Delineating volcanic aquifer recharge areas using geochemical and isotopic tools |
| |
Authors: | Brendan M. Mulligan M. Cathryn Ryan Tom��s Padilla C��mbara |
| |
Affiliation: | 1. Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada 2. Facultad de Agronomía, Universidad de San Carlos de Guatemala, Ciudad Universitaria, Zona 12, Ciudad de Guatemala, 01012, Guatemala
|
| |
Abstract: | Relative recharge areas are evaluated using geochemical and isotopic tools, and inverse modeling. Geochemistry and water quality in springs discharging from a volcanic aquifer system in Guatemala are related to relative recharge area elevations and land use. Plagioclase feldspar and olivine react with volcanically derived CO2 to produce Ca-montmorillonite, chalcedony and goethite in the groundwater. Alkalinity, Mg, Ca, Na, and SiO2(aq) are produced, along with minor increases in Cl and SO4 concentrations. Variations in groundwater δD and δ18O values are attributed to recharge elevation and used in concert with geochemical evolution to distinguish local, intermediate, and regional flow systems. Springs with geochemically inferred short flow paths provided useful proxies to estimate an isotopic gradient for precipitation (??.67 δ18O/100?m). No correlation between spring discharge and relative flow-path length or interpreted recharge elevation was observed. The conceptual model was consistent with evidence of anthropogenic impacts (sewage and manure) in springs recharged in the lower watershed where livestock and humans reside. Spring sampling is a low-budget approach that can be used to develop a useful conceptual model of the relative scale of groundwater flow (and appropriate watershed protection areas), particularly in volcanic terrain where wells and boreholes are scarce. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|