Sampling techniques

Environmental Sampling Techniques-
General Guidelines of Environmental Sampling
Techniques
Sequence of Sampling Matrices and Analyses
 Project deals with multimedia and/or multiple parameters use
following sequence:
 Collect from least to most contaminated sampling locations
 If sediment and water is being collected, collect water first to
minimize effects from suspended bed materials
 For shallow streams, start downstream and work upstream to
minimize sediment effects due to sampling disturbances
 If sampling at different depths, collect surface samples first and
then proceed deeper
 Always collect VOCs first, followed by SVOCs (e.g. pesticides,
PCBs, oil, etc.), then total metals, dissolved metals, microbiological
samples, and inorganic nonmetals

Environmental Sampling Techniques
General Guidelines of Environmental Sampling Techniques
Sample Amount
 Minimum sample required depends on the
concentration of the analyses present
 Should take enough for all analyses and additional
for any QA/QC work required
 Heterogeneous samples generally require larger
amounts to be representative of sample variations
 Taking too much sample can lead to problems with
storage and transportation

SampleAmount – Water SampleAmount –
Soil/Sediment/Solid Waste
• 5 mL for total petroleum
hydrocarbons (TPHs),
100 mL for metals, 1 L
for trace organics
(pesticides)
• As a general rule the
minimum volume
collected should be 3-4
times the amount
required for analysis
(EPA, 1995)
• For physiochemical properties
(particle size, texture etc.) requires a
minimum of 200 g soil
• For contaminant analysis 5-100 g is
sufficient
• More samples are required if the goal
is to detect low solubility
(hydrophobic) organic contaminants
• Sample volume of waste samples
should be kept small to reduce
disposal costs

SampleAmount – Air Samples SampleAmount –
Water/SedimentSamplesfor
Toxicity Testing
• Volume of air required depends
on the minimum chemical
concentration that can be
detected and the sensitivity of
the measurement
• Concentration range may be
unknown – sample size
determined by trial and error
• 20-40 L Water for an effluent
toxicity test
• 15 L sediment for
bioaccumulation tests
• 8-16 L sediment for benthic
macro invertebrate
assessments (EPA, 2001)

Sample Preservation and Storage
 Purpose – minimize physical, chemical and biological changes
 3 approaches:
 Refrigeration
 Use of proper sample container
 Addition of preserving chemicals

 Refrigeration is a universally accepted method to slow down loss
processes
 Container choice (material type and headspace) is critical to
reduce
 Volatilization
 Adsorption
 Absorption
 Diffusion
 Photodegradation
 Addition of preservatives is critical to reduce losses due to
chemical reactions and bacterial degradation

Sample Preservationand Storage
 Maximum Holding Time (MHT) is the length of time a sample can
be stored after collection and prior to analysis
 MHTs vary by agency
 Immediate: pH, temperature, salinity, DO
 Within 1-2 days: careful pre-planning is required to avoid
sampling on Friday, Saturday or near holidays

 American Public Health Association (APHA) MHTs:

Selection of Sample Containers
Water
 Glass vs. Plastics:
 Glass may leach boron and silica, metals may stick to walls
 Glass is generally used for organics and plastic for metals, inorganics
and physical properties
 For trace organics cap and liner should be made of inert materials
(teflon)
 Headspace vs. no Headspace:
 No headspace is allowed for VOC samples
 40 mL vial with a teflon-lined septum
 Oil and grease should only be half-filled in wide mouthed glass bottles
 Special containers:
 e.g. BOD/DO bottles and VOC vials

Soil Biological
• Low temperature storage
• No preservatives except
ethanol or sodium bisulfite
for VOC analysis (Popek,
2003)
• Aluminum foil (shiny side
out) and closed glass
containers with inert seals
or cap liners

Air
 Various collection media:
 Filter cassettes
 Adsorbent tubes
 Bags
 Canisters
Reeve, 2002

Selection of Sampling Equipment
Surface Water and Wastewater Sampling
 Grab sampler, weighted bottle sampler,
Kemmerer bottle

Selection of Sampling
Equipment
Groundwater Sampling
 Collected from wells using a
bailer or by pumps
(peristaltic and bladder)
 Samples do not come into
contact with mechanical
components of the pump

Soil Sampling
 Soil depth and whether or not each soil horizon is necessary to sample
are main considerations
 Scoops and trowels, tube sampler, augers, split spoon sampler (drilling)

Equipment
Sediment Sampling
 Dredges (Ekman dredge,
Peterson dredge,
Ponar dredge)
 Core samplers (Livingstone,
Kullenberg,and
Mackereth)

Equipment
Sediment Sampling
 Dredges (Ekman dredge,
Peterson
dredge, Ponar dredge)
 Core samplers
(Livingstone, Kullenberg,
and Mackereth)
Glew et al, 2001

Hazardous Waste
 Sludges: Dredges, scoops, trowels, buckets
 Composite liquid waste: coliwasa, Thief and Trier samplers

Biological Sampling
 Very unique and diverse range of equipment
 Mammals - Trapping(live and kill)
 Fish - Electrofishing, gill nets, trawl nets, sein nets, minnow
traps
 Benthic macroinvertebrates - Petersen and Ekman dredges

Air Sampling
 Many direct-reading instruments for monitoring (real-time)
levels
 Sampling still needed for trace level analysis (expensive and
complex)
e.g. High volume total suspended particulate samplers (TSP),
PM-10 samplers, PM-2.5 samplers, personal sampling pumps,
canister samplers

