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New Perspectives on the Maintenance of Aqueous Ozone Residuals in Greenhouse and Nursery Irrigation Solutions

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dc.contributor.advisor Dixon, Michael A. Graham, Gary Thomas 2012-08-24T19:28:43Z 2012-08-24T19:28:43Z 2012-08 2012-08-08 2012-08-24
dc.description.abstract Ozonation has been utilized for water treatment for over 100 years. During that time, the range of applications has grown considerably, and includes the remediation of nursery and greenhouse irrigation water. Ozone is dissolved into irrigation water to kill pathogens and degrade chemical contaminants. By convention, growers remove ozone from solutions, prior to distribution to the crop, to avoid phytotoxic effects. The available literature regarding aqueous ozone (O3(aq)) phytotoxicity is limited, making this a sagacious practice, although the removal does preclude any ancillary benefits beyond the point of treatment. The effects of applying O3(aq) under two irrigation systems are examined. Initial studies suggested O3(aq) concentrations as high as 20 mg⋅L-1 could be applied directly to mineral wool substrate in a limited (one time) fashion without a negative response. To be effective as a remediation tool, however, ozone would need to be applied more frequently (e.g. daily). The effects of daily O3(aq) application, via drip irrigation in mineral wool hydroponic tomato culture, was examined. In the first of two studies, daily applications of 3.0 mg⋅L-1 O3(aq) elicited an overall positive growth response. In a follow-up study, 6.0 mg L-1 elicited a negative response. Nursery operators often utilize overhead irrigation. A study was conducted to determine if overhead irrigation utilizing O3(aq) was compatible with select woody perennial nursery species. The amount of ozone lost from solution during application was examined, as well as crop response to the ozone environment generated. It was shown that 60 to 70% of the ozone was unaccounted for at canopy level, while phytotoxic effects were elicited at emitter concentrations above 1.5 mg L-1. Marchantia polymorpha is a significant weed species in greenhouse and nursery production; a species with few control options. Anatomical features of M. polymorpha suggested sensitivity to O3(aq). Studies were performed to examine contact time (CT) and exposure frequencies required for M. polymorpha suppression. A CT of 0.84 mg⋅L-1⋅min at an application frequency of 3-times/week achieved measurable suppression. en_US
dc.description.sponsorship Natural Science and Engineering Research Council (NSEARC); Ontario Ministry of Agriculture Food and Rural Affairs (OMAFRA); Ontario Centres of Excellence (OCE); Purification Research Technologies INC (PRTI); Flowers Canada (Ontario). en_US
dc.language.iso en en_US
dc.subject ozone en_US
dc.subject agricultural water treatment en_US
dc.subject irrigation en_US
dc.subject tomato en_US
dc.subject cucumber en_US
dc.subject nursery production en_US
dc.subject irrigation en_US
dc.subject water use efficiency en_US
dc.subject liverwort en_US
dc.subject woody perennials en_US
dc.subject drip irrigation en_US
dc.subject overhead irrigation en_US
dc.title New Perspectives on the Maintenance of Aqueous Ozone Residuals in Greenhouse and Nursery Irrigation Solutions en_US
dc.type Thesis en_US Environmental Science en_US Doctor of Philosophy en_US School of Environmental Sciences en_US
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