Table 3. Concentration (g/L) of metals found
AS-60 autosampler. Instrument operating proce-
leaching from well casings.
dures followed the general recommendations
found in the manufacturer 's analytical methods
a. Barium
manual (Perkin-Elmer 1981). Working standards
were serial dilutions prepared from a certified (En-
Contact time, days
vironmental Resource Associates) primary mixed
Treatment
1
5
20
40
metal standard (1 mg/L). A range of four stan-
CONTROL
27.6
56.9
18.8
38.7
dard concentrations, analyzed in duplicate, was
CONTROL
25.6
71.5
19.0
37.9
used to calibrate the instrument for each metal. A
CONTROL
29.4
28.0
21.5
31.4
27.5a
52.2a
19.8a
36.0a
X
calibration check standard for each metal was pre-
% RSD
7.05
42.4
7.50
11.1
pared from serial dilutions of a certified (Fisher
PVC
49.8
73.7
17.9
35.3
Scientific Co.) metal standard (1,000 mg/L). The
PVC
55.0
75.0
10.5
29.4
check standard was analyzed every ten samples.
PVC
48.1
94.1
48.1
51.3
If analyses indicated that drifting from the stan-
51.0e
81.0b
25.5a
38.7a
X
dard curve was occurring, the instrument was
% RSD
7.05
14.1
78.0
29.3
recalibrated and any samples analyzed since the
PTFE
39.1
76.3
13.7
42.2
last check were reanalyzed. All dilutions of stan-
PTFE
40.1
68.3
13.9
30.5
PTFE
39.2
102
18.9
56.5
dards were in deionized water containing nitric
39.5c
82.2b
15.5a
43.0a
X
acid (2% v/v).
% RSD
1.31
21.4
18.9
30.3
Method Detection Limits (MDLs) (Table 2) were
FEP
37.1
60.2
21.6
28.6
determined following the procedure outlined in
FEP
38.1
77.7
17.7
26.5
the Federal Register (1984). All the samples were
FEP
34.9
92.0
311
101
analyzed twice and means were taken. Analysis
36.7b,c
76.6a,b
117a
52.0a
X
% RSD
4.48
20.8
144
81.4
of Variance (ANOVA) tests were performed on
samples that showed metal concentrations con-
FRE
41.3
65.6
13.5
25.4
sistently higher than the established MDL. If a
FRE
47.6
58.6
12.6
38.2
FRE
49.4
86.1
36.4
109
significant difference was detected by the ANO-
46.1d
70.1a,b
20.8a
57.6a
X
VA, then Fisher's Least Significant Difference
% RSD
9.27
20.4
64.6
78.5
(LSD) test was performed to determine which
FRP
28.8
70.8
21.7
45.7
materials differed from the controls and from each
FRP
33.8
68.5
27.7
28.9
other. A 95% confidence level was used in these
FRP
33.0
74.2
33.9
74.7
31.9a,b
71.1a,b
27.8a
49.8a
statistical tests.
X
% RSD
8.35
4.0
21.9
46.5
Values with the same letter for the same time were not signi-
ficantly different.
RESULTS AND DISCUSSION
Leaching study
Barium
The results for those analytes where detectable
All the samples, including the control samples,
levels were observed (Ba, Cd, Cr, Cu, Pb, Ni, Zn,
showed considerable variability from day to day
and Ag) are given in Tables 3ah. In instances
and among the replicates (Table 3a). Throughout
where one or more of the three replicate values
the study, the samples exposed to the casings all
for a given metal, material, and time were below
had slightly elevated mean normalized concen-
the MDL, the MDL was used in estimating a mean
trations, although usually less than 2.0 (Table 4).
value. Mean normalized concentrations were de-
After one day of exposure, concentrations in sam-
termined by dividing the mean concentration for
ples exposed to the PVC, PTFE, FEP, and FRE cas-
a particular material, analyte, and time by the
ings were significantly greater than the controls
mean concentration of the control samples for the
(Table 3a), with leaching greatest from the PVC
same analyte and time. A normalized mean con-
and FRE casings and least from the FRP casings.
centration of 1.0 meant no sorption or leaching
Because of the sizable variability among replicates,
occurred. Table 4 shows the mean normalized con-
most of the samples were not significantly differ-
centrations for these same analytes, except for Ag.
ent from the controls on the subsequent days (Ta-
Because the concentration of Ag was often less
ble 3a), even though the concentrations remained
than the detection limit, mean normalized con-
consistently higher than the controls.
centrations were not determined for this metal.
4
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