Influence of nozzle type upon the control of the stalkborer using chlorpyrifos and cyfluthrin 1

Abstract

Field experiments were conducted in corn plots during 1988 that were artificially Infested with stalkborers, Papianema nebris (Guenee'). Two atomizers, a flatfan and a flood nozzle chosen for different droplet size distributions were used to apply two insecticides, chlorpyrifos and cyfluthrin at two application rates. Nozzles, insecticides, rates, and associated interactions were evaluated for control of stalkborer in the field. Laboratory studies involved application of insecticides to soil and glass via a spray track for bioassay at field application rates. Image analysis of percent area travelled on water sensitive paper by stalkborers was compared to droplet percent area covered to obtain percent area contacted per insect. Droplet size distributions for each nozzle were obtained using an Aerometrics particle sizing instrument. Significant differences in stalkborer control were attributed to percent area covered by smaller droplets measured by image analysis.     

Polymer and invert emulsifying oil effects upon droplet size spectra of sprays

Abstract

A series of wind tunnel atomization studies were carried out to investigate the effects of polymer and invert suspension oil “drift control adjuvants” upon the droplet size distribution spectra produced by nozzles typically used in aerial and ground based spraying of pesticides. A D8–46 disc and core was used as a typical aerial application nozzle, and an 8003 fan nozzle was used for the ground based sprayers simulation. The droplet size spectra were evaluated in a wind tunnel using a Malvern 2600 laser particle size analyzer immediately upon mixing and at 15 minutes after re‐circulation through a pumping system. The addition of the polymer‐based adjuvants significantly increased the droplet size spectra parameters of the spray cloud, but all the polymer products showed signs of breakdown of their molecular arrangements in the liquid medium, as a result of agitation. The invert suspension oil adjuvant did not change the droplet size spectra markedly, nor did it show signs of breakdown of the internal liquid structure after re‐circulation.     

气液两相旋流喷嘴雾化特性

为提高烟尘净化用喷嘴的雾化性能,提出一种气液两相旋流喷嘴,用CFX软件对该喷嘴内部流场模拟的结果表明,强烈的气旋作用使液流呈环状,使气液混合流在达到喷嘴末端时易于破碎成雾。在实验室条件下,利用Winner313型喷雾激光粒度分析仪对喷嘴进行了雾化粒度测定,分析发现雾滴中位径与气液比的关系呈幂函数衰减,这一规律将有助于在工程应用时确定喷嘴工况。     

Effect of sunlight radiation,rainfall and droplet spectra of sprays on persistence of bacillus thuringiensis deposits after application of dipel® 76af formulation onto conifers

Abstract

The effect of sunlight radiation, rainfall and droplet spectra of sprays on per ‐sistence of a Bacillus thuringiensis subspp. kurstaki (Btk) formulation, DiPel^® 76AF, was examined after application onto spruce [Picea glauca (Moench) Voss] foliage. The investigation consisted of three studies: (i) Study I: a laboratory microcosm study to examine the photostability of DiPel 76AF deposits on foliage after different periods of exposure to two radiation intensities, (ii) Study II: a laboratory microcosm study to examine the rainfastness of foliar deposits after exposure to different amounts of rainfall consisting of two separate droplet spectra, and (iii) Study III: a field microcosm study to investigate the influence of two different droplet spectra of DiPel 76AF sprays on foliar persistence of Btk under natural weathering conditions. In all studies, persistence of Btk was investigated both by bioassay [using spruce budworm (Choristoneura fumiferana Clemens)] and total protein assay.

The findings of Study I indicated that bioactivity of foliar deposits decreased with increasing duration of exposure to radiation, and with increasing radiation intensity. The half‐life (DT₅₀, the exposure period required for 50% of the initial bioactivity to disappear) was 5.1 d for the low intensity, and 3.9 d for the higher intensity. In contrast with the bioassay results, the total protein levels [determined by the bicinchoninic acid (BCA) method] showed no decrease with increasing duration of exposure, or with increasing radiation intensity.

