Graduation Year

2017

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Public Health

Major Professor

Foday Jaward, Ph.D.

Co-Major Professor

Amy Stuart, Ph.D.

Committee Member

Jeffrey Cunningham, Ph.D.

Committee Member

Steven Mlynarek, Ph.D.

Committee Member

Ira Richards, Ph.D.

Keywords

pesticides, distribution, persistence, environment

Abstract

Many organic compounds, although beneficial, are associated with negative health and ecological impacts. It is therefore imperative to understand the environmental fates of these contaminants. Whereas the fates and health impacts of many persistent organic pollutants have been extensively examined, there is limited research characterizing the fates of these and the less persistent organic compounds in tropical multi-use watersheds. This study therefore aimed to evaluate the roles of forests and climate change on the environmental fates and health impacts of select organic chemicals in the Rio Cobre watershed, a tropical river basin in Jamaica. A total of 16 organic compounds were selected for this assessment, including some polybrominated diphenyl ethers (PBDEs), dioxins, furans and current-use pesticides. In the first portion of the assessment, field measurements of the concentrations of select PBDEs (PBDE-28, -47, -99, -100, -153, -154, -183 and -209) in the deposition, soil, litterfall and atmosphere of a forest and nearby clearing in the aforementioned watershed were evaluated. The mean air and litterfall concentrations of the PBDEs were lower in the forest than in the clearing, whereas the deposition flux rate and soil concentrations were higher in the forest. It was therefore concluded that the tropical forest filtered the PBDEs by transferring them from the atmosphere to the soil. In the next segment of the assessment, a multimedia environmental model of contaminant fate and transport, reflective of a region with three vegetative covers – urban, agricultural/grassland and forests – was developed to assist with the evaluations. This model, RioShed, was used to compute and compare fate metrics, including persistence and long range transport potential, for the aforementioned 16 organic compounds given varying forest parameters and climatic conditions. The atmospheric long range transport potentials and overall persistence of the organics were generally lower in the forested tropical watershed than in the un-forested tropical watershed, especially when the forests were fully evergreen. In this tropical watershed, the fate metrics were particularly responsive to precipitation rates. The atmospheric long range transport potentials and overall persistence of the evaluated organics increased and decreased, respectively, under the climate change condition of decreased precipitation rates. However, the effects of precipitation on the atmospheric long range transport potentials and overall persistence were more varied for the current-use pesticides. It was therefore concluded that the fates of the evaluated chemicals differed in forested versus un-forested tropical watersheds and that such differences were influenced by forest parameters, climate drivers and the chemical properties of the organics. The results and methods described in this dissertation are applicable in environmental multi-media model development and can be used to inform land management practices, as well as assist in decision-making for environmental sustainability in tropical developing countries.

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