Date of Award

December 2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Geosciences

First Advisor

Timothy J Grundl

Committee Members

Lindsay J McHenry, Shangping Xu, Erik Gulbranson

Keywords

Blood Lead, Heavy Metals, Lead, Urban Agriculture, Vegetables, XRF

Abstract

Childhood Pb exposure is associated with a multitude of poor health outcomes. In food-insecure areas, growing fresh produce in residential backyard gardens is one option for parents; however, commonly grown crops are known to accumulate Pb in consumable tissues when grown in metals-rich soils. A variety of produce representing a continuum of consumable tissues were grown in soils collected from two residential vegetable gardens, a former metal foundry, and commercial topsoil purchased from a local hardware store. The concentrations of heavy metals in crop tissues were measured with custom wavelength dispersive X-ray Fluorescence (WD-XRF) spectroscopy and portable energy dispersive X-ray Fluorescence (ED-XRF) spectroscopy quantification routines. A general linear model was used to evaluate the factors contributing to the accumulation of Pb in tissues as a surrogate evaluation of common best management practices in urban agriculture. An exposure risk evaluation was completed based on the concentration of Pb in consumable tissues to determine if consuming produce increased a child’s risk for Pb exposure. Due to the heterogeneous and anisotropic nature of urban soil, this work demonstrates the difficulty of predicting Pb accumulation in crops based on Pb in the soil. It is therefore recommended that direct monitoring of Pb in produce be used for a more accurate prediction of child exposure to ingested Pb. Through direct measurements, the accumulation of Pb in consumable tissues was the greatest in vegetables with a modified taproot (turnip, beetroot, radish, carrot), with lesser concentrations in fruits (tomato, pepper), and produce grown on modified stems (potato). The accumulation of Pb varied between three cultivars of carrots of varying pigments; however, accumulation of Pb in beetroot did not vary between pigmented cultivars. Although several urban agriculture best management practices were confirmed in this study, children are at a potential increased risk for Pb exposure through consumption of produce grown in metals-rich residential soils.

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