Nitrate In Samples Research Articles

Centimeter-wave reflection in the nitrates and nitrites of sodium and potassium: Experiment and theory

Temperature-dependent centimeter-wave reflection is studied in powdered samples of potassium nitrate (KNO3), potassium nitrite (KNO2), sodium nitrate (NaNO3), and sodium nitrite (NaNO2). Temperature-dependent reflection measurements at centimeter-wave frequencies were performed on an HP8510B Network analyzer based reflectometer. These measurements are compared to calculations utilizing a Debye relaxation model. Reflection losses seen in KNO2 and NaNO2 are expected to be due to the presence of permanent dipoles that are excited to “hopping’’ modes as the temperature is raised. Although NaNO3 shows little reflection losses, KNO3 shows significant losses as the temperature is raised toward the order/disorder transition temperature of 128 °C. This is believed to be due to the development of “induced’’ dipole moments as the lattice becomes increasingly disordered.

LONG-TERM TILLAGE AND CROP ROTATION EFFECTS ON RESIDUAL NITRATE IN THE CROP ROOT ZONE AND NITRATE ACCUMULATION IN THE INTERMEDIATE VADOSE ZONE

Tillage influences the physical and biological environment of soil. Rotation of crops with a legume affects the soil N status. A furrow irrigated site was investigated for long-term tillage and crop rotation effects on leaching of nitrate from the root zone and accumulation in the intermediate vadose zone (IVZ). The investigated tillage systems were diskplant (DP), ridge-till (RT) and slot-plant (SP). These tillage treatments have been maintained on the Hastings silt loam (Udic Argiustoll) and Crete silt loam (Pachic Argiustoll) soils since 1976. Continuous corn (CC) and corn soybean (CS) rotations were the subtreatments. Since 1984, soybeans have been grown in CS plots in even calendar years. All tillage treatments received the same N rate. The N rate varied annually depending on the root zone residual N. Soybeans were not fertilized with N-fertilizer. Samples for residual nitrate in the root zone were taken in 8 of the 15 year study while the IVZ was only sampled at the end of the study. In seven of eight years, root zone residual soil nitrate-N levels were greater with DP than RT and SP. Residual nitrate- N amounts were similar in RT and SP in all years. Despite high residual nitrate-N with DP and the same N application rate, crop yields were higher in RT and SP except when DP had an extremely high root zone nitrate level. By applying the same N rates on all tillage treatments, DP may have been fertilized in excess of crop need. Higher residual nitrate-N in DP was most likely due to a combination of increased mineralization with tillage and lower yield compared to RT and SP. Because of higher nitrate availability with DP, the potential for nitrate leaching from the root zone was greater with DP as compared to the RT and SP tillage systems. Spring residual nitrate-N contents of DP were larger than RT and SP in both crop rotations. Ridge till and SP systems had greater nitrate-N with CS than CC rotations. Nitrate accumulation in IVZ at the upstream end of the field was twice as high with DP compared to RT and SP. At the downstream end, it was 2.4 and 1.6 times greater with DP than RT and SP, respectively. Nitrate concentration was greater in the IVZ of DP compared to RT and SP tillage systems. Nitrate accumulations in IVZ of RT and SP were not different. Continuous corn had slightly higher nitrate levels in IVZ than CS. The depth of nitrate penetration at the upstream end was greater than that of the downstream end. Estimated rates of nitrate movement ranged from 0.87 to 0.92 m yr–1 at the upstream end and 0.73 to 0.78 m yr –1 at the downstream end.

DETERMINING EFFECTS OF FERTILIZER PARTICLE SHAPE ON AERODYNAMIC PROPERTIES

A method was investigated for determining the extent to which aerodynamic properties of fertilizer particlescan be explained by a combination of turbulent airflow theory and a response surface involving geometric shape andmass of particles for a sample of specific fertilizer material. Fall tests were conducted, where particles were dropped andfall times were described by a mathematical model using turbulent airflow theory. Secondly, a measure of particle shapewas determined to explain the difference between theoretical and measured fall times. Various dimensions of particleswere measured using digital image processing. Absolute radius deviations from a preassumed best-fit circular shape wererecorded and combined from two perpendicular particle images and designated shape factor. For a sample of calciumammonium nitrate (CAN) particles, the shape factor ranged from 11.8 to 73.0 (perfect spheres are zero). Over that range,the difference between theoretical and measured fall times was satisfactorily explained (R2 = 0.82 ) by a function of shapefactor and particle mass. A new approach to characterize a bulk of fertilizer material and its spreading properties wasproposed.

