Processes affecting groundwater chemistry in a zone of saline intrusion into an urban sandstone aquifer

摘要: Abstract Samples have been collected from inflows into railway tunnels in the Triassic sandstone aquifer beneath Liverpool and Mersey Estuary, England, U.K. These provide a profile through saline–freshwater mixing zone. Analyses were made of major anions cations, δ34S δ18O SO4, δ13C dissolved inorganic C 87Sr/86Sr. The data demonstrate that presence low permeability fault exerts strong control on local groundwater chemistry. On estuary side fault, chemistry is dominated by intruding water, which modified SO4 reduction calcite dissolution, with fresh groundwater. environment tidal one repeated re-oxidation S an open system has resulted virtually no change isotopic composition, but enrichment residual 1.5‰. Groundwater landward primarily result recharge urban environment. There also evidence saline water present this region past now flushed groundwaters. This was either transported along nearer or more probably transmitted across fault. Both mechanisms would driven large head gradients caused heavy industrial abstraction earlier century. produced zone groundwaters depleted Ca radiogenic Sr enriched Na as ion exchange between previously occupied water. Sulphur however, shows variation since does not undergo significant exchange. A tracer test borehole to showed multiple breakthroughs some locations indicating number different flow paths aquifer. maximum velocity recorded 140 m/d suggesting fractures.