Design of a Multipoint Cost-Effective Optical Instrument for Continuous In-Situ Monitoring of Turbidity and Sediment.

T Matos,M S Martins,L M Goncalves,C L Faria,Renato Henriques,P A Gomes

doi:10.3390/s20113194

Abstract

A cost-effective optical instrument for continuous in-situ monitoring applications is presented. With a production cost in raw materials of 38 €, a power consumption of 300 µA in sleep mode and 100 mA in active mode (5 ms reading), and a capacity to monitor turbidity and sedimentary displacement at eight different depths in the water column, the sensor was developed for sediment monitoring in coastal areas. Due to the extent and dynamics of the processes involved in these areas, observations require a wide spatial and temporal resolution. Each of the eight monitoring nodes uses one infrared backscatter channel, to estimate turbidity and sediment concentration, and one ultraviolet with one infrared transmitted light channels to distinguish organic/inorganic composition of the suspended material load. An in-lab calibration was conducted, using formazine to correlate turbidity with the electronic outputs of the instrument. An analysis of the influence of external light sources and correction techniques were performed. Moreover, an in-lab experiment was conducted to study the behaviour of the sensor-to-sediment transport, wash load and sediment accumulation. The device was deployed, with a water level sensor, in an estuarine area with high sediment dynamics. The monitoring data were analysed, showing the potential of the device to continuously monitor turbidity, sediment processes, and distinguish between organic and inorganic matter, at the different depths in the water column.

Highlights

Sediment is a set of naturally occurring particles that are broken down from rocks by weathering and erosion or formed by natural chemical processes or by biological processes
Whenever any of these particles are carried in the course of the water or any other moving fluid, such as air, it is called sediment transport
The devices take advantage of the technology previously developed in an optical turbidity single-point sensor [21], using infrared backscattering and infrared and ultraviolet transmitted light techniques, in a radial configuration, that allows to estimate the turbidity and suspended sediment concentration and distinguish between organic/inorganic suspended mater, at

Summary

Introduction

Sediment is a set of naturally occurring particles that are broken down from rocks by weathering and erosion or formed by natural chemical processes or by biological processes These particles are subsequently transported by the action of wind, water or ice, or by the force of gravity and form deposits when the transportation agents weaken or stop acting [1,2,3]. Sensors 2020, 20, 3194 of the water (in liquid or solid-state) or any other moving fluid, such as air (wind), it is called sediment transport. Whenever any of these particles are carried in the course of the water (in liquid or Sediment transport, or sediment load, is the movement of organic and inorganic particles in a solid-state) or any other moving fluid, such as air (wind), it is called sediment transport

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