Campbell-scientific OBS-3A Turbidity and Temperature Monitoring System Manuel d'utilisateur télécharger pdf (Page 64)

OBS-3A Turbidity and Temperature Monitoring System

10.1 Particle Size

The size of suspended sediment particles typically ranges from about 0.2 to

500 µm in surface water (streams, estuaries and the ocean). Everything else

being equal (size, shape, and color), particle area normal to a light beam will

determine the intensity of light scattered by a volume of suspended matter.

Results from laboratory experiments and natural material support this and

indicate a wide range of backscatter associated with very fine mud and coarse

sand (about two orders of magnitude). Laboratory tests with coarse silt to

medium sand material show that sensitivity changes by a factor of about 3.5

(see FIGURE 10-1). The significance is that size variations between the field

and laboratory and within in a survey area cannot be ignored.

10 100 1000 10000 100000

Sediment Concentration (mg/l)

100

1000

10000

OBS Signal (mV)

Clay

Silt

Sand

FIGURE 10-1. Response to sand, silt and clay

1 2 ... 59 60 61 62 63 64 65 66 67 68 69 70 71 72

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Campbell-scientific OBS-3A Turbidity and Temperature Monitoring System Manuel d'utilisateur Page 64