The findings of Study II indicated that bioactivity of foliar deposits decreased with increasing cumulative rainfall. A new term, RF₅₀ [the amount of rain (in mm) required to washoff 50% of the initial deposit], was introduced to understand the relationship between rainfall intensity and reduction in bioactivity. When the same amount of rain was applied in different droplet sizes, the RF₅₀ value was high (5.2 mm) for the small rain droplets, and was low (2.9 mm) for the large rain droplets. Similar to the bioassay results, the total protein concentrations (determined by the BCA method) decreased with increasing amount of rain and with increasing rainfall intensity. The RF₅₀ value (obtained using ng protein /cm²) was 5.4 mm for the small rain droplets, and was 3.4 mm for the large rain droplets.

The field microcosm study indicated that when DiPel 76AF was applied in small droplets (D_v.5 of 65 μm), the persistence of bioactivity was ca 8.0 d, whereas when it was applied in large droplets (D_v.5 of 130 nm) it was ca 11 d. Bioactivity decreased with time after spray, and the DT₅₀ was 1.98 d for the spray of small droplets, and 2.87 d for that of large droplets. Similar to the bioactivity, the total protein concentrations also decreased with time after spray, and the DT₅₀ values for the small and large droplet spectra were 3.45 and 6.07 d respectively.     

Heterogeneous Oxidation by Ozone of Naphthalene Adsorbed at the Air-Water Interface of Micron-Size Water Droplets

Abstract

The mass transfer of naphthalene vapor to water droplets in air was studied in the presence of ozone (O₃) in the gas phase. A falling droplet reactor with water droplets of diameters 55, 91, and 182 μm was used for the study. O₃ reacted with naphthalene at the air-water interface, thereby decreasing the mass transfer resistance and increasing the rate of uptake of naphthalene into the droplet. A Langmuir-Hinshelwood reaction mechanism at the air-water interface satisfactorily described the surface reaction. The first-order surface reaction rate constant, k_s, increased with decreasing droplet size. Three organic intermediates were identified in the aqueous phase as a result of ozonation of naphthalene at the surface of the droplet indicating both peroxidic and nonperoxidic routes for ozonation. The presence of an organic carbon surrogate (fulvic acid) increased both the partition constant of naphthalene and the surface reaction rate of O₃. The heterogeneous oxidation of naphthalene by O₃ on the droplet was 15 times faster than the homogeneous oxidation by O₃ in the bulk air phase, whereas it was only 0.08 times the homogeneous gas-phase oxidation by hydroxyl radicals under atmospheric conditions.     

Dry FGD at United Power Association’s Stanton Station

The United Power Association’s dry FGD system at Stanton, North Dakota was the first utility-operated lime spray dryer to be put into service in the United States. At 60 MW in size, it utilizes a single spray dryer vessel with three rotary atomizers and a ten-compartment fabric filter. It is currently operating at better than expected efficiency and Is meeting state and federal air quality requirements. Start-up and operation have shown that certain areas of design and operating conditions are critical to reliable operation. Flue gas, slurry, and water distribution and mixing must be carefully controlled if reliable, long term operation is to be achieved. Likewise, water chemistry Is Important in the reagent preparation equipment. Start-up of the system was accomplished In a step-wise fashion to bring the baghouse on line first, followed by the spray dryer. The spray dryer was operated at gradually lower outlet temperatures until design conditions were met. Measures taken since start-up to ensure reliable operation, and operation over an eighteen month period are discussed. Both particulate and SO₂ emission performance are evaluated.     

