PROGRAMS AND PLANS--Trace Element Concentrations in Deionized Water Processed Through Selected Surface-Water Samplers: Study Results and Implications




In Reply Refer To:
Mail Stop 412                                       July 17, 1992


OFFICE OF WATER QUALITY TECHNICAL MEMORANDUM 92.12

Subject:  PROGRAMS AND PLANS--Trace Element Concentrations in 
                              Deionized Water Processed Through 
                              Selected Surface-Water Samplers:
                              Study Results and Implications

                            SYNOPSIS

The Office of Water Quality is conducting a series of studies 
dedicated to identifying equipment, supplies, and cleaning 
procedures suitable for a part-per-billion protocol for dissolved 
trace elements.  As part of this effort, a study was conducted to 
determine the levels of trace-element contamination originating 
from selected surface-water samplers during the processing of 
deionized water through the samplers.  The major findings are:

1.  The highest levels of contamination in the sampler blanks were 
observed for aluminum, copper, lead, and zinc.

2.  The levels of observed trace-element contamination depended on 
both the type and physical condition of the sampler.

3.  No sampler type was clean enough--following pre-rinsing with 
deionized water--to use in a part-per-billion protocol for 
dissolved trace elements.  Therefore, a cleaning procedure 
using acid will be necessary in the part-per-billion protocol.

4.  The least contaminating samplers were D77 Teflon, D77 frame, 
and D77 bag.  Certain D77 standard (plastic) samplers also 
yielded low levels of contamination.  Accordingly, these four 
sampler types have been selected for further study using a 
prescribed cleaning procedure.

5.  Five sampler types--D74, DH49, P61, P63, and P72--were found 
to produce unacceptably high levels of trace-element 
contamination.  Accordingly, these sampler types have been 
dropped from further consideration as samplers for dissolved 
trace elements.

                            BACKGROUND

Recent studies indicate that contamination occurs for a number of 
dissolved trace elements in the Division data base.  The study 
findings were reported in Office of Water Quality (OWQ) Technical 
Memorandum (Tech Memo) 91.10.  OWQ Tech Memo 92.03 suggested a 
caveat for inclusion in State data reports; the caveat was revised 
in OWQ Tech Memo 92.04.  OWQ Tech Memo 92.05 suggests how the 
Division can address issues of uncertainty in the validity and 
usefulness of existing dissolved trace-element data.

Tech Memo 91.10 reported that Division operational program data 
are probably significantly contaminated for dissolved analyses of 
arsenic, boron, beryllium, cadmium, chromium, copper, lead, 
mercury, and zinc.  The contamination appears to result from 
sample collection and sample processing, rather than from the 
laboratory.  Accordingly, the nine elements were dropped from the 
NASQAN schedule beginning October 1, 1991.  Since the summer of 
1991, OWQ has sponsored a series of experiments (mentioned in Tech 
Memo 91.10) to identify the sources of the reported contamination.  
The experiments were designed to identify materials, samplers, 
filters, filtration systems, and cleaning procedures that can be 
used in a unified protocol to successfully measure trace elements 
in a "contaminant free manner" at the parts-per-billion (ppb) 
level (equivalent to 5g/L).

                         PURPOSE OF THIS MEMO 

This memo presents and describes the results and implications from 
an August 1991 study of contamination from selected surface-water 
samplers.

                          STUDY OBJECTIVES

The objectives of the study were to:

1.  Determine the trace-element contamination levels arising from 
use of selected surface-water samplers currently in use by 
several Districts;

2.  Determine if a relation exists between trace-element 
contamination and the physical condition of samplers;

3.  Determine the variance of trace-element contamination for (a) 
comparative tests on different categories and types of 
samplers, and (b) tests on identical types of samplers; 

4.  Select a subset of the least contaminating samplers for 
further study;

5.  Identify the samplers that cannot be used for collecting 
samples for trace-element analysis at the ppb or lower levels; 
and

6.  Update the provisional list cited in Tech Memo 91.10 of trace 
elements in the Division data base that are significantly 
contaminated.

