scholarly journals Air–snow exchange of nitrate: a modelling approach to investigate physicochemical processes in surface snow at Dome C, Antarctica

2016 ◽  
Vol 16 (19) ◽  
pp. 12531-12550 ◽  
Author(s):  
Josué Bock ◽  
Joël Savarino ◽  
Ghislain Picard
Keyword(s):  
Nitrate Concentration ◽  
Bulk Diffusion ◽  
Chemical Reactor ◽  
Early Spring ◽  
Temperature Cycle ◽  
Special Role ◽  
Physicochemical Processes ◽  
Exchange Processes ◽  
Surface Snow ◽  
Modelling Studies

Abstract. Snowpack is a multiphase (photo)chemical reactor that strongly influences the air composition in polar and snow-covered regions. Snowpack plays a special role in the nitrogen cycle, as it has been shown that nitrate undergoes numerous recycling stages (including photolysis) in the snow before being permanently buried in the ice. However, the current understanding of these physicochemical processes remains very poor. Several modelling studies have attempted to reproduce (photo)chemical reactions inside snow grains, but these have relied on strong assumptions to characterise snow reactive properties, which are not well defined. Air–snow exchange processes such as adsorption, solid-state diffusion, or co-condensation also affect snow chemical composition. Here, we present a physically based model of these processes for nitrate. Using as input a 1-year-long time series of atmospheric nitrate concentration measured at Dome C, Antarctica, our model reproduces with good agreement the nitrate measurements in the surface snow. By investigating the relative importance of the main exchange processes, this study shows that, on the one hand, the combination of bulk diffusion and co-condensation allows a good reproduction of the measurements (correlation coefficient r = 0.95), with a correct amplitude and timing of summer peak concentration of nitrate in snow. During winter, nitrate concentration in surface snow is mainly driven by thermodynamic equilibrium, whilst the peak observed in summer is explained by the kinetic process of co-condensation. On the other hand, the adsorption of nitric acid on the surface of the snow grains, constrained by an already existing parameterisation for the isotherm, fails to fit the observed variations. During winter and spring, the modelled concentration of adsorbed nitrate is respectively 2.5 and 8.3-fold higher than the measured one. A strong diurnal variation driven by the temperature cycle and a peak occurring in early spring are two other major features that do not match the measurements. This study clearly demonstrates that co-condensation is the most important process to explain nitrate incorporation in snow undergoing temperature gradient metamorphism. The parameterisation developed for this process can now be used as a foundation piece in snowpack models to predict the inter-relationship between snow physical evolution and snow nitrate chemistry.

scholarly journals Air–snow exchange of nitrate: a modelling approach to investigate physicochemical processes in surface snow at Dome C, Antarctica

2016 ◽  
Author(s):  
Josué Bock ◽  
Joël Savarino ◽  
Ghislain Picard
Keyword(s):  
Nitrate Concentration ◽  
Bulk Diffusion ◽  
Chemical Reactor ◽  
Early Spring ◽  
Temperature Cycle ◽  
Condensation Process ◽  
Special Role ◽  
Physicochemical Processes ◽  
Exchange Processes ◽  
Surface Snow

Abstract. Snowpack is a multiphase (photo)chemical reactor that strongly influences the air composition in polar and snow-covered regions. Snowpack plays a special role in the nitrogen cycle, as it has been shown that nitrate undergoes numerous recycling stages (including photolysis) in the snow before being permanently buried in the ice. However, the current understanding of these physicochemical processes remains very poor. Several modelling studies have attempted to reproduce (photo)chemical reactions inside snow grains, but these required strong assumptions to characterise snow reactive properties, which are not well defined. Air–snow exchange processes such as adsorption, solid state diffusion or co-condensation also affect snow chemical composition. Here, we develop a model including a physically based parameterisation of these processes for nitrate. Using as input a one-year long time series of atmospheric nitrate concentration measured at Dome C, Antarctica, our process-resolving model reproduces with good agreement the nitrate concentration measured in surface snow. By investigating the relative importance of the main exchange processes, this study shows that, on the one hand, the combination of bulk diffusion and co-condensation incorporation processes allows a good reproduction of the measurements (correlation coefficient r = 0.95), with a correct amplitude and timing of summer peak concentration of nitrate in snow. During wintertime, nitrate concentration in surface snow is mainly driven by thermodynamic equilibrium, whilst the peak observed in summer is explained by the kinetic process of co-condensation. On the other hand, the adsorption of nitric acid on the surface of the snow grains, constrained by an already existing parameterisation for the isotherm, fails to fit the observed variations. During winter and spring, the modelled adsorbed concentration of nitrate is 2.5 and 8.3-fold higher than the measured one, respectively. A strong diurnal variation driven by the temperature cycle and a peak occurring in early spring are two other major features that do not match the measurements. This study clearly demonstrates that the co-condensation process is the most important to explain nitrate incorporation in snow subject to temperature gradients. The parameterisation developed for this process can now be used as a foundation piece in snowpack models to predict the inter-relationship between snow physical evolution and snow nitrate chemistry.