Predicting Cutoff Aerodynamic Diameter and Sharpness of Single Round-Nozzle Impactors with a Finite Impaction Plate Diameter

Abstract

This investigation numerically examined the cutoff aerodynamic diameter (da₅₀) and the sharpness (GSD) of the particle collection efficiency curve of impactors with a finite impaction plate diameter. Results revealed that the inertial impactors have a limited cutoff aerodynamic diameter at different air velocities. The extreme value of the cutoff aerodynamic diameter increases with the nozzle diameter (W)/the plate diameter (D_c). The computed da₅₀/D_c values of the impactors increase with W/D_c at various Reynolds numbers (Re) and with the nozzle-toplate distance (S)/D_c when Re is 100. The value of GSD slightly increases with W/D_c for Re of 10 and 100, although the effect of S/D_c on GSD is not evident at various Res. The particle collection efficiency curve of the impactor with a lower Re is less sharp than that with a high Re at various W/D_c and S/D_c values. Statistical equations closely fitted the obtained numerical results for Res of 10–3000. The equations are useful for directly calculating the cutoff aerodynamic diameter and the sharpness of the particle collection efficiency curve for single round-nozzle impactors with a finite impaction D_c.     

柴油机Urea-SCR系统喷射雾化的数值模拟

为研究柴油机Urea-SCR系统喷射雾化规律,应用CFD软件建立喷射雾化模型,对喷嘴喷射距离、喷射位置与方向、喷孔数目与孔径对催化剂载体入口处的浓度分布情况的影响进行了数值模拟。结果表明,喷嘴距反应器距离为排气管直径5倍为宜;采用四喷孔、孔径为0.5 mm、喷嘴处于管道中心,喷射方向为径向时喷射雾化均匀性最好。通过台架实验,验证了采用喷距5D、径向、四孔、小孔径喷嘴方案可使NOx的转化率达到95%以上。     

Estimations of Real-World N2O Emissions from Road Vehicles by Means of Measurements in a Traffic Tunnel

Abstract

Ambient air measurements of N₂O, NO_x, CO, and HC based on grab sampling were conducted in a major traffic tunnel in Sweden, that carries up to 4,000 vehicles per hour, in order to estimate real-world emissions of N₂O for road traffic. Two different methods—relative and mass balance—were used to calculate a N₂O emission factor for the mixed vehicle fleet, which gave an average emission factor, at average speeds of 30-70 km/h, of approximately 25 mg N₂O/ km, with a range of 7-56 mg/km.     

Application of the Active Soda Process for Removing Sulphur Dioxide from Flue Gases

The active soda process1 was applied for desulfurlzatlon of flue gases emitted by a plant burning heavy fuel oil In a rotary drum drier for stone aggregate. The flue gas capacity of the plant was about 6,7 m³/s at normal conditions. The SO₂ concentration varied between 400– 500 ppm. The solid, dry and fine-grained NaHCO₃ of good quality was fed directly into the hot gas stream at the outlet of the rotary drier In two variants—with and without grinding. The mean particle size was 0.180 m^-3 or 0.070 m^-3, respectively. The achieved desulfurizatlon degree was shown to be directly dependent on the flue gas temperature and on the grinding effect, as well as on the normalized stoichiometric ratio. The highest achieved desulfurization degree amounted up to 74 percent. During the design of the desulfurization process no pilot plant installations and tests were necessary, and for the final process no special chemical reactor was used.     

Mathematical Modeling of SO2 Absorption in a Venturi Scrubber

Abstract

A three-dimensional mathematical model was used to predict the removal efficiency of a venturi scrubber for SO₂ absorption into a water and alkaline solution. In order to obtain better results, nonuniform droplet concentration distribution was considered. The results of the model with nonuniform droplet concentration distribution are compared with several sets of experimental data, as well as with prediction data of a mathematical model with uniform droplet concentration distribution. Without exception, all comparisons indicated that including nonuniformity of droplet concentration distribution in the model will significantly improve the agreement between the experimental data and predicted values.     

