ASTM D6051-96(2006)
(Guide)Standard Guide for Composite Sampling and Field Subsampling for Environmental Waste Management Activities (Withdrawn 2015)
Standard Guide for Composite Sampling and Field Subsampling for Environmental Waste Management Activities (Withdrawn 2015)
SIGNIFICANCE AND USE
This guide provides guidance to persons managing or responsible for designing sampling and analytical plans for determining whether sample compositing may assist in more efficiently meeting study objectives. Samples must be composited properly, or useful information on contamination distribution and sample variance may be lost.
The procedures described for mixing samples and obtaining a representative subsample are broadly applicable to waste sampling where it is desired to transport a reduced amount of material to the laboratory. The mixing and subsampling sections provide guidance to persons preparing sampling and analytical plans and field personnel.
While this guide generally focuses on solid materials, the attributes and limitations of composite sampling apply equally to static liquid samples.
SCOPE
1.1 Compositing and subsampling are key links in the chain of sampling and analytical events that must be performed in compliance with project objectives and instructions to ensure that the resulting data are representative. This guide discusses the advantages and appropriate use of composite sampling, field procedures and techniques to mix the composite sample and procedures to collect an unbiased and precise subsample(s) from a larger sample. It discusses the advantages and limitations of using composite samples in designing sampling plans for characterization of wastes (mainly solid) and potentially contaminated media. This guide assumes that an appropriate sampling device is selected to collect an unbiased sample.
1.2 The guide does not address: where samples should be collected (depends on the objectives) (see Guide D 6044), selection of sampling equipment, bias introduced by selection of inappropriate sampling equipment, sample collection procedures or collection of a representative specimen from a sample, or statistical interpretation of resultant data and devices designed to dynamically sample process waste streams. It also does not provide sufficient information to statistically design an optimized sampling plan, or determine the number of samples to collect or calculate the optimum number of samples to composite to achieve specified data quality objectives (see Practice D 5792). Standard procedures for planning waste sampling activities are addressed in Guide D 4687.
1.3 The sample mixing and subsampling procedures described in this guide are considered inappropriate for samples to be analyzed for volatile organic compounds. Volatile organics are typically lost through volatilization during sample collection, handling, shipping and laboratory sample preparation unless specialized procedures are used. The enhanced mixing described in this guide is expected to cause significant losses of volatile constituents. Specialized procedures should be used for compositing samples for determination of volatiles such as combining directly into methanol (see Practice D 4547).
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
WITHDRAWN RATIONALE
This guide discussed the advantages and appropriate use of composite sampling, field procedures, and techniques to mix the composite sample and procedures to collect an unbiased and precise subsample(s) from a larger sample. It discussed the advantages and limitations of using composite samples in designing sampling plans for characterization of wastes (mainly solid) and potentially contaminated media.
Formerly under the jurisdiction of Committee D34 on Waste Management, this guide was withdrawn in January 2015 in accordance with section 10.5.3.1 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6051 − 96(Reapproved 2006)
Standard Guide for
Composite Sampling and Field Subsampling for
Environmental Waste Management Activities
This standard is issued under the fixed designation D6051; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 Compositing and subsampling are key links in the chain
responsibility of the user of this standard to establish appro-
of sampling and analytical events that must be performed in
priate safety and health practices and determine the applica-
compliance with project objectives and instructions to ensure
bility of regulatory limitations prior to use.
that the resulting data are representative. This guide discusses
the advantages and appropriate use of composite sampling,
2. Referenced Documents
field procedures and techniques to mix the composite sample
2.1 ASTM Standards:
andprocedurestocollectanunbiasedandprecisesubsample(s)
C702 PracticeforReducingSamplesofAggregatetoTesting
from a larger sample. It discusses the advantages and limita-
Size
tions of using composite samples in designing sampling plans
D1129 Terminology Relating to Water
for characterization of wastes (mainly solid) and potentially
D4439 Terminology for Geosynthetics
contaminated media. This guide assumes that an appropriate
D4547 Guide for Sampling Waste and Soils for Volatile
sampling device is selected to collect an unbiased sample.
Organic Compounds
1.2 The guide does not address: where samples should be
D4687 Guide for General Planning of Waste Sampling
collected (depends on the objectives) (see Guide D6044),
D5088 Practice for Decontamination of Field Equipment
selection of sampling equipment, bias introduced by selection
Used at Waste Sites
of inappropriate sampling equipment, sample collection proce-
D5792 Practice for Generation of Environmental Data Re-
duresorcollectionofarepresentativespecimenfromasample,
lated to Waste Management Activities: Development of
or statistical interpretation of resultant data and devices de-
Data Quality Objectives
signed to dynamically sample process waste streams. It also
D6044 Guide for Representative Sampling for Management
doesnotprovidesufficientinformationtostatisticallydesignan
of Waste and Contaminated Media
optimized sampling plan, or determine the number of samples
E856 Definitions of Terms and Abbreviations Relating to
to collect or calculate the optimum number of samples to
Physical and Chemical Characteristics of Refuse Derived
composite to achieve specified data quality objectives (see 3
Fuel (Withdrawn 2011)
Practice D5792). Standard procedures for planning waste
sampling activities are addressed in Guide D4687.