Table 1 provides a basis for evaluating the results from this 
study by presenting (a) the 1991 reporting limits (RLs) for the 
NASQAN Program, (b) the RLs targeted for the new ppb protocol 
being prepared by the OWQ, and (c) one-half of the values of the 
targeted RLs.  The goal in developing the new protocol is to keep 
the cumulative contamination measured from all sources at or below 
one-half the targeted RLs.

                             STUDY DESIGN

Surface-water samplers were selected from a number of Districts 
and shipped to two locations for testing.  Aliquots of deionized 
water were processed through each sampler to obtain sampler 
blanks, and the blanks thus collected were analyzed for selected 
trace elements.

                            Tested Samplers

To minimize the variability of trace-element contamination due to 
several people processing sampler blanks, all samplers were 
shipped from home Districts to two locations where the testing was 
conducted by one person, Larry Shelton.  Nine types of samplers 
were tested.  The locations, dates, and types of samplers tested 
are listed below.  When multiple samplers of a given type were 
tested, the number tested is shown in parenthesis.

Pennsylvania District Office         Sacramento Subdistrict Office
Lemoyne, Pennsylvania                Sacramento, California
August 7, 1991                       August 13, 1991                    

     P61                                  P63 (2)
     DH49 (4)                             P72
     D74 (4)                              D77 plastic
     D77 standard (referred to in         D77 Teflon 
         this memo as D77 plastic)(3)     D77 frame
     D77 bag                           
     D77 Teflon 

Table 2 presents detailed information on each of the tested 
samplers.  For purposes of this study, the nine types of tested 
samplers were separated into three broad categories based on the 
following definitions:

1.  Standard -- non-solenoid samplers in common use by Districts 
to collect water/suspended-sediment mixtures; includes D77 
plastic, D74, and DH49 samplers.

2.  Solenoid -- solenoid activated point samplers used by 
Districts to collect water/suspended-sediment mixtures; 
includes P61, P63, and P72 samplers.


3.  Modified -- samplers modified from the standard D77 sampler.  
This category includes:  D77 Teflon--modified to have a Teflon 
nozzle, cap, adapter, and bottle; D77 bag--with a plastic 
freezer bag inserted in a slotted plastic bottle; and D77 
frame--with a plastic cooking bag attached to a standard D77 
plastic cap and nozzle, held in place and suspended with the 
aid of a metal frame, and placed above a lead sounding weight.

In general, these three categories divide the samplers according 
to the potential for sample water (and, hence, the DIW in this 
study) to contact metal surfaces.  Contact of water with metal 
definitely occurs in solenoid samplers.  In addition, in all 
standard samplers except the D77, the potential for contact with a 
metal surface occurs in the space around the gasket and with the 
metal air vent.

                     Sampler Condition Rating

Larry Shelton devised and used a system to rate the physical 
condition of tested samplers.  The system included four 
categories:

1.  Very good--sampler is painted (no chips) and visibly clean; 
special precautions taken during storage to prevent 
contamination; 

2.  Good--sampler is painted (but with some minor chips) and 
visibly clean; no special storage precautions are evident;

3.  Fair--sampler is painted (but with numerous chips) and visibly 
dirty; no special storage precautions are evident; and

4.  Poor--sampler is only partially painted, or in need of 
repainting, and is visibly very dirty; no special storage 
precautions are evident.  For point samplers, mechanical 
problems are evident.

The intent of the rating was to determine if a relation exists 
between easily observable criteria of physical condition and 
storage, and the level of measured trace-element contamination.  
As can be seen in Table 2, a relation exists between sampler 
category and rated sampler condition.  The four tested modified 
samplers received three very good and one good ratings.  The 12 
standard samplers included one very good, eight good, one fair, 
and two poor ratings.  The four solenoid samplers received one 
good, one fair, and two poor ratings.  Thus, the general order of 
sampler condition was: modified better than standard better than 
solenoid.  This may result from (a) District crews taking better 
care of modified samplers because of the intent to collect "clean 
samples" for chemical analysis, and (b) progressively less 
attention to caring for standard and solenoid samplers because of 
the lack of a specific intent to collect clean samples.  

                  Processing of Sampler Blanks

To mimic normal field procedure, each sampler was pre-rinsed three 
times with deionized water (DIW).  Samplers intentionally were not 
pre-cleaned with a dilute acid wash.  The intent was to measure 
the trace-element contamination emanating from the samplers as 
used in normal District operations.

