Abstract: The environmental interface is an important research field in environmental science. The concentration levels, distribution, transformation and transportation of pollutants are often controlled by micro-solid-liquid interface processes. The microscopic molecular structure of pollutants on various micro-surfaces in water, soil, and air is directly responsible for their toxicity and macroscopic environmental behavior. Molecular environmental science (MES) will therefore become more and more important in the near future. As the field develops, both experimental analysis and theoretical calculation methods that can be applied to environmental samples (often specimens that are live, contain water, consist of multi-elements, or contain low levels of the target element) must be developed to identify information at the molecular or atomic levels. For this purpose, synchrotron radiation is one of the most fundamental and important tools for MES. Here, based on our own research, some applications of both X-ray absorption fine structure analysis and quantum chemical computation to environmental systems are described. The basic principles of metastable equilibrium adsorption theory and its applications to chemical the modynamics as well as to environmental problems that cannot be explained by existing theories are also briefly presented.