Ppm Nitrogen Research Articles

Programmed flowering of the F1 long-day strawberry cultivar ‘Elan’ with nitrogen and daylength manipulation

Consumer demand for locally grown, high quality strawberries is increasing even though California, Florida and Mexico provide a year-round source of strawberries for the world market. In most of the US, locally grown strawberries are only available for a short time in late spring from seasonal fruiting short-day cultivars thus off-season strawberry production is an attractive option for growers. Seed propagated hybrids such as ‘Elan’ are becoming more widely available and offer an alternative to often low yielding cultivars used for off-season production. To determine whether or not ‘Elan’ could be programmed to flower with photoperiod or nitrogen, seedlings were fertilized with either 100 or 800 ppm nitrogen for 4 weeks in September beginning one week after exposure to either short days, the natural photoperiod, or long days, the natural photoperiod supplemented with 24 hours of incandescent radiation. Plants were then greenhouse forced under both photoperiods and floral phenology evaluated. Elevated nitrogen during floral initiation in September enhanced and accelerated flowering and plants receiving elevated nitrogen during initiation under long days flowered more than any other treatment. To determine whether or not flowering could be enhanced a second time in the same plants, another 4 week period of elevated nitrogen was provided in December and plant phenology evaluated through mid-January. Elevated nitrogen (800 ppm) in December enhanced December and January flowering. Seedlings were conditioned with elevated nitrogen for a third time in late spring then field planted (early summer) on raised beds with white or black plastic mulch. Elevated nitrogen in late spring enhanced yield in field production. No effects of mulch color, initiation photoperiod or interaction of considered factors were detected. Flowering differences detected in greenhouse studies translated into differences observed in the production field suggesting programmed fruiting with elevated fertilization under field or greenhouse conditions would be feasible.

Adjustable-Rate Fertigation System

<abstract> <bold><sc>Abstract. </sc></bold>Site-specific fertigation can limit fertilizer waste and loss to the environment, but is not easily implemented when there are many small hydrozones, each demanding a unique rate of fertilizer application. With a simple and inexpensive fertilizer injection system, a separate injector could be installed at each zone to provide a unique fertilizer delivery rate, even when those zones are in simultaneous operation. Integration with a wireless control network would allow automated adjustment of the fertilizer delivery rate for each hydrozone and aid installation in existing facilities. A variable-rate injector was developed using a simple venturi injector, solenoid valve, electrical conductivity (EC) sensor, and small computer board (controller). EC was related to fertilizer concentration expressed as parts-per-million (ppm) nitrogen (N). Fertilizer injection rate was controlled by opening and closing a solenoid valve connected to the suction line of the venturi injector. The rate was adjusted by changing the valve duty cycle (percentage of time that the valve was open). For initial testing with a 2000 ppm N stock solution, the duty cycle was manually adjusted from 0 to 100% to deliver an applied fertilizer concentration of 0 to 200 ppm N at an injection ratio of about 1:10. For closed-loop control, the controller was programmed to monitor EC and automatically increase or decrease the valve duty cycle in order to achieve the target fertilizer concentration. The root mean square percentage error for the closed-loop control injection system was 4.8% in laboratory tests over a target range of 0 to 200 ppm N. A mobile injector station was assembled and integrated with a wireless sensor and control network in order to test adjustable-rate fertigation in container nurseries. Field trials to deliver specified nitrogen concentrations to several different nursery beds gave a root mean square percentage error of 2.2% over a target range of 50 to 150 ppm N. The fertilizer concentrations matched that specified by the user, indicating that the system did a good job of adjusting the duty cycle to meet the target rate, and the irrigation and fertilizer injection durations were correct. Furthermore, the wireless network performed well and exhibited acceptable range.

