Groundwater sampling procedures

R. Puls and M. Barcelona, Low-Flow (Minimal Drawdown) Groundwater Sampling Procedure, EPA/540/S-95/504, [US Environmental Protection Agency, 1995]. 

Lindorf, D. E., Feld, J., and Connelly, J., 1987, Groundwater sampling procedures guidelines Wisconsin Department of Natural Resources Publication PUBL-WR-153-87, 44 p. 

The method using GC/MS with selected ion monitoring (SIM) in the electron ionization (El) mode can determine concentrations of alachlor, acetochlor, and metolachlor and other major corn herbicides in raw and finished surface water and groundwater samples. This GC/MS method eliminates interferences and provides similar sensitivity and superior specificity compared with conventional methods such as GC/ECD or GC/NPD, eliminating the need for a confirmatory method by collection of data on numerous ions simultaneously. If there are interferences with the quantitation ion, a confirmation ion is substituted for quantitation purposes. Deuterated analogs of each analyte may be used as internal standards, which compensate for matrix effects and allow for the correction of losses that occur during the analytical procedure. A known amount of the deuterium-labeled compound, which is an ideal internal standard because its chemical and physical properties are essentially identical with those of the unlabeled compound, is carried through the analytical procedure. SPE is required to concentrate the water samples before analysis to determine concentrations reliably at or below 0.05 qg (ppb) and to recover/extract the various analytes from the water samples into a suitable solvent for GC analysis. 

The method for chloroacetanilide soil metabolites in water determines concentrations of ethanesulfonic acid (ESA) and oxanilic acid (OXA) metabolites of alachlor, acetochlor, and metolachlor in surface water and groundwater samples by direct aqueous injection LC/MS/MS. After injection, compounds are separated by reversed-phase HPLC and introduced into the mass spectrometer with a TurboIonSpray atmospheric pressure ionization (API) interface. Using direct aqueous injection without prior SPE and/or concentration minimizes losses and greatly simplifies the analytical procedure. Standard addition experiments can be used to check for matrix effects. With multiple-reaction monitoring in the negative electrospray ionization mode, LC/MS/MS provides superior specificity and sensitivity compared with conventional liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/ultraviolet detection (LC/UV), and the need for a confirmatory method is eliminated. In summary,... 

The quantity of QC samples to be collected is dependent on the study design, but Aeld blanks and held replicates should represent approximately 5-10% of the groundwater samples collected for the study. QC samples should be collected on the same day, using the same supplies and equipment, and be stored and shipped under the same conditions as the groundwater samples collected for pesticide analysis. Document all procedures, equipment, and reference chemicals used to generate the QC samples. 

Suction lysimeters are required for some field-scale groundwater monitoring studies to monitor the transport of compounds of interest through the unsaturated zone. Unlike monitoring wells or water supply wells that sample water from the saturated zone, suction lysimeters sample water from the unsaturated zone. This section provides a summary of the installation and sampling procedures for pressure-vacuum suction lysimeters. A detailed discussion of unsaturated zone sampling devices is available elsewhere. 

Field parameter measurements (pH, temperature, conductivity, etc.) may be part of the sampling procedure as indicators of surface water quality (not stabilization indicators as in groundwater sampling). 

This chapter aims to provide a step-by-step guide for practitioners involved in the collection of contaminated samples by reviewing current groundwater sampling techniques and procedures and highlighting the major sources of uncertainty associated with sample collection. On-site water-quality measurements, quality assurance procedures and sample handling techniques designed to maintain the representativeness of the sample from field to laboratory are also discussed. 

In 1996, Puls and Barcelona (1996) published a US EPA—GroundWater Issue to provide background information on the development of low-flow sampling procedures and its application under a variety of hydrogeological settings. 

Reliable data on groundwater quality are essential to guide policy for sustainable resource management and effective resource protection. Whilst appropriate and standardised analytical and sampling procedures are required for this purpose, they on their own are not enough, since it is even more critical that the groundwater samples collected are ... 

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