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Quorer: field and laboratory protocol for quoter

Quorer: a simple method for estimating deposited fine sediment.

Introduction to quorer.

Equipment

1 stirring stick marked with centimetre graduations, 1 corer (section of PVC pipe, diameter 24 cm, height 32 cm), 120 ml plastic screw top containers (1 per sample + 1 for background).

Field protocol

  1. Select sampling area. Use of the quorer is constrained by depth, velocity, and substrate conditions. Use is generally limited to depth and velocities where Surber sampler is effective (i.e., depths < 30 cm, velocity < 0.5 m/s; see Stark et al. 2001). Quorer does not work in streambeds dominated by boulders or bedrock.
  2. Collect background sample (c. 120 ml) from surface water. Do not overfill container, particularly if samples are to be frozen before laboratory analysis.
  3. Place quorer on bed and force down into substrate with twisting action. Ensure a tight seal so that suspended sediments are not lost to the stream.
  4. Measure and record water depth at 10 random locations within quorer.
  5. Stir the upper 5–10 cm of sediment with stirring stick for c. 1 minute. As with any sampling method consistency in effort is very important.
  6. Collect sample of slurry (c. 120 ml).
  7. Measure the stirred depth (i.e. depth of sediment disturbance) by re-stirring the sediment and measuring the water depth (n = 5). This allows results to be expressed volumetrically.
  8. Repeat procedure to achieve desired replication. (We recommend a minimum of 7 random samples.)
  9. Transport samples to laboratory on ice.

Laboratory protocol:

  1. Measure volume of quorer samples and stream water background sample. Express values in m3.
  2. Calculate concentration of sediment in each sample (g/m3) following the standard protocol for Total Suspended Solids (TSS method 2540D in APHA 1998).
  3. Correct for background (TSSsample – TSSbackground).
  4. Calculate concentration of organic matter in each sample (g/m3) following the standard protocol for Volatile Suspended Solids (VSS method 2540E in APHA 1998).
  5. Correct for background (VSSsample – VSSbackground).
  6. Calculate Suspendable Inorganic Sediments (SIS):
     Areal SIS (g/m2) = (TSS – VSS) x average depth (m) in cylinder
     Volumetric SIS (g/m3) = Areal SIS / (average stirred depth (m) - average depth (m))
  7. Calculate Suspendable Organic Sediments (SOS):
     Areal SOS (g/m2) = VSS x average depth (m) in cylinder
     Volumetric SOS (g/m3) = Areal SOS / (average stirred depth (m) - average depth (m))

Typical range in data values

We have used the quorer in a range of research and monitoring situations over more than 10 years. Here are two examples of the distribution of SIS data:

a) Results from quarterly stream habitat monitoring programme (April 1995–June 1997) of seven stream sites at Whatawhata Research Station (see Quinn & Cooper 1997 for description of streams) (n = 491). The median values for a native forest and pasture stream are shown for comparison.

b) Survey data from 32 rivers in North Island and upper South Island (M. Scarsbrook, unpublished data) (n = 160).

References

APHA. (1998). Standard methods for the examination of water and wastewater. 19th Edition. American Public Health Association, American Water Works Association, Water Pollution Control Federation, Washington, DC.

Quinn, J.M.; Cooper, A.B. (1997). Land–water interactions at Whatawhata, New Zealand: Introduction and synthesis. New Zealand Journal of Marine and Freshwater Research 31: 569–577. http://www.rsnz.govt.nz/publish/nzjmfr/1997/50.php

Stark, J.; Boothroyd, I.; Harding, J.; Maxted, J.; Scarsbrook, M. (2001). Protocols for sampling macroinvertebrates in wadeable streams. New Zealand Macroinvertebrate Working Group Report No. 1. Ministry for the Environment, Wellington. 57 p. http://www.smf.govt.nz/results/5103_protocols_manual.pdf

Field and laboratory protocol for quoter. [NIWA]