Origin of sub-lithospheric diamonds from the Juina-5 kimberlite (Brazil): constraints from carbon isotopes and inclusion compositions

Forty-one diamonds sourced from the Juina-5 kimberlite pipe in Southern Brazil, which contain optically identifiable inclusions, have been studied using an integrated approach. The diamonds contain <20 ppm nitrogen (N) that is fully aggregated as B centres. Internal structures in several diamonds revealed using cathodoluminescence (CL) are unlike those normally observed in lithospheric samples. The majority of the diamonds are composed of isotopically light carbon, and the collection has a unimodal distribution heavily skewed towards δ13C ~ −25 ‰. Individual diamonds can display large carbon isotope heterogeneity of up to ~15 ‰ and predominantly have isotopically lighter cores displaying blue CL, and heavier rims with green CL. The light carbon isotopic compositions are interpreted as evidence of diamond growth from abiotic organic carbon added to the oceanic crust during hydrothermal alteration. The bulk isotopic composition of the oceanic crust, carbonates plus organics, is equal to the composition of mantle carbon (−5 ‰), and we suggest that recycling/mixing of subducted material will replenish this reservoir over geological time. Several exposed, syngenetic inclusions have bulk compositions consistent with former eclogitic magnesium silicate perovskite, calcium silicate perovskite and NAL or CF phases that have re-equilibrated during their exhumation to the surface. There are multiple occurrences of majoritic garnet with pyroxene exsolution, coesite with and without kyanite exsolution, clinopyroxene, Fe or Fe-carbide and sulphide minerals alongside single occurrences of olivine and ferropericlase. As a group, the inclusions have eclogitic affinity and provide evidence for diamond formation at pressures extending to Earth’s deep transition zone and possibly the lower mantle. It is observed that the major element composition of inclusions and isotopic compositions of host Juina-5 diamonds are not correlated. The diamond and inclusion compositions are intimately related to subducted material and record a polybaric growth history across a depth interval stretching from the lower mantle to the base of the lithosphere. It is suggested that the interaction of slab-derived melts and mantle material combined with subsequent upward transport in channelised networks or a buoyant diapir explains the formation of Juina-5 diamonds. We conclude that these samples, despite originating at great mantle depths, do not provide direct information about the ambient mantle, instead, providing a snapshot of the Earth’s deep carbon cycle.

Effect of Addition of Boron and Nitrogen on the Corrosion Resistance of Modified 9Cr-1Mo Ferritic Steel

Abstract Electrochemical noise (EN) studies were conducted on three different sets of modified 9Cr-1Mo steels containing different contents of nitrogen and boron in air-saturated 0.05 M NaCl solution at 1 Hz sampling frequency for 72 h continuously, in order to study the metastable pitting corrosion behaviour of these steels. These specimens had different combinations of boron and nitrogen (60 ppm boron and 110 ppm nitrogen, 60B + 110N), (90 ppm boron and 100 ppm nitrogen, 90B + 100N) and (100 ppm boron and 47 ppm nitrogen, 100B + 47N) respectively, while base metal composition was same. Current signal analysis was carried out to know the total number of current transients as a function of current amplitude. The statistical parameter like σI was studied to indicate the extent of localized corrosion activity. It was observed that the total number of current transients was highest for the specimen with comparable concentrations of boron and nitrogen, 90B + 100N; also it showed highest number of high current transients, suggesting its tendency towards pitting corrosion. This is mainly due to the formation of boronitrides which reduces dissolved boron and nitrogen causing increased pitting corrosion activity. Low boron (60 ppm) and high nitrogen specimen showed lowest number of high current transients, indicating improved passivation. The plots of σI as a function of time as well as cumulative probability (CP) vs. σI showed inferior pitting corrosion resistance for the former while the latter showed the least corrosion activity.

