scholarly journals Development of a Cost-Effective Optical Sensor for Continuous Monitoring of Turbidity and Suspended Particulate Matter in Marine Environment

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4439 ◽  
Author(s):  
T. Matos ◽  
C. L. Faria ◽  
M. S. Martins ◽  
Renato Henriques ◽  
P. A. Gomes ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Suspended Particulate Matter ◽  
Optical Sensor ◽  
Dynamic Range ◽  
Cost Effective ◽  
In Situ Monitoring ◽  
Suspended Particulate Matter Concentration ◽  
Inorganic Matter ◽  
Suspended Particulate

A cost-effective optical sensor for continuous in-situ monitoring of turbidity and suspended particulate matter concentration (SPM), with a production cost in raw materials less than 20 €, is presented for marine or fluvial applications. The sensor uses an infrared LED and three photodetectors with three different positions related to the light source—135º, 90º and 0º—resulting in three different types of light detection: backscattering, nephelometry and transmitted light, respectively. This design allows monitoring in any type of environment, offering a wide dynamic range and accuracy for low and high turbidity or SPM values. An ultraviolet emitter–receiver pair is also used to differentiate organic and inorganic matter through the differences in absorption at different wavelengths. The optical transducers are built in a watertight structure with a radial configuration where a printed circuit board with the electronic signal coupling is assembled. An in-lab calibration of the sensor was made to establish a relation between suspended particulate matter (SPM) or the turbidity (NTU) to the photodetectors’ electrical output value in Volts. Two different sizes of seashore sand were used (180 µm and 350 µm) to evaluate the particle size susceptibility. The sensor was tested in a fluvial environment to evaluate SPM change during sediment transport caused by rain, and a real test of 22 days continuous in-situ monitoring was realized to evaluate its performance in a tidal area. The monitoring results were analysed, showing the SPM change during tidal cycles as well as the influence of the external light and biofouling problems.

scholarly journals Annual cycles of chlorophyll-<i>a</i>, non-algal suspended particulate matter, and turbidity observed from space and in-situ in coastal waters

Ocean Science ◽  
2011 ◽  
Vol 7 (5) ◽  
pp. 705-732 ◽  
Author(s):  
F. Gohin
Keyword(s):  
Particulate Matter ◽  
Continental Shelf ◽  
Mediterranean Sea ◽  
North Sea ◽  
Suspended Particulate Matter ◽  
Chlorophyll Concentration ◽  
Statistical Characteristics ◽  
Monitoring Networks ◽  
Suspended Particulate

Abstract. Sea surface temperature, chlorophyll, and turbidity are three variables of the coastal environment commonly measured by monitoring networks. The observation networks are often based on coastal stations, which do not provide a sufficient coverage to validate the model outputs or to be used in assimilation over the continental shelf. Conversely, the products derived from satellite reflectance generally show a decreasing quality shoreward, and an assessment of the limitation of these data is required. The annual cycle, mean, and percentile 90 of the chlorophyll concentration derived from MERIS/ESA and MODIS/NASA data processed with a dedicated algorithm have been compared to in-situ observations at twenty-six selected stations from the Mediterranean Sea to the North Sea. Keeping in mind the validation, the forcing, or the assimilation in hydrological, sediment-transport, or ecological models, the non-algal Suspended Particulate Matter (SPM) is also a parameter which is expected from the satellite imagery. However, the monitoring networks measure essentially the turbidity and a consistency between chlorophyll, representative of the phytoplankton biomass, non-algal SPM, and turbidity is required. In this study, we derive the satellite turbidity from chlorophyll and non-algal SPM with a common formula applied to in-situ or satellite observations. The distribution of the satellite-derived turbidity exhibits the same main statistical characteristics as those measured in-situ, which satisfies the first condition to monitor the long-term changes or the large-scale spatial variation over the continental shelf and along the shore. For the first time, climatologies of turbidity, so useful for mapping the environment of the benthic habitats, are proposed from space on areas as different as the southern North Sea or the western Mediterranean Sea, with validation at coastal stations.

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