Doctor of Philosophy
Acute and chronic toxicity resulting from exposure to heavy metals in natural and built environments critically affects public health and aquatic safety. Heavy metals such as lead (Pb), zinc (Zn), and copper (Cu) are released into the urban runoff by vehicles emission. They also could be released from corroded metallic potable water plumbing fixtures to the tap water. In this dissertation, several knowledge gaps regarding the combined physical and chemical processes that control Pb accumulation onto plastic materials, including microplastics (MPs) as urban litter and plastic potable water pipes, were addressed. In the second chapter, the surface morphology and chemistry alterations of low-density polyethylene (LDPE) and polyethylene terephthalate (PET) MPs due to accelerated photodegradation were studied. Moreover, the impacts of MPs photodegradation on their Pb uptake from urban stormwater were examined. The surface morphology investigation revealed the formation of crazes and the crack networks, and the surface chemistry analysis revealed the generation of several oxidized carbon functional groups onto the photodegraded MPs. The degradation of the MPs increased Pb accumulation which followed the pseudo-second-order reaction model. The third chapter examined the role of plastic potable water pipes’ surface aging on their Pb deposition characteristics. The accelerated aging of crosslinked polyethylene-A (PEX-A) and high-density polyethylene (HDPE) pipes was conducted. Surface chemistry analysis of aged pipes revealed the formation of several oxidized carbon functional groups on the surface of the pipes. The kinetics experiments showed that the aged plastic pipes accumulated a significantly greater amount of Pb, which followed the first-order kinetics. The fourth chapter elucidates the mechanistic role of biofilm presence on Pb accumulation onto the PEX-A and HDPE potable water pipes compared to the copper pipes. The kinetics experiments under stagnant conditions showed the biofilm-laden PEX-A and HDPE pipe accumulated more than three times Pb than their new pipes, but the biofilm presence did not influence Pb accumulation onto the copper pipes. However, under the flow condition, the Pb accumulation on biofilm-laden plastic pipes was lower than their new pipes.
Dissertation or thesis originally submitted to ProQuest
Embargoed until 4/13/2024
Hadiuzzaman, Md, "An Investigation of Physicochemical Processes that Influence Heavy Metals Fate within Plastic Materials" (2023). Electronic Theses and Dissertations. 3113.
Available for download on Saturday, April 13, 2024