After rinsing, samplers were gravity fed with DIW using a pre-
cleaned glass funnel and Teflon tube to simulate sampling.  The 
DIW was removed from the samplers using normal field procedures, 
poured into pre-cleaned Teflon bottles, and acidified with 0.5 
milliters (mL) of ultra pure nitric acid.  Two or three blanks 
were processed for each sampler.  Aliquots of the DIW, with and 
without the acid preservative, and an atmospheric blank with added 
preservative were also collected.  

                       Laboratory Analysis

All samples were shipped from each site as a batch to the National 
Water-Quality Laboratory for analysis.  Analysis order was based 
on the likelihood of contamination, with those samples likely to 
be contaminated analyzed last.  The samples were interspersed with 
laboratory blanks and standards for quality assurance.  Lynda 
Faires provided research grade-custom analysis using ICP/MS with a 
RL of 0.2 5g/L for each analyzed element.  All reported data are 
the average of triplicate analyses.  The elements analyzed were 
aluminum (Al), barium (Ba), beryllium (Be), cadmium (Cd), chromium 
(Cr), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), 
molybdenum (Mo), nickel (Ni), silver (Ag), thorium (Th), thallium 
(Tl), uranium (U), and zinc (Zn).  The estimated accuracy of 
results are:

          <0.2 -   1 5g/L              50-100 percent
             1 -  10 5g/L              10- 50 percent
            10 - 100 5g/L               1- 10 percent


          OVERVIEW OF RESULTS, DATA INTERPRETATIONS,
                   AND STATISTICAL ANALYSES

All results for six elements--Co, Mo, Ag, Th, Tl, and U--were 
below the study RL in the DIW and in the blanks from all tested 
samplers.  All values for Be were below the RL except one, which 
was at the RL.  No further mention is made in this memo of these 
seven elements.  In contrast, concentrations were commonly 
measured for nine elements--Al, Ba, Cd, Cr, Cu, Pb, Mn, Ni, and 
Zn.  The ensuing sections describe the results for these nine 
elements.

Table 3 presents the detailed data for the nine elements.  The 
table shows the sample type and identification number (ID) (for 
DIW and each tested sampler), the date of testing, the sampler 
condition rating, and the respective elemental concentrations.

Based on the study results, the ensuing sections:

1.  Compare the median concentrations for the trace elements 
between the three major categories of samplers--modified, 
standard, and solenoid.

2.  Compare the median concentrations for each sampler category to 
(a) the 1991 NASQAN RLs, and (b) the targeted reporting levels 
for the ppb trace-element protocol.

3.  Statistically compare the populations of trace-element 
concentrations for each category of sampler against (a) the 
population of trace-element concentrations in the DIW, and (b) 
concentrations in each of the other sampler categories.

4.  Compare the median concentrations for the trace elements 
between the four sampler condition ratings--very good, good, 
fair, and poor.

5.  Compare the median concentrations for each sampler condition 
rating against (a) the 1991 NASQAN RLs, and (b) the targeted 
RLs for the ppb trace-element protocol.

6.  Statistically compare the populations of trace-element 
concentrations for each sampler condition rating against (a) 
the population of trace-element concentrations in the DIW, and 
(b) concentrations in each of the other sampler condition 
ratings.

7.  Compare the highest concentration observed for each trace 
element in each of the nine types of samplers against (a) the 
1991 NASQAN RLs, (b) one-half the targeted RLs for the ppb 
trace-element protocol, and (c) the trace elements reported in 
OWQ Tech Memo 91.10 as being significantly contaminated in the 
Division data base.

8.  Examine the variance of contamination found for tests on 
identical types of samplers.

These cited comparisons are given in Tables 4-9 and many are 
illustrated in Figures 1-10.

Elemental concentration data for sampler categories and sampler 
condition rating were statistically tested for differences (see 
Tables 5 and 7).  In each comparison, the non-parametric Mann-
Whitney test was applied to determine if the populations of trace-
element concentrations were statistically different.  For example, 
Table 5 presents the test results comparing the concentration 
population of each trace element in the sampler blanks, compiled 
by sampler category, to the respective concentration populations 
in DIW.  Values shown in bold print denote a statistically 
significant difference (p = 0.05) in the concentration populations 
of elements.

