A stochastic model for the synthesis and degradation of natural organic matter part II: molecular property distributions

摘要: A stochastic biogeochemical model has been developed to simulate the transformation and degradation of natural organic matter (NOM) using an agent-based algorithm which treats each molecule as a separate potentially unique entity. Molecules react when pseudo-random number is lower than calculated reaction probability in given time step; repeated steps precursor molecules into complex NOM assemblage. The data for molecule—elemental functional group composition—can be used calculate many properties directly exactly assemblage, e.g., molecular weight (MW), fraction aromatic C (Ar), charge at pH 7 (Z). Empirical quantitative structure activity relationships (QSARs) are permit estimation thermodynamic quantities Kow (the octanol–water partition coefficient) pKa (acidity) molecule. Root mean square errors these QSARs 0.39 log units 0.45 pKa. Distributions both (MW, Ar, Z) estimated (Kow, pKa) examined compared with published experimental data. Molecular distributions from size exclusion HPLC experiments on aquatic quantitatively similar simulation results. titrations polarity reversed-phase qualitatively This agreement suggests that can explore hypotheses regarding compositional NOM.