Module 4 Stream Ecology Laboratory

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Module 4 Stream Ecology Laboratory

• SolidsTSS and Turbidity

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Total Suspended Solids

• Sediment plume off the south shore of Lake
  Superior

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Total Suspended Solids

• SAMPLING CONCERNS
• collect from undisturbed water
• when standing in a stream, reach upstream into
  the current for the sample

• In lakes, boat propeller action also may disrupt
  sediments in shallow areas
• avoid sampling from temporarily disrupted area

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Total Suspended Solids
TSS, as well as turbidity and any other parameter
dominated by the particulate fraction, can be
very patchy - it may be wise to composite from a
number of spots within the sites area
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Total Suspended Solids
Figure 1
- filter a known amount of water through a
pre-washed, pre-dried at 103-105 oC, pre-weighed
( 0.5 mg) filter - rinse, dry and reweigh to
calculate TSS in mg/L  - possibly save the
filters for other analyses such as volatile
suspended solids (VSS) that estimates organic
matter
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Total Suspended Solids
Analytical balance
Drying oven
Filter and petri dish
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TSS Methodology

• Calculate TSS by using the equation below
• TSS (mg/L) (A-B1000)/C
• where
• A final dried weight of the filter (in
  milligrams mg)
• B Initial weight of the filter (in milligrams
  mg)
• C Volume of water filtered (in Liters)

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How does Turbidity relate to TSS ?
A general rule of thumb 1 mgTSS/L 1.0 - 1.5
NTUs of turbidity BUT Turbidity scattering
depends on particle size so this is only a rough
approximation
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• Turbidity-Transparency Tube

• (for streams, ponds, wetlands, some coastal zones)

May have stopper and valve
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• Turbidity-Transparency Tube

• Analogous to secchi depth in lakes a measure of
  the dissolved and particulate material in the
  water
• Useful for shallow water bodies where a secchi
  would still be visible on the bottom or fast
  moving streams
• Best for clearwater bodies of water (not stained
  with dissolved organic compounds from bogs) but
  not too clear water
• It is a good measure of turbidity and suspended
  sediment (TSS)
• Used in many volunteer stream monitoring programs

Image http//www.watermonitoringequip.com/
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How does Turbidity relate to TSS ?
A general rule of thumb 1 mgTSS/L 1.0 - 1.5
NTUs of turbidity BUT Turbidity scattering
depends on particle size so this is only a rough
approximation
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Field Profiles-Turbidity

• Turbidity measures the scattering effect
  suspended particles have on light
• inorganics like clay and silt
• organic material, both fine and colored
• plankton and other microscopic organisms
• Field turbidity measurements are made with
• turbidimeters (bench meter for discrete samples)
• Submersible turbidity sensors (Note - USGS
  currently considers this a qualitative method)
• Transparency or turbidity tubes

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Turbidimeters -Nephelometric optics

• Principle
• nephelometric turbidity estimated by the
  scattering effect suspended particles have on
  light
• detector is at 90o from the light source
• Units
• Nephelometric Turbidity Units (NTU)
• standards are formazin or other certified
  material
• JTUs are from an older technology in which a
  candle flame was viewed through a tube of water
• 1 NTU 1 JTU (Jackson Turbidity Unit)

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Bench vs Submersible Turbidimeters
Discrete depth - collect water sample and analyze
water in Lab
vs Continuous profile using submersible sensor
YSI 6820 with unwiped turbidity
YSI wiping turbidity
Hydrolab
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Field profiles-turbidity

• Sensor calibration
• Turbidity free water zero (0 NTU) standard
• USGS recommends filtering either sample water or
  deionized water through a 0.2 um or smaller
  filter to remove particles
• WOW uses deionized water that is degassed by
  sparging (bubbling) with helium to minimize air
  bubbles that give false turbidity readings
• Standards range depends on anticipated sample
  values
• lakes - typically 0-20 NTU
• streams and wetlands - 0-20, 0-50 or 0-100 NTU
• 2 non-zero standards typically adequate (response
  is linear)
• formazin particles (either from a recipe or
  purchase a certified, concentrated stock solution
  (usually 4000 NTU)
• other commercially available materials -
  polystyrene
• need to worry about storage limits - Primary
  stock of 400 NTUs lasts lt 1 month when
  refrigerated. Dilute working standards from
  intermediate stock solution daily.

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Field profiles-turbidity - calibration standards
prep
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Field Probes-turbidity

• Comparability of different methods
• With the proliferation of automated in situ
  turbidity sensors there is concern about the
  comparability of measurements taken using very
  different optical geometries, light sources and
  light sensors.
• The US Geological Survey and US Environmental
  Protection Agency are currently (August 2002)
  developing testing procedures for a field
  comparison of a number of instruments produced by
  different manufacturers. We will include these
  results when they become available.
• Standard Methods refers to
• APHA.1998. Standard methods for the examination
  of water and wastewater. American Public Health
  Association, Washington, D.C.