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Carbonyl sulphide as a fumigant for grain and timber : efficacy towards organisms and formation of residuesRen, YongLin, n/a January 1997 (has links)
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.
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Effects of Metam Sodium on Soil Microbial Communities: Numbers, Activity, and DiversitySederholm, Maya, Sederholm, Maya January 2016 (has links)
Metam sodium is a fumigant often used as a crop pretreatment in agriculture to control a wide array of pests that may inhibit plant yields. Previously, there have only been limited studies conducted on the effects of metam sodium on native soil microbial communities and plant pathogens, and results have been inconsistent. This present study utilized control and metam sodium-treated field plots to examine the effects of metam sodium on soil microbes in terms of numbers, activity, and diversity. Metam sodium did not cause significant changes in culturable heterotrophic numbers, as shown by heterotrophic plate counts, but may have adversely affected non-culturable microbes since metam sodium did affect microbial activity. Specifically, the LuminUltra® and dehydrogenase activity assays both showed a significant decrease in total activity in treated plots one day after soil treatment, with a return to pre-application conditions within seven days. Illumina Next-Generation Sequencing of the 16S rRNA gene showed slight changes in richness and community composition throughout the 28-day study, but initial and final communities were similar in both control and treated soils. Overall, some soil microbes were adversely affected by metam sodium, but the resilience of the soil microbial community allowed for an apparent rapid recovery in terms of numbers, activity, and diversity.
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Etude des effets d'un composé soufré libéré par les Allium, le disulfure de diméthyle, sur les neurones d'insecte et sur l'activité électroencéphalographique de sourisGautier, Hélène 18 September 2007 (has links) (PDF)
Le disulfure de diméthyle (DMDS), molécule volatile libérée par les Allium, est un fumigant prometteur en remplacement du bromure de méthyle. Par l'utilisation des techniques d'électrophysiologie (patch-clamp), de biologie moléculaire et d'imagerie calcique sur neurones d'insectes, nous avons identifié de nouvelles cibles altérées par le DMDS à une faible concentration (1 µM). Le DMDS modifie l'activité spontanée régulière des DUM neurones en des bouffées de potentiels d'action séparées par des phases de silence. Cette altération de fréquence est la conséquence d'effets sur plusieurs cibles. Nous avons montré que le DMDS décale la dépendance vis-à-vis du potentiel de l'activation et de l'inactivation du courant Na2 vers de potentiels plus négatifs, rendant la cellule plus excitable. Dans un deuxième temps nous avons mis en évidence que le DMDS induit une augmentation de la concentration en calcium intracellulaire via l'activation des canaux TRPg et une sortie de calcium des stocks intracellulaires. Cette variation de calcium module, en cloche, les courants potassium dépendants du calcium (KCa). Grâce à l'étude du mode d'action du DMDS sur DUM neurones et au développement de nouvelles techniques associant la biologie moléculaire à l'électrophysiologie, nous avons apporté de nouveaux arguments en faveur de l'existence de deux courants KCa distincts. Parallèlement, grâce à une technique d'électroencéphalographie par télémétrie sur souris, nous avons révélé que le DMDS est susceptible d'engendrer des anomalies de l'activité électroencéphalographique.
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TOXICOLOGY OF PLANT ESSENTIAL OILS IN BED BUGSSudip Gaire (8703072) 17 April 2020 (has links)
<p>Bed bugs (<i>Cimex lectularius</i>
L.) are globally important human ectoparasites. Their management necessitates the use of multiple control
techniques. Plant-derived essential oils are extracts from aromatic plants that
represent one of the alternative control measures for bed bug control, in
addition to mechanical options and synthetic pesticides. However, there is
limited information available on the efficacy and toxicology of plant essential
oils against bed bugs. This project was designed with the aim to provide
in-depth information on efficacy, toxicology and mode-of-action of essential
oils and their insecticidal constituents in bed bugs. Initially, I evaluated topical
and fumigant toxicity of fifteen essential oil components against adult male
bed bugs of the Harlan strain (an insecticide susceptible strain). Neurological
effects of the six most toxicologically active compounds were also determined.
