Environmental Engineering Reference
In-Depth Information
TABLE 4.1
EPA Recommended Sample Containers, Preservatives, and Holding Times
Method
Container
Preservation
Holding Time
Notes
8260B
Standard 40 mL glass
screw-cap VOA vials with
Tel on-lined silicone septa
Cool to 4°C and
adjust pH to less
than 2 with H 2 SO 4 ,
HCl, or NaHSO 4
14 days
8270C
1 L amber glass with
Tel on-lined silicone septa
Cool to 4°C
Extract within 7 days;
analyze within 40
days of extraction
3 mL 10% sodium
thiosulfate per gallon if
sample is chlorinated
1624
1 L amber glass with
Tel on-lined silicone septa
Cool to 4°C; acidify
to pH 2 with HCl
(1:1) for aromatics
Analyze within 14
days of collection
Sodium thiosulfate (10 mg
per 40 mL) recommended
if sample of drinking
water is chlorinated
Source: U.S. Environmental Protection Agency (USEPA), 2006a, Test Methods SW-846 on line. http://www.epa.gov/
epaoswer/hazwaste/test/main.htm (accessed May 4, 2005).
Note: VOA, Volatile organic analysis.
4.2.1.1 Passive-Diffusion Bag Samplers
PDB samplers are narrow plastic sampling bags made of low-density polyethylene (LDPE), typi-
cally 18 in. long. The bags are closed at the ends after i lling with pure deionized water and then
lowered into a monitoring well to a specii ed depth for a period of 1-2 weeks. During the sampling
interval, the deionized water comes into equilibrium with the surrounding well water by diffusion
through the semipermeable polyethylene sampling bag, which has a pore size of less than 0.001
m
(10 Å, or 1 × 10 -6 mm). Multiple PDBs can be lowered into a single monitoring well with a long
screen to characterize vertical stratii cation of contaminants within a monitoring well screen and
to reveal variations in l ow rates along different portions of the screen. The primary analytes in
PDB sampling programs are VOCs in groundwater monitoring wells. PDBs can also be used to
monitor the discharge of contaminated groundwater to surface water (Vroblesky et al., 2000;
O'Neill, 2006).
Unfortunately, 1,4-dioxane is not amenable to sampling using PDB samplers. In a i eld trial com-
paring different no-l ow samplers, results for 1,4-dioxane in a PDB sampler were compared to
results for samples obtained by other no-l ow samplers and conventional samples. Although 1,4-
dioxane was detected in other samples from the same well, it was not detected in the PDB sample.
Apparently 1,4-dioxane does not diffuse well through the polyethylene bag (Parsons, 2005).
μ
4.2.1.2 Rigid Porous Polyethylene Samplers
The RPP system is based on a rigid polyethylene tube, about 7 in. long and i lled with reagent grade
water. The RPP is capped at both ends and lowered into the monitoring well to equilibrate with
ambient groundwater. Diffusion occurs through the rigid tube, which has pores ranging in size from
6 to 15
m (0.006-0.015 mm). RPP samplers are used for VOCs and soluble inorganic compounds
(O'Neill, 2006).
1,4-Dioxane recovery from RPP samplers was found to be comparable to recovery from samples
obtained by conventional means. In a 14-day test (i.e., the RPP device remained in the monitoring
well for 14 days), the RPP sampler yielded 74 parts-per-billion (ppb) 1,4-dioxane, whereas conven-
tional sampling produced 80 ppb. In a 28-day comparison, the RPP device produced a result of
67 ppb; the result from conventional sampling was 64 ppb. These results are within the margin of
μ
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