No description available.

Methyl bromide (CH3Br) and methyl chloride (CH3Cl) are two halocarbons that are unique in that they play a significant role in stratospheric ozone destruction, and are mainly produced by natural systems. The current average tropospheric mixing ratios are 7.9 pptv CH3Br and 550 pptv CH3Cl (WMO, 2007). Although CH3Br and CH3Cl are present in such low concentrations, their atmospheric life times are sufficiently long that they can be transported to the stratosphere via the tropical tropopause at the equator. This process takes approximately six months.

The ocean is both a source and a sink for atmospheric methyl bromide (CH3Br) and methyl chloride (CH3Cl). It plays a significant role in their global biogeochemical cycling. In response to the Montreal Protocol, the atmospheric CH3Br is declining and the saturation state of CH3Br in the surface ocean is becoming more positive. Results from two large-scale transect studies in the eastern Pacific and the eastern Atlantic suggest that the ocean became near equilibrium with atmospheric CH3Br in 2010. Results from a "top-down" two-box model indicate that, if the remaining anthropogenic emissions are eliminated, atmospheric CH3Br is likely to drop to the pre-industrial level and the ocean would become a net source to atmospheric CH3Br. This study also represents an effort to improve current understanding of the oceanic and atmospheric budgets of CH3Cl. The global net sea-to-air flux of CH3Cl was estimated at 335 (210 ? 480) Gg yr-1 with improved parameterizations on the solubility, seasonal saturation anomaly ? (sea surface temperature, wind speed) relationships and the use of an updated parameterization on gas transfer velocity. For the first time, we estimated the gross oceanic emission and gross oceanic uptake rates of CH3Cl in the surface ocean, which was 700 (490 to 920) Gg yr^-1 and -370 (-440 to -280) Gg yr^-1, respectively. The ocean accounts for 10 - 19 % in the global CH3Cl emission and 6 - 9 % in its global sinks. Methane (CH4) is a potent greenhouse gas, which has a warming potential 72 times that of carbon dioxide over a 20 year time horizon. Gas hydrates are the largest CH4 reservoir in the planet. How much CH4 is transported from marine gas hydrates to the atmosphere is under debate. In this study, we investigated CH4 fluxes over three deepwater hydrocarbon seeps in the northern Gulf of Mexico using continuous air-sea flux measurements. Extrapolating the highest daily flux from this study to other deepwater seeps in the northern Gulf of Mexico suggests that CH4 fluxes to the atmosphere from the deepwater hydrocarbon seeps in this region are an insignificant source to atmospheric CH4 budget.

CH3Br and CH3Cl (methyl halides) are the most abundant natural vectors of bromine and chlorine into the stratosphere and play an important role in stratospheric ozone destruction. The current knowledge of their respective natural sources is incomplete leading to large uncertainties in their global budgets. Beside the issue of quantification, characterisation of possible sources is needed to assist modelling of future environmental change impacts on these sources and hence the stratosphere. This study describes measurements conducted at two temperate salt marsh and three temperate forest sites in Scotland, and one tropical rainforest site in Malaysian Borneo to quantify and characterise natural methyl halide producing processes in these respective ecosystems. Measurements were conducted with static enclosure techniques, and methyl halide fluxes were calculated from the concentration difference between blank/background and afterenclosure samples. Methyl halide concentrations were determined via oxygen-doped GCECD with a custom-built pre-concentration unit. External factors such as photosyntheticallyactive radiation (PAR), total solar radiation, air temperature, soil temperature, internal chamber temperature and soil moisture were recorded in parallel to the enclosures to determine possible dependencies. Salt marsh studies were carried out at Heckie’s Hole in East Lothian, and Hollands Farmin East Dumfriesshire for 2 years. The study subjects were salt marsh plants that were enclosed during daylight hours in transparent enclosures for 10min each at 2–4 week intervals throughout the year. Parallel to this monitoring programme, systematic manipulation experiments and diurnal studies were carried out to learn more about the possible influence of potential drivers such as sunlight and temperature. Mean annual net fluxes ( standard deviation (sd)) were 300 44 ngm-2 h-1 for CH3Br and 660 270 ngm-2 h-1 for CH3Cl, with fluxes of both gases following a diurnal as well as an annual cycle, being lowest during winter nights and highest during summer days. A possible link between variations of daytime fluxes over the course of a year and changes in temperature was found. CH3Cl and CH3Br fluxes were positively correlated to each other and average fluxes of CH3Cl were linked to dry mass of certain species such as Puccinellia maritima, Aster tripolium, Juncus gerardi and Plantago maritima as found at the different measurement locations. No link between methyl halide fluxes and total halogen content or halogen concentration of the enclosed vegetation was found. Work in temperate forests was carried out for over one year at Fir Links, a mixed beech/ sycamore forest in East Lothian, and on one occasion each in Griffin Forest, a sitka spruce plantation in Perthshire, and finally the Hermitage of Braid, a mixed woodland park in Edinburgh. The study subject was leaf and needle litter which was enclosed in opaque 12 L containers for 10min–24h. During enclosure, internal chamber temperature was recorded, and leaf/needle litter water content was determined after enclosure. Combined average CH3Br and CH3Cl fluxes from temperate forest litter were 4.3 10-3 ngg-1 h-1 and 0.91 ngg-1 h-1, respectively. Average fluxes measured from leaf and needle litter were comparable in magnitude and CH3Br and CH3Cl were positively correlated. However no correlation of methyl halide fluxes to either temperature or litter water content was observed. Work at Danum Valley inMalaysian Borneo focused on flux measurements from both trees and leaf litter in a tropical dipterocarp forest. Fluxes from tropical trees were measured with transparent branch chambers at 20min enclosure times whilst methyl halide fluxes from leaf litter were measured with opaque 12 L containers at 24h enclosure times. Mean CH3Br and CH3Cl fluxes from branch enclosures were 0.53 ngg-1 h-1 and 27 ngg-1 h-1, respectively, and CH3Br and CH3Cl fluxes from tropical leaf litter were 1.4 10-3 ngg-1 h-1 and 2.3 ngg-1 h-1 respectively. Again fluxes of CH3Br and CH3Cl were positively correlated but no direct environmental driver for flux variations was found. The magnitude of methyl halide fluxes was species specific with individuals of the genus Shorea generally producing large amounts of methyl halide. Tropical rainforests were confirmed to be potentially the largest single natural source of CH3Cl. Global estimates were derived from extrapolating measured fluxes from the respective global land cover areas. These estimates suggest that the ecosystems examined in this study could account for over 1/3 of global CH3Cl production and up to 13%of global CH3Br production in nature. The ratio of CH3Br to CH3Cl emissions for these ecosystems is likely to be dependent on the abundance of bromine in the plant material with higher bromine content boosting CH3Br production and suppressing CH3Cl production. For this reason salt marshes are only a very minor source of CH3Cl.

