3/21/2002. Prepared by DynCorp Information & Engineering Technology Science and Engineering Group

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1 W Section: 1(0,Z PC, K.) 1(o9Li 1 Evaluation of Sulfide Results for Metal Products and Machinery Samples Analyzed by MCAWW Method 376.1, MCAWW Method 376.2, and Standard Method 4500-S -a (E) 3/21/2002 Prepared by DynCorp Information & Engineering Technology Science and Engineering Group Prepared for Cindy Simbanin Statistics and Analytical Support Branch Engineering and Analysis Division U.S. Environmental Protection Agency Prepared under EPA Contract No. 69 -C Sample Control Center

2 Summary Evaluation and General Recommendations Because the true concentrations of sulfide in these 236 samples are not known, it is not possible to state with certainty which of the three methods used in this study performs best overall. The results for the 236 samples in this study suggest that there are potential interferences with Method that may be better addressed by either Method or SM 4500-S'Z (E) and its associated sample pretreatment step. The fact that sulfide was not detected by any of the methods in 66% of all the samples, suggests that the differences between the methods need to be viewed in the context of specific samples and sample types. Sulfide was detected by all three methods in eight of the effluent samples. These results indicate that the performance of the three methods can be comparable in the sample type to which these methods are most often applied (i.e., treated effluents), and in samples whose sulfide concentrations fall within the range of all three methods. The data from the other effluent samples and from the influents and unit process samples suggest that (1) Method may perform better than SM 4500-S'2 (E), and (2) when the sample pretreatment procedure in SM 4500-S'Z [C] is employed, SM 4500-S'2 (E), in turn, may perform better than Method SCC recommends the following general rules for using the results of this study and other studies in which more than one of these methods are applied to MP&M samples. 1. When the results from all three of the methods are non-detects, use the lowest of the reported detection limits. If only two of the three methods were applied to other MP&M samples (e.g., preproposal), use the lower of the detection limits reported. The lower detection limits in this study were usually associated with Method Where sulfide was reported by all three of the methods, use the mean of the three results for each sample. 3. Where only the results by either Method or SM 4500-S'2 (E) indicate sulfide is present, compare the non-detect results from the other two methods and use the lower of the detection limits for the other two methods reported (in this study, usually Method 376.2). 4. Where only the results by Method indicate sulfide is present, use those results if they are below the detection limits reported for the other two methods. Otherwise, use the lower of the detection limits from the other two methods. Beyond these four general rules, data users should consider how a specific decision may be affected by the results from another of the methods. It may be necessary to make alternative calculations using the results from another of the methods and compare the affects on the decision in question, using professional judgement. Tables Al through A5 in Attachment 1 contain sample-specific recