Last changed: 18 February 2018

Turbidity is a measure of the proportion of incoming light that is deviated from its linear path as it passes through the sample, which in surface waters mostly depends on reflection of particle surfaces. Thus, turbidity comprises a measure of the amount of suspended particles in the water. The unit used here is FNU (formazine nephelometric units), an expression of how the signal measures compared to that obtained from a formazine suspension, prepared in a standardised way.

Known issues in the databases

Current method of measurement

Valid since January 2010
Method: SS-EN ISO 7027:1999.
Instruments: Turbidimeter Hach 2100AN IS (870 nm, angle of measurement 90°), and sample changer Metrohm 815 with piston pump. The measurement is made statically (the flow is stopped), and the data is collected promptly after a short period of stabilisation.

Page editor: Lars.Sonesten@slu.se