Intro to sampling

1
Intro to sampling

• Adapted from Fundamentals of Environmental
  Sampling and Analysis by Chunlong Zhang

2
Why are you sampling?

• Comply with regulations!
• Determine concentrations or loads
• Measure background, ambient concentrations
• Determine degree of pollution
• Identify trends (spatial, temporal)
• Detect accidental releases or evaluate risk
• Risk to humans? Wildlife? Both?
• Study fate and transport, evaluate effectiveness
  of control or remediation strategies

3
Scientifically defensible data

• Can it stand up in court?
• Components of legal defensibility include (but
  are not limited to)
• Custody or control (chain of custody forms, to
  prevent tampering)
• Documentation (paper trail)
• Traceability (esp standards certificates of
  analysis)

4
Lab notebooks

• In govt and industry, lab notebooks are LEGAL
  DOCUMENTS
• Date and signature are part of GLP
• Do not remove pages or obliterate or erase
  anything.
• In academia, the rules are loose.
• The lab notebook is your journal, diary, best
  friend. Make your notes excruciatingly detailed.
  
• Why? To help YOU when you write up your data
  (sometimes years later)

5
Sampling issues

• Where to take samples
• When to take samples
• How to take samples
• How many samples to take
• How often samples will be taken
• How much sample is needed
• How to preserve samples
• How long the sample will be stable
• What to take (air, water, soil?)
• What to analyze (physical, chemical, biological)
• Who will take samples (sample custody)

6
Why is environmental sampling unique?

• Numerous analytes, high cost
• Many samples
• Sample matrices are complex, interferences are
  variable and unpredictable.
• Concentrations are low
• Some analyses must be done on site and/or
  continuously
• Analysts need to know not just how to analyze,
  but also be familiar with regulations
• Huge data sets require knowledge of statistics,
  data management

7
Jargon

• DQO data quality objectives
• What are you trying to measure and why?
• Relative vs. absolute data, operationally defined
  parameters (i.e. organic carbon), total metals or
  speciation?
• QAPP quality assurance project plan
• QA/QC quality assurance/quality control
• Representativeness
• Many agencies (EPA, NIOSH, USGS, ASTM) have
  standard methods. Often your lab must be
  certified to produce results that are admissible
  in court or valid for regulatory purposes.

8
Hazards during sampling/storage

• Volatilization
• Change in speciation (dissolved/particle, metal
  speciation, degree of sorption)
• Biodegradation
• Photolytic degradation
• Chemical degradation (Cl2?)

9
Sample containers and preservation

• Metals
• Dangers are sorption to container and
  precipitation
• Use plastic bottles acidify to pH2 with HNO3
• VOCs
• Danger is volatilizationavoid headspace
• Organics in drinking water
• Danger is reaction with Cl2 add Na2S2O3
• PAHs
• Photochemical degradation use amber glass
• All organics (some inorganics)
• Biodegradation freeze or refrigerate, add
  something to kill bacteria

10
Air sampling

• Air or atmospheric samples may consist of
• Gas phase
• Airborne particles (aerosols)
• Rain/snow precipitation

11
Why do air sampling?

• Comply with regulations
• Ex. Ozone, PM2.5
• Fate and transport (research)
• Loadings via atmospheric deposition
• Locate sources

12
Sampling for common air analytes

• High vapor pressure - Gas phase only
• Ozone, NOx, VOCs
• Continuous monitors (ozone, NOx)
• VOC canisters
• Low vapor pressure - Particle phase and precip
• Metals, nutrients (P)
• Filters for particles, rain collectors for precip
• No need to worry about gas/particle partitioning
  or gas absorption artifacts
• Intermediate vapor pressure - Gas, particle, and
  precip
• Semivolatile organics (PCBs, PAHs, etc)
• High volume air samplers to separate gas and
  particle phases
• Worry about changing gas/particle partitioning
• Rain collectors with immediate solid phase
  extraction

13
Analyzing air samples

• VOCs
• Purge and trap GC/MS
• Semivolatiles
• Extract, cleanup, analyze by GC/ECD or GC/MS

14
Factors to consider when choosing a
sampling/analysis method

• Quantity vs quality of data
• Quantity may refer to measuring spatial and/or
  temporal variability
• Quality may refer to absolute vs. relative
  concentrations (accuracy vs precision)
• Cost including manpower
• Detection limits contamination issues
• Holding times other logistics