Induction of Sulfated Polysaccharides in Spirulina platensis as Response to Nitrogen Concentration and its Biological Evaluation

Sulfated polysaccharides (SPS) extracted with hot water from Spirulina grown on nutrient medium containing 412 ppm (optimal N2 level) and 45 ppm (limited N2 level) ppm nitrogen were found to be rich in sulfate contents with values 5.02 % and 4.13%), respectively. Monosaccharides content of SPS in both algae cells were analyzed by HPLC and the results showed that: glucouronic acid and galactose were the predominating sugar in all extracts, followed by rhamnose, arabinose, glucose and ribose. The SPS analyzed by FT-IR spectra showed an intense band of absorption at 790-850 cm-1 indicating the presence of sulfate group of polysaccharides. SPS of S. platensis exhibited anticoagulant activities as compared with heparin (standard anticoagulant drug). SPS showed a significant growth inhibit (%) against HepG2 and MCF7 cancer cell lines, with IC50 value ranged between 4.0 and 0.54 g/ml. SPS showed antiviral activity against HSV-1 (standard strain) as a model of DNA virus (as assessed by a plaque reduction test and antioxidant activities toward DPPH. and ABTS.+ radical.

Influence of Nitrogen Enrichment during Reproductive Growth Stage on Leaf Nitrogen Accumulation and Seed Yield in Soybean

Nitrogen assimilation during seed filling limits the seed yield in soybean. Seed nitrogen dependence on either redistributed nitrogen or absorbed nitrogen from soil during seed filling shows varietal differences. The objective of this study was to investigate the timing of nitrogen enrichment for effective nitrogen assimilation. Two soybean cultivars Sachiyutaka and Tamahomare were sown in the pots filled with well-washed fine sand. The plants were well watered with nutrient solution containing 100 ppm nitrogen and other nutrient elements before and after the treatment. The treatments were conducted from reproductive stage R1 to R5 or from R5 to R7 by applying the nutrient solution with different nitrogen concentrations. The high nitrogen concentration from R1 to R5 delayed the decline in SPAD value and leaf nitrogen concentration and improved the seed yield performance in Sachiyutaka, whereas stimulated the decline in SPAD value and leaf nitrogen concentration and had no effect on seed yield in Tamahomare. However, high nitrogen concenntration during R5 to R7 delayed the decline in SPAD value and leaf nitrogen concentration and improved the yield performance more significantly in Tamahomare than in Sachiyutaka. The large seed yield increase by nitrogen enrichment during R5 to R7 in Tamahomare could be caused by both the high photosynthetic rate and vigorous nitrogen uptake during seed filling. These results suggested that the most effective timing of nitrogen enrichment during the reproductive growth period to increase seed yield varies with the cultivar due to the difference in the pattern of nitrogen assimilation.

Correlation between Continuous/Discontinuous Yielding and Hall&amp;ndash;Petch Slope in High Purity Iron

High purity iron specimens containing 11 ppm carbon and 8 ppm nitrogen with different grain sizes were fabricated by cold rolling and subsequent annealing. It was found that the specimens exhibited entirely different yielding behavior in tensile tests depending on different cooling processes after annealing. The water-cooled specimens exhibited continuous yielding while the air-cooled ones exhibited discontinuous yielding. It was found that the Hall­Petch slope, ky, significantly changed depending on the different yielding behaviors. [doi:10.2320/matertrans.MA201326]

Growth‐rate Enhancement of High‐quality, Low‐loss CVD‐produced Diamond Disks Grown for Microwave Windows Application

AbstractThe effect of nitrogen addition on the growth rate, quality, and properties of polycrystalline diamond grown by microwave plasma assisted (MPA)CVD is investigated. Two series of experiments are performed at two different microwave power densities (40 and 110 W cm‐3) using a 2.45 GHz cylindrical microwave reactor. The results show that the beneficial effect of nitrogen is more distinct at higher microwave power densities. To investigate the properties of polycrystalline diamond grown with nitrogen addition, a thick diamond disk of 50 mm diameter is grown with an addition of 50 ppm nitrogen using a 2.45 GHz ellipsoidal microwave reactor. The grown diamond disk has a thermal conductivity of 17.3 W cm‐1 K‐1 and dielectric loss tangent of 3.7 × 10‐5 at a frequency of 170 GHz, and its parameters are suitable for application in microwave windows (e.g., gyrotron windows). Our results indicate that it is possible to achieve the increased (by a factor of 2.5) growth rates by nitrogen addition without significant degradation of diamond quality, and properties such as thermal conductivity and dielectric loss tangent.