Ureaform as a Nitrogen Fertilizer for Bananas

1976 ◽  
Vol 12 (2) ◽  
pp. 121-128 ◽  
Author(s):  
Aviva Hadas ◽  
A. Peled ◽  
U. Kafkafi
Keyword(s):  
Nitrogen Fertilizer ◽  
Standard Treatment ◽  
Root Zone ◽  
Nitrate Concentration ◽  
Poultry Manure ◽  
Residual Effect ◽  
Late Summer ◽  
Early Spring ◽  
Nitrogen Requirement ◽  
Banana Plantation

SUMMARYUreaform, applied twice a year, in early spring and late summer, was compared with poultry manure and (NH4)2SO4 top dressings as nitrogen suppliers in a banana plantation. No significant differences between the treatments were obtained in any of the plant criteria, but nitrate concentrations in the soil were higher in the ureaform treatment at the standard nitrogen level than in the standard treatment, within the root zone as well as below it. The spring application of ureaform affected the nitrate concentration in soil for 8 months and was better utilized by the crop than the autumn application, which left a greater residual effect. It therefore seemed that one spring application might be sufficient to meet the banana's nitrogen requirement.

scholarly journals Seasonal variations of accumulation and the isotope record in ice cores: a study with surface snow samples and firn cores from Neumayer station, Antarctica

2002 ◽  
Vol 35 ◽  
pp. 97-101 ◽  
Author(s):  
Elisabeth Schlosser ◽  
Hans Oerter
Keyword(s):  
Air Temperature ◽  
Ice Core ◽  
Ice Cores ◽  
Early Spring ◽  
Late Winter ◽  
Short Time Scale ◽  
High Time Resolution ◽  
Water Vapour Diffusion ◽  
Surface Snow ◽  
Snow Samples

AbstractAt the German wintering base Neumayer, an intensive glacio-meteorological programme has been carried out during the last two decades. A complete meteorological dataset and data from surface snow samples, snow pits, firn cores and weekly accumulation measurements from a stake array are available. We first investigated the attenuation of the seasonal δ18O signal due to water-vapour diffusion in the snowpack. A comparison of surface snow samples and firn cores of different ages shows that only one-third of the seasonal δ18O signal of the surface snow samples remains in the cores after the first year. No further significant change in the amplitude of the seasonal δ18O signal is found later. Changes in the seasonal distribution of accumulation can lead to a bias in ice-core properties. This is studied on a short time-scale, using high-time-resolution data of accumulation, stable-isotope ratios and air temperature. Mean annual δ18O values from firn cores are not well correlated to annual mean air temperatures. However, the correlation is improved considerably by calculating an annual mean air temperature using monthly mean temperatures weighted by monthly accumulation. At Neumayer, it is mainly the cyclonic activity in late winter/early spring that determines whether and how the core data are biased.

The Physical Oceanography of Bute Inlet, British Columbia

1957 ◽  
Vol 14 (4) ◽  
pp. 487-520 ◽  
Author(s):  
Susumu Tabata ◽  
George L. Pickard
Keyword(s):  
River Runoff ◽  
Seasonal Fluctuation ◽  
Large River ◽  
Early Spring ◽  
Temperature Cycle ◽  
Seasonal Temperature ◽  
Surface Salinity ◽  
Runoff Water ◽  
Sea Temperature ◽  
Seasonal Temperature Variation

Distributions of salinity, temperature, and oxygen of Bute Inlet based on twelve oceanographic surveys between the period August 1950 to July 1953 have been examined. The salinity structures of the shallow water during the various seasons can be classified under two main groups, one occurring at periods of small river runoff and the other at periods of large river runoff. In general, the surface salinity increases to seaward and with depth during all seasons. The surface water along the western shore is almost always observed to be less saline than along the eastern shore. The salinity of the deep water is 30.6 to 30.8‰ during both periods. The seasonal fluctuation of salinity at the surface is well marked but below a depth of 60 feet no obvious cycle exists. The temperature distributions can be divided into two main groups, winter and summer. During both seasons the surface temperature generally increases to seaward. The temperature gradient in the upper layers during the winter is positive (increasing vertically downward) and during the summer is negative (decreasing vertically downward). From early spring to late autumn, a well-defined temperature minimum, in the middle and upper reaches of the inlet, is evident in the intermediate depths. The water in the greater depths has a temperature of 8.0 to 8.2 °C. and remains almost unchanged throughout the seasons. A seasonal temperature variation is observed down to a depth of 150 feet and is in phase with the air temperature cycle, but below this it is less noticeable. Insolation and cold runoff water from the rivers are predominant factors in determining the fluctuation in the sea temperature. The concentration of dissolved oxygen is usually high in the surface layer. The water at the greater depth is not stagnant as evidenced by the oxygen concentration.Values from 0.2 to 1.5 g./cm./sec. for the eddy coefficient of conductivity have been determined for the intermediate depths.

