latitudes under daytime geomagnetically quiet conditions at low solar activity     

A. V. Pavlov  N. M. Pavlova 《Geomagnetism and Aeronomy》2016,56(4):401-406

Month-to-month changes in the statistical characteristics of the ionospheric E layer peak electron density NmE at medium and low geomagnetic latitudes under daytime geomagnetically quiet conditions are investigated. Critical frequencies of the ionospheric E layer measured by the middle latitude ionosonde Boulder and low latitude ionosondes Huancayo and Jicamarca at low solar activity from 1957 to 2015 have been used in the conducted statistical analysis. The mathematical expectation of NmE, standard deviation of NmE from the expectation of NmE, and NmE variation coefficient have been calculated for each month of the year. The months of the formation of extrema of these statistical parameters of NmE were found.  相似文献