Fumigation Conditions Research Articles

A Lagrangian particle model of fumigation by breakdown of the nocturnal inversion

Several fumigation modelling studies are reviewed and an approach involving a coupled mesoscale grid point model and a Lagrangian particle dispersion model is chosen for further study. A number of particle model formulations are evaluated for their ability to maintain a well-mixed profile under steady-state convective conditions. The importance of using a formulation of the Langevin equation which is compatible with the specified turbulence parameterization is emphasised. Other considerations such as the form of the parameterizations and the magnitude of the timestep must also be taken into account. For prediction of hourly-averaged surface concentrations under fumigation conditions, it is found that a simple homogeneous turbulence formulation is equally effective as more sophisticated parameterizations involving inhomogeneity and skewness. Such a particle model, in conjunction with a mesoscale model for predicting the growth of the mixed layer, is able to reproduce well the results of the Deardorff and Willis (1982, Atmospheric Environment 16, 1159–1170) laboratory experiments on fumigation.

Effects of ozone, acid mist and soil characteristics on clonal Norway spruce ( Picea abies (L.) Karst.)—An introduction to the joint 14 month tree exposure experiment in closed chambers

This paper introduces a series of publications referring to a single 14-month laboratory study testing the hypothesis that the recent decline of Norway spruce ( Picea abies (L.) Karst.) at higher elevations of the Bavarian Forest and comparable forests in medium-range mountains and in the calcareous Alps is caused by an interaction of elevated ozone concentrations, acid mist and site-specific soil (nutritional) characteristics. The effect of climatic extremes, a further important factor, was not included as an experimental variable but was considered by testing of the frost resistance of the experimental plants. Results of these individual studies are presented and discussed in the following 14 papers. Plants from six pre-selected clones of 3-year-old Norway spruce ( Picea abies (L.) Karst.) were planted in April 1985 in an acidic soil from the Bavarian Forest, or a calcareous soil from the Bavarian Alps. After a transition period, plants were transferred, in July 1986, into four large environmental chambers and exposed for 14 months to an artificial climate and air pollutant regime based on long-term monitoring in the Inner Bavarian Forest. The climatic exposure protocol followed realistic seasonal and diurnal cycles (summer maximum temperature, 26°C; total mean temperature, 9·8°C; winter minimum, −14°C; mean relative humidity, 70%; maximum irradiance, 500 W m −2; daylength summer maximum, 17 h; winter minimum, 8 h). Plants were fumigated with ozone, generated from pure oxygen (control: annual mean of 50 μg m −3; pollution treatment: annual mean of 100 μg m −3 with 68 episodes of 130–360 μg m −3 lasting 4–24 h), and background concentrations of SO 2 (22 μg m −3) and NO 2 (20 μg m −3); windspeed was set at a constant 0·6 m s −1. Plants were additionally exposed to prolonged episodes of misting at pH 5·6 (control) and pH 3·0 (treatment). Simulation of the target climatic and fumigation conditions was highly reliable and reproducible (temperature ± 0·5° C; rh±10%; ozone ±10 μg m −3; SO 2 and NO 2 ± 15 μg m −3).

Non-destructive method for estimating methyl bromide residues in apples during aeration following fumigation

A method is presented for estimating the persistence and concentration of residual free methyl bromide (MB) present in apples during the aeration period following fumigation. The method is based on determining the rate of decline in concentration of methyl bromide in the exhaust air stream during aeration. The rate was shown to follow two consecutive pseudo-first-order decay curves. The first component of the curve resulted primarily from removal of MB from the free air space in the chamber, and the second component resulted from the desorption of MB from the apples. Estimates of the concentration of MB residue in apples were obtained from the regression parameters for the second decay curve. The technique gave good estimates of the residue concentration over a wide range of fumigation conditions and ventilation rates, and may be useful for determining the duration of aeration period required to achieve a proposed residue tolerance of 0.2 mg kg −1 methyl bromide.

