Quorer: field and laboratory protocol for quoter
Quorer: a simple method for estimating deposited fine sediment.
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).
- 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.
- Collect background sample (c. 120 ml) from surface water. Do not overfill container, particularly if samples are to be frozen before laboratory analysis.
- 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.
- Measure and record water depth at 10 random locations within quorer.
- 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.
- Collect sample of slurry (c. 120 ml).
- 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.
- Repeat procedure to achieve desired replication. (We recommend a minimum of 7 random samples.)
- Transport samples to laboratory on ice.
- Measure volume of quorer samples and stream water background sample. Express values in m3.
- Calculate concentration of sediment in each sample (g/m3) following the standard protocol for Total Suspended Solids (TSS method 2540D in APHA 1998).
- Correct for background (TSSsample – TSSbackground).
- Calculate concentration of organic matter in each sample (g/m3) following the standard protocol for Volatile Suspended Solids (VSS method 2540E in APHA 1998).
- Correct for background (VSSsample – VSSbackground).
- 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))
- 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).
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