Impact of organic soil amendments on heavy metal losses and nutrient cycling – medium-sized controlled lysimeter experimental assessment

Heavy metals accumulate due to various human activities in sediments thereby negatively impacting on aquatic ecosystems and potentially via food chain transfers harming human health. To maintain the hydraulics of water bodies heavy metal (HM) polluted sediments are frequently simply dig out of the riverbeds and channels, and subsequently dumped on sites in their vicinity. We studied the ability of such clay and organic rich ‘waste’ sediments to acts as amendments for marginal soils. Their added organic matter could play a crucial positive role in soil fertility, nutrient cycling, and carbon sequestration.

The introduction of organic amendments can either diminish or mobilize heavy metals when applied to marginal soils. Lysimeters were filled with marginal sandy soil collected from the Danube riverbanks in Novi Sad, Serbia, ensuring it was free of HM contamination. Six distinct organic soil amendments (OSA) were introduced to the lysimeters: i) biochar, ii) sludge, iii) compost, iv) biochar + sludge, v) biochar + compost, and vi) biochar + sludge + compost.

The sludge utilized is derived from aquatic sediment in the Begej Canal, Serbia, known for its heavy pollution. Among others, this study aims to assess whether this specific sludge type can serve as a viable soil amendment rather than being relegated to landfill disposal. The compost utilized originated from green waste in Novi Sad, while the biochar was produced from Miscanthus, a C₄ plant feedstock, at 550°C at the Technical University Aachen. Both the OSA and sandy soil underwent chemical and physical characterization before application. The maximum added amendments varied from 1 to 5% (w/w), depending on the OSA type.

All probes were established at Faculty of Science, University of Novi Sad, in triplicates, featuring lysimeters with a height of 435 mm and a diameter of 180 mm. The results of heavy metal leaching data under different OSAs will be presented at the meeting, highlighting key findings and conclusions. Additionally, we will discuss the role of water event-driven transport in the overall process.

Acknowledgement: "Funded by EU grant #101059546"