This work recognises the widespread deterioration of the natural environment, and the continual emergence of sudden environmental changes resulting from complex non-linear interactions of apparently disparate phenomena. Incorporating contemporary views of complexity and evolution, this paper presents a dynamic complex systems model which displays the discontinuous and non-linear characteristics which emerge from the inter-relationships of two such phenomena – acid rain and eutrophication – within the soil domain. A description is given of the chemical and hydrological sub-modules which provide the basis of this spatio-temporal model, and the inter-relationships between the buffering of acid and the adsorption of phosphates by the soil. Various representations of soil acidification, phosphate adsorption and hydrology drawn from existing models and literature are used to address both the chemical interactions and the spatial hydrological flows within the context of a river catchment. The resulting model can be easily applied to any chosen catchment due to the minimal data requirements and its generic representation. It may be utilised to describe non-point sources of phosphates as part of assessments of potential eutrophication, overcoming some of the limitations found in existing models, and provides the basis for the examination of Chemical Time Bomb (CTB) phenomena whereby the soil changes from being a phosphate sink to being a phosphate source.