3. Terminology
1.3 The sample mixing and subsampling procedures de-
3.1 Definitions:
scribed in this guide are considered inappropriate for samples
3.1.1 composite sample, n—a combination of two or more
to be analyzed for volatile organic compounds. Volatile organ-
samples. D1129
ics are typically lost through volatilization during sample
3.1.2 sample, n—a portion of material taken from a larger
collection, handling, shipping and laboratory sample prepara-
quantity for the purpose of estimating properties or composi-
tion unless specialized procedures are used. The enhanced
tion of the larger quantity. E856
mixing described in this guide is expected to cause significant
3.1.3 specimen, n—a specific portion of a material or
losses of volatile constituents. Specialized procedures should
laboratory sample upon which a test is performed or which is
be used for compositing samples for determination of volatiles
taken for that purpose. D4439
suchascombiningdirectlyintomethanol(seePracticeD4547).
1 2
This guide is under the jurisdiction of ASTM Committee D34 on Waste For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Managementand is the direct responsibility of Subcommittee D34.01.01 on Plan- contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ning for Sampling. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2006. Published October 2006. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2001 as D6051 – 96(2001). The last approved version of this historical standard is referenced on
DOI: 10.1520/D6051-96R06. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6051 − 96 (2006)
3.1.4 subsample, n—a portion of a sample taken for the analyticalcosts (3).Thesemainadvantagesarediscussedinthe
purpose of estimating properties or composition of the whole followingparagraphs.However,aprincipleassumptionneeded
sample.
to justify compositing is that analytical costs are high relative
3.1.4.1 Discussion—a subsample, by definition, is also a
to sampling costs. In general, appropriate use of sample
sample.
compositing can:
6.2.1 Reduce inter-sample variance, that is, improve the
4. Summary of Guide
precisionofthemeanestimationwhilereducingtheprobability
4.1 This guide describes how the collection of composite
of making an incorrect decision,
samples, as opposed to individual samples, may be used to:
6.2.2 Reduce costs for estimating a total or mean value,
more precisely estimate the mean concentration of a waste
especiallywhereanalyticalcostsgreatlyexceedsamplingcosts
analyte in contaminated media, reduce costs, efficiently deter-
(also may be effective when analytical capacity is a limitation),
mine the absence or possible presence of a hot spot (a highly
6.2.3 Efficiently determine the absence or possible presence
contaminated local area), and, when coupled with retesting
of hot spots or hot containers and, when combined with
schemes, efficiently locate hot spots. Specific procedures for
retesting schemes, identify hot spots, as long as the probability
mixing a sample(s) and collecting subsamples for transport to
of hitting a hot spot is low,
a laboratory are provided.
6.2.4 Be especially useful for situations, where the nature of
5. Significance and Use
contaminant distribution tends to be contiguous and non-
5.1 This guide provides guidance to persons managing or random and the majority of analyses are “non-detects” for the
responsible for designing sampling and analytical plans for
contaminant(s) of interest, and
determining whether sample compositing may assist in more
6.2.5 Provide a degree of anonymity where population,
efficiently meeting study objectives. Samples must be compos-
rather than individual statistics are needed.
ited properly, or useful information on contamination distribu-
6.3 Improvement in Sampling Precision—Samples are al-
tion and sample variance may be lost.
ways taken to make inferences to a larger volume of material,
5.2 The procedures described for mixing samples and ob-
and a set of composite samples from a heterogeneous popula-
taining a representative subsample are broadly applicable to
tion provides a more precise estimate of the mean than a
waste sampling where it is desired to transport a reduced
comparable number of discrete samples. This occurs because
amount of material to the laboratory. The mixing and subsam-
compositing is a “physical process of averaging.” Averages of
pling sections provide guidance to persons preparing sampling
samples have greater precision than the individual samples.
and analytical plans and field personnel.
Likewise, a set of composite samples is always more precise
5.3 While this guide generally focuses on solid materials,
than an equal number of individual samples. Decisions based
the attributes and limitations of composite sampling apply
on a set of composite samples will, for practical purposes,
equally to static liquid samples.
always provide greater statistical confidence than for a com-
parable set of individual samples.
