Calibration of a Par-Tec 200 laser back-scatter probe FOR in situ sizing of fluvial suspended sediment
✍ Scribed by J. M. Phillips; D. E. Walling
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 185 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0885-6087
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✦ Synopsis
The in situ or eective particle size distribution of ¯uvial suspended sediment may dier considerably from that of the chemically dispersed mineral fraction owing to ¯occulation. Obtaining a meaningful measure of the eective particle size distribution ideally requires that measurements should be made in situ. A rigorous assessment of the associated degree of ¯occulation also requires that the same measurement technique is used subsequently to establish the absolute particle size composition of the suspended sediment by analysis of the chemically dispersed mineral fraction. While few in situ measurement devices currently exist, a Par-Tec 200 laser back-scatter probe has previously been shown to be capable of making both in situ and laboratory particle size measurements of ¯uvial sediment. The accuracy and precision of this device is assessed in this paper. While able to distinguish relative size dierences with a high degree of precision, the Par-Tec 200 performed poorly in terms of accuracy when compared with measurements made using a laser diraction device. A calibration algorithm has been devised for the Par-Tec 200 size data, using standard sediment samples sized by means of a laser diraction device as the reference. Application of the calibration to Par-Tec 200 measurements of heterogeneous sediment samples signi®cantly improved the representativeness of the particle size distribution, both in terms of overall form, and the median particle size.