This thesis presents an investigation of carbonyl sulphide as a new fumigant and related methodology studies. The first part involved the investigation of a new fumigant - carbonyl sulphide, which has the potential to replace methyl bromide. Its biological response or activity was investigated, e.g. toxicity to target organisms and phytotoxicity, environmental and worker safety considerations. In the second investigation, analytical methods were developed for the determination of fumigant movement through timber and fumigant residues in grains as well as a method of chemical fractionation to determine the fate of carbonyl sulphide. A comprehensive literature review of 161 references in these two areas is reported. Carbonyl sulphide was highly toxic to adults of three coleopteran species tested, namely Rhyzopertha dominica (F.), Tribolium confusum du Val, and Sitophilus oryzae (L.), the most sensitive species was R. dominica. For 6 hr exposure at 25�C, the L(CxT)95 value for R. dominica, S. oryzae and T. confusum were, respectively, 36.48, 99.82 and 113.0mg h L-1. Carbonyl sulphide inhibited 100% of mould in wet wheat and more than 90% of mould on dry wheat at lOOmg L-1. Both carbonyl sulphide and hydrogen cyanide were low in phytotoxicity without affecting germination of wheat, at levels needed to control insects. Unlike hydrogen cyanide, carbonyl sulphide can be used at minimum levels without decreasing plumule length of wheat. Chemical data on the sorption of carbonyl sulphide are compared with data from methyl bromide. The levels of carbonyl sulphide in the headspace of five commodities (wheat, barley, paddy, sorghum and peanut) and timbers (hardwood and softwood) decay more slowly than do levels of methyl bromide. Carbonyl sulphide was blown through a column of wheat as easily as was phosphine and more easily than was methyl bromide, and its front was blown out faster than phosphine and methyl bromide. Movement of two fumigants (methyl bromide and carbonyl sulphide) through, and sorption on, softwood and hardwood were studied. Each fumigant was sorbed less on softwood than on hardwood and penetrated softwood better than hardwood. Carbonyl sulphide penetrated timber better than did methyl bromide, and was less sorbed on timber. A rapid method of solvent extraction was developed to enable rapid estimation of the amount on intact fumigant sorbed in wood. This procedure enabled near quantitative recovery of methyl bromide as either intact fumigant or as bromide ion. Carbonyl sulphide residue in unfumigated wheat was found to be around 25- SOppb. Carbonyl sulphide left little residue on fumigated grains. Desorption of carbonyl sulphide from the wheat was extremely fast, 85% of it was released after one day aeration which was very much greater than that of methyl bromide and carbon disulphide. After 6 days aeration the incorporation of 14COS on mungbean, wheat, paddy, rice and safflower was lower than 7Oppb (calculated as COS equivalent). Food value or nutritional quality of foodstuffs is not harmed by carbonyl sulphide fumigation. This result was assessed by identifying any nonreversible change or combined residues in biochemical fractions of commodities including lipids, protein, amino acids, carbohydrate, etc., and no irreversible reaction between carbonyl sulphide and any constituent such as B vitamin, atocopherol, lysine, maltose and starch. Fumigants did not affect lipids, although each fumigant was applied to wheat at exaggerated concentrations, nor wheat germ oil and canola oil treated with extremely high concentration of fumigants. Factors which affect analysis of fumigants including stability of chemicals in extraction solvent and partitioning of fumigant between solvent and air, were examined. The partition ratio, defined as the fumigant concentration in extraction solvent to that in the headspace, varied with fumigant. Methods for multi-fumigant analysis were developed or modified and gave high recoveries and efficiency. The procedure of Daft of solvent extraction followed by partitioning was modified by being performed in sealed flasks. This raised the recovery of carbonyl sulphide, methyl bromide, phosphine and carbon disulphide. Recoveries were near quantitative at levels down to 6-16ppb (w/w) for tested fumigants. Thus the modified Daft method can be adapted to enable determination of the main fumigants used on staple foodstuffs. Microwave irradiation method give higher efficiency of removal of fumigants from grains. Limits of quantification were < 0.2ng g-1 (ppb w/w) for each tested fumigant. The detection limit of COS was calculated, as natural levels of the fumigant were detected in commodities. These are feasible, simple and rapid (< 2 min.) to be use to analyse fumigant residue in grains. Carbonyl sulphide has potential as a fumigant for grain and timber and may replace methyl bromide in some uses, subject to further investigation in commercial situations.