6. Attributes of Composite Sampling for Waste
Characterization 6.3.1 If an estimated precision of a mean is desired, then
more than one composite sample is needed; a standard devia-
6.1 In general, the individual samples to be composited
tion cannot be calculated from one composite sample.
should be of the same mass, however, proportional sampling
However, the precision of a single composite sample may be
may be appropriate in some cases depending upon the objec-
estimated when there are data to show the relationship between
tive. For example, if the objective is to determine the average
the precision of the individual samples that comprise the
drum concentration of a contaminant, compositing equals
composite sample and that of the composite sample. The
volumes of waste from each drum would be appropriate. If the
precision (standard deviation) of the composite sample is
objective is to determine average contaminant concentration of
approximately the precision of the individual samples divided
the waste contained in a group of drums, the volume of each
by the square root of the number of individual samples in the
sample to be composited should be proportional to the amount
of waste in each drum. Another example of proportional composite.
sampling is estimating the contaminant concentration of soil
6.4 Example 1—An example of how a single composite
overlying an impermeable zone. Soil cores should be collected
sample can be used for decision-making purposes is given
from the surface to the impermeable layer, regardless of core
here. Assume a regulatory limit of 1 mg/kg and a standard
length.
deviation of 0.5 mg/kg for the individual samples. If the
6.2 The principal advantages of sample compositing in-
concentration of a site is estimated to be around 0.6 mg/kg,
clude: reduction in the variance of an estimated average
how many individual samples should be composited to have
concentration (1), increasing the efficiency of locating/
relatively high confidence that the true concentration does not
identifying hot spots (2), and reduction of sampling and
exceed the regulatory limit when only one composite sample is
used? Assuming the composite is well mixed, then the preci-
4 sion of a composite is a function of the number of samples as
The boldface numbers in parentheses refer to a list of references at the end of
this guide. follows:
D6051 − 96 (2006)
Precision (standard deviation ÷ n)
Number of Individual
œ
Samples in Composite
of One Composite Sample
2 0.35
3 0.29
4 0.25
5 0.22
6 0.20
Thus, if six samples are included in a composite, the
composite concentration of 0.6 mg/kg is two standard devia-
tions below the regulatory limit. Therefore, if the composite
FIG. 2 Example of Within Cell Compositing
concentration is actually observed to be in the neighborhood of
0.6 mg/kg, we can be reasonably confident (approximately
mean concentration of the site. If there is a need to estimate the
95 %) that the concentration of the site is below the regulatory
cell-to-cellvariability,thentheapproachinFig.2issuitable.In
limit, using only one composite sample.
addition, if the precision of estimating the mean concentration
6.5 Example 2—Another example is when the standard
of the cell is needed, multiple composite samples should be
deviation of the individual samples in the previous example is
collected from that cell.
relatively small, say 0.1 mg/kg. Then the standard deviation of
6.6 Effect on Cost Reduction—Because the composite
a composite of 6 individual samples is 0.04 mg/kg (0.1 mg/kg
samples yield a more precise mean estimate than the same
divided by the square root of 6 = 0.04 mg/kg), a very small
number of individual samples, there is the potential for
number relative to the regulatory limit of 1 mg/kg. In this case,
substantial cost saving. Given the higher precision associated
simple comparison of the composite concentration to the
with composite samples, the number of composite samples
regulatory limit is often quite adequate for decision-making
required to achieve a specified precision is smaller than that
purposes.
requiredforindividualsamples.Thiscostsavingopportunityis
6.5.1 The effectiveness of compositing depends on the
especially pronounced when the cost of sample analysis is high
relative magnitude of sampling and analytical error. When
relative to the cost of sampling, compositing, and analyzing.
sampling uncertainty is high relative to analytical error (as is
6.7 Hot Container/Hot Spot Identification and Retesting
usuallyassumedtobethecase)compositingisveryeffectivein
Schemes—Samples can be combined to determine whether an
improving precision. If analytical errors are high relative to
individual sample exceeds a specified limit as long as the
field errors, sample compositing is much less effective.
action limit is relatively high compared with the actual
6.5.2 Because compositing is a physical averaging process,
detection limit and the average sample concentration. Depend-
composite samples tend to be more normally distributed than
ing on the difficulty and probability of having to resample, it
the individual samples. The normalizing effect is frequently an
may be desirable to retain a split of the discrete samples for
advantage since calculation of means, standard deviations and
possible analysis depending on the analytical results from the
confidence intervals generally assume the data are normally
composite sample.
distributed. Although environmental residue data are com-
monly non-normally distributed, compositing often leads to
6.8 Example 3—One hundred drums are to be examined to
approximate normality and avoids the need to transform the
determine whether the concentration of PCBs exceeds 50
data.
mg/kg.Assume the detection limit is 5 mg/kg and most drums
6.5.3 The spatial design of the compositing scheme can be
have non-detectable levels. Compositing samples from ten
important. Depending upon the locations from which the
drums for analysis would permit determining that none of the
individual samples are collected and composited, composites
drums in the composite exceed 50 mg/kg as long as the
can be used to determine spatial variability or improve the
concentration of the composite is <5 mg/kg. If the detected
precision of the parameter being estimated. Fig. 1 and Fig. 2
concentration is >5 mg/kg, one or more drums may exceed 50
represent a site divided into four cells. Composite all samples
mg/kg and additional analyses of the individual drums are
with the same number together. The sampling appro
...
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