Emissions analysis from combustion of eco-fuel briquettes for domestic applications

In this study, flue gas emissions from combustion of eco-fuel briquettes in a ceramic lined stove were investigated. The eco-fuel briquettes were made of biomass such as spent coffee beans, mielie husks, saw dust, paper pulp and coal fines using a hand operated screw press. A combustion set-up consisting of digital weightometer, a ceramic lined stove and a complete chimney system was used. The emissions from the combustion process were measured using a Testo 350 gas analyser linked to the chimney system. The eco-fuel briquettes made from a mixture of biomass and coal fines burnt within the acceptable exposure limits as set out by the Occupational Safety and Health Agency (OSHA). The flue gas emissions from the combustion of eco-fuel briquettes were found to contain 74 parts per million (ppm) carbon monoxide (CO), 4.32 ppm hydrogen sulphide (H2S), 1.34ppm nitrogen oxides (NOx) and 3.67 ppm sulphur oxides (SOx). The measured gross calorific value was 18.9MJ/kg, with a burning rate of 2g/min. These properties make eco-fuel briquettes suitable for domestic applications. A survey conducted as part of this study also revealed a significant demand for eco-fuel briquettes in many informal settlements in Gauteng Province, South Africa, at a competitive selling price of R2.60/kg.

Global fold of human cannabinoid type 2 receptor probed by solid‐state 13C‐, 15N‐MAS NMR and molecular dynamics simulations

ABSTRACTThe global fold of human cannabinoid type 2 (CB2) receptor in the agonist‐bound active state in lipid bilayers was investigated by solid‐state 13C‐ and 15N magic‐angle spinning (MAS) NMR, in combination with chemical‐shift prediction from a structural model of the receptor obtained by microsecond‐long molecular dynamics (MD) simulations. Uniformly 13C‐ and 15N‐labeled CB2 receptor was expressed in milligram quantities by bacterial fermentation, purified, and functionally reconstituted into liposomes. 13C MAS NMR spectra were recorded without sensitivity enhancement for direct comparison of Cα, Cβ, and CO bands of superimposed resonances with predictions from protein structures generated by MD. The experimental NMR spectra matched the calculated spectra reasonably well indicating agreement of the global fold of the protein between experiment and simulations. In particular, the 13C chemical shift distribution of Cα resonances was shown to be very sensitive to both the primary amino acid sequence and the secondary structure of CB2. Thus the shape of the Cα band can be used as an indicator of CB2 global fold. The prediction from MD simulations indicated that upon receptor activation a rather limited number of amino acid residues, mainly located in the extracellular Loop 2 and the second half of intracellular Loop 3, change their chemical shifts significantly (≥1.5 ppm for carbons and ≥5.0 ppm for nitrogens). Simulated two‐dimensional 13Cα(i)13CO(i) and 13CO(i)15NH(i + 1) dipolar‐interaction correlation spectra provide guidance for selective amino acid labeling and signal assignment schemes to study the molecular mechanism of activation of CB2 by solid‐state MAS NMR. Proteins 2014; 82:452–465. © 2013 Wiley Periodicals, Inc.

Production of High Nitrogen Stainless Steel X8CrMnN18-18 through EAF-AOD-LRF-CC-Steckel Mill Route and its Hot Deformation Study by Gleeble Thermomechanical Simulator

High nitrogen containing austenitic stainless steel X8CrMnN18-18 exhibits attractive combination of high strength, toughness and corrosion resistance.This grade containing more than 5000 ppm of nitrogen was produced commercially through EAF-AOD-LRF-CC-Steckel mill route and its microstructure and mechanical properties were studied. Excellent combination of strength,ductility and toughness is achieved in the entire range of 6mm to 50mm thick hot rolled plates. Uniaxial compression tests were carried out to understand the hot deformation behavior by varying temperature and strain rate. Softening behavior during deformation was analyzed from flow stress strain curves and microstructural analysis. Dynamic recrystallization (DRX) behavior of the material was observed during thermo mechanical processing. Critical strain related to DRX and Avrami kinetics of DRX was calculated by analyzing the flow curve data. Microstructural characterization was done by optical microscopy and EBSD analysis. Extensive grain refinement can be achieved by thermo-mechanical processing controlled by DRX. Keywords: High nitrogen stainless steel, Strength and toughness, DRX, Grain refinement, TMCP