Randomized complete block designs with three replications were utilized to evaluate the effects of fumigation with sulfuryl fluoride (SF) (0, 12, 24, 36 and 72 mg/L), phosphine (PH3) (0, 200 and 1000 ppm at 48 hr), methyl bromide (MB) (0, 4, 8, 16, and 32 mg/L for 48 hr), carbon dioxide (CO2) (0, 60% at 48 hr and 60% at 96 hr) and ozone (O3) (0 ppm and 175 ppm for 48 hr) on the volatile flavor compound concentrations in dry cured ham. Fluoride and SF concentrations increased (P < 0.05) in dry cured hams as SF fumigation concentration increased, but all samples contained fluoride and SF concentrations below the legal limits of 20 and 0.01 ppm, respectively. Also, as phosphine fumigation concentration increased, the residual concentration of phosphine also increased in the hams (P < 0.05), but all samples contained levels that were lower than the legal limit of phosphine in stored food products (0.01 ppm). Minimal differences existed in the presence and concentration of aroma active compounds in fumigated hams when compared to the control. Triangle tests indicated that consumers could not discern (P > 0.75) between the control hams and the fumigated hams. This study revealed that there were minimal aroma/flavor differences among control hams and hams that were fumigated with SF, PH3, MB, CO2 or O3 and that fumigation of dry cured ham with SF and PH3 were safe and met legal requirements for consumption. This reveals that SF, PH3, CO2 and O3 could be tested at the industrial level to determine their efficacy as potential alternatives to methyl bromide to treat dry cured hams for insect pests.

Master of Science / Department of Grain Science and Industry / Subramanyam Bhadriraju / Heat treatment involves raising the ambient temperature of food-processing facilities such as flour mills to 50-60oC for killing stored-product insects. However, very little is known about the influence of sanitation on responses of stored-product insects to structural heat treatments. The impact of sanitation on responses of life stages of the red flour beetle, Tribolium castaneum, an economically important pest in flour mills, were investigated during three 24 h structural heat treatments of the Kansas State University pilot flour mill. Two sanitation levels, dusting of wheat flour (~0.5 g) and 2-cm deep flour (~43 g), were created in 25 plastic bioassay boxes each holding 50 eggs, 50 young larvae, 50 old larvae, 50 pupae, and 50 adults of T. castaneum in separate compartments. Five boxes were placed on each of five floors of the pilot mill during 13-14 May 2009, 25-26 August 2009, and 7-8 May 2010 heat treatments using forced air gas heaters. During the August 2009 and May 2010 heat treatments, 100 eggs or 100 adults of T. castaneum were exposed inside each 20 cm diameter by 15 cm high PVC ring placed only on first and third floors and holding 0.1 (15 g), 0.2 (38 g), 1 (109 g), 3 (388 g), 6 (937 g), or 10 (1645 g) cm deep wheat flour. Among the mill floors, first floor had lower maximum temperature. The first floor rests on a thick concrete foundation, did not get heated from both sides unlike other floors, and had poor air movement resulting in cold pockets (temperatures <50oC). Mortality of life stages was lower on first floor than other floors and adults were less susceptible than other life stages especially on first floor. In general, both these tests have shown that the mortality of T. castaneum life stages were influenced by how quickly temperatures reached 50oC, how long temperatures were held above 50oC, and the maximum temperature. Protective effects of sanitation were evident only if temperatures did not reach 50oC. However, removal of flour accumulations is essential to improve heat treatment effectiveness against all T. castaneum life stages during a 24 h treatment.

