An 8-pool organic matter module is outlined in the figure below, able to capture the variable reactivity of the OM pool and its stoichiometry. Under this conceptual model the decomposition of particulate detrital material is broken down through a process of enzymatic hydrolysis that slowly converts POM to labile DOM. A small fraction, f_ref, of this material is diverted to the DOM-R pool. The bioavailable DOM material enters the bacterial terminal metabolism pathways. These are active depending on the ambient oxygen concentrations and presence of electron acceptors, and of most relevance to the SCE, these pathways aerobic breakdown, denitrification, sulfate reduction, and methanogenesis. In most model approaches it is assumed these communities vary in response to temperature, and are mediated using a simple oxygen dependence or limitation factor. Ultimately, extending the mineralization rates to be computed from thermodynamic arguments is possible and has been discussed recently by Paraska et al. (2014), with the potential for advances in this area as analytical tools for NOM characterization are applied within the SCE system. Reoxidation of reduced by-products is also included to account the role of nitrifiers, sulfate oxidising bacteria (SOB) and methane oxidising bacteria (MOB).

Figure 1: Schematic overview of organic matter (OM) pools and their interactions. Grey dashed line indicates optional process pathway. Different tributaries to the model must be prescribed OM pool boundary concentrations based on land-use specific ratios of POM and DOM reactivity.

Ultraviolet light is also known to drive photochemical breakdown of chromophoric DOM, conceptually equivalent to the DOM-R pool in Figure 2. This photolysis process can take shape either as phototransformation of complex DOM-R molecules to more bioavailable molecules (ie., DOM in Figure 2), or as photomineralisation, where by components of the DOM-R molecule are mineralised. This is modelled based on a known intensity of UV photons, which drives a stoichiometrically equivalent loss of DOM-R via the photolysis reaction, and f_(photo) is introduced as an empirically defined fraction that indicates the extent to which the process transforms the DOM-R molecules to bioavailable molecules or completely mineralises them.

Filterable reactive phosphorus also is known to adsorb onto suspended solids (SS), however, the rate is often site specific (Froelich, 1988). In particular the adsorbed fraction varies considerably within estuaries depending on the nature of the particle origin and their size distribution, and both Langmuir and Freundlich isotherm models have been demonstrated to capture the adsorption process well (Zhang et al., 2009).

Filterable reactive phosphorus also is known to adsorb onto suspended solids (SS), however, the rate is often site specific (Froelich, 1988). In particular the adsorbed fraction varies considerably within estuaries depending on the nature of the particle origin and their size distribution, and both Langmuir and Freundlich isotherm models have been demonstrated to capture the adsorption process well (Zhang et al., 2009).

The above descrioption is summarized in the equation tables in the right 'Equations' tab and in the 'Inorganic nutrient' module in the form of balance equations.

Note: Equations of C/N/P/Si breakdown from organic matter to inorganic nutrients can be found in the 'Inorganic Nutrient' Module. This section contains only equations relative to organic C/N/P and the generic parameterization of organic matter process.

---------------Dissolved and partical organic carbon --------------------

---------------Dissolved and partical organic nitrogen --------------------

---------------Dissolved and partical organic phosphorus --------------------

---------------Generic parameterization --------------------

---------------Parameters --------------------