Arsenic and selenium mobilisation from organic matter treated mine spoil with and without inorganic fertilisation

Organic matter amendments are applied to contaminated soil to provide a better habitat for re-vegetation and remediation, and olive mill waste compost (OMWC) has been described as a promising material for this aim. We report here the results of an incubation experiment carried out in flooded conditions to study its influence in As and metal solubility in a trace elements contaminated soil. NPK fertilisation and especially organic amendment application resulted in increased As, Se and Cu concentrations in pore water. Independent of the amendment, dimethylarsenic acid (DMA) was the most abundant As species in solution. The application of OMWC increased pore water dissolved organic-carbon (DOC) concentrations, which may explain the observed mobilisation of As, Cu and Se; phosphate added in NPK could also be in part responsible of the mobilisation caused in As. Therefore, the application of soil amendments in mine soils may be particularly problematic in flooded systems.

Energy and charge transfer dynamics in DNA based light harvesting antennae

DNA can serve as a versatile scaffold for chromophore assemblies. For example, light-harvesting antennae have been realized by incorporating phenanthrene and pyrene building blocks into DNA strands. It was shown that by exciting at 320 nm (absorption of phenanthrene), an emission at 450 nm is observed which corresponds to a phenanthrene-pyrene exciplex. The more phenanthrenes are added into the DNA duplex, the higher is the fluorescence intensity with no significant change in quantum yield. This shows that phenanthrene acts as a donor and efficiently transfers the excitation energy to the pyrene. Up to now, the mechanism of this energy transfer and exciplex formation is not known. Therefore, we first aim at studying the photo-cycle of such DNA assemblies through transient absorption spectroscopy. Based on the results, we will explore ways to manipulate the energy transfer by application of intense THz fields. Ground as well as excited state Stark effect dynamics will be investigated.