The Mann-Whitney test compares the composited ranks of data values 
for the compared populations.  Therefore, the comparison is for 
the entire population of data values, not merely the median.  The 
reader should bear this in mind when comparing the median 
concentrations in Table 4 to the statistical results in Table 5.  
(Also for comparing Tables 6 and 7.)  For example, in Table 4, 
even though the median concentrations for DIW and the sampler 
categories are identical for Ba, populations of the concentrations 
differ (see Figure 10), and therefore, some statistically 
significant differences are reported for Ba in Table 5.


        COMPARISON OF CONTAMINATION BY SAMPLER CATEGORY

Table 4 presents the median concentrations of the nine elements in 
sampler blanks by sampler category in relation to the respective 
concentrations for the DIW, the 1991 NASQAN RLs, and one-half the 
targeted RLs for the new ppb trace-element protocol.  For DIW, the 
medians for all elements but Al were <0.2 5g/L (although there 
were 
individual measurements at or just above the RL for Cu, Ni, and 
Zn; see Table 3).  For Al, the concentration in DIW ranged from 
<0.2-4.2 5g/L with a median of 0.5 5g/L.  (The source of Al 
contamination in DIW is unknown.)  The trace-element 
concentrations in DIW are taken as a base, and markedly higher 
values observed in the sampler blanks are considered to represent 
contamination from the samplers.

The results in Table 4 indicate:

1.  In general, the highest levels of contamination in the sampler 
blanks were observed for Al, Cu, Pb, and Zn.

2.  The levels of trace-element contamination varied for the three 
examined categories of samplers.

3.  The modified samplers had the lowest or equally lowest median 
concentrations for all elements except Ni (for which the 
concentration was 0.4 5g/L).  The standard samplers had the 
second lowest median values for Al, Cu, and Pb, whereas the 
solenoid samplers had the second lowest median values for Mn 
and Zn; and the lowest, overall, for Ni.

4.  For the modified samplers, the median concentrations of Ba, 
Cd, Cr, and Mn were <0.2 5g/L compared to values of <0.2 5g/L 
in the DIW.  In contrast, the median concentrations of Al, Cu, 
Pb, Ni, and Zn from the modified samplers exceeded the 
respective median values in DIW.

5.  Except for Cu, the median concentrations in the modified 
samplers were less than the respective NASQAN RLs.  The median 
concentration of Cu was 1.7 5g/L.

6.  Except for Cu, the median concentrations in the modified 
samplers were less than one-half of the new protocol's targeted 
RLs.  

Table 5 shows the results of Mann-Whitney statistical testing of 
the populations of elemental concentrations by sampler category.  
The test results support the observations cited above.

1.  The comparison of the sampler categories to the DIW show 
significant differences (at p = 0.05) for three of eight 
testable elements for the modified samplers, eight of nine 
testable elements for the standard samplers, and five of eight 
testable elements for the solenoid samplers.

2.  For the modified samplers, significant differences from DIW 
occurred for Cu, Pb, and Zn.  In addition, weakly significant 
differences occurred for Al (p = 0.114) and Ni (p = 0.052).  
These five elements show median concentrations in the modified 
samplers that exceed the respective median values in DIW (see 
Table 4 and refer to item 3 above).

3.  Comparison for the three sampler categories shows that the 
modified samplers were statistically different (at p = 0.05) 
from the standard samplers for Al, Ba, Cr, Pb, Mn, and Zn; and 
from the solenoid samplers for Al, Cd, Cu, Pb, Mn, and Zn.

        COMPARISON OF CONTAMINATION BY SAMPLER CONDITION

Table 6 presents the median concentrations of the nine elements in 
sampler blanks by sampler condition in relation to the respective 
concentrations for DIW, the 1991 NASQAN RLs, and one-half the 
targeted RLs for the new ppb trace-element protocol.  As for the 
comparisons of sampler categories, the elemental concentrations in 
sampler blanks that exceed the levels in DIW are considered to 
represent contamination from the samplers.

The results in Table 6 indicate:

1.  A relation exists between the levels of trace-element 
contamination in the sampler blanks and the rated condition of 
samplers (as rated according to descriptive criteria by an 
experienced field person).

