NS36A-06 - Subsurface hydrological control on nutrient retention within geographically isolated wetlands
Presentation Information
TitleNS36A-06 - Subsurface hydrological control on nutrient retention within geographically isolated wetlands
Session Start2022-12-14 16:45:00 CST
Session End2022-12-14 18:15:00 CST
LocationMcCormick Place, S105a
AuthorNana-Aboagye
AbstractThe paucity of information on the role subsurface hydrology plays in nutrient (Nitrogen and Phosphorous) sequestration within wetlands is a subject that requires attention. The objective of this research is to develop a coupled surface � subsurface water and contaminant transport flow models using HydroGeosphere (HGS), to determine the fate and transport of leached nutrients and how it affects downstream hydrology. The first phase consists of characterizing the geology using electrical resistivity tomography (ERT), electromagnetic induction (EMI) and the ground penetrating radar (GPR). A SuperSting R8 resistivity meter, an EM38-MK2 and the Sensors and Software Pulse EKKO system were used for the ERT, EMI and GPR respectively. The geophysical result showed a top layer of 1.5 m thick lying on top of a sandy layer of about 3 m thickness. The sand is underlain by a glacial lacustrine � glacial till that is about 2.5m thick. The top layer is composed mainly of clayey loam with lenses of silty loam material. GPR radargram show an approximate depth to water table of 0.65m which was useful in understanding the flow regime at the study site. The EMI displayed a spatial distribution of electrical conductivity values across the study area. Areas of low conductivity corresponded with silty loam material whereas high conductive areas were identified as clayey loam. The EMI data was used to delineate regions of silty loam topsoil which are potential zones of direct infiltration. Constant head double ring infiltrometer test was conducted on different sections of the site to estimate the infiltration ratef the soil. The equilibrium saturated hydraulic conductivity from the infiltrometer test was estimated as 6.67 10-6 ms-1 for the silty loam and 5.79 10-8 ms-1 for the clayey loam. Further study will estimate other hydraulic parameters of the sand such as the average linear velocity, hydraulic retardation and dispersion coefficients to calibrate the flow and transport model of the site. Knowledge of the hydraulic properties of both the surface and subsurface media will help to understand how the interaction between the surface and subsurface hydrology enhance the nutrient retention capacity of the soil which is vital for wetland restoration globally.