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 ======================================================================= TABLES: Tables 1, 4, 5, 6, and 7 are presented below in this document. Tables 2, 3, 8, and 9 are presented as separate graphical documents. Figures 1 to 10 are also presented as separate graphical documents. ======================================================================= Table 1.--Reporting limits of selected elements for NASQAN, 1991, and the new parts-per-billion (ppb) protocol One-half targeted 1991 Targeted reporting NASQAN reporting limit limit for reporting limit1 for ppb protocol ppb protocol2 Element (ug/L) (ug/L) (ug/L) Al 10 10 5.0 Ba 2 2 1 Be 0.5 0.5 .25 Cd 1 1 0.5 Co 3 1 0.5 Cr 1 1 0.5 Cu 1 1 0.5 Fe 3 3 1.5 Pb 1 1 0.5 Mn 1 1 0.5 Mo 10 1 0.5 Ni 1 1 0.5 Ag 1 0.2 0.1 Zn 3 3 1.5 1 For samples in which specific conductance < 2,000 FS/cm. 2 Maximum limit from all sources of contamination. Table 4.--Median concentration of elements in DIW and in sampler blanks by sampler category in relation to reporting limits for NASQAN and one-half the reporting limits for the new parts-per-billion protocol [Number of samples for DIW and in each sampler category is given in parenthesis] Reporting limits (ug/L) 1/2 ppb Median concentration (ug/L) NASQAN- protocol Sampler categories Element 1991 target DIW Modified Standard Solenoid (12) (12) (32) (9) Aluminum 10 5 0.5 1.9 4.5 7.1 Barium 2 1 <0.2 <0.2 <0.2 <0.2 Cadmium 1 0.5 <0.2 <0.2 <0.2 0.4 Chromium 1 0.5 <0.2 <0.2 <0.2 <0.2 Copper 1 0.5 <0.2 1.7 3.4 5.9 Lead 1 0.5 <0.2 0.3 3.1 3.2 Manganese 1 0.5 <0.2 <0.2 0.8 0.3 Nickel 1 0.5 <0.2 0.4 0.3 <0.2 Zinc 3 1.5 <0.2 1.3 5.9 4.8 Table 5.--Mann-Whitney statistical comparison of the populations of elemental concentrations for DIW and sampler blanks by sampler categories1 Comsarison of samsler categories Modified Modified Standard DIW versus sampler categorv versus versus versus Element Modified Standard Solenoid standard solenoid solenoid Aluminum 0.114 0.000* 0.000* 0.003* 0.001* 0.196 Barium 0.755 0.007* 0.096 0.021* 0.062 0.476 Cadmium2 - 0.381 0.487 0.381 0.001* 0.000* Chromium2 0.755 0.043* _ 0.043* _ 0.078 Copper 0.002* 0.000* 0.000* 0.073 0.006* 0.431 Lead 0.015* 0.000* 0.000* 0.000* 0.000* 0.962 Manganese 0.178 0.000* 0.002* 0.002* 0.010* 0.356 Nickel 0.052 0.044* 0.294 0.835 0.853 0.660 Zinc 0.001* 0.000* 0.000* 0.000* 0.000* 1.000 1 Highlighted (*) values are significant at p = 0.05 level. 2 Because all values were less than the reporting limit, the Mann-Whitney test could not be applied. Table 6.--Median concentration of elements in DIW and sampler blanks by condition rating in relation to reporting limits for NASQAN and one-half the reporting limits for the new parts-per-billion protocol [Number of samples for DIW and in each sampler condition category is given in parenthesis] Reporting limits (ug/L) Median concentration (ug/L) 1/2 ppb For samplers rated NASQAN- protocol Very Element 1991 target DIW good Good Fair Poor (12) (12) (25) {5) (11) Aluminum 10 5 0.5 1.9 2.9 12 7.1 Barium 2 1 <0.2 <0.2 <0.2 0.7 0.3 Cadmium 1 0.5 <0.2 <0.2 <0.2 1.0 <0.2 Chromium 1 0.5 <0.2 <0.2 <0.2 0.4 <0.2 Copper 1 0.5 <0.2 1.0 1.7 22 11 Lead 1 0.5 <0.2 0.4 0.6 10 4.8 Manganese 1 0.5 <0.2 <0.2 0.2 2.4 1.2 Nickel 1 0.5 <0.2 <0.2 <0.2 1.9 0.5 Zinc 3 1.5 <0.2 0.9 2.8 45 15 Table 7.--Mann-Whitney statistical comparisons of the populations of elemental concentrations for DIW and sampler blanks by condition ratings Comparison of sampler conditions Very good Good Fair Very good DIW versus sampler condition versus versus versus versus Element Very good Good Fair Poor good fair poor fair & poor Aluminum 0.143 0.000* 0.001* 0.000* 0.002* 0.016* 0.377 0.000* Barium 0.755 0.253 0.064 0.000* 0.413 0.090 0.441 0.001* Cadmium2 - 0.713 0.OO9* 0.486 0.713 0.010* 0.163 0.100 Chromium2 0.755 0.860 0.064 0.151 0.860 0.046* 0.267 0.095 Copper 0.002* 0.000* 0.000* 0.000* 0.109 0.001* 0.320 0.000* Lead 0.014* 0.000* 0.000* 0.000* 0.047* 0.006* 0.267 0.000* Manganese 0.178 0.003* 0.000* 0.000* 0.083 0.001* 0.069 0.000* Nickel 0.378 0.181 0.104 0.006* 0.471 0.152 0.510 0.016* Zinc 0.001* 0.000* 0.000* 0.000* 0.000* 0.001* 0.013* 0.000* l Highlighted (*) values are significant at p = 0.05 level 2 Because all values were less than the reporting limit, the Mann-Whitney test could not be applied.