Measurement of the water cycle in mixed ammonium acid sulfate particles

A single ammonium-hydrogen-sulfate particle is levitated in an evacuated quadrupole trap at room temperature and the temperature of an attached tube containing bulk water is slowly cycled introducing then removing water vapor. With increasing pressure the particle dissolves in stages, then grows as a solution droplet by water absorption. With decreasing pressure the droplet supersaturates, crystallizes, then dehydrates completely to return to its initial state. Particle mass, and thus composition, is measured continuously with an electrostatic balance. Twenty-six cycles were studied as solute composition ranged from ammonium bisulfate through letovicite to ammonium sulfate in roughly equal steps. Composition was changed in situ by reaction with ammonia at low partial pressure. With solute composition characterized by x = [NH₄]/[SO₄], deliquescence was found to occur at water activity a_w = 0.394−0.029 (x− 1) for 1 ⩽ x < 1.5 and a_w = 0.710−0.023(x−1.5) for 1.5 ⩽ x < 2. Particle growth occurs at deliquescence and subsequently is in excellent agreement with that predicted in a model proposed by Tang for dissolution of a two-component mixed solute. Water activities of the solution droplets are measured up to a_w = 0.9. The results are compared with those predicted by the Zdanovskii-Stokes-Robinson method of interpolation from binary data and with those obtained using the mixing rule of Meissner and Kusik. Particle crystallization from supersaturated solution is analyzed thermodynamically using measured water activities, the Gibbs-Duhem equation, and classical nucleation theory. The specific free energy barrier to crystallization, ΔG/n, is found to increase from near zero to 0.04 eV as composition ranges from x = 1 to 2, where n is the number of formula units in the critical nucleus. New phase diagrams are presented and used to discuss the dynamics of mixed sulfate particles in the atmosphere.     

Rain‐washing of mimic®, RH‐5992, from balsam fir foliage following application of two formulations

Abstract

Two formulation concentrates of the insecticide, RH‐5992 [N'‐t‐butyl‐N'‐(3,5‐dimethylbenzoyl)‐N‐(4‐ethylbenzoyI) hydrazine], an aqueous flowable (2F) and an emulsion‐suspension (ES), were diluted with water to provide spray mixes containing dosage rates ranging from 35 to 150 g of the active ingredient (AI)/ha. The mixes were sprayed in a laboratory chamber, onto balsam fir branch tips collected from field trees and greenhouse‐grown seedlings. Droplet spectra and spray mass recovery were determined on artificial samplers. Simulated rainfall of two different intensities was applied at different rain‐free periods, and rain droplet sizes were determined. Foliar washoff of RH‐5992 was assessed after application of different amounts of rain, and the increase in soil residues was evaluated.

A direct relationship was indicated between the amount of rainfall and RH‐5992 washoff. The larger the rain droplet size, the greater the amount washed off. Longer rain‐free periods made the deposits more resistant to rain. Regardless of the amount of rainfall, rain droplet size and rain‐free period, foliar deposits of the 2F formulation were washed off to a greater extent than the ES formulation. The increase in soil residues due to foliar washoff was greater for the 2F than for the ES formulation. The deposits of the emulsion‐suspension were consistently more resistant to rain‐washing than those of the aqueous flowable formulation.     

Effect of additives in the Neem formulations on deposition,volatilization and persistence of Azadirachtin in spruce foliage

Abstract

Foliar deposits, volatilization and persistence of azadirachtin‐A (AZ‐A) were investigated after application of four spray mixes prepared from a wettable powder (WP) and three emulsifiable concentrate (EC) formulations of neem. They were applied at the dosage rate of 50 g AI in 4 L/ha onto potted spruce seedlings in a laboratory spray chamber. Droplet‐size spectra and deposits were assessed using Kromekote^® card/glass plate collection units. Foliar residues [dislodgeable residues (DR), penetrated residues (PR) and total residues (TR)] of AZ‐A and their volatilization were measured by HPLC at different intervals of time up to 60 h after treatment. Differences in the droplet‐size spectra and deposit levels were observed among the four spray mixes due to the influence of additives present in them. Dissipation half‐lives (DT₅₀) of the DR, PR and TR in the foliage were low (range, 19.5 to 38.9 h) and varied according to the residue type and the spray mix used. The DT₅₀ values of the DR were consistently lower (range, 19.5 to 31.9 h) than those of the PR (range, 30.5 to 38.9 h) due to preferential loss of the surface residues. The low DT₅₀ values observed for the DR and TR in the foliage sprayed with the WP spray mix were attributed to the particulate nature of the deposit. AZ‐A volatilized appreciably from the DR rather than from the PR. The variations found in the amounts of AZ‐A volatilized (42 to 58%) and unaccountable (38 to 46%) from the initial TR values in spruce foliage, after 60 h, were attributed to the physical form of the deposits on the target surface and the influences of additives present in the different spray mixes.     