2.  The samplers rated in "very good condition" had the lowest or 
equally lowest median concentrations for all nine elements.  
The "good condition" samplers had the second lowest or equally 
lowest median concentrations for all nine elements.  In 
contrast, the "fair condition" samplers had the highest median 
concentrations for all nine elements, whereas the "poor 
condition" samplers had the second highest median 
concentrations for Al, Ba, Cu, Pb, Mn, Ni, and Zn.

3.  For the samplers rated in "very good condition", the median 
concentrations of Ba, Cd, Cr, Mn, and Ni were <0.2 5g/L, 
compared to values of <0.2 5g/L in the DIW.  In contrast, the 
median concentrations of Al, Cu, Pb, and Zn from the "very good 
condition" samplers exceeded the respective median values in 
DIW.

4.  Except for Cu, the median concentrations in the "very good 
condition" samplers were less than the respective NASQAN RLs.  
(The median concentration of Cu was 1.0 5g/L).

5.  Except for Cu, the median concentrations in the "very good 
condition" samplers were less than one-half of the new 
protocol's target RLs.

Table 7 shows the results of the Mann-Whitney statistical testing 
of the populations of elemental concentrations by sampler 
condition.  In general, the test results support the observations 
cited above in items 1-5.  Especially noteworthy are the values 
given in the last column of table 7 that compares samplers rated 
in "very good condition" versus "fair and poor condition."

     COMPARISON OF CONTAMINATION BY SAMPLER CATEGORY AND 
                     SAMPLER CONDITION

As noted in the section entitled "Sampler Condition Rating," a 
relation exists between the sampler categories used in this study 
and the sampler condition ratings.  A statistical analysis to 
separate these two effects is problematic, because when elemental 
concentrations are sorted by both sampler category and sampler 
condition rating, the number of data in certain classes is very 
small.  Therefore, although the statistical analysis was run, the 
results are not reported.  Moreover, the overriding finding is 
that both factors are important in determining: (a) the levels of 
resultant elemental contamination, and, hence, (b) the utility of 
samplers for collecting samples for trace-element analysis at the 
ppb and lower levels.


  COMPARISON OF HIGHEST ELEMENTAL CONCENTRATIONS IN EACH SAMPLER 
    TYPE TO SPECIFIED REPORTING LEVELS AND RESULTS REPORTED IN 
                         TECH MEMO 91.10

Comparison To 1991 NASQAN Reporting Limits

Table 8 compares the highest elemental concentrations observed for 
each sampler type versus the respective 1991 NASQAN RLs.

1.  Among the modified sampler types, each--the D77 Teflon, the 
D77 bag, and D77 frame--had Cu concentrations that exceeded the 
NASQAN RL.  The D77 bag also exceeded the RL for Ni, and the 
D77 Teflon the RL for Pb.

2.  Among the standard samplers, each set of the four samplers 
(D77 
plastic, D74, and DH49) had exceedances for five elements--Al, 
Cu, Pb, Mn, and Zn.  In addition, the D77 plastic samplers had 
an exceedance for Ni, and the D74s for Cd and Ni.

3.  Among the solenoid samplers, the P61 had exceedances for Al, 
Cu, Pb, Ni, and Zn; and the two P63s had an additional 
exceedance for Cd.  The P72 had exceedances for Cd, Cu, Pb, Mn, 
and Zn.

Comparison To List of Elements Reported as Significantly 
Contaminated in the Division Data Base in Tech Memo 91.10

As previously noted, Tech Memo 91.10 (see page 33) identified 
significant contamination in Division trace-element data for As, 
B, Be, Cd, Cr, Cu, Pb, Hg, and Zn.  Most of the samples collected 
in the comparative study which formed the basis of Tech Memo 91.10 
conclusions were collected by standard type samplers.  In the 
present study, As, B, and Hg were not analyzed.  Of the remaining 
six elements, the results for the standard type samplers (Table 8) 
show contamination above the NASQAN RLs as follows:

1.  D77s -- for Cu, Pb, and Zn; also for Al, Mn, and Ni; but not 
for Be, Cd, or Cr.

2.  D74s -- for Cd, Cu, Pb, and Zn; also for Al, Mn, and Ni; but 
not for Be or Cr.

3.  DH49s -- for Cu, Pb, and Zn; also for Al and Mn; but not for 
Be, Cd, Cr, or Ni.

Comparison To One-Half the Target RLs for the New PPB Protocol

Table 9 compares the highest elemental concentrations for each 
sampler type versus one-half of the targeted RLs for the new ppb 
trace-element protocol.

