[Back to TOC] [Previous] [Next]
[Back to TOC] [Previous] [Next]
The field quality assurance program is a systematic process which, together with the laboratory and data storage quality assurance programs, ensures a specified degree of confidence in the data collected for an environmental survey. The field quality assurance program involves a series of steps, procedures, and practices which are described below.
The quality of data generated in a laboratory depends, to a large degree, on the integrity of the samples that arrive at the laboratory. Consequently, the field investigator must take the necessary precautions and have the appropriate knowledge to collect representative samples and protect samples from contamination and deterioration. Included in this category are consistency of sampling, correct use of equipment, and detailed field notes.
There are many sources of contamination; the following are some basic precautions to heed for biological samples particularly where tissue samples are to be obtained and processed:
· Sample containers, new or used, must be cleaned according to the recommended methods and certified by the issuing laboratory as `contamination free' (if pre-cleaned by the laboratory). Pre-cleaned bottles must be supplied with caps attached. Always label and store pre-cleaned bottles in plastic bags to avoid confusion and contamination during transport.
· Only the recommended type of sample container for each analysis should be used. Use only certified contamination free preservatives.
· The inner portion of sample bottles and caps must not be touched with anything (e.g., bare hands, gloves, etc.) other than the sample itself .
· Sample containers must be kept in a clean environment, away from dust, dirt, fumes and grime. Bottles must be capped at all times and stored in clean shipping coolers both before and after the collection of the sample. Vehicle cleanliness is an important factor in eliminating contamination problems.
· Petroleum products (gasoline, oil, exhaust fumes) are prime sources of contamination. Spills or drippings (which are apt to occur in boats) must be removed immediately. Exhaust fumes and cigarette smoke can contaminate samples with lead and other heavy metals. Air conditioning units are also a source of trace metal contamination.
· Samples must never be permitted to get warm; they should be stored in a cool place. Coolers packed with ice packs are recommended (most samples must be cooled to 4°C during transit to the laboratory; some are required to be frozen through the use of dry ice). Conversely, samples must not be permitted to freeze unless freezing is part of the preservation protocol.
· Samples must be shipped to the laboratory without delay so that they arrive within 24 hours of sampling. Samples must be analyzed within the time limits set out in Appendix 2 of this chapter.
· The sample collectors should keep their hands clean and refrain from smoking or eating while working with biological samples.
For taxonomic samples:
The following is the basic information which must accompany samples:
· Collection site (gazetted name, preferably with latitude and longitude and the sample site number),
· Collection date (using the Y/M/D convention written as "1999 June 12" not 99/06/12!!),
· Sampler's name,
· Collection method and details (e.g., net mouth size).
All of these data should be recorded in such a way that they will remain legible. Labels inside bottles filled with wet samples should be written with pencil on paper labels designed for this use.
As part of the lab taxonomic identification process, verification of taxa by recognized experts should be routine.
Voucher specimens should be retained for future reference and reverification. Voucher material should be stored using museum standards for preservation. At present, this is 125 mL Flint glass jars with wide mouth, plastic caps with a plastic gasket and liner. Preservatives should be noted under different sample types.
[Back to TOC] [Previous] [Next]
Quality control is an essential element of a field quality assurance program. In addition to standardized field procedures for biological sampling, field quality control requires, at the very minimum, the submission of replicate samples for all variables and reference samples for macro-invertebrate and fish tissue samples. Replicate samples detect heterogeneity within the environment, allow the precision of the measurement process to be estimated, and provide a check on the reproducibility of the sampling. There are many aspects to laboratory QA/QC noted below, and the field and lab aspects typically have to be considered together. One essential component is reference samples. They are used to document the bias of the analytical (laboratory) process. The timing and the frequency of replicate samples are established in the project design and will vary with each project.
To determine the degree of heterogeneity within the biological community being sampled, it is necessary to take replicate samples. These replicates can consist of multiple samples (grabs, tows, or whole fish) from the same general area (to measure how well a single sample represents the community or how many samples are necessary to achieve some level of sampling confidence), or portions of a single sample (i.e., sectioned grabs - to measure more localized invertebrate heterogeneity).
Split samples are aliquots taken from the same container and assumed to be identical. These samples can be sent to two or more laboratories for separate analysis and the results can be used to determine interlab variability of the different laboratories or the consistency of results within one lab.
For tissue samples, laboratory tested and preserved reference materials are available. For example, the National Research Council of Canada has dogfish liver and muscle tissue and lobster hepatopancreas tissue for the determination of trace elements and organomercury. These reference tissues have been subjected to a large number of analyses performed by independent laboratories using several different analytical techniques. Consequently, the NRC provides mean values and confidence intervals for these substances. Other reference tissues are available from other sources.
For taxonomy samples, some basic taxonomic reference materials are available. The US EPA is one source of these at least for algal taxonomy, chlorophyll a and some bacterial species.
These reference samples should be submitted to the analyzing laboratory along with the samples collected during a field trip. They should be transferred to a regular sample container and labeled with plausible site names and numbers (the codes used for identification must be documented in the field log book).
[Back to TOC] [Previous] [Next]
HTML Created:Mar 98
