Characterization of Buoyant Fluorescent Particles for Field Observations of Water Flows

Flavia Tauro,Matteo Aureli,Maurizio Porfiri,Salvatore Grimaldi

doi:10.3390/s101211512

Abstract

In this paper, the feasibility of off-the-shelf buoyant fluorescent microspheres as particle tracers in turbid water flows is investigated. Microspheres’ fluorescence intensity is experimentally measured and detected in placid aqueous suspensions of increasing concentrations of clay to simulate typical conditions occurring in natural drainage networks. Experiments are conducted in a broad range of clay concentrations and particle immersion depths by using photoconductive cells and image-based sensing technologies. Results obtained with both methodologies exhibit comparable trends and show that the considered particles are fairly detectable in critically turbid water flows. Further information on performance and integration of the studied microspheres in low-cost measurement instrumentation for field observations is obtained through experiments conducted in a custom built miniature water channel. This experimental characterization provides a first assessment of the feasibility of commercially available buoyant fluorescent beads in the analysis of high turbidity surface water flows. The proposed technology may serve as a minimally invasive sensing system for hazardous events, such as pollutant diffusion in natural streams and flash flooding due to extreme rainfall.

Highlights

Watershed surface processes control downstream runoff phenomena [1,2], waste and pollutant diffusion [3], erosion mechanics [4,5], and sediment transport [6,7]
The experimental campaign focuses on the particle visibility in turbid aqueous suspensions and at different bead immersion depths below the water surface
For a fixed immersion depth, fluorescence visibility is tested in suspensions of increasing clay concentrations from 0 g/L to 60 g/L

Summary

Introduction

Watershed surface processes control downstream runoff phenomena [1,2], waste and pollutant diffusion [3], erosion mechanics [4,5], and sediment transport [6,7] These flows are largely dominated by ephemeral microchannel drainage networks in hillslope areas [8,9,10,11]. Commonly used tracers, such as isotopes, dyes, and chemicals, are not directly applicable to monitor surface hillslope processes and large-scale microchannel networks due to elaborate detection processes and dispersion issues [12,15,18,20,21,22,23,24,25] Most of these traditional tracing methodologies tend to infer global parameters from local measurements [15] and are not generally capable of capturing the fast evolution of processes at the watershed-scale [26]. The bulkiness of such devices restricts them to channel flow tracking and oceanography applications [27,28]

Methods

Results

Conclusion