1.  Among the modified samplers, all three types had exceedances 
for Cu and Zn, and the D77 bag and D77 Teflon had additional 
exceedances for  Pb and Ni.  In addition, the D77 Teflon had an 
exceedance for Al.

2.  Among the standard type samplers, each of the four sampler 
sets for D77 plastic, D74, and DH49 had exceedances for six 
elements--Al, Cu, Pb, Mn, Ni, and Zn.  The D74s also had 
exceedances for the remaining three elements--Ba, Cd, and Cr.  
The D77 plastic samplers had an additional exceedance for Cr.

3.  Among the solenoid type samplers, the P61, the two P63s, and 
the P72 all had exceedances for Al, Cu, Pb, and Zn.  The P61 
had additional exceedances for Mn and Ni; the two P63s had 
additional exceedances of Cd and Ni, and the P72 had additional 
exceedances of Cd and Mn.

       VARIABILITY AMONG IDENTICAL TYPES OF SAMPLERS

Table 3 and Figures 1-9 show the degree of variability found when 
testing multiple samplers of the same type.

1.  For D77 Teflon, 2 samplers--both rated in very good condition-
- 
were tested (Table 2).  The first sampler (tested on August 7, 
1991), had exceedances of the study RLs (0.2 5g/L) for Al, Cu, 
Pb, Mn, Ni, and Zn.  The second (tested on August 13, 1991), had 
exceedances for Pb, Ni, and Zn.

2.  For D77 plastic, one sampler--rated in poor condition--stood 
out with very high contamination of Al, Cu, Pb, and Zn.  A 
second sampler--rated poor--gave high levels of Zn, and 
relatively moderate levels of Al, Cu, and Pb.  The other two 
samplers--rated very good and good--gave exceedances for, but 
relatively low levels of all elements except Cd.

3.  For the D74s, one sampler--rated fair and having a brass 
nozzle--gave very high contamination for Al, Cu, Pb, Ni, and 
Zn.  A second sampler--rated good--gave high contamination of 
Cu, relatively moderate levels of Pb, and one high level of Zn.  
In contrast, the other two samplers--both rated good--gave 
relatively low levels of all elements.

4.  For the DH49s, all four samplers were rated good.  However, 
two of the four gave high contamination of Cu, Pb, and Zn and 
relatively moderate levels of Ni and Mn.  In addition, two 
samplers had high individual values for Al.

5.  For the P63s, one sampler--rated good--gave high contamination 
of Al, whereas the second sampler--rated poor--gave relatively 
high concentrations of Cd, Cu (especially on one test), Pb and 
Zn.

                IMPLICATIONS OF STUDY RESULTS

The study results have the following implications concerning (a) 
development of a ppb trace-element protocol for Divisionwide use 
in the Federal-State Cooperative, Other Federal Agency, and 
Federal Programs, and (b) contaminated results in the Division 
data base.

1.  The highest levels of contamination in sampler blanks were 
observed for Al, Cu, Pb, and Zn.

2.  As a group, the types of samplers in the modified category--
D77 Teflon, D77 frame, and D77 bag--gave the lowest levels of 
trace-element contamination.  This result was expected because 
none of these samplers: (a) cause contact of the sample with an 
internal metal surface (such as in the solenoid samplers), or 
(b) provide the potential for such contact (as in all tested 
standard samplers, except the D77 plastic).

3.  Based on the estimated accuracy of the analytical results 
(<0.2 - 1 5g/L = 50-100 percent; 1-10 5g/L = 10-50 percent), an 
examination of Table 3 and Figures 1-9 indicates that the D77 
plastic samplers (categorized as standard type samplers) 
produced considerably more contamination than the modified 
samplers for Al, Cu, Pb, Mn, Zn, and possibly Ba, Cr, and Ni.  
However, when the two D77 plastic samplers rated in poor 
condition are dropped from the comparison (so that all compared 
samplers are rated in good or very good condition), the 
contamination from the D77 plastic samplers is comparable to 
the contamination from the modified samplers.  This suggests 
that for trace-element work at the ppb level, plastic may be a 
suitable material for the sampler's nozzle, cap, and bottle.

