New Zealand Journal of Marine and Freshwater Research abstracts
Comparison of portable nephelometric turbidimeters on natural waters
and effluents
Paul J. Barter
Toni Deas
Cawthron Institute
Private Bag 2
98 Halifax Street East
Nelson, New Zealand
email: paul.barter@cawthron.org.nz
Abstract Five different cuvette-style portable turbidimeters
using a nephelometric (side scattering of light) principle were assessed
simultaneously to determine between-meter variability. The assessment was
conducted using primary formazin standards, and a variety of different effluent
types and receiving waters encompassing a wide range of turbidities and optical
properties. For the formazin standards, the coefficient of variation (CV)
ranged from 1.5% to 6.8% providing an indication of precision. For the effluents
and receiving waters, the CV ranged from 6.6% to 44.1%, which compares favourably
with previous interlaboratory studies reporting CVs ranging from 23% to 144%;
however, the previous studies were not direct side-by-side comparisons of
meters. A power analysis showed that, with the exception of very clear headwater
streams, single turbidity samples are sufficient to detect changes in clarity
recommended in the New Zealand guidelines for the management of water colour
and clarity.
Keywords turbidity; water clarity; nephelometry
M02077 Received 26 September 2002; accepted 23 April 2003; Published 5
August 2003
New Zealand Journal of Marine and Freshwater Research, 2003, Vol. 37:
485-492
0028-8330/03/3703-0485 $7.00 © The Royal Society of New Zealand
2003
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