A study about the environmental impact of a large particulate matter source by means of a sampling station interactive with the environment

The contribution of the particulate matter relapsed from a large oil-fired power plant into the surrounding environment was investigated by means of an automated sampling station interactive with the environment. This station performs real-time measurements of some meteorological parameters and of the concentrations of some gaseous pollutants, thus carrying out aerosol samplings only in situations of environmental interest such as fumigation or blank conditions. Elemental composition of the fractionated particulate matter and morphological observations on single particles were obtained using PIXE (particle-induced X-ray emission) and SEM (scanning electron microscopy) techniques.

THE INHERITANCE OF OZONE INSENSITIVITY IN SELECTED Phaseolus vulgaris L. POPULATIONS

Broad sense heritability estimates (H) for ozone (O3) insensitivity in four P. vulgaris F2 populations were high (0.66–0.88) under artifical fumigation conditions. In the F3, under field conditions, broad sense H in two populations had declined to 0.16 and 0.21, probably as a result of the interaction of maturity and injury. The results suggest that selection for O3 insensitivity in early generations should be conducted under controlled fumigation conditions followed by field evaluations as lines approach homozygosity.

Accumulation of foliar soluble proline in sulphur dioxide-stressed Glycine max CV. ‘Essex’ and Hordeum vulgare CVS ‘Proctor’ and ‘Excelsior’ seedlings

We examined foliar soluble proline levels of 14-day-old Hordeum vulgare and Glycine max seedlings which had been fumigated with SO 2 and harvested each under a variety of conditions. Visibly injured leaves of fumigated H. vulgare, cvs ‘Proctor’ and ‘Excelsior’ seedlings always contained more soluble proline than did non-fumigated leaves. The soluble proline levels of necrotic and non-necrotic areas of fumigated H. vulgare leaves (10 ppm, 4 h) were 15–30 and 1·5–18·0-fold, respectively, greater than those of comparable areas of non-fumigated leaves. Soluble proline accumulation occurred prior to the appearance of visible foliar injury in barley plants which were grown under winter glasshouse conditions (short daylength, temperatures of 18–21°C, high relative humidity). The extent (31–107%) to which soluble proline accumulated within G. max leaves was dependent upon both growth and fumigation conditions. Exposure to SO 2 did not alter the dry weight/fresh weight ratios of those leaf areas which remained non-necrotic subsequent to fumigation, nor did it decrease leaf water potential. Other foliar soluble amino acids did not increase to the same extent that proline did as a result of fumigation, although slight quantitative changes in amino acids were observed.

The Nanticoke shoreline diffusion experiment, June 1978—IV. A. Oxidation of sulphur dioxide in a power plant plume. B. Ambient concentrations and transport of sulphur dioxide, particulate sulphate and nitrate, and ozone

The oxidation rate of sulphur dioxide to sulphate in the Nanticoke coal-fired power plant plume was measured at distances of 3–43 km during fumigation conditions in June 1978; the average rate was 4 % h −1. Airborne measurement of SO 2, O 3, b scat , paniculate sulphate and paniculate nitrate were made over Lake Erie during the same period. These were compared to 4-day back-trajectories: south to south-westerly trajectories associated with the western or back side of high pressure systems led to high concentrations and the north to north-westerly trajectories associated with the eastern or front side of high pressure systems correlated with low pollutant concentrations.

Eine einfache Methode zur SO2-Begasung von Fichtenpfropflingen im Labor

A simple method for SO2 fumigation of Norway spruce grafts in the laboratory. To investigate the resistance mechanism of Norway spruce to SO2 a simple fumigation chamber was used. The conditions of fumigation gave the desired range of symptom expression.

The Use of a Monostatic Acoustic Radar to Assess the Stability of the Lower Atmosphere Over Johannesburg

Abstract Acoustic radar observations are discussed and shown to provide useful information relating to the nature and diurnal variation of the lower boundary layer of the atmosphere over Johanesburg. Particular phenomena considered include inversion formation and dissipation. development of fumigation conditions and the occurrence of daytime thermal convection.

