PREDICTING NET NITROGEN MINERALIZATION OVER A GROWING SEASON: MODEL VERIFICATION

1988 ◽  
Vol 68 (3) ◽  
pp. 537-552 ◽  
Author(s):  
C. A. CAMPBELL ◽  
Y. W. JAME ◽  
R. DE JONG
Keyword(s):  
Rate Constant ◽  
Nitrogen Mineralization ◽  
Field Measurements ◽  
Growing Season ◽  
Model Verification ◽  
Effect Of Temperature ◽  
Mineralization Rate ◽  
Temperature Function ◽  
Plastic Bags

In a previous study a nitrogen mineralization model was developed by combining the potentially mineralizable nitrogen (No) with functions representing the effect of temperature and soil moisture on the mineralization rate constant (k). The model performed well in predicting the amount of net nitrogen mineralized during a growing season when soil was incubated in plastic bags placed in incubators or buried in the field. In the present study a similar model was used to estimate net nitrogen mineralized in situ from Wood Mountain loam an Orthic Brown soil at Swift Current, Saskatchewan under (a) summerfallow, (b) cropped-dryland and (c) cropped-irrigated conditions. Model output showed good agreement to field measurements especially for the first 45–60 d, but thereafter tended to underestimate the measured data particularly under cropped-dryland conditions. During a growing season the cropped-irrigated system predicted 69 kg ha−1 net nitrogen mineralized, but 81 kg ha−1 was measured; the corresponding values for summerfallow were 64 and 86 kg ha−1, and for cropped-dryland 36 and 52 kg ha−1, respectively. The model is not dynamic since it does not allow for No to be replenished continuously by nitrogen derived from decomposition of fresh residues and rhizosphere microbial biomass. Net nitrogen mineralized from this source might explain at least part of the underestimate predicted by the model. Other sources of possible discrepancy could be imprecision in measuring the mineralization of nitrogen and in estimating the parameters in the model. Nonetheless, it was established that one of the main shortcomings of the model was that it underestimated the amount of nitrogen mineralized whenever the soil became very dry and was then rewetted by rainfall. This was probably because the latter process resulted in large flushes in mineral nitrogen in situ while in the laboratory estimate of No and k, this effect is not adequately simulated. Key words: Q10, No, N mineralization, rate constant, temperature function

TEMPERATURE DEPENDENCE OF NITROGEN MINERALIZATION RATE CONSTANT

Soil Science ◽  
1995 ◽  
Vol 159 (5) ◽  
pp. 294-300 ◽  
Author(s):  
BHABANI S. DAS ◽  
GERARD J. KLUITENBERG ◽  
GRAY M. PIERZYNSKI
Keyword(s):  
Temperature Dependence ◽  
Rate Constant ◽  
Nitrogen Mineralization ◽  
Mineralization Rate

scholarly journals Underwater Holographic Sensor for Plankton Studies In Situ Including Accompanying Measurements

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4863
Author(s):  
Victor Dyomin ◽  
Alexandra Davydova ◽  
Igor Polovtsev ◽  
Alexey Olshukov ◽  
Nikolay Kirillov ◽  
...  
Keyword(s):  
World Ocean ◽  
Field Tests ◽  
Field Measurements ◽  
Measuring Systems ◽  
Water Turbidity ◽  
Background Data ◽  
Average Size ◽  
Size Dispersion

The paper presents an underwater holographic sensor to study marine particles—a miniDHC digital holographic camera, which may be used as part of a hydrobiological probe for accompanying (background) measurements. The results of field measurements of plankton are given and interpreted, their verification is performed. Errors of measurements and classification of plankton particles are estimated. MiniDHC allows measurement of the following set of background data, which is confirmed by field tests: plankton concentration, average size and size dispersion of individuals, particle size distribution, including on major taxa, as well as water turbidity and suspension statistics. Version of constructing measuring systems based on modern carriers of operational oceanography for the purpose of ecological diagnostics of the world ocean using autochthonous plankton are discussed. The results of field measurements of plankton using miniDHC as part of a hydrobiological probe are presented and interpreted, and their verification is carried out. The results of comparing the data on the concentration of individual taxa obtained using miniDHC with the data obtained by the traditional method using plankton catching with a net showed a difference of no more than 23%. The article also contains recommendations for expanding the potential of miniDHC, its purpose indicators, and improving metrological characteristics.

scholarly journals Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1131
Author(s):  
Soonkie Nam ◽  
Marte Gutierrez ◽  
Panayiotis Diplas ◽  
John Petrie
Keyword(s):  
Hydraulic Conductivity ◽  
Field Measurements ◽  
Natural Soil ◽  
In Situ Tests ◽  
Seepage Analysis ◽  
Soil Deposits ◽  
Seepage Modeling ◽  
Sample Disturbance

This paper critically compares the use of laboratory tests against in situ tests combined with numerical seepage modeling to determine the hydraulic conductivity of natural soil deposits. Laboratory determination of hydraulic conductivity used the constant head permeability and oedometer tests on undisturbed Shelby tube and block soil samples. The auger hole method and Guelph permeameter tests were performed in the field. Groundwater table elevations in natural soil deposits with different hydraulic conductivity values were predicted using finite element seepage modeling and compared with field measurements to assess the various test results. Hydraulic conductivity values obtained by the auger hole method provide predictions that best match the groundwater table’s observed location at the field site. This observation indicates that hydraulic conductivity determined by the in situ test represents the actual conditions in the field better than that determined in a laboratory setting. The differences between the laboratory and in situ hydraulic conductivity values can be attributed to factors such as sample disturbance, soil anisotropy, fissures and cracks, and soil structure in addition to the conceptual and procedural differences in testing methods and effects of sample size.