4.  Because of (a) the lack of potential for a sample to contact 
an internal metal surface, and (b) the reported test results, 
the modified samplers and the D77 plastic samplers have been 
selected for further study with a prescribed cleaning 
procedure.

5.  All other samplers--both those tested in this study and 
additional non-tested samplers--have been dropped from further 
study at this time.  This includes: D74s, DH49s, P61s, P63s, 
and D72s.  If individual District projects wish to use these or 
untested samplers, they should: (a) test the samplers for 
contamination before use, and (b) if the sampler is selected 
for use, implement rigorous quality control including a high 
percentage (up to 25 percent) of sampler blanks (in proportion 
to the number of environmental samples collected).

6.  None of the sampler types selected for further study were 
clean enough for direct use in a ppb trace-element protocol 
(see Table 9).  Therefore, the OWQ asked Art Horowitz to 
develop a cleaning procedure for samplers (and other field 
apparatus). The subsequent draft procedure has undergone 
intensive review within and outside of the USGS.  The revised 
cleaning procedure has, hence, been applied to an additional 
sampler study which included: (a) the surface-water samplers 
selected from this study, and (b) ground-water sampling devices 
of wide use within the Division.  The results of this second 
study will be reported later this year in another OWQ technical 
memorandum.

7.  The six tested types of samplers in the standard and solenoid 
categories gave contamination above the 1991 NASQAN RLs for Al 
(5 of 6), Cd (3 of 6), Cu (6 of 6), Pb (6 of 6), Mn (4 of 6), 
Ni (4 of 6), and Zn (6 of 6) (see Table 8).  Based on these 
results, Al, Mn, and Ni are, hereby, added to the list of trace 
elements categorized as significantly contaminated in the 
Division data base (see OWQ Tech Memo 91.10, page 33).  In 
91.10 (see Table 2, pages 24 and 33), Al and Mn were 
categorized  as "significantly different from NRP data but the 
differences may result largely from filtration artifacts, 
rather than contamination."  We believe filtration artifacts do 
occur with Al and Mn, as well as with Fe.  However, the results 
from this study are free of filtration artifacts and show that 
selected samplers widely used in the Division do produce 
contamination above NASQAN RLs for Al and Mn.  In 91.10, Ni was 
found to have a statistically significant difference from NRP 
for the sampling step (median difference of 0.32 5g/L; 0.01-0.1 
probability).  However, the sampling difference was considered 
small and inconclusive, and Ni was categorized as 
"noncontaminated or minimally contaminated."  Based on the 
present study, Ni is moved to the significantly contaminated 
category.  The reader should note that the classification of 
Al, Mn, and Ni in the "significantly contaminated" category was 
drawn from multiple lines of evidence and signifies that some 
unknown portion of the Division's data base for these elements 
is contaminated.

8.  Two elements--Be and Cr--were found from the studies reported 
in Tech Memo 91.10 to be significantly contaminated, but were 
not found to be contaminating in this study.  However, the 
results in 91.10 included contamination from all field steps, 
not just the sampling device.  Moreover, the contamination 
noted for Be in 91.10 occurred in the field processing step 
(sample splitting, filtration, etc.), rather than the sample 
collection step), as did the most statistically significant 
contamination observed for Cr.  Therefore, Be and Cr will 
remain on the list of significantly contaminated elements.

9.  Tech Memo 91.10 listed Ag on the "as yet undetermined list" 
for contamination, and did not cover analyses for Th and Tl.  
In the present study, the tested sampling devices were 
noncontaminating for these three elements.  These three 
elements remain to be assessed for contamination from field 
processing steps (sample splitting, filtration, etc.)




                                    David A. Rickert
                                    Chief, Office of Water Quality

Key Words:  NASQAN, trace elements, contamination, 
            water/suspended-sediment samplers

This memorandum refers to Office of Water Quality Technical 
Memorandums 91.10, 92.03, 92.04, and 92.05.

Distribution:  A, B, S, FO, PO