Quality and quantity of pre-drainage methane and responding strategies in Chinese outburst coal mines

The potential sources of recharge of both water and solutes to the Quaternary aquifer in the area between Ismailia and El Kassara canals in northeastern Egypt include seepage from the irrigation canals and conduits, return flow after irrigation in the cultivated fields, local precipitation, and the upward flow of groundwater from the underlying Miocene aquifer system. Water isotopes, solute concentrations, and sulfate isotopes were used to investigate the geochemical sources, reactions, and the impacts of the hydraulic connections among recharge sources. The obtained results indicate a minimal influence of the underlying Miocene aquifer as a water and solute source while old and new contributions from the irrigation canals represent the main sources of recharge. The chemical reactions responsible for the chemical constituents and salinity in the aquifer include silicate weathering, evaporite dissolution, and carbonate precipitation. Most of groundwater samples appear to lie at/or close to equilibrium with montmorillonite, kaolinite, and illite where clay minerals are quite common in the local soils of the Quaternary aquifer.