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ENEA internal best practices for seawater Total Suspended Solids measurement experimental assessment of measurement uncertainty and correlation with Turbidity. Test case in a near shore area (Ligurian Sea, La

ENEA has published the first technical report in the framework of MINKE project: Best practices for seawater total suspended solids measurement uncertainty and correlation with turbidity

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Authors: A. Bordone (a), G. Cerrati (a), T. Ciuffardi (a), F. Conte (a), F. Pennecchi (b), G. Raiteri (a), F. Reseghetti (a)

Affiliations:
a- ENEA – Marine Environment Research Centre of S. Teresa, 19032 Pozzuolo di Lerici (SP), Italy
b- INRiM – Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino (TO), Italy

Corresponding author: giancarlo.raiteri@enea.it

To read the full document click here

Abstract: Total Suspended Solids (TSS) is considered a very important oceanographic quantity to  describe the status of the seawater column. The ENEA Marine Environment Research Centre of  Santa Teresa, devoted since the ‘70s to the monitoring, analysis and comprehension of physical,  chemical and biological processes in marine environment, has therefore developed an historical  experience also in TSS measurement. Aim of the present work is to collect ENEA expertise and  internal procedure related to experimental TSS measurement, formalizing in particular the  assessment of TSS measurement uncertainty in accordance with reference guidelines and  standards. The contribution of mass and volume in the laboratory-based gravimetric method to  measure TSS (by filtering process) has been analysed, together with the effect due to repeatability  proper of this type of experimental activity. TSS combined standard uncertainty has been finally  evaluated, and just the repeatability contribution proved to be the most relevant one (about 10 % in  terms of relative standard uncertainty). The link between TSS and Turbidity, continuously optically  measured along the water column, is also discussed. Turbidity of a water sample can in fact be  used to infer the mass of particles in suspension by means of a sort of a calibration curve that  relates TSS to Turbidity itself. This relation can be reasonably approximated by a linear model,  whose slope is sample-dependent: consequently, the conversion from a Turbidity profile to a TSS one has to be determined each time. Results prove that this consolidated approach can be applied  in the near-shore area, where ENEA performs its monitoring campaigns. The present technical  report is intended to serve as a possible basis for developing procedures more and more compliant  to international metrological standards, with the aim of further guaranteeing the metrological  traceability of oceanographic quantities (EOVs). 

Keywords: Total Suspended Solids; Column Water; Turbidity; Standard Uncertainty.

 

Fig. 1 – Area of interest. Red dots indicate the stations where ENEA, starting from May 2015, usually perform paired TSS and Turbidity profile measurements. Stations are periodically repeated during routine monitoring campaigns.

 

Fig. 2 – Repeated Turbidity profiles and corresponding TSS measures.

 

Fig. 3 – Linear relation between TSS and Turbidity.

 

 

Fig. 4 – TSS discrete measures and continuous profile obtained by TSS vs Turbidity relation.

 

Minke