Selection of Sampling Equipment -Air Sampling
Polyurethane Foam Sampler (PUF)
• For organics need both solid and vapor
phases
• Vapor cartridge is placed in-line with
quartz fiber filter for semi-volatile
organics
• PUF plug
• Adsorbent resin (XAD-2)
SUMMA canister
• Electroplated with Ni and Cr
oxides to prevent adsorption of
VOCs
• Low-ultra low ppt-ppb range
concentrations

Selection of Sampling Equipment -Air Sampling
Palmes diffusion tubes (PDTs) TSP/ PM10

-Techniques for Sampling
Surface Water and Wastewater Sampling
 Fresh surface waters: flowing waters, static waters and estuaries
 Wastewaters: mine drainage, landfill leachate, industrial effluents etc.
 Differ in their characteristics, samples collection is specific for each
 Streams and rivers – size and amount of turbulenceimpact
representativeness of samples
 Small streams (<20 ft wide) possible to select a location where a grab
sample represents the entire cross-section
 Larger streams and rivers multiple samples across the channel width
are required
 (Also at least one vertical composite (surface, middle, bottom))
 Fast moving rivers and streams difficult to collect mid-channel sample
 Ponds and impoundments use a single vertical composite at deepest
point
 Estuaries inland fresh water mixes with oceanic saline water have
specific sampling routines

- Techniques for Sampling
 Requires installation of a sampling well
 Well must not change integrity of surrounding waters
 Routine groundwater sampling tasks:
 Characterize flow
 Purge and stabilize groundwater prior to sampling
 Minimize cross-contamination due to well materials and sampling
devices
Groundwater Flow Direction
 Hydraulic gradient – slope of water table measured from high point to low
point across a site
 Flow is proportional to gradient, in direction of gradient
 Hydraulic head is a vertical measurement from sea level to the water
table
Hydraulic gradient = Difference in Hydraulic Head/Distance between two
wells

Well Purging
 Used to remove stagnant water in the well borehole and
sandpack for representative sample
 USGS stabilization parameters:
 DO ± 0.3 mg/L
 Turbidity ± 10 % (for samples > 10 NTUs)
 Specific conductivity ± 3%
 ORP ± 10 mV
 pH ± 0.1 unit
 Temp. ± 0.1 oC

Cross Contamination

Soil and Sediment Sampling
 Soil sampling at shallow depths relatively easy
 Sediments are treated similarly with regard to post-sampling
pretreatment (homogenizing, splitting, drying and sieving)
 Horizontal (grab) or vertical (core) sampling
 Composite sampling is common (except for VOCs)
 Non-soil/sediment or no sieved materials should be noted and
not discarded
 Sediments from lakes, ponds and reservoirs should be collected
at the deepest point (contaminants tend to concentrate in fine
grained material in depositional zones)

Hazardous Waste Sampling
 Sources: drums, storage tanks, lab packs, impoundments, waste
piles, debris
 Sampling approach varies considerably
 Requires HAZWOPER training
Drums etc.
 Research documentation (labels etc.) for health and safety
precautions
 Use proper protective equipment
 Unknown wastes should be opened remotely
 Should not be moved since some chemicals are shock-sensitive,
explosive or reactive
 Sample each phase separately

Biological Sampling
 Biological samples difficult to collect
 Species availability - Insufficient sample size may result in
invalid statistical inference
 Sampling protocol needs to account for size differences
between species, tissue differentiations, growth stage, and
habitat
 Susceptible to decomposition of organic analyses

Air and Stack Emission Sampling
 Ambient air, indoor workplace air and stack/emission exhausts
 Concentrations for most atmospheric pollutants are very low
 Analysis of organic compounds requires huge volumes
 Large variation in analyze concentration due to changes in
meteorology
 Meteorological parameters must be noted
IndoorAir
 Ventilation systems can alter air flow and add pollutants
 Sampler location will influence the results obtained
 Household chemicals can add compounds to the air

References
 Bodger,K. (2003) Fundamentals of Environmental Sampling,GovernmentInstitutes,
Rockville, MD.
 Cowgillum (1988)Sampling Waters:The Impactof sample variability on planning and
confidenceLevels,In: Keith, L.H. (1988) Principlesof EnvironmentalSampling.American
Chemical Society,Washington, DC.
 US EPA(1995) SuperfundProgram RepresentativeSampling Guidance:Volume 2,Air
(Short-Term Monitoring),Interim Final, EPA540-R-95-140,OSWER Directive 9360.4-09,
PB96-963206,December1995.
 US EPA(2001) Methods for Collection,Storage and Manipulation of Sediments for
Chemical and ToxicologicalAnalyses:Technical Manual.EPA-823-B-01-002,October
2001.
 Keith, L.H. (1988) Principles of Environmental Sampling.AmericanChemicalSociety,
Washington, DC.
 Keith, L.H. (1991) EnvironmentalSampling and Analysis:A PracticalGuide.Lewis
Publishers,Boca Raton, Fl.
 Reeve,R.N. (2002) Introduction to Environmental Analysis.Wiley.
 Popek,E.P. (2003) Sampling and Analysisof EnvironmentalChemical Pollutants:A
Complete Guide.Academic Press,San Diego,CA.

Sampling techniques

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Sampling techniques