Occurrence and distribution of nitrate and pesticides in bowdle aquifer, south dakota

A shallow aquifer in central South Dakota was monitored for thepresence of nitrate and pesticides. A total of 593 nitrate samples and428 pesticide samples were analyzed from nine different sites and 14wells between 1989 and 1994. Nested wells were installed at four sitesto characterize the distribution pattern of nitrate and pesticidemovement in ground water. Nitrate concentrations and pesticidedetections were qualitatively compared with area precipitation and watertable fluctuations. The results indicate that nitrates tend to betransported by a leaching mechanism in a matrix flow and may appearin ground water within months after the fertilizer application in thefields. The pesticide movement is primarily controlled by geologicaland chemical characteristics of medium and pesticides.

Nitric acid, particulate nitrate and ammonium in the continental free troposphere: Nitrogen deposition to an alpine tundra ecosystem

Atmospheric sampling of nitric acid vapor, particulate nitrate and ammonium has been ongoing at a 3540 m a.s.l. alpine tundra site on Niwot Ridge, Colorado, since January, 1993. These nitrogen (N) species data, in conjunction with meteorological data, N data at a 3020 m a.s.l. subalpine site, and back-trajectory information, show that over 90% of the sampling was obtained under free tropospheric but, apparently, N-enriched conditions. Seasonal concentration and estimated N dry deposition trends are presented. Dry plus wet atmospheric N loading is found to provide 2.5–3 kg N ha −1 of new, available N to tundra plants during the growing season (mid-May to mid-September), of which 50%, or more, is dry deposited. During the eight-month, nongrowing season about 5 kg N ha −1 is wet plus dry deposited to the aggrading snowpack or dormant tundra plants. Up to half of this nongrowing season N loading is made available to growing tundra plants during snowmelt. Thus, a total of 3–5 kg N ha − is annually made available to tundra plants by atmospheric deposition of, primarily, anthropogenically derived N. This annual input of new, available N to nutrient N-limited tundra plants may be compared with the dominant pathway for plant N availability at Niwot Ridge—net mineralization of 10–12 kg N ha −1yr −1 recycled through the soil. The ratio of atmospheric N deposition to net N mineralization, presently approaching 0.5, is higher at the Niwot Ridge alpine tundra ecosystem than at most other ecosystems in the continental U.S.

Morphological changes in pressure annealed polyethylene

Polyethylene samples have been annealed under high pressures in order to transform the morphology and thereby make specimens, which on subsequent orientation by hydrostatic extrusion, produce high-modulus materials for comparatively low deformation ratios. The pre-extrusion morphology, as revealed by permanganic etching followed by transmission electron microscopy, is shown to be highly sensitive to the annealing conditions, especially in the vicinity of the orthorhombic/hexagonal phase boundary. The morphological changes have also been studied by gel permeation chromatography of nitrated samples and by differential scanning calorimetry. The moduli of samples, extruded to a standard extrusion ratio of 7, reflect differences in the morphology of the starting material. It is shown that the highest modulus is not obtained by annealing totally within the hexagonal phase but rather in the changeover region between it and the orthorhombic phase. Although the lamellar size can be dramatically increased by annealing within the hexagonal phase, this development occurs at the expense of reducing the integrity of the molecular network so that for high lamellar size the modulus falls and the samples become increasingly incoherent.

Aerial Photography to Detect Nitrogen Stress in Corn

Summary Economic and environmental benefits can result from improved nitrogen (N) management in corn (Zea mays L.) production. This research project was conducted to determine the utility of aerial photographs to detect N deficiency in a crop canopy caused by natural soil variability and variable fertilizer N application rates. Chlorophyll meter readings and digitized aerial photograph data were compared to corn grain yield and stalk nitrate concentrations from a 60-ha field in Central Nebraska. In addition to natural field variability, 30.4-m long treatments were imposed through the center of the field by applying fertilizer at rates of 0, 56, 112, 168, and 224 kg N ha -1 . Grain yield, chlorophyll meter readings, photographic brightness and stalk nitrate samples were collected. Despite a significant effect from fertilizer treatments, chlorophyll meter readings did not correlate well with grain yields. The brightness of the red component in a digitized color photograph showed a significant inverse relationship (r 2 = 0.42) with grain yield. Stalk nitrate concentrations at harvest, when compared to red brightness from the digitized photograph, provided a better confirmation of N status than grain yield. Aerial photographs appear to be capable of detecting management induced variability as well as reduced yield portions of a field that result from natural variability.

