Water Chemistry Field Sampling
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to the field with premarked lake outlines showing the locations of these stations.
The observations at each station included quantitative and semiquantitative
observations of vegetation structure, anthropogenic disturbances, and bank
substrate. In-lake littoral measurements and onshore observations dealt with
littoral water depth, bottom substrate, nearshore fish cover, and aquatic macrophyte cover. With quantifiable confidence, investigators condensed these
observations into descriptions applicable to the whole lakeshore and littoral
zone. For example, team observations led to quantitative descriptions such as
the mean canopy or aquatic macrophyte cover along the lakeshore, the extent of
shoreline disturbed by various human activities, and the dominant littoral substrate in the lake. There are similar physical habitat evaluation procedures for
streams, developed for EPA’s national surveys, such as the WSS.
2.3.3.4 On-Site Processing of Samples
In general, we do not recommend filtering lake or stream samples in the field
except where immediate filtering is required for a particular measurement.
To avoid the possibility of sample contamination, it is generally preferable to
perform this step within the controlled conditions of a laboratory. Similarly,
measurement of pH in the field is not recommended for most studies. This measurement is best performed in the laboratory under controlled conditions.
For most chemical constituents of interest for atmospheric deposition studies, sample preservation in the field is not necessary. Types of sample preservation may include addition of chemicals or filtering to remove particulates.
Preservation procedures are generally done for a specific measurement and
usually render the sample unusable for other measurements. Therefore, if preservation in the field is needed for a specific measurement, an aliquot will need
to be removed from the sample prior to preservation. The volume of the aliquot will be dependent on the analytical requirements of the measurement.
In general, we do not recommend sample preservation in the field for chemical
analyses.
Most samples contain dissolved or particulate organic matter and associated microbes that can change sample chemistry through decomposition and
assimilation. All samples should therefore be placed out of the sunlight and in
a cooler with ice as soon as possible for transport back to the laboratory where
they can be refrigerated. This procedure is usually sufficient to slow biological
processes enough to prevent measurable changes in chemical concentrations.
As a rule of thumb, samples should be returned from the field as quickly as possible to enable processing in the laboratory, and filtration (if needed) should be
performed in the laboratory. An exception applies to the collection and analysis of samples for measurement of chlorophyll a. Those samples are most commonly filtered in the field, and the filter (not the filtrate water) is transported in
a zipper-lock bag on ice in the dark to the laboratory for analysis. It is essential
72
to the field with premarked lake outlines showing the locations of these stations.
The observations at each station included quantitative and semiquantitative
observations of vegetation structure, anthropogenic disturbances, and bank
substrate. In-lake littoral measurements and onshore observations dealt with
littoral water depth, bottom substrate, nearshore fish cover, and aquatic macrophyte cover. With quantifiable confidence, investigators condensed these
observations into descriptions applicable to the whole lakeshore and littoral
zone. For example, team observations led to quantitative descriptions such as
the mean canopy or aquatic macrophyte cover along the lakeshore, the extent of
shoreline disturbed by various human activities, and the dominant littoral substrate in the lake. There are similar physical habitat evaluation procedures for
streams, developed for EPA’s national surveys, such as the WSS.
2.3.3.4 On-Site Processing of Samples
In general, we do not recommend filtering lake or stream samples in the field
except where immediate filtering is required for a particular measurement.
To avoid the possibility of sample contamination, it is generally preferable to
perform this step within the controlled conditions of a laboratory. Similarly,
measurement of pH in the field is not recommended for most studies. This measurement is best performed in the laboratory under controlled conditions.
For most chemical constituents of interest for atmospheric deposition studies, sample preservation in the field is not necessary. Types of sample preservation may include addition of chemicals or filtering to remove particulates.
Preservation procedures are generally done for a specific measurement and
usually render the sample unusable for other measurements. Therefore, if preservation in the field is needed for a specific measurement, an aliquot will need
to be removed from the sample prior to preservation. The volume of the aliquot will be dependent on the analytical requirements of the measurement.
In general, we do not recommend sample preservation in the field for chemical
analyses.
Most samples contain dissolved or particulate organic matter and associated microbes that can change sample chemistry through decomposition and
assimilation. All samples should therefore be placed out of the sunlight and in
a cooler with ice as soon as possible for transport back to the laboratory where
they can be refrigerated. This procedure is usually sufficient to slow biological
processes enough to prevent measurable changes in chemical concentrations.
As a rule of thumb, samples should be returned from the field as quickly as possible to enable processing in the laboratory, and filtration (if needed) should be
performed in the laboratory. An exception applies to the collection and analysis of samples for measurement of chlorophyll a. Those samples are most commonly filtered in the field, and the filter (not the filtrate water) is transported in
a zipper-lock bag on ice in the dark to the laboratory for analysis. It is essential