METEOROLOGICAL EFFECTS ON ATMOSPHERIC CONCENTRATIONS OF RADON (Rn222), RaB (Pb214), AND RaC (Bi214) NEAR THE GROUND1

Atmospheric concentrations of radon were calculated from filtered radon daughter β activity, obtained from 1- and 15-m. elevations at a rural site, and from 1- and 91-m. elevations at a semi-rural site near Washington, D.C. Measurements were obtained from the successive filtration of air over 20-min. periods for durations of several hours, during various meteorological conditions. The extent of secular equilibrium between radon and its daughter products in the atmosphere near the ground (≤ 15 m.) was determined from a calculation of the RaC/RaB atom ratio (ρ) in the air, derived from the measured rate of decay of the filtered β activity. Estimates of an effective residence time (τ) in the atmosphere of the radon conglomerate, based on either a continuous or single emission of radon into the air, are presented. The relationship between ρ and τ for various weather conditions is discussed, as well as possible effects of (a) wind, (b) thermal stability, (c) atmospheric scavenging, and (d) precipitation on measured levels of natural radioactivity. Radon concentrations measured during an “air pollution potential” episode and during fumigation conditions are presented. In general, the response of measured β activity in the air to changes in the turbulent state of the atmosphere near the ground gives evidence of the feasibility of using naturally occurring radon and radon daughter products as tracers for determining atmospheric diffusivity.

Studies on Sterilization Effect of Fumigation (III)

Time and dosage-mortality curves are obtained experimentally, first, of Aspergillus oryzae to which methyl bromide was applied and second, of Penicillium islandicum to which chloropicrin was applied.It is confirmed through a X2-test that these curves represent a normal distribution on the time and dosage and are expressed as sigmoid curves. These findings give many suggestions which would help determine a practical combination of fumigation conditions applicable to food.These findings also suggest a means of expressing fumigation effectiveness.

Effects of Methyl Bromide Fumigation on the Viability of Barley, Corn, Grain Sorghum, Oats, and Wheat Seeds1

Methyl bromide is a highly efficient fumigant, and is widely used for the fumigation of stored grain, mills, and warehouses. One of its undesirable qualities, at least for seed fumigation, is its phytotoxicity. Viability of seeds may be seriously impaired by excessive treatments with methyl bromide. Tests were conducted to determine the effects of methyl bromide on the viability of barley, corn, grain sorghum, oats, and wheat seeds when fumigated at 80°F. with different combinations of dosage, exposure, and seed moisture content. Gas analyses were made at the end of each fumigation to verify the methyl bromide concentrations. Germination tests were conducted 24 hours, 30 days, and with wheat only, 6 months after fumigation to observe immediate and delayed effects. There was a pronounced decrease in viability in some cases with the increased period of storage after fumigation. In some experiments standardized seedling evaluations were made so that sublethal, injurious effects could be observed. Many of the fumigated seeds sprouted but did not develop normally. A margin of tolerance usually exists between the dosages required for insect control and those which are lethal to high quality, dry seeds. This margin of tolerance is dependent upon the complex interaction of several variable factors, including (1) the fumigant dosage applied, (2) the seed moisture content, (3) the length of exposure, (4) the kind of seed, (5) the period and conditions of storage after fumigation, (6) the fumigation temperature, (7) the history of the seed (age, previous fumigations, etc.), (8) the ratio of commodity to total space in the fumatorium (the sorption capacity), and (9) leakage factors in the fumatorium. Some of these factors were explored here, some have been reported by other workers. In general, the results of the study show that little or no injury occurred when the following combination of condition, existed: (1) the seed moisture was less than 12%, (2) the dosage was less than 2 lb/1000 cu. ft., (3) the exposure period was less than 24 hours, and (4) the temperature was 80° F. High temperature, moisture, dosage, and long exposure all contribute to seed injury from fumigation. When combinations of fumigation conditions occur in which one (or more) of these variables is of a higher order than named above, moderate to extensive germination damage may be expected. The over-all relative order of tolerance of the five species tested was oats> barley> grain sorghum> corn> wheat.