Nanostructured SnO2 thin films for NO2 gas sensing applications

Abstract We report the synthesis of nanostructured SnO2 by a simple inexpensive sol–gel spin coating method using m-cresol as a solvent. This method facilitates rapid synthesis at comparatively lower temperature enabling formation of nanostructures suitable for gas-sensing applications. Various physicochemical techniques have been used for the characterization of SnO2 thin films. X-ray diffraction analysis confirmed the single-phase formation of tetragonal SnO2 having crystallite size 5–10 nm. SnO2 showed highest response (19%) with 77.90% stability toward 100 ppm nitrogen dioxide (NO2) at 200 °C. The response time of 7 s and recovery time of 20 min were also observed with the same operating parameters. The probable mechanism is proposed to explain the selective response toward nitrogen dioxide. Impedance spectroscopy studies showed that the response to nitrogen dioxide is mainly contributed by grain boundaries. The reproducibility and stability study of SnO2 sensor confirmed its candidature for detection of NO2 gas at low concentration (10–100 ppm) and lower operating temperature.

Mitigation of Pollution-induced Deterioration of Digital Prints through Low-Temperature Storage

An IPI survey found that approximately 87% of museums, libraries and archives already have digital prints in their collections and that they are concerned about increasing influxes of these materials. The survey also showed that objectionable deterioration has already occurred to some of their prints including fading, yellowing, color bleed, surface cracking and delamination. In total, 71% of institutions have already experienced deterioration in their digital print collections. Previous experimental research, both by IPI and others, has been able to establish a clear connection between ozone and nitrogen dioxide exposure and each of those forms of decay. Development of effective methods to mitigate such damage will, therefore, be critical to the survival of these objects for future generations. This study was aimed specifically at determining the efficacy of one particular approach, mitigating pollutant damage to digital prints through lowered-temperature storage. Since the deterioration due to pollutants occurs through chemical reactions, it may be possible to slow decay through cool or cold storage.The Arrhenius method was used to predict the times to significant fade or yellowing of prints exposed to 1 ppm ozone or 5 ppm nitrogen dioxide. Test targets were incubated at 25&#xB0;C, 30&#xB0;C, 35&#xB0;C, 40&#xB0;C, and 45&#xB0;C at 50% RH for multiple intervals up to 56 days. Cyan, magenta, yellow, and black color patches were monitored using ANSI Status A density for density loss. Unprinted, white areas were monitored using ANSI Status A blue density for paper yellowing. It was found that lower temperature does in fact reduce the rates of decay but not equally for both pollutants. Low temperature was more effective at reducing yellowing caused by nitrogen dioxide than it was at reducing the fade caused by ozone; however, cool or cold storage can clearly mitigate damage and extend the usable life of digital prints in collections.

X-ray Detection Performance of 100-pixel Superconducting Tunnel Junction Array Detector in the Soft X-ray Region

The overall performance of a 100-pixel superconducting tunnel junction (STJ) array detector in the soft X-ray region was determined by measuring fluorescent X-rays from light elements. The yield of working STJs in the fabricated detector was 90%, and the leakage current for these 90 STJs was 11.6±2.5 nA. The STJs had an intrinsic energy resolution for O-Kα X-rays (524.9 eV) of 10.2±1.7 eV (FWHM). The deviation from energy linearity was −0.042±0.45%, 0.793±0.91%, and 0.135±1.31% for O-Kα (524.9 eV), N-Kα (392.4 eV) and B-Kα (183.3 eV) X-rays, respectively. Most of the STJs exhibited uniform X-ray detection characteristics. In addition, the detector could discriminate the N-Kα peak in the fluorescent X-ray spectrum from n-type SiC doped with 300 ppm nitrogen.

