Public thesis defense of Aubry VANDEUREN
"Occurrence and mobility of arsenic and other trace elements in high background concentration soils: A case study in Wallonia (Belgium)"
Abstract:
Elevated arsenic (As) contents in topsoils with high background levels of potentially toxic elements (PTEs) poses human, environmental and regulatory challenges, as total PTE contents may exceed soil quality values. Understanding As distribution and mobility in these soils is important, as total content measurements alone are insufficient for reliably estimating potential exposure risks. This PhD thesis investigates the presence, origin and mobility of As and other PTEs in soils with high background contents in Liège’s industrial basin and Belgian Lorraine. In Liège, As originates from historical industrial activities, whereas in Belgian Lorraine, it is linked to Fe-rich sedimentary formations (Aubange and Grandcourt). To assess variability at three spatial scales and along the soil profile (0–85 cm depth), total As content was measured in 495 soil samples from Lorraine. Topsoil As mobility was estimated through phytoavailability using plant-based biotests, selective extractions and human bioaccessibility analysis. The solid-phase As was also characterized. The results indicate that As phytoavailability correlates positively with total As content in the Liège soils but not in Belgian Lorraine. The bioaccessible fraction ranges from 19 to 27% in Liège soils and from 8 to 11% in Lorraine soils, decreasing to 4% in the eastern part of the Aubange Formation. This reflects the increasing incorporation of As (and other PTEs) into Fe oxyhydroxides formed during a paleoweathering episode. Pedogenesis occurred in a heterogeneous context, with exogenous processes further redistributing As across the landscape. Together, the Liège basin and Belgian Lorraine encompass over 100 km² of soils where total As contents likely exceed soil quality values. However, our results indicate that the potentially mobilizable As fraction does not exceed 30% of the total content. The PhD research will contribute to informed decision-making for the sustainable management of soils.
Jury members:
Supervisors:
Prof. Pierre DELMELLE - UCLouvain
Prof. Patrick BOGAERT – UCLouvain
President of the jury:
Prof. Marnik VANCLOOSTER - UCLouvain
Other jury members:
Prof. Valérie CAPPUYNS - KU LEUVEN - SIM²
Prof. Sophie OPFERGELT | UCLouvain
Prof. Aurélie PELFRÊNE | JUNIA
