A Method to Create a Horizontal Resistance Layer by Injection of a Viscous Fluid: PLAID.

We present a method to create a horizontal resistance layer at desired depth below soil surface to decrease seepage over a relatively large area. The layer is produced in a continuous process by means of numerous temporary screens of wells. Between each pair of screens groundwater flow is forced in horizontal direction. In the center of such flow, along virtual parallel flow lines, a chemical, viscous and dense fluid is injected that produces a clogging substance within several hours. The impact of density is overcome by the forced flow between screens. The impact of viscosity on the flow distribution is handled by adaptation of the fluxes and heads at the filters in the screens. The resulting procedure includes multistep injection and is supported by model simulations. Though a small-scale proof of concept has been successful, the composition of the optimal chemical mixture needs further research.

BIOCHEM-ORCHESTRA: a tool for evaluating chemical speciation and ecotoxicological impacts of heavy metals on river flood plain systems.

The chemical speciation model BIOCHEM was extended with ecotoxicological transfer functions for uptake of metals (As, Cd, Cu, Ni, Pb, and Zn) by plants and soil invertebrates. It was coupled to the object-oriented framework ORCHESTRA to achieve a flexible and dynamic decision support system (DSS) to analyse natural or anthropogenic changes that occur in river systems. The DSS uses the chemical characteristics of soils and sediments as input, and calculates speciation and subsequent uptake by biota at various scenarios. Biotic transfer functions were field-validated, and actual hydrological conditions were derived from long-term monitoring data. The DSS was tested for several scenarios that occur in the Meuse catchment areas, such as flooding and sedimentation of riverine sediments on flood plains. Risks are expressed in terms of changes in chemical mobility, and uptake by flood plain key species (flora and fauna).

Fate of Trace Metals in Anaerobic Digestion.

A challenging, and largely uncharted, area of research in the field of anaerobic digestion science and technology is in understanding the roles of trace metals in enabling biogas production. This is a major knowledge gap and a multifaceted problem involving metal chemistry; physical interactions of metal and solids; microbiology; and technology optimization. Moreover, the fate of trace metals, and the chemical speciation and transport of trace metals in environments--often agricultural lands receiving discharge waters from anaerobic digestion processes--simultaneously represents challenges for environmental protection and opportunities to close process loops in anaerobic digestion.