Hydrogen Sulfide Absorption Phenomena in Brine/Oil Mixtures

Summary Brine and oil absorb hydrogen sulfide (H2S) under pressure in the underground oil reservoir and then undergo a decompression during the extraction process, during which a certain amount of H2S is released from the liquid phase. This paper reports experimental data on how much of the corrosive gas is absorbed into different brine/oil mixtures [0, 33, 66, and 100% water cuts (WCs)]. Different reservoir-simulation scenarios were created at 20 and 70 atm at room temperature. H2S gas concentration was varied as tests were conducted with 50, 100, and 300 ppm in nitrogen. These experiments took place in an autoclave system that simulates the hydrostatic process that occurs inside a reservoir. This paper also reports Henry's law constants for H2S in different WCs. It is found that for all WCs, total pressure plays only a minor role in the absorption phenomena when the initial H2S concentration is increased. In addition, the highest mass-absorption ratios are found at lower H2S concentrations.

Metallurgy of Type IV fracture in advanced ferritic power plant steels

The mechanisms responsible for lower creep strength of fine-grained heat-affected-zone (HAZ) than base metal, the microstructural evolution in the HAZ during heating and the suppression of Type IV fracture by boron have been investigated using simulated-HAZ specimens and welded joint specimens of Gr.92, Gr.122 and newly developed 9Cr steel with boron. Creep tests were carried out at 650°C for up to about 30,000 h. In Gr.122, the time to rupture has its minimum after heating the specimens to a peak temperature near AC3, while the hardness has its minimum after heating to a peak temperature near AC1. In Gr.92, the reduction of boundary and sub-boundary hardening in fine-grained HAZ is more important than the grain refinement for a significant decrease in time to rupture after the AC3 thermal cycle. The addition of boron without the formation of any boron nitrides suppresses the formation of fine-grained HAZ and produces substantially the same microstructure as the base metal, even after the AC3 thermal cycle. A newly designed alloy 9Cr steel with 160 ppm boron and 85 ppm nitrogen exhibits not only much higher creep rupture strength of base metal than P92 but also no Type IV fracture in welded joints.

DIAGNOSIS AND RECOMMENDATION INTEGRATED SYSTEM APPROACH FOR NITROGEN, PHOSPHORUS, POTASSIUM, AND ZINC FOLIAR DIAGNOSTIC NORMS FOR AONLA IN CENTRAL INDO-GANGETIC PLAINS

A survey was conducted for the nutritional status of aonla orchards in the state of Uttar Pradesh lying in Central Indo-Gangetic plains. Preliminary diagnosis and recommendation integrated system (DRIS) norms were established for different nutrient ratios and used to compute the DRIS indices, which assessed the nutrient balance and order of limitations to yield. Maximum fruit yield of 40.2 kg plant−1 was recorded for the plants at the age group of 10–15 years and lowest yield was recorded 28.3 kg plant−1 in the age of above 20 years. Nutrient sufficiency ranges for aonla derived from DRIS norms were 1.30– 1.64, 0.054–0.092, 0.40–0.64%, and 32.4–45.9 ppm for nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn), respectively. On the basis of these sufficiency ranges 33, 51, 47, and 46% of samples were found sufficient whereas 34, 22, 18 and 27% of samples were low and 26, 8, 1 and 17% deficient in N, P, K, and Zn, respectively. When compared age wise, a relative deficiency for N, P, and K corresponding to relative sufficiency for Zn was detected by DRIS technique for the plants above the age group of 15 onwards. For the younger orchards (5yrs old) a relative deficiency of N, Zn, and K corresponding to the relative sufficiency of P was detected. Nitrogen was found most limiting elements in all age group of plant. When the DRIS indices were compared on basis of soil pH, Zn and K was found to be relatively lesser in order of requirement than N and P.