Responses of Pests to Fumigation.VII.—The Relation between Fumigation Techniques, Mortality, and the Amount of Hydrogen Cyanide sorbed by Calandra spp.

The relation between fumigation techniques, mortality and sorption of fumigant was investigated by two factorial experiments in which adults of Calandra granaria (L.) and C. oryzae (L.) were exposed to hydrogen cyanide at concentrations of 12, 26 or 44 mg. per litre and pressures of 2, 27, 52 and 76 cm. mercury for 30, 60 or 90 min., or at given concentration-time products (36, 72 or 108 mg. hr. per litre), in each of which the time component was 1, 4 or 12 hr., and pressures of 2, 37 and 76 cm. mercury. The methods of fumigation and estimation of sorption and mortality were those used in earlier investigations and the results are shown in a series of graphs.For both species, sorption of hydrogen cyanide increased as the total pressure was reduced, about three times as much being sorbed, in the first experiment, at a pressure of 2 cm. as at atmospheric pressure, the increase in sorptive capacity being greater in the case of C. oryzae than in that of C. granaria. In the second experiment, sorption by both species, for a given concentration-time product, was greater at a high concentration applied for a short period (1 hr.) than at a lower concentration applied for a long period (12 hr.); in the former conditions, C. granaria consistently sorbed more fumigant than did C. oryzae, in the latter, the reverse was the case, and in intermediate conditions (4 hr. exposure), the amounts sorbed by the two species did not differ materially. This result was inconsistent with that of the first experiment, in which C. oryzae sorbed more than did C. granaria during short exposures (30.90 min.).These effects on sorptive capacity of differing conditions of fumigation could account for most of the reported departures from the rule that the biological effects of fumigation can be described by the product of the mean concentration of fumigant applied and the period of exposure. Comparison between mortality and sorption at pressures of 27–76 cm. in the first experiment showed, however, that while these were broadly associated, the increased mortality at higher concentrations was greater than would be expected from the associated increase in sorption, and this discrepancy was significantly larger for C. oryzae than for C. granaria.

The fate of labelled insecticide residues in food products. V.—The nature and significance of ethylene dibromide residues in fumigated wheat

AbstractEthylene dibromide labelled with bromine‐82 has been used to study the absorption and decomposition of ethylene dibromide in wheat under the conditions of fumigation and on subsequent airing and heating. In spite of the high physical sorption of the fumigant and its slow rate of airing, the amount of chemical reaction between it and the wheat is small at room temperature. On heating imperfectly aired, fumigated wheat some decomposition of the ethylene dibromide to ethylene glycol occurs. There is some evidence that the glycol so formed reacts with the —SCH3 of the methionine residues of the wheat protein. The hydrogen bromide liberated when ethylene dibromide is decomposed on heating appears to cause some splitting of the starch‐granule sheaths. A brief appraisal of the possible nutritional and toxicological significance of the residues occurring as a result of ethylene dibromide fumigation has been made.

Problems connected with ethylene dibromide fumigation of cereals. I.—sorption of ethylene dibromide by grain

AbstractIn this paper experiments on ethylene dibromide fumigation of different cereal species are described in which the influence of various fumigation conditions on the content of bromine is studied. Two bromine forms were found to be present in fumigated grain: a volatile bromide (unchanged ethylene dibromide), and a non‐volatile, water‐soluble bromide. Differences in sorption of ethylene dibromide by various cereals seemed to result from differences in seed structures.By airing of fumigated grain free ethylene dibromide is removed gradually, but the content of bound bromine is not markedly changed. Under usual conditions of fumigation of whole grain in silos, the volatile bromide disappears after airing for 6‐7 weeks.