In both topical and fumigant bioassays, carvacrol and thymol were the most
active compounds. Spontaneous electrical activity measurements of the bed bug
nervous system demonstrated neuroinhibitory effects of carvacrol, thymol and
eugenol, whereas linalool and bifenthrin (a pyrethroid class insecticide) produced
excitatory effects. Further, I evaluated the efficacy and neurological impacts of
a mixture of three neuroinhibitory compounds; carvacrol, eugenol and thymol in
1:1:1 ratio against adult male bed bugs of the Harlan strain. This mixture of
monoterpenoids as well as the mixture of synthetic insecticides exhibited a
synergistic affect in topical bioassays. In electrophysiology experiments, the
monoterpenoid mixture led to higher neuroinhibitory effects, whereas a mixture
of synthetic insecticides caused higher neuroexcitatory effects in comparison
to single compounds. </p>
<p>In the next objective of my
dissertation, I compared the efficacy of five plant essential oils (thyme,
oregano, clove, geranium and coriander), their major components (thymol,
carvacrol, eugenol, geraniol and linalool) and EcoRaider<sup>®</sup>
(commercial product) between pyrethroid susceptible (Harlan) and field
collected (Knoxville) bed bug populations. Initially, I found that the
Knoxville strain was 72,893 and 291,626 fold resistant to topically applied
deltamethrin (a pyrethroid class insecticide) compared to the susceptible
Harlan strain at the LD<sub>25</sub> and LD<sub>50</sub> lethal dose levels,
respectively. Synergist bioassays and detoxification enzyme assays showed that
the Knoxville strain possesses significantly higher activity of cytochrome P450
and esterase enzymes. Further, Sanger sequencing revealed the presence of the
L925I mutation in the voltage gated sodium channel gene. The Knoxville strain,
however, did not show any resistance to plant essential oils, their major components
or EcoRaider<sup>®</sup> in topical bioassays (resistance ratios of ~ 1). In the
final objective, I evaluated the efficacy of binary mixtures of above-mentioned
essential oils or their major components or EcoRaider<sup>®</sup> with deltamethrin
in susceptible and resistant bed bugs. In topical application bioassays, binary
mixtures of essential oils or their major components or EcoRaider<sup>®</sup> and
deltamethrin at the LD<sub>25</sub> dose caused a synergistic increase in
toxicity in resistant bed bugs. Further, I studied the inhibitory effects of
major essential oil components on detoxification enzyme activities (cytochrome P450s,
esterases and glutathione transferases). Detoxification enzyme assays conducted
using protein extracts from bed bugs pre-treated with essential oil constituents
showed that these compounds significantly inhibited cytochrome P450 activity in
the resistant strain, but esterase and glutathione transferase activity were
unaffected. No inhibition of detoxification enzyme activities was observed in
the Harlan strain bed bugs pre-treated with essential oil constituents.</p>
<p>In conclusion, my dissertation
research has created the foundation for utilization of natural products for bed
bug management by (i) describing the efficacy of plant essential oils and their
components against bed bugs, (ii) discovering synergistic interactions between essential
oil components at the nervous system level, (iii) determining susceptibility of
deltamethrin-resistant bed bugs to plant essential oils and their constituents and
(iv) identifying synergistic effects of essential oils or their components on
toxicity of pyrethroid insecticides and underlying mechanisms of this synergistic interaction. </p>
<br>
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Exponering av luftföroreningar : -vid arbete i hamnmagasin / Occupational exposure to air pollution : -at port warehouseNordgren, Susanne January 2015 (has links)
Syftet med examensarbetet var att översiktligt undersöka vilka hälsofarliga luftföroreningarsom medarbetarna vid hamnmagasinen eventuellt exponeras föroch huruvida något hygieniskt gränsvärde riskerade att överskridas samt att seom de skyddsåtgärder som vidtagits kan förbättras. Resultatet från studien visaratt det finns vissa exponeringsrisker för de som arbetar vid hamnen både frångods, dieselavgaser samt rester av gasbehandlingsmedel i containrar.Arbetsmomenten där truckföraren befinner sig inne i trucken bedöms somrelativt skyddat både från partiklar och gaser, men det finns andra arbetsuppgifterdär arbetaren inte är lika skyddad. Mätningarna av kvävedioxid visadeatt exponeringen av dieselavgaser för den medarbetare som öppnadecontainrarna inte översteg några hygieniska gränsvärden, under de dagar sommätningarna genomfördes, men var något högre än för truckföraren som satt ihytten. Huruvida exponeringen av damm från gods riskerar att utvecklas tillhälsoproblem är omöjligt att avgöra utan en grundlig riskbedömning, därdammätningar kan ge en fingervisning om hur riskfylld situationen är för desom eventuellt exponeras.Organisationen bör implementera säkrare rutiner och genomföra åtgärder sommotiverar medarbetarna att använda befintlig skyddsutrustning. Det gäller intebara för exponering av dieselavgaser och damm från lossning och lastning avgods utan