Investigation on soil and water contaminants by Diffusive Gradients in Thin Films (DGT) and Chemical Activated LUciferase gene eXpression (CALUX)

Soil and water contamination by heavy metals and estrogens poses significant threats to environmental and agricultural sustainability. Heavy metals, due to their toxicity, persistence, and bioaccumulation potential, can disrupt soil health, reduce crop productivity and endanger human health, while estrogens in aquatic environments may interfere with endocrine systems, threatening both ecosystems and human health. Understanding the mobility, bioavailability, and risks associated with these contaminants is essential for improving soil and water management and designing effective mitigation strategies in agricultural and
aquatic environments.

To address these challenges, this dissertation first focuses on heavy metal contamination in fertilized soils, as fertilizer application is a major source of heavy metals in these environments. Firstly, the study investigates the effects of various fertilizers, including manure, sludge, and phosphate fertilizers, on the mobility and bioavailability of trace metals in agricultural soils, focusing on their interactions with soil physio-chemical parameters under various application rates. The study reveals that factors such as pH, redox potential and dissolved organic carbon (DOC) significantly influence the release and transport of trace metals from soil oxides to plants. Based on this understanding, the second chapter shifts the focus to precious metals, which have received less attention in agriculture soil, despite their increasing use and potential risks. Given the absence of reliable methods to measure the bioavailable concentrations of precious metals in soils, this work develops the S920 Diffusive Gradients in Thin-Films (DGT) method, a novel and robust tool specifically designed to quantify bioavailable concentrations of silver, gold and platinum in soils. The application of the S920-DGT in soils treated with sludge revealed distinct behaviors of the three metals. The findings contribute to a deeper understanding of metal behavior in fertilized soils under the influence of factors such as pH, redox potential, and DOC.

In parallel, the research investigates estrogen pollution in the Scheldt estuary, with a focus on its spatial variability and time evolution. Using the ER-CALUX bioassay, the research assessed estrogenic activity in dissolved, particulate and sediment phases in the Scheldt estuary, revealing a clear spatial trend of dilution from upstream to downstream in the water column. The moderate to low levels of estrogen contamination in water column compared to other estuaries and a general declining trend in sediments over 40 years highlight the contribution of improved wastewater treatment and the implementation of the EU Water Framework Directive.