Effect of temperature on streambed vertical hydraulic conductivity

2013 ◽  
Vol 45 (1) ◽  
pp. 89-98 ◽  
Author(s):  
Weihong Dong ◽  
Gengxin Ou ◽  
Xunhong Chen ◽  
Zhaowei Wang
Keyword(s):  
Hydraulic Conductivity ◽  
Water Temperature ◽  
Sediment Cores ◽  
Effect Of Temperature ◽  
In Situ Tests ◽  
Effect Of Water ◽  
Vertical Hydraulic Conductivity ◽  
Increasing Trend ◽  
Streambed Vertical Hydraulic Conductivity

In this study, in situ and on-site permeameter tests were conducted in Clear Creek, Nebraska, USA to evaluate the effect of water temperature on streambed vertical hydraulic conductivity Kv. Fifty-two sediment cores were tested. Five of them were transferred to the laboratory for a series of experiments to evaluate the effect of water temperature on Kv. Compared with in situ tests, 42 out of the 52 tests have higher Kv values for on-site tests. The distribution of water temperature at the approximately 50 cm depth of streambed along the sand bar was investigated in the field. These temperatures had values in the range 14–19 °C with an average of 16 °C and had an increasing trend along the stream flow. On average, Kv values of the streambed sediments in the laboratory tests increase by 1.8% per 1 °C increase in water temperature. The coarser sandy sediments show a greater increase extent of the Kv value per 1 °C increase in water temperature. However, there is no distinct increasing trend of Kv value for sediment containing silt and clay layers.

Assessment of Moisture Content in Sandy Beach Environments from Multispectral Satellite Imagery

2021 ◽  
Author(s):  
Julie Paprocki ◽  
Nina Stark ◽  
Hans C Graber ◽  
Heidi Wadman ◽  
Jesse E McNinch
Keyword(s):  
Moisture Content ◽  
Laboratory Data ◽  
Field Measurements ◽  
Weather Conditions ◽  
Sandy Beaches ◽  
Percent Error ◽  
Moisture Contents ◽  
Multispectral Satellite Imagery ◽  
Factor C

A framework for estimating moisture content from satellite-based multispectral imagery of sandy beaches was tested under various site conditions and sensors. It utilizes the reflectance of dry soil and an empirical factor c relating reflectance and moisture content for specific sediment. Here, c was derived two ways: first, from in-situ measurements of moisture content and average NIR image reflectance; and second, from laboratory-based measurements of moisture content and spectrometer reflectance. The proposed method was tested at four sandy beaches: Duck, North Carolina, and Cannon Beach, Ocean Cape, and Point Carrew, Yakutat, Alaska. Both measured and estimated moisture content profiles were impacted by site geomorphology. For profiles with uniform slopes, moisture contents ranged from 3.0%-8.0% (Zone 1) and from 8.0%-23.0% (Zone 2). Compared to field measurements, the moisture contents estimated using c calibrated from in-situ and laboratory data resulted in percent error of 3.6%-44.7% and 2.7%-58.6%, respectively. The highest percent error occurred at the transition from Zone 1 to Zone 2. Generally, moisture contents were overestimated in Zone 1 and underestimated in Zone 2, but followed the expected trends based on field measurements. When estimated moisture contents in Zone 1 exceeded 10%, surface roughness, debris, geomorphology, and weather conditions were considered.

In-situ Full Field Measurements During Inter-Facial Debonding in Single Fiber Composite Under Transverse Load

2018 ◽  
Vol 58 (9) ◽  
pp. 1451-1467 ◽  
Author(s):  
I. Tabiai ◽  
R. Delorme ◽  
D. Therriault ◽  
M. Levesque
Keyword(s):  
Fiber Composite ◽  
Field Measurements ◽  
Single Fiber ◽  
Transverse Load ◽  
Full Field

scholarly journals Effect of Temperature on Stiffness of Sandstones from the Deep North Sea Basin

2020 ◽  
Author(s):  
Tobias Orlander ◽  
Katrine Alling Andreassen ◽  
Ida Lykke Fabricius
Keyword(s):  
North Sea ◽  
Temperature Effects ◽  
Mass Density ◽  
Thermal Strain ◽  
High Stress ◽  
Testing Temperature ◽  
Effect Of Temperature ◽  
Stress Regime ◽  
The North

Abstract Development of high-pressure, high-temperature (HPHT) petroleum reservoirs situated at depths exceeding 5 km and in situ temperature of 170 °C increases the demand for theories and supporting experimental data capable of describing temperature effects on rock stiffness. With the intention of experimentally investigating temperature effects on stiffness properties, we investigated three sandstones from the deep North Sea Basin. As the North Sea Basin is presently undergoing substantial subsidence, we assumed that studied reservoir sandstones have never experienced higher temperature than in situ. We measured ultrasonic velocities in a low- and high-stress regime, and used mass density and stress–strain curves to derive, respectively, dynamic and static elastic moduli. We found that in both regimes, the dry sandstones stiffens with increasing testing temperature and assign expansion of minerals as a controlling mechanism. In the low-stress regime with only partial microcrack closure, we propose closure of microcracks as the stiffening mechanism. In the high-stress regime, we propose that thermal expansion of constituting minerals increases stress in grain contacts when the applied stress is high enough for conversion of thermal strain to thermal stress, thus leading to higher stiffness at in situ temperature. We then applied an extension of Biot’s effective stress equation including a non-isothermal term from thermoelastic theory and explain test results by adding boundary conditions to the equations.

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