Public defence in environmental science: Maria Lundgren

In order to receive the Zoom link for the thesis defense, please contact Faculty Administrator Linnéa Larsson: linnea.larsson@lnu.se

Abstract

Cultivation in urban environments presents both opportunities and challenges, particularly when it takes place in soils affected by historical and ongoing human activities. This doctoral thesis investigates the transfer of potentially toxic elements (PTEs) from soil to crops cultivated in urban environments. To address the research questions and account for the structure of the experimental designs, a suite of tailored statistical methods was applied: Multiple Linear Regression (MLR) was used where predictor independence was assured; Partial Least Squares Regression (PLS-R) was employed to manage multicollinearity and high-dimensional data; and Linear Mixed Models (LMMs) were used to account for hierarchical data structures and site-specific variability. These approaches enabled the development of predictive models that incorporate both geochemical soil properties and crop-specific responses. More phytoavailable elements, such as cadmium (Cd), showed to be more easily modelled, compared to elements with stronger binding to soil particles, such as lead (Pb). Variable selection techniques were used to identify the most influential soil parameters, with soil pH, organic matter and clay content, together with total metal concentrations, frequently emerging as key predictors of metal uptake.

In addition to modelling root uptake, the thesis evaluates the contribution of physical contamination through particle adherence. This was achieved through controlled experiments and field sampling, including washing trials and quantification of adhering soil and dust particles. The findings demonstrate that surface deposition can significantly influence metal concentrations in crops, underscoring the need to consider both geochemical and physical pathways in exposure evaluations.

The practical implications of this work are twofold. First, it provides examples of suitable and appropriate modelling strategies based on data structure, research questions, and experimental conditions. Second, it offers evidence-based guidance for urban growers, planners, and regulators on how soil properties, fertilisation practices, and crop handling influence contamination levels. The results support the development of soil-specific management strategies that reduce human exposure to PTEs and promote safer food production in urban environments.

Keywords: Urban cultivation, Statistical modelling, Soil contamination, Metal uptake, Physical contamination, Risk management