The status of the QPAC player for the ASGARD site : implications for the RISCS project

The RISCS project is a 4-year EU funded project starting in January 2010 that will assess the impacts of CO2 storage on ecosystems/near-surface environments. One of the experimental test facilities will be the ASGARD site at the Nottingham’s University campus. Previous research at ASGARD has investigated the impacts of shallow injection of CO2 on plants as part of the CO2GeoNet programme. BGS collected botanic data, and Quintessa developed an initial version of a soil-plant model for the site using Quintessa’s general purpose modelling code QPAC. In preparation for RISCS, Quintessa developed prototype software for BGS to familiarise itself with the model and understand the model data needs in order to provide information relevant to discussions on the experimental design at ASGARD during the RISCS project kick off meeting. The current version of the model has the following capabilities and limitations: It can represent the fertilisation and toxicity effects of CO2 on plants in terms of plant biomass and height change  Experimental data can be used to optimise model fertilisation and toxicity parameters  It was initially developed to model a single plant species, but has been used to model two species, with one species assumed to be dominant. This could be further developed to allow species competition to be modelled in the presence of elevated levels of CO2 effects.  Currently CO2 transport in the rooting zone is assumed to be primarily by diffusion. In the RISCS project it may be necessary to extend the model to consider advective transport. Depending on the purpose of the experiment, the model could include the movement of CO2 from the injection point to the rooting zone by using the QPAC-CO2 code developed by Quintessa. Conclusions relevant to the experimental design at ASGARD for RISCS include the following:  Measurements of key parameters, such as CO2 concentration and flux, will be needed. Depending on the measurement frequency, this might require automated instrumentation.  The variability in the plant species in the grassed plots and the limited area of high CO2 at the surface makes it hard to quantify the relationship between CO2 concentration and effect on plant species. It is therefore suggested that the plots are planted with one or two species, such as grass and clover.  Measurements of plant biomass and CO2 concentration in the rooting zone, the surface and the canopy are needed for the model calibration.  The application of herbicides on the plots should depend on what is aimed to be represented; grazed or uncultivated land might be expected to be herbicide free.  Vertical barriers might be envisaged to prevent CO2 from migrating to controlled sites, to have better control of where the CO2 goes and thus facilitate comparisons between measurements and model calculations. They could help with increasing the surface area exposed to high CO2 levels, which currently is very small.  To better understand the effect of CO2 on plants, it is necessary to expose the plants to a range of CO2 concentration levels. This requires careful consideration of the injection type and depth and of the size of the plots.  Different injection types might be envisaged depending on the plant composition; mixed pasture which contains several plant species would benefit from a uniform CO2 concentration within the plot.