Using dissolved silica to quantify transit times in aquifers and streams

摘要: Inferring the time groundwater spends in subsurface at catchment scale is critical to assessing vulnerability nutrient loading and establish realistic restoration frameworks. This especially true for intermediate transit times (a few years a century), which are timescales corresponding intensive agriculture associated eutrophication problems. However, limitations current suite of proxies makes it unclear how climatic, geologic, topographic controls interact shape distributions (TTD) specific catchment. We developed framework test utility dissolved silica (DSi) infer TTDs shallow aquifers regional scales. hypothesized that silicate weathering could be approximated by zero-order kinetic reaction since transport-limited process. calibrated this method with derived from atmospheric tracers (chlorofluorocarbons) found DSi was cheap robust proxy estimating times. then used non-intensive, process-based hydrological model informed discharge data mean dilution patterns streams. when related characteristics, “young” water flow depended on dynamic interactions between surface flow. These results have several practical implications evaluation resources quality.