SEASONAL CHANGES IN THE GERMINATION RESPONSES OF FALL PANICUM TO TEMPERATURE AND LIGHT

1983 ◽  
Vol 63 (4) ◽  
pp. 973-979 ◽  
Author(s):  
JERRY M. BASKIN ◽  
CAROL C. BASKIN
Keyword(s):  
Late Summer ◽  
Early Spring ◽  
Early Summer ◽  
Temperature Cycle ◽  
Late Autumn ◽  
Fine Mesh ◽  
Temperature Regimes ◽  
June July ◽  
Panicum Dichotomiflorum ◽  
Autumn And Winter

Seeds of fall panicum (Panicum dichotomiflorum Michx.) were buried in fine-mesh nylon bags in soil and exposed to the annual temperature cycle. Fresh seeds and seeds exhumed after 1–15 mo were tested in light and darkness at five temperature regimes simulating those in the field from early spring through late autumn. Freshly matured seeds were dormant, but they came out of dormancy during late autumn and winter. Thus, by spring (April) seeds germinated to near 100% in light at 20/10, 25/15, 30/15 and 35/20 °C. However, except at 35/20 °C during June, July and August, the majority of the seeds required light for germination. In the field, germination does not begin until April when temperatures come within the range of those required for germination. Seeds retained the ability to germinate to a high percentage at 30/15 and 35/20 °C throughout the summer, but they lost this ability at 20/10 °C in early summer and at 25/15 °C in late summer. Thus, seeds stop germinating in early autumn when diurnal field temperatures decrease below about 20–25 °C maximum and 10–15 °C minimum. In autumn, seeds lost the ability to germinate even at the high temperatures, but they regained it by the following January.Key words: Germination, dormancy, after-ripening, fall panicum, summer annual, buried seeds

scholarly journals Combining atmospheric and snow layer radiative transfer models to assess the solar radiative effects of black carbon in the Arctic

2020 ◽  
Author(s):  
Tobias Donth ◽  
Evelyn Jäkel ◽  
André Ehrlich ◽  
Bernd Heinold ◽  
Jacob Schacht ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Black Carbon ◽  
Heating Rate ◽  
Mass Concentration ◽  
Early Spring ◽  
Early Summer ◽  
The Arctic ◽  
Radiative Effect ◽  
Snow Layer ◽  
Surface Snow

Abstract. Solar radiative effects (cooling or warming) of black carbon (BC) particles suspended in the Arctic atmosphere and surface snow layer were explored by radiative transfer simulations on the basis of BC mass concentrations measured in pristine early summer and polluted early spring conditions under cloudless and cloudy conditions. To account for the radiative interactions between the black carbon containing snow surface layer and the atmosphere, a snow layer and an atmospheric radiative transfer model were coupled iteratively. For pristine summer conditions (no atmospheric BC) and a representative BC particle mass concentration of 5 ng g−1 in the surface snow layer, a positive solar radiative effect of +0.2 W m−2 was calculated for the surface radiative budget. Contrarily, a higher load of atmospheric BC representing springtime conditions, results in a slightly negative radiative effect of about −0.05 W m−2, even when the same BC mass concentration is suspended in the surface snow layer. This counteracting of atmospheric BC and BC suspended in the snow layer strongly depends on the snow optical properties determined by the snow specific surface area. However, it was found, that the atmospheric heating rate by water vapor or clouds is one to two orders of magnitude larger than that by atmospheric BC. Similarly, the total heating rate (6 K day−1) within a snow pack due to absorption by the ice water, was found to be more than one order of magnitude larger than the heating rate of suspended BC (0.2 K day−1). The role of clouds in the estimation of the combined direct radiative BC effect (BC in snow and in atmosphere) was analyzed for the pristine early summer and the polluted early spring BC conditions. Both, the cooling effect by atmospheric BC, as well as the warming effect by BC suspended in snow are reduced in the presence of clouds.

scholarly journals Nitrate concentration and accumulation on vegetables related to altitude and sunlight intensity