The fate of labelled insecticide residues in food products. IV. —The possible toxicological and nutritional significance of fumigating wheat with methyl bromide

AbstractThe major products of the chemical reactions between methyl bromide and the constituents of wheat under the conditions of fumigation have been characterized or identified. Their rate of absorption by an adult human consuming fumigated flour products has been estimated. The likely nature of the effective end‐products of human digestion has been considered and is believed to be represented by the compounds, methanol, methylglucoses, S‐methylcysteine, methyl methionine sulphonium salts, and N‐methyl derivatives of histidine and lysine. These appear to be compounds which have been fed experimentally to mammals at concentrations very much larger than those likely to obtain in fumigated wheat. In some cases their metabolism in vivo has also been studied. On the basis of all the available data an appraisal has been made of the toxicological and nutritional significance of consuming fumigated flour products. There is no evidence that the principal fumigant decomposition products are toxic or that their formation would be associated with any significant reduction in essential food constituents.

The fate of labelled insecticide residues in food products. II. —The nature of methyl bromide residues in fumigated wheat

AbstractThe chemical fate of methyl bromide absorbed by wheat under the conditions of fumigation has been studied. Whole‐wheat flour was exposed to 14C‐labelled methyl bromide. The fat, starch, gluten, and water‐soluble fractions were prepared from the exposed flour and their 14C‐content assayed. The gluten or protein fraction was responsible for some 80% of the decomposition of the absorbed fumigant. By measuring the 14C of the volatile products obtained on treating the gluten with sodium hydroxide or hydriodic acid under different conditions, it was shown that the decomposition of methyl bromide in gluten was due almost entirely to methylation with the formation of 50% of N‐methyl derivatives, 30% of dimethyl sulphonium derivatives, and of 20% of methoxyl and thiomethoxyl derivatives in about equal proportions. Similar results were obtained when gluten alone was exposed to the labelled fumigant. The production of free methanol in the flour by hydrolysis of the absorbed fumigant was about 10% or less. The rate of spontaneous decomposition of the dimethyl sulphonium compounds formed as a result of fumigation was estimated by using wheat which had been grown on 35S‐labelled sulphate.

The fate of labelled insecticide residues in food products. III. —N‐methylation as a result of fumigating wheat with methyl bromide

AbstractThe principal reaction between 14C‐labelled methyl bromide and the nitrogen‐containing groups of wheat protein has been shown, by combined radioactive tracer‐chromatographic techniques, to be with the histidine residue. Three methylated histidines are present in the hydriodic acid hydrolysate of the protein that has been exposed to methyl bromide, and these have been identified as I‐N‐methylhistidine, 3‐N‐methylhistidine and I:3‐N‐dimethylhistidine. The amount of reaction occurring under typical fumigation conditions is so small that the loss of the semi‐essential amino‐acid, histidine, is negligible.

Specific Susceptibility to HCN and the amount of HCN recovered from Fumigated Insects

