2.3 Field Methods
53
backup sample locations, to be used only if access is not available to the
intended sampling sites at the time of sample collection. Such an approach
may be useful if, for example, road or trail access is blocked by late snowpack, road washout, avalanche, landslide, or other impediment to access of
remote sites.
2.3.1.2 Laboratory and Sample Bottle Arrangements
Appropriate agreements will need to be made or contracts established with
a qualified water chemistry laboratory well in advance of field sampling.
If waters are expected to be dilute, the laboratory must be able to implement
low-ionic-strength methods to achieve the necessary DQOs. The laboratory, or
some other entity, should prepare and provide sample bottles, insulated shipping containers, and refrigerant.
We recommend that plasticware and plastic aliquot bottles should be highdensity polyethylene (HDPE), low-density polyethylene (LDPE), or polypropylene. The sample bottle must be made of a material that is nonreactive with
the chemical constituents to be measured. Polyethylene and polypropylene are
commonly assumed to be essentially inert with respect to most dissolved substances. Harder plastics such as polycarbonate tend to be less reactive but will
crack more easily than softer plastics. For measurement of low concentrations
of dissolved carbon, glass is generally preferred. Teflon ® , not only the most inert
plastic but also the most expensive, can be used for measurements of trace concentrations of highly reactive substances.
New bottles should be soaked in deionized water (DIW) prior to use. Samples
can also be collected into previously used bottles that have been rinsed with a
dilute wash acid (e.g., HCl 2%) and soaked in DIW for at least 24 h. The laboratory should follow a procedure to check acid-washed bottles to ensure that all
traces of the acid are undetectable in a chemical analysis. In general, we do not
recommend that bottles be acid washed. Rather, we suggest using new bottles
that have been washed and subsequently checked with DIW blanks to ensure
that cleaning has been adequate. Bottle processing should involve multiple
rinses of both the bottle and the lid with distilled or DIW. Generally, the laboratory is responsible for providing contamination-free bottles for the sampling.
Sample bottle preparation should involve triple rinsing of each bottle with DIW.
The bottles should then be stored overnight, or longer, filled with DIW, followed
by another rinse with DIW. Ideally, each bottle should then be filled with DIW
(which can be poured out after 24 h or at the time of sample collection). Treating
the sample bottles in this manner will help ensure a contamination-free sample.
Laboratory conductivity analyses of blank samples typically employ a standard
acceptance criterion of less than about 1.2 to 2 μS/cm.
The size of sample collection bottles can vary depending on the parameters
to be analyzed but should normally be 500- or 1000-ml (large enough to allow
53
backup sample locations, to be used only if access is not available to the
intended sampling sites at the time of sample collection. Such an approach
may be useful if, for example, road or trail access is blocked by late snowpack, road washout, avalanche, landslide, or other impediment to access of
remote sites.
2.3.1.2 Laboratory and Sample Bottle Arrangements
Appropriate agreements will need to be made or contracts established with
a qualified water chemistry laboratory well in advance of field sampling.
If waters are expected to be dilute, the laboratory must be able to implement
low-ionic-strength methods to achieve the necessary DQOs. The laboratory, or
some other entity, should prepare and provide sample bottles, insulated shipping containers, and refrigerant.
We recommend that plasticware and plastic aliquot bottles should be highdensity polyethylene (HDPE), low-density polyethylene (LDPE), or polypropylene. The sample bottle must be made of a material that is nonreactive with
the chemical constituents to be measured. Polyethylene and polypropylene are
commonly assumed to be essentially inert with respect to most dissolved substances. Harder plastics such as polycarbonate tend to be less reactive but will
crack more easily than softer plastics. For measurement of low concentrations
of dissolved carbon, glass is generally preferred. Teflon ® , not only the most inert
plastic but also the most expensive, can be used for measurements of trace concentrations of highly reactive substances.
New bottles should be soaked in deionized water (DIW) prior to use. Samples
can also be collected into previously used bottles that have been rinsed with a
dilute wash acid (e.g., HCl 2%) and soaked in DIW for at least 24 h. The laboratory should follow a procedure to check acid-washed bottles to ensure that all
traces of the acid are undetectable in a chemical analysis. In general, we do not
recommend that bottles be acid washed. Rather, we suggest using new bottles
that have been washed and subsequently checked with DIW blanks to ensure
that cleaning has been adequate. Bottle processing should involve multiple
rinses of both the bottle and the lid with distilled or DIW. Generally, the laboratory is responsible for providing contamination-free bottles for the sampling.
Sample bottle preparation should involve triple rinsing of each bottle with DIW.
The bottles should then be stored overnight, or longer, filled with DIW, followed
by another rinse with DIW. Ideally, each bottle should then be filled with DIW
(which can be poured out after 24 h or at the time of sample collection). Treating
the sample bottles in this manner will help ensure a contamination-free sample.
Laboratory conductivity analyses of blank samples typically employ a standard
acceptance criterion of less than about 1.2 to 2 μS/cm.
The size of sample collection bottles can vary depending on the parameters
to be analyzed but should normally be 500- or 1000-ml (large enough to allow