2021 ◽  
Vol 896 (1) ◽  
pp. 012052
Author(s):  
H Agusta ◽  
J G Kartika ◽  
K R Sari
Keyword(s):  
Nitrate Concentration ◽  
Health Impact ◽  
Nitrate Content ◽  
Special Role ◽  
Nitrate Accumulation ◽  
Lower Altitude ◽  
Environmental Status ◽  
Plant Sampling ◽  
Sunlight Intensity ◽  
Vegetable Quality

Abstract Nitrate absorption and concentration in consumed vegetables should be also interrelated with its quality, where it is now less noticed in standard vegetable quality. The higher nitrate content is associated with the human health impact such as the baby blue syndrome and stimulating the tumor growth. The environmental status on especially sunlight intensity and quality has a special role to control nitrate concentration in the leaves. The purpose of this study was to characterize the nitrate concentration and accumulation in Brassica rapa L. grown in an open field and screen shading at lower and medium altitudes. Plant sampling was arranged at lower altitudes under 500 m asl (meters above sea level) and medium altitudes 500-700 m asl. Plant growth under shading and unshaded condition were observed for nitrate status as absorbed and its concentration in the sap plants. The study site at the lower altitude exposed sunlight intensity by 27.2% higher, where it decreased nitrate accumulation by 39.3%. Nitrate accumulation under shaded condition rate of 54.9% exhibited more 17.7% nitrate concentration in the vegetable.

scholarly journals Reciprocity “by Blessing”: Debatable Issues of Gift Exchange in The Church Community

2019 ◽  
Vol 18 (4) ◽  
pp. 186-211
Author(s):  
Boris Knorre ◽  
Anna Murashova
Keyword(s):  
Gift Exchange ◽  
Theoretical Explanation ◽  
Special Role ◽  
Social Milieu ◽  
Exchange Processes ◽  
The Status ◽  
Distribution Of Resources ◽  
Key Issues ◽  
Client Relations ◽  
The Church

The article is an attempt to analyze the most significant aspects of gift exchange in the context of the models of economic integration in the Church’s social milieu. The most important points of the discussion are the propositions and mechanisms of gift exchange designated in recent works by G. Yudin, I. Zabaev, the archpriest N. Emelyanov, and some other researchers providing an idea of the opportunity and the special role of the priest in generating gift exchange. We argue that a number of key issues concerning the opportunity for priests to generate gift exchange remains debatable and sensible. To what extent are priests today free from the competition in, engagement with, and from aiming at maximizing resources? What are the modes of personal dependence/independence in the Church’s social milieu? What are the mechanisms for the formation of solidarity, moral duty, and formal and informal obligations between the priest, parishioners, major donators, and non-Church actors? What is the nature of the exchange processes, and how much do they match the criteria of gift exchange so that they can be distinguished from patron-client relations, the hierarchical distribution of resources, or processes launched by bigmen? These and other issues with regard to the Church environment are analyzed in the article using empirical material and the observations illustrating the specifics of social integration and certain options for exchange relations. We are aiming to delineate approximately what the “status quo” is of today’s gift-exchange processes in the Church, their obstacles, and the points of failure and risks. At the same time, we offer our theoretical explanation of these obstacles and the resulting conflicts that arise during the organization of gift exchange in the Church’s social milieu.

scholarly journals Effects of substrate type on plant growth and nitrogen and nitrate concentration in spinach

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Carina Barcelos ◽  
Rui M.A. Machado ◽  
Isabel Alves-Pereira ◽  
Rui Ferreira ◽  
David R. Bryla
Keyword(s):  
Plant Growth ◽  
Spinacia Oleracea ◽  
Nitrate Concentration ◽  
Drainage Water ◽  
Early Spring ◽  
The Other ◽  
Substrate Type ◽  
Forest Residues ◽  
Leaf Chlorophyll ◽  
Complete Nutrient Solution

The effects of three commercial substrates (a mixture of forest residues, composted grape husks, and white peat, black peat and coir) on plant growth and nitrogen (N) and nitrate (NO3) concentration and content were evaluated in spinach (<em>Spinacia oleracea</em> L. cv. Tapir). Spinach seedlings were transplanted at 45 days after emergence into Styrofoam boxes filled with the substrates and were grown during winter and early spring in an unheated greenhouse with no supplemental lighting. Each planting box was irrigated daily by drip and fertilized with a complete nutrient solution. The NO3 content of the drainage water was lower in coir than in the other substrates. However, shoot NO3 concentration was not affected by substrate type, while yield and total shoot N and NO3 content were greater when plants were grown in peat than in the mixed substrate or the coir. Leaf chlorophyll meter readings provided a good indication of the amount of N in the plants and increased linearly with total shoot N.

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