Antimony uptake as a function of waterlogging in the rhizosphere

Antimony (Sb) is a relatively rare element in the earth's crust, but mining, traffic, waste incineration and an increasing multitude of industrial uses have led to elevated levels in soils and sediments in many locations and consequently increased exposure of plants, animals and humans to this toxic element. In some countries including Switzerland, Sb contamination of shooting range soils has become of great concern due to the Sb contained in lead bullets as a hardening agent. Antimony can be very mobile and there is great potential for it to be transferred from soil via plants to the food chain. Principal objectives in this project are to investigate the role of waterlogging, iron plaque formation in the rhizosphere, and histological adaptations such as the development of aerenchyma within roots on the uptake of Sb(V) and Sb(III) by plant species relevant to agricultural or pastoral use. In order to answer these questions, the following sequence of experiments using hydroponics, artificial soil substrate and real soil in a multi-system approach will be carried out: (i) comparison of Sb(Ill) and Sb(V) uptake by candidate plant species that have shown to have differential uptake of these redox species or are known to produce aerenchyma, under well controlled hydroponic cultures; (ii) investigation into the formation of aerenchyma in candidate plant species grown under different levels of hypoxia in hydroponic and artificial soil cultures; (iii) determination of the influence of aerenchyma formation and Fe²⁺ solution concentration on the formation of Fe plaques on plant roots in hydroponics and artificial soil; (iv) investigation into the influence of aerenchyma and iron plaque formation on plant uptake of Sb(III) and Sb(V) in hydroponics and artificial soil; (v) comparison of plant uptake of Sb(III) and Sb(V) from water saturated soils with varying pH and Fe(hydr)oxide levels both in artificial and real soil. The results will provide understanding of the processes and mechanisms governing Sb availability for plant uptake in soils with poor aeration and allow better prediction of the risks associated with plant uptake of Sb from poorly drained contaminated soils.