No description available.

Doctor of Philosophy / Department of Entomology / Thomas W. Phillips / Robert "Jeff" J. Whitworth / Dry-cured ham is protected from infestations of Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) with the fumigant methyl bromide. Developing feasible alternatives to methyl bromide is necessary due to the phase out of methyl bromide. The effectiveness of food-safe compounds for preventing infestations of T. putrescentiae on dry-cured hams was evaluated by dipping ham pieces in solutions of various food additives. Propylene glycol (1, 2-propanediol), lard, ethoxyquin and butylated hydroxytoluene prevented or significantly reduced mite population growth. A combination of carrageenan + propylene glycol alginate + 40% propylene glycol was effective in reducing mite numbers on treated whole-aged hams compared with untreated hams. Dose/response tests with twelve registered residual insecticides were conducted to assess contact toxicity to T. putrescentiae. Three of these insecticides were evaluated for persistence over a 2-month period on different surfaces. Commercial formulations of deltamethrin plus chlorpyrifos-methyl, chlorfenapyr, and malathion showed promising results for contact toxicity against T. putriscentiae. Chlorfenapyr applied to metal, concrete, and wood resulted in 100% mortality of treated ham mites for up to 8 weeks. The effect of high and low temperatures on mortality of T. putrescentiae was studied in the laboratory. Groups of 10 eggs and groups of a mixture of 40 adults and nymphs were separately exposed to several high and low temperatures, ranging from +35 to 45°C and from −20 to +5°C, for several time periods. Eggs were found to be more tolerant to both high and low temperatures compared with adults and nymphs. Results showed that high temperatures from 40-45°C killed all T. putrescentiae eggs, adults, and nymphs within 4-1 d, while −10°C or lower killed all the same stages in less than 1 d. Combinations of the fumigant sulfuryl fluoride (SF) applied under high temperatures ranging from 25-40ºC, were studied to determine the highest temperature, shortest exposure time, and the lowest value of a concentration-by-time product (CTP) of SF against T. putrescentiae. Results showed that complete control of all life stages of T. putrescentiae was achieved at 40ºC with SF. More than one day of exposure was required to kill adults and nymphs and eggs at 40ºC at a CTP close to the EPA labeled rate of 1500 gh.m⁻³. Results indicated that adults and nymphs were more susceptible to SF compared to eggs. This study focused on investigating different control methods for T. putrescentiae in dry-cured ham facilities and most of examined techniques are preventive, although some of them can be applied as remedial methods after mite infestations are noticed.

Wood products all require treatment to mitigate phytosanitary risk prior to exportation. The most common phytosanitary treatment applied to Pinus radiata logs is Methyl Bromide (MeBr). The Environmental Protection Agency (EPA) in 2010 stated that MeBr must not be release into the atmosphere past 2020. This poses a problem for New Zealand log exports. Radiation has been identified as a possible alternative phytosanitary treatment for export wood products. This study aimed to quantify the effective dose of radiation necessary to sterilise two forest pest species; Arhopalus ferus and Hylurgus ligniperda. These species are representative of two different types of forestry pests; bark beetles (H. ligniperda) and wood borers (A. ferus). All applicable life stages for both species were tested. Arhopalus ferus adults were the most susceptible life stage identified with an LD99 of 30.2Gy ± 13.5 Gy (95% confidence interval). Arhopalus ferus eggs were less susceptible with a LD99 of 750Gy ± 776Gy observed; however there is low confidence in this result due to a methodological issue in one treatment replicate. Hylurgus ligniperda eggs were observed to be less susceptible than A. ferus eggs with a LD99 of 289Gy ± 92Gy. Results for the other life stages were inconclusive due to poor control survival, however the information gained was used to develop improved methods for further experimentation, which is on-going and showing positive results so far. The results of this experiment have indicated that radiation can be an effective method of sterilising forestry pests. To date radiation has not been used as phytosanitary risk mitigation for wood exports; however it is widely used for risk mitigation in agricultural products. Currently there remains a large amount of unknown information regarding, the effectiveness for irradiation of logs, the effective dose require for sterilisation of the most tolerant forestry pest and public acceptability of irradiation as a phytosanitary treatment. These knowledge gaps and an economic assessment must be completed before irradiation can be used as a phytosanitary risk mitigation technique for forestry products.