även vid öppnandet av containrar där rester av gasbehandlingsmedelkan finnas kvar i containern och där några ämnen misstänkts varacancerframkallande.Slutsatser: Genomföra en grundlig riskbedömning och kartlägga möjliga hälsoriskerkring luftföroreningar. Upprätta skriftliga arbetsbeskrivningar där eventuella risker föreligger. Installera ventilation i magasinen som styrs av halten kvävedioxid för attsäkerställa att höga halter av dieselavgaser inte uppstår. Behov av motivationshöjande insatser kring säkerhetskultur ochanvändningen av skyddsutrustning. Implementera fungerande rutiner som följer lagstiftningen förhanteringen av damm och gaser som gäller för cancerframkallandeämnen. / The purpose of this thesis was to examine the risk of hazardous air pollutantsthat employees at the harbor may be exposed to and assess whether anyexposure limits might be exceeded, and to review if the security measures taken,can be improved. The results of the study show that there is some risk ofexposure for those working in the harbor from both the cargo, diesel exhaustand residues from fumigants in the containers. The operations when the truckdriver is inside the forklift is considered relatively protected from both particlesand gases, but there are other tasks where the worker is not as protected.Measurements of nitrogen dioxide showed that exposure to diesel exhaust forthe employee who opened the containers during the days that the measurementswere performed did not exceed some critical values, but was slightly higherthan for the driver who was sitting in the forklift. Whether the exposure to dust,from the cargo, constitutes a risk for health effects is impossible to determinewithout a thorough risk assessment, where measurements of dust can give anindication of how risky the situation is for the exposed workers.The organization should implement safer practices and implementing measuresthat motivates employees to use existing protective equipment. This applies notonly for exposure to diesel exhaust and dust from loading and unloading ofgoods, but also at the opening the doors on the containers in which residues offumigants, in which some are suspected to be carcinogenic, can remain in thecontainer.Conclusions: Conduct a thorough risk assessment and identify potential health riskswith air pollution. Establish written work instructions where potential hazards exist. Install ventilation in the warehouses, which is controlled by the levels ofnitrogen dioxide, to ensure that high levels of diesel exhaust does notoccur. Need to increase motivation for safety and the use of protectiveequipment. Implement procedures to comply with the legislation for the managementof dust and gases that applies to carcinogens substances.
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Managing Weeds and Soilborne Pests with Fumigant and Non-Fumigant Alternatives to Methyl BromideMcAvoy, Theodore Porter 06 June 2012 (has links)
Methyl bromide (MBr) was widely used as a soil fumigant to manage soilborne pests in plasticulture vegetable production; however, it has been banned by the United Nations Environment Programme. Alternatives to MBr must be implemented to sustain fresh market tomato productivity. Possible MBr alternatives include new fumigant compounds, improved plastic mulch, and grafting. Methyl iodide (MeI) and dimethyl disulfide (DMDS) were tested as fumigant alternatives to MBr for the control of yellow nutsedge and soilborne pathogens of tomato. Virtually impermeable film (VIF) and totally impermeable film (TIF) were tested for fumigant retention and yellow nutsedge control in tomato. Grafting onto resistant rootstocks was tested for bacterial wilt and nematode management in tomato. In the absence of a soil fumigant, TIF suppressed yellow nutsedge better than VIF. TIF increased fumigant retention compared to VIF at similar application rates. Reduced fumigant application rates could be used in combination with TIF while maintaining fumigant concentrations, weed control, and crop yields comparable to greater use rates with VIF. Shank applied DMDS rates could be lowered to 281 L/ha under TIF from 468 L/ha under VIF; shank applied MeI application rates could be reduced to 56 L/ha under TIF compared to 93 L/ha under VIF and drip applied DMDS could be reduced from 561 L/ha under VIF film to 374 L/ha under TIF. Grafting susceptible commercial tomato cultivars onto resistant tomato hybrid rootstocks increased yields and plant survival in bacterial wilt infested fields. "Cheong Gang", "BHN 998", and "BHN 1054" were the best performing rootstocks for bacterial wilt resistance and tomato fruit yield in severely infested fields. Grafting increased tomato yield and decreased root galling from root-knot nematodes in an infested field. Hybrid rootstock "RST 106" resulted in the lowest root-knot nematode galling. In conclusion, TIF with reduced rates of DMDS or MeI is a viable MBr alternative for fresh market tomato production to retain effective doses of fumigant, manage yellow nutsedge and maintain yields. Grafting is an effective MBr alternative to manage bacterial wilt and root-knot nematode and maintain tomato yields. / Ph. D.
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