The relationship was studied between susceptibility of a number of different species of insects to HCN fumigation and the recovery of HCN from them immediately after fumigation.The test insects used were Tribolium castaneum, seventh stage caterpillars of Corcyra cephalonica, first-and second-instar nymphs of Drosicha sp., third-and fourthinstar nymphs of Drosicha sp. and adult females of Drosicha sp.The apparatus and methods used in the fumigation and in the recovery of HCN from the fumigated insects are fully described.Preliminary expsriments showed that the processes of distillation and redistillation did not affect the recovery of HCN but that the result obtained for recovery from distillation could be affected if some volatile reducing substance were produced and carried over to the distillate. It was found that this did actually take place in the case of one of the test insects—T. castaneum—but that redistillation got rid of the impurity.In the main experiments it was shown that, on the assumption that the concentration of HCN to which insects are exposed is the effective dosage, the susceptibility of the test insects varied in the following descending order : firstand second-stage nymphs of Drosicha sp. > third- and fourth-stage nymphs of Drosicha sp.>C. cephalonica> T. castaneum>the adult females of Drosicha sp.When the same insects were arranged in descending order of the quantities of HCN recovered per 100 gm. of body weight, the order was identical except for the nymphs of Drosicha sp. which occupied a different relative position. The two categories of nymphs of Drosicha sp. were found to occupy a different relative position again with regard to the other three test insects when exposed to a superlethal concentration and assessed for recovery of HCN per 100 gr. body weight.Parallel batches of T. castaneum and C. cephalonica were fumigated and the HCN was recovered from the dead and survivors. More HCN was recovered from the dead insects than from those that survived.Both recovery and sorption of HCN were estimated separately in parallel batches of insects (adult females of Drosicha sp. and C. cephalonica). Recovery was found to be less than sorption showing that a part of the HCN absorbed is converted into a non-recoverable state. Further, that the weight of HCN sorbed per gram body weight of adult females of Drosicha sp. is much less than in the case of C. cephalonica under similar conditions of fumigation and that the amount of HCN converted into non-recoverable products is less in Drosicha adults than in C. cephalonica.A comparison of the water content of T. castaneum, C. cephalonica and Drosicha sp. (adults) showed that there was a positive correlation between water content and higher susceptibility to HCN and greater recovery of HCN was also indicated. It is suggested that this may be a factor in the “ Surface Resistance ” of an insec to a fumigant.The observations of previous workers that larger amounts are sorbed by or recovered (after fumigation) from more susceptible species than for those less susceptible was corroborated by the results obtained with C. cephalonica, T. castaneum and adult females of Drosicha sp. but not with those from nymphs of Drosicha sp.When dosage-mortality graphs were prepared by taking the amount of HCN recovered per gram body weight as an index of internal dose, the order of resistance of different test insects based on this new criterion was found to be entirely different from that based on the usual criterion of the concentration of HCN in the fumatorium being the index of effective dosage.These apparently anomalous observations may be explained by assuming that the resistance shown by an insect in an actual fumigation operation, i.e., to the concentration of HCN to which it is exposed (external dose) is what may be called the total “ Effective Resistance ” and that this “ Effective Resistance ” is the resultant of (a) “ Surface Resistance ” to the entry of fumigant and (b) “ Internal Resistance ” to the amount of HCN which actually gains entry into the body in some way or other. Thus the “Effective Resistance ” of an insect may be due to a combination either of low “ Surface Resistance ” and high “ Internal Resistance ”, giving a very low “ Effective Resistance ” as in the case of C. cephalonica, or vice versa giving the maximum “ Effective Resistance ” as in adult females of Drosicha sp. The lower recovery of HCN from the nymphs of Drosicha sp., although they were more susceptible to fumigation than C. cephalonica, is explained by their higher “ Surface Resistance ” combined with a very much lower “ Internal Resistance ”, leading to a lower “ Effective Resistance ”.

Factors affecting the recovery of hydrocyanic acid from fumigated citrus tissues

Abstract does not appear. First page follows. Under certain conditions of fumigation for scale insects of citrus trees, hydrocyanic acid (HCN) is known to cause injury to the foliage and fruit. The physiological reactions involved in the injury have received but slight quantitative investigation. Undoubtedly the reasons for this have been the difficulties encountered in distilling HCN from materials containing volatile substances which are reactive with HCN. The lack of a method with sufficient accuracy to recover relatively small amounts of HCN from the tissues may also have been an important factor. The results reported in this paper are concerned only with the factors affecting the distillation and recovery of HCN from solutions in the absence of tissues and also in the presence of citrus foliage and fruits. Earlier attempts to recover HCN from fumigated citrus tissues by aspiration, partial vacuum, immersing and shaking the tissues in an alkaline solution, or by a combination of these processes have given unsatisfactory results. All statements in this paper concerning the recovery of HCN from citrus tissues refer to HCN added by fumigation or by other methods. Repeated tests by Bartholomew and Raby (3) and in the present investigation have shown that citrus tissues do not contain autogenous HCN. An investigation is being made of the physiological effects of HCN in citrus tissues.