Solid‐state lead‐207 NMR of lead(II) nitrate: Localized heating effects at high magic angle spinning speeds

AbstractSolid‐state Pb‐207 NMR spectra of lead(II) nitrate were found to be highly sensitive to variations in temperature. The Pb‐207 chemical shift exhibits a linear dependence on temperature with a positive slope of 0.70 ± 0.02 ppm K−1, i.e. increases in temperature cause a change in chemical shift to higher frequency. This slope is within experimental error of the value obtained from parallel experiments on the static solid, 0.72 ± 0.06 ppm K−1. At higher magic angle spinning (MAS) speeds and ambient probe temperature, the Pb‐207 signal splits into several components owing to localized heating effects. These effects are more pronounced in rotors made from partially stabilized zirconia than those made from silicon nitride and are attributed to the poorer thermoconductive properties of the zirconia ceramic. In the zirconia rotors, discrete thermal regions within the lead(II) nitrate sample were located and differ by 5 K at 12 kHz MAS speeds. The response of the Pb‐207 lead(II) nitrate signal to temperature variation suggests that it could be used for calibrating solid‐state NMR probes.

Self-sufficiency of velocity sedimentation for the determination of molecular characteristics of linear polymers

General possibilities of velocity sedimentation in the hydrodynamic study of macromolecules are discussed. It is shown that, using the mass-spectrometric effect of the ultracentrifuge together with the calculation of molecular weights by means of a recently introduced sedimentation parameter β s , allows complete analysis of all the macromolecular parameters of polymers by velocity sedimentation only, without additional procedures. The sedimentation parameter is given by β s =N a [S]k s 1 3 M −2 3 , where [S]=S o η o /(1− νϱ o ) is the intrinsic sedimentation constant, k s is Gralen's concentration coefficient, M is the molecular weight and N a is Avogadro's number. In this way molecular weight distributions etc. can be obtained. The validity of the suggested approach is demonstrated on a cellulose nitrate (CN) sample with a substitution degree of 2.7, in acetone. The sample is characterized by the polydispersity index M w/ M n=1.66 in the molecular weight range 20⪕M × 10 3⪕620 . By means of velocity ultracentrifugation, values of the equilibrium rigidity of CN (Kuhn's segment length), A=(360±13) × 10 −8 cm, and of hydrodynamic diameter, d=(4.8±0.4) × 10 −8 cm, are obtained. All data obtained are in good agreement with published data for real fractions of CN in acetone.

Studies on Thermal Decomposition Kinetics of Polyvinyl Nitrate

AbstractNon‐isothermal TG curves for four samples of polyvinyl nitrate (PVN), having 15.71%, 14.95%, 13.34% and 11.76% nitrogen contents, were obtained at 5°C/min heating rate. The weight loss of PVN samples depends directly on their % N and occurs in three or more temperature zones. For PVN with 15.71% N (max 15.73% N in theory), the main decomposition step results in more rapid and complete weight loss than for PVN with lower % N, probably due to higher oxygen balance of the former. The TG data were subjected to kinetic analysis using a computer programme. For each decomposition step, the kinetic parameters (E and A) and the regression coefficient (r) were calculated on the basis of several kinetic models and equations consistent with the Arrhenius relationship. It was concluded that the thermal decomposition kinetics of all four PVN sample are best expressed by the Random nucleation model (Mampel unimolecular law) first‐order reaction. For the initial and slowest decomposition step, E ranged between 188 kJ/mol − 217 kJ/mol and In A between 46.88 s−1 ‐ 60.13 s−1. The In A versus E plots for all PVN samples exhibited a linear relationship, probably due to the kinetic compensation effect.

