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


Sample Amount – Water Sample Amount –

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


Sample Amount – Air Samples Sample Amount –

Water/Sediment Samples for

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



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:

Environmental Sampling TechniquesGeneral Guidelines of Environmental Sampling Techniques

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

1-33

Standard Methods (1998)



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

Environmental Sampling Techniques -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 turbulence impact 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

Environmental Sampling Techniques - 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

Indoor Air

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, Government Institutes, Rockville, MD.

Cowgillum (1988) Sampling Waters: The Impact of sample variability on planning and confidence Levels, In: Keith, L.H. (1988) Principles of Environmental Sampling. American Chemical Society, Washington, DC.

US EPA (1995) Superfund Program Representative Sampling Guidance: Volume 2, Air (Short-Term Monitoring), Interim Final, EPA 540-R-95-140, OSWER Directive 9360.4-09, PB96-963206, December 1995.

US EPA (2001) Methods for Collection, Storage and Manipulation of Sediments for Chemical and Toxicological Analyses: Technical Manual . EPA-823-B-01-002, October 2001.

Keith, L.H. (1988) Principles of Environmental Sampling. American Chemical Society, Washington, DC.

Keith, L.H. (1991) Environmental Sampling and Analysis: A Practical Guide. Lewis Publishers, Boca Raton, Fl.

Reeve, R.N. (2002) Introduction to Environmental Analysis. Wiley.

Popek, E.P. (2003) Sampling and Analysis of Environmental Chemical Pollutants: A Complete Guide. Academic Press, San Diego, CA.

sampling techniques

Education