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Carechem Marine Sea Trials
We firmly believe that validation is essential for all modelling activities and for marine spills that means appropriately scaled at-sea releases.
The ChemSIS development process followed an iterative approach of laboratory studies and small-scale sea trials. These trials enabled empirically derived mass transfer coefficients to be calibrated with small-scale experimental releases at sea. Stringent testing of model integrity then required larger scaled releases simulating real spill conditions.
In September 1995, AEA Technology carried out controlled releases of 10m3 of styrene and styrene/divinylbenzene (9:1 mix). The chemical fate of the surface slick was monitored through remote IR sensing and direct water sampling. Water column concentrations were monitored at depths between 0.5-5m using in-situ fluorometry and water sampling.
The styrene release was used to validate the spill model using a chemical that is routinely transported in bulk at sea. Styrene has a relatively low but measurable vapour pressure and solubility and so was used to test the model algorithms for evaporation and solution.
Styrene and divinylbenzene have different physical properties meaning that they will partition differently over time. The mixed styrene and divinylbenzene release was, therefore, used to validate the ratio of mass transfer coefficients for evaporation and solution used in the model.
The comparisons between the model and the sea trial data showed excellent agreement in the overall fate of the chemical slicks in terms of trajectory, surface area and the relative partitioning of styrene and divinylbenzene from the surface slick.
Full details of the trials and the comparisons with the model may be found in published technical papers, such as:
Rusin J., Lunel T. and Davies L., 1996. Validation of the Eurospill Chemical Spill model. In: Proc. 19th arctic and Marine Oilspill Program (AMOP) Technical Seminar, 1996, pp1437-1478.
Corps J. and Lunel T., 2000. Spill Plans of the Future - Assessment of Chemical Hazards and responses. In: Proc. Interspill 2000, Brighton, UK.
These validation studies were funded by the UK's Coastguard Agency (now the Maritime and Coastguard Agency), with input from the European Chemical Industry council (Cefic).