Titrimetric determination of free and total acidity and the subsequent deduction of zirconium content in process samples of zirconium nitrate

A simple titrimetric method for the rapid determination of free nitric acid concentration and total acidity in process samples of zirconium nitrate is described. This paper also details a theoretical method of deducing the zirconium oxide content of these samples based on the free and total acidity values. Sodium fluoride is used to complex the hydrolysable ions and sodium hydroxide is used as the titrant for the free acid. A mixed indicator of Bromocresol Purple and Bromothymol Blue (sodium salt, 0.1% each in water) was used to detect the endpoint where there is a sharp change in colour from yellow to deep blue. A precision of ±0.02 mol l–1 and ±0.5 g l–1 is attainable for acidity values and zirconium oxide concentrations, respectively. The free acidity values are in good agreement with those calculated, based on the total acidity and total concentration of the hydrolysable ions present in the medium. The zirconium throughput values calculated from the total and free acidities compared favourably with the gravimetric values estimated by precipitating zirconium (hafnium) as mandelate followed by ignition to produce the oxide. Applicability of various ligands such as oxalate, tartrate, citrate and ethylenediaminetetraacetic acid as alternative complexants is also investigated and it is observed that the zirconium complexes formed with these complexants (except that with cupferron) hydrolyse significantly and cannot be used as complexants for the direct determination of free acidity. The use of cupferron was found to be limited because of poor precision.

Determination of lead isotope distributions by means of a computer-controlled Zeeman scanning atomic absorption spectrometer (ZSAAS)

For isotope determination, the Zeeman scanning atomic absorption spectroscopy (ZSAAS) technique has been improved by constructing a new PC-controlled spectrometer and by developing new calibration procedures. The spectrometer is a modified instrument for direct ZAAS with a low pressure graphite furnace. The light source, containing 208Pb or lead of natural abundance, is placed in an ac magnetic field. Thus, the σ-components scan the absorption line profile of the analyte. The instrument was calibrated with samples of pure 204Pb, 206Pb, 207Pb, 208Pb and the reference material NBS SRM 982. Another calibration procedure was tested by synthetic lead nitrate samples spiked with one single isotope. Complete isotope distributions of certified lead sulphide samples as well as recovery measurements with natural lead samples spiked with one of the isotopes 204Pb, 206Pb, 207Pb and 208Pb could be determined with standard deviations of about 1%.

Force Detection of Nuclear Magnetic Resonance

Micromechanical sensing of magnetic force was used to detect nuclear magnetic resonance with exceptional sensitivity and spatial resolution. With a 900 angstrom thick silicon nitride cantilever capable of detecting subfemtonewton forces, a single shot sensitivity of 1.6 x 10(13) protons was achieved for an ammonium nitrate sample mounted on the cantilever. A nearby millimeter-size iron particle produced a 600 tesla per meter magnetic field gradient, resulting in a spatial resolution of 2.6 micrometers in one dimension. These results suggest that magnetic force sensing is a viable approach for enhancing the sensitivity and spatial resolution of nuclear magnetic resonance microimaging.

Optical-fiber-based position-sensitive detector for thermo-optic deflection studies

We describe the construction and operation of an optical-fiber-based position-sensitive detector and a few of its applications. The p01- shed tip of a multimode fiber serves as an aperture with finite width and an avalanche photodiode coupled to the other end of the fiber functions as the optical detector. We demonstrate the utility of this detector system for imaging and mirage effect studies. Measurements made on a bulk sample of potassium nitrate (KNO 3 ) undergoing phase transition and surface imaging of a patterned brass disk are given as illustrations.

Seasonal trends of nitric acid, particulate nitrate, and particulate sulfate concentrations at a southwestern U.S. mountain site

Abstract Nitric acid, particulate nitrate, and particulate sulfate samples were collected on filter media on an approximately weekly basis between 26 October 1989 and 26 September 1990 at a mountain site in southern Nevada, U.S.A. Wind velocity and direction data were obtained for each sampling date from two locations in the nearby urban area of Las Vegas. NV. Seasonal differences in species concentrations are correlated to the seasonal meteorology: transport of nitrate from distant sources may be prevalent during part of the year.