Measurements of Sulfur Oxides,Nitrogen Oxides,Haze and Fine Particles at a Rural Site on the Atlantic Coast

During August, 1982 and January and February, 1983, General Motors Research Laboratories operated air monitoring sites on the Atlantic Coast near Lewes, Delaware and 1250 km to the east on the southwest coast of Bermuda. The overall purpose of this project was to study the transformations of the principal acid precipitation precursors, NO _x and SO _x species, as they transport under conditions not complicated by emissions from local sources. In this paper, the measurements of gas and particulate species from Lewes are described and the composition and sources of sulfate aerosol, which is the most important haze-producing species, are investigated.

On the average, the total suspended particulate (TSP) concentration was 27.9 μg/m³ while the PM₁₀ (mass of particles with a diameter less than or equal to 10 μm) concentration was 22.0 μg/m³ or 79 percent of the TSP. The PM₁₀ consisted of 6.1 μg/m³ of coarse particles (CPM, diameter = 2.5 ? 10μm) and 15.9 μg/m³ of fine particles (FPM, diameter < 2.5 μm).

On a mass basis the most important constituents of the fine particulate fraction were sulfate compounds, 50 percent, and organic compounds, 30 percent. The mean light extinction coefficient corresponds to a visual range of 18-20 km. Most of the extinction can be attributed to the sulfate (60 percent) and organic carbon (13 percent). Particle size measurements show that the mass median aerodynamic diameter for both species is 0.43 μm. This is a typical size for a hydrated sulfate aerosol. For carbon, however, this is a larger size than previously reported and results in a more efficient light scattering aerosol. Principal component analyses indicate that coal combustion emissions from the midwestern U.S. are the most significant source of sulfate in Lewes during the summer and winter.     

The effects of drop size and formulation upon the spread of pesticide droplets impacting on water‐sensitive papers

Abstract

The effects of drop size and formulation upon the spread of pesticide droplets impacting on water‐sensitive papers (WSPs) was investigated. Droplets of diameter 70–350 μm, of four permethrin formulations, were produced using a monosize droplet generator. The droplets were collected on WSPs and in Dow Corning fluid and their diameters measured using a binocular microscope. Spread factors, upon the WSPs, for each dropsize/formulation combination were then calculated. Spread factors varied with both formulation and droplet size and for droplets of 200 and 300 μm diameter spread was significantly correlated with the dynamic surface tension of the formulation. The results suggest that proper calibration of WSPs is necessary for effective droplet sizing.     

Regenerative Thermal Oxidation of Airborne N,N-Dimethylformamide and Its Associated Nitrogen Oxides Formation Characteristics

