Application of Electromagnetic Sensing and Infiltration Measurements to Evaluate Salinity Reclamation and Turfgrass Management Options for Improved Leaching

Scarce freshwater resources in arid and semiarid regions means that recreational landscapes should use recycled or low quality waters for irrigation, increasing the risk of salinity and infiltration problems. We map salinity distribution within turf fields using electromagnetic sensing, evaluate need for leaching and evaluate post leaching results for subsequent management decisions. Electromagnetic measurements were made with two EM38 instruments positioned vertically and horizontally in order to determine salinity distribution. Sensor readings were coupled to GPS data to create spatial salinity maps. Next, optimal calibration point coordinates were determined via ESAP software. Soil samples were taken from 0-60 cm at 5 depths for each calibration point. Laboratory soil saturation percentage, moisture content, ECe and pHe of saturation extracts were determined for calibration to convert resistivity measurements to ECe. Next, ECe maps were created using ESAP software. Leaching for reclamation was performed by means of sprinkling. Treated municipal wastewater was utilized both for irrigation and for reclamation leaching. Low water content and high spatial variability of soil texture adversely affected the accuracy of the readings. Pre and post leaching surveys indicate that there was only a 30% decrease in salinity, very low relative to expected results considering the amount of water applied. This relatively low reduction in salinity and the lack of runoff during irrigation combined with infiltration measurements suggests that aeration techniques for healthier grasses led to water bypassing small pores thus limiting leaching efficiency. In this instance practices to improve infiltration lead paradoxically to less salinity reclamation than expected.

An integrated approach for structural behavior characterization of the Gravina Bridge (Matera, Southern Italy)

An integrated geophysical approach using non-invasive, non-destructive, and cost-effective seismic and electromagnetic techniques has been implemented to recognize the static and dynamic properties (i.e. eigenfrequencies, equivalent viscous damping factors, and related modal shapes) of the Gravina Bridge and its interaction with foundation soils. The “Gravina” is a bow-string bridge located on outcropping calcarenites in the city of Matera (Southern Italy) and develops for 144 m along a steel-concrete deck. The foundation soil characteristics have been evaluated by means of three high-resolution geo-electrical tomographies, one Vs velocity profile, and two site amplification functions. The main structural characteristics of the bridge have been estimated through permanent and on-demand monitoring using seismic and electromagnetic sensing. The former consisted of accelerometers and velocimeters installed with different geometrical arrangements for permanent earthquake and on-demand ambient vibration test recordings. The electromagnetic sensing was realized by a microwave radar interferometer placed below the deck to measure the displacements of the whole scenario illuminated by the antenna beam providing a continuous mapping of the static and dynamic displacements of the entire target. Acquired data have been analyzed in both frequency and time-frequency domain with the aim to study the stationary and non-stationary response of the monitored bridge. These experimental campaigns allowed us to assess the robustness of the proposed approach and to set up the zero-time reference point of the bridge dynamic parameters.