Equilibrium and mass spectrometry of nitrate decomposition in electrothermal atomic absorption spectrometry

The decomposition of metal nitrates to oxides is assumed to occur in electrothermal atomic absorption spectrometry during the pre-atomization drying or thermal pre-treatment of nitrate samples. The mechanism of thermal decomposition of nitrates to solid oxides and gaseous NO2 is well established, but some evidence from recent electrothermal mass spectrometry (ET-MS) experiments has been used to support an alternative mechanism, that of gaseous metal oxide formation, e.g. MNO3→MO(g)+ NO2(g) The ET-MS of nickel, cobalt, copper, magnesium and lead nitrate samples have been re-examined using a quadrupole mass spectrometer with cross-beam rather than axial sampling of gas from the furnace. With this new sampling geometry, no gaseous metal oxides were detected over a range of heating rates from slow drying to rapid atomization. These results are in keeping with thermochemical equilibrium calculations, as is the observation of gaseous phosphorus oxides in the thermal decomposition of NH4H2PO4. Earlier observations of gaseous metal oxides of the above elements by ET-MS are attributed to the formation of molecular clusters of oxides and/or nitrates during rapid decomposition of the metal nitrates.

Urban wet deposition nitrate: A comparison to non-urban deposition

The concentration of nitrate in both wet and dry deposition has both increased historically and currently, and recently parallels emissions in NOx. Since NOx is produced in amounts comparable to SO2, it is an important contributor to acid deposition, and is produced in higher amounts in urban areas due to concentrated sources. Prior to this study, national acid deposition monitoring networks in the United States have been and remain established in non-urban areas. This research study consisted of a comparison of precipitation sampling and analysis of wet deposition nitrate and pH for each deposition event in each of two urban sites over a 15 mo period. Also, a comparison of urban data and data generated at a nearby non-urban NADP site was made by examination of both monthly and seasonal data. This research suggests that national monitoring programs should consider inclusion of urban and non-urban monitoring sites in order to achieve a more representative regional assessment.

Evaluation of storage and display conditions for cellulose nitrate objects

Because cellulose nitrate slowly degrades under normal room conditions, some important works of art made out of this early polymeric material have been and are being lost. Since decomposition is magnified by elevated temperatures, relative humidities and exposures to ultraviolet (UV) light, it is important to define the effects these conditions have on the degradation rate of cellulose nitrate. This paper presents preliminary results of an evaluation of comparative effects of temperature (50, 25, 15°C), relative humidity (81, 53, 11% RH), oxygen (20.9, 0.1%) and UV light on the condition of cellulose nitrate samples. The changes III elemental composition of new and 80-year-old cellulose mtrate are monitored by the measurement of their carbon, hydrogen and nitrogen content using organic elemental analysis. The effects of the controlled conditions on cellulose nitrate are shown in relation to the initial composition of the samples. After 75 days exposure to the relatively mild conditions, only small changes have been found in the elemental composition of the samples.

Effect of composition on the lattice parameters and thermal behaviour of nickel(II)–cobalt(II) hydroxide nitrate solid solutions

A series of coprecipitated nickel(II)–cobalt(II) hydroxide nitrate samples with different cationic compositions has been studied by means of X-ray diffraction, infrared spectroscopy and thermal analysis. A continuous series of solid solutions NixCo2–x(OH)3NO3(0⩽x⩽2) is formed between the end members Ni2(OH)3NO3 and Co2(OH)3NO3. The observed changes in the IR spectra have been interpreted in terms of increased polarization of the NO3– group and increased strength of the hydrogen bonds when Ni2+ is gradually substituted for Co2+. The thermal stability of the solid solutions as well as the phase composition of the solid products of thermal decomposition depend upon the initial Ni : Co ratio in the samples.

Multivariate Geostatistïcal Analysis of Ground‐Water Contamination: A Case History

AbstractA case history is presented for the application of multivariate geostatistical methods to the problem of estimating pesticide concentrations in ground water from measured concentrations of nitrate and pesticide, when pesticide is under‐sampled. The shallow, poorly confined, sand and gravel aquifer underlying the lower Malheur River basin near Ontario, Oregon is contaminated by nitrate and metabolites of the herbicide Dacthal (dimethyl tetrachloroterephthalate) or DCPA. The results of extensive ground‐water sampling indicate that a significant positive correlation exists between measured nitrate and DCPA concentrations in the aquifer. This suggests that future sampling should include a large number of the less‐expensive nitrate analyses, and these data should be used to support the interpretation of fewer, more expensive DCPA analyses. Sample variograms were computed for nitrate and DCPA concentrations and were fit with isotropic, spherical variogram models with correlation ranges of 4 km. Incorporating measured nitrate concentrations in the DCPA estimates obtained by cokriging reduced estimation variances from 14 to 34%. A simple economic analysis demonstrated that for this aquifer, acquiring additional nitrate samples is a cost‐effective way to reduce estimation variances for DCPA.