Metallurgy of Type IV fracture in advanced ferritic power plant steels

The mechanisms responsible for lower creep strength of fine-grained heat-affected-zone (HAZ) than base metal, the microstructural evolution in the HAZ during heating and the suppression of Type IV fracture by boron have been investigated using simulated-HAZ specimens and welded joint specimens of Gr.92, Gr.122 and newly developed 9Cr steel with boron. Creep tests were carried out at 650°C for up to about 30,000 h. In Gr.122, the time to rupture has its minimum after heating the specimens to a peak temperature near AC3, while the hardness has its minimum after heating to a peak temperature near AC1. In Gr.92, the reduction of boundary and sub-boundary hardening in fine-grained HAZ is more important than the grain refinement for a significant decrease in time to rupture after the AC3 thermal cycle. The addition of boron without the formation of any boron nitrides suppresses the formation of fine-grained HAZ and produces substantially the same microstructure as the base metal, even after the AC3 thermal cycle. A newly designed alloy 9Cr steel with 160 ppm boron and 85 ppm nitrogen exhibits not only much higher creep rupture strength of base metal than P92 but also no Type IV fracture in welded joints.

Histological Effect of Nitrous Acid with Secondary Products of Nitrogen Dioxide and Nitric Oxide Exposure on Pulmonary Tissue in Mice

Numerous epidemiological studies of respiratory effects of nitrogen dioxide may have included exposures to nitrous acid, because conventional assays of nitrogen dioxide measure nitrous acid as nitrogen dioxide. A few epidemiological studies and human inhalation experiments of nitrous acid reported that nitrous acid is associated with decrements in lung function and possibly with respiratory symptoms. Moreover, our guinea pig exposure experiment of nitrous acid demonstrated that nitrous acid inducible the pulmonary emphysema-like disease and the architecture alterations of the alveolar duct centriacinar regions with the thickened interstitium. The purpose of this study was to assess the acute toxicity and the injury of exposure to nitrous acid with histopathological alterations in the respiratory tract in mice. We continuously exposed only filtered air and the filtered air with 8.4 ppm nitrous acid with secondary products of 2.8 ppm nitrogen dioxide and 7.2 ppm nitric oxide (24 hr/day) to two mice groups (n=5) for 3 weeks. We conducted histopathological analyses. We found the hyperplasia of the terminal bronchial epithelial cells with the meandering irregularly and without dysplasia in nitrous acid mice exposure group. In nitrous acid mice exposure group, we did not observe the architectural alterations such as the emphysema-like alterations which we have observed in our guinea pig exposure experiment of 3.6 ppm nitrous acid. Moreover, the collagen bundles and thickened interstitium were also indistinct in the alveolar duct centriacinar regions in this concentration of nitrous acid exposure to mice. These histopathological results suggest that the injury effects of HONO were weak.

Remediation of Nitrogen and Phosphorus from Nursery Runoff during the Spring via Free Water Surface Constructed Wetlands

Abstract Agricultural operations face increasing pressure to remediate runoff to reduce deterioration of surface water quality. Some nursery operations use free water surface constructed wetland systems (CWSs) to remediate nutrient-rich runoff. Our objectives were twofold, first to examine the impact of two hydraulic retention times (HRT, 3.5 and 5.5 day) on CWS performance, and second to determine if increased nutrient loading from internal CWS and nursery sources during the spring contributed to nutrient export in excess of regulatory limits. We quantified nutrient loading and removal efficiency in a free water surface CWS from late winter through late spring over three years and monitored various water quality parameters. Total nitrogen in runoff was reduced from 20.6 ± 2.8 mg·liter−1 (ppm) to 4.1 ± 1.3 mg·liter−1 (ppm) nitrogen after CWS treatment. Phosphorus dynamics in the CWS were more variable and unlike nitrogen dynamics were not consistently influenced by water temperature and hydraulic loading rate. Phosphorus concentrations were reduced from 1.7 ± 0.8 mg·liter−1 (ppm) PO4-P in influent to 1.2 ± 0.6 mg·liter−1 (ppm) PO4-P in CWS effluent, but substantial variability existed among years in both phosphorus loading and removal rates. The CWS was able to efficiently remediate nitrogen even under high spring loading rates.