Abstract

In this study, a two-bed electrically heated regenerative thermal oxidizer (RTO) was used to test the thermal destruction and oxides of nitrogen (NO_x) formation characteristics in burning airstreams that contain either N, N-dimethylformamide or dimethylformamide (DMF) mixed with methyl ethyl ketone (MEK). The RTO contained two 0.152 m × 0.14 m × 1 m (L × W times] H) beds, both packed with gravel particles with an average diameter of approximately 0.0111 m and a height of up to 1 m with a void fraction of 0.42 in the packed section. The thermal recovery efficiency (TRE) and the gas pressure drop over the beds were also studied. Experimental results reveal that, with a valve shifting time (t _s) of 1.5 min, a superficial gas velocity (U _g) of 0.39 m/sec (evaluated at an influent air temperature of around 30 °C) and preset maximum destruction temperatures (T _S) of 750–950 °C, no NO_x was present in the effluent gas from the RTO when it was loaded with DMF-free air. When only DMF was present in the influent air, the average destruction efficiencies exceeded 96%, and increased with the influent DMF concentration from 300 to 750 mg/N?m³. The “NO_x-N formation/DMF-N destruction” mass ratios were in the range 0.76–1.05, and decreased as the influent DMF concentration increased within the experimental range. When both DMF and MEK were present in the influent gas, the NO_x formation ratio was almost the same and the DMF destruction efficiency increased with the influent MEK/DMF ratio from 150/300 to 4500/300 (mg/mg) and in the preset temperature range. The NO_x formation ratios were in the range 0.75–0.96. The TRE decreased as U _g increased but was invariant with T _s. The Ergun equation was found to suffice in the estimation of the pressure drop when the gas flowed over the packing beds.     

Field Testing and Computer Modeling of an Oxygen Combustion System at the EPA Mobile Incinerator

The LINDE® Oxygen Combustion System has been demonstrated successfully at the EPA Denney Farm site as part of the modified EPA mobile incinerator. This paper describes the field testing results and computer modeling of the LINDE system. The oxygen system enables the EPA unit to incinerate dioxin and PCB contaminated soil at a consistent rate of 4000 lb/h—200 percent of the original maximum capacity. The pure oxygen combustion system improved the thermal efficiency of the incinerator by over 60 percent and reduced the flue gas volume dramatically. Therefore, the dust carryover problem was mitigated. The destruction and removal efficiencies of hazardous wastes exceeded EPA requirements.

The design of the proprietary burner allows the use of up to 100 percent oxygen in place of air for incineration with improvements over conventional oxy-fuel burners. As a result, the temperature distributions in the rotary kiln are uniform and NO_x emissions are low.

The oxygen combustion system, controlled by a programmable controller, provided much better response and flexibility than conventional air based systems. The system generated a stable flame and responsed well to the transient conditions of the rotary kiln. Kiln puff occurrence was virtually eliminated in the operation of the mobile incinerator.

A computer model of the incinerator was developed and used for the process design of the LINDE system. The model predicted the test results reasonably well. This model can be a useful tool in the design and operation of rotary kiln incineration systems.     

The Spatial Variation of the Weekday/Weekend Differences in the Baltimore Area

ABSTRACT

This study examined the spatial distribution of the weekday/weekend difference in Baltimore, MD, and vicinity. The difference in Baltimore was characterized by having ~39% more NO_x , ~59% more CO, and ~27% more volatile organic compounds (VOCs) on the average weekday, but there was ~13% more O₃ on the weekend day. Spatially, the difference was elongated in the northeast-southwest direction. It decreased from 13% more O₃ in Baltimore to 6% at ~20 km west of Baltimore and to 4% at ~40 km south of Baltimore. It also appeared to decrease to the east, but the magnitude of the decrease could not be determined because of the lack of data east of the Chesapeake Bay. However, the difference increased to the north, reaching a value of almost 18% at a northern Delaware site.     

A Study on the Treatment of CO2, SO2, Nox,and Fly Ash by Pulse Activation

ABSTRACT

This paper presents a technique for the complete, simultaneous decomposition of CO₂, SO₂, and NO_x, as well as the simultaneous removal of fly ash by ultra-high voltage pulse activation. Ultra-high voltage narrow pulse is used to make the gases in the reactor become active molecules, which are then dissociated into nonpoisonous gas molecules and solid particles under the control of a directional reaction model. By using a sufficient charge and a strong electric field, the fly ash can be removed. It becomes the carrier of C and S, and its efficiency is 99.5%. Owing to the action of catalyst B (using Ni as the mother's body), the activation energy of CO₂, SO₂, and NO_x gases is reduced in great magnitude, and their removal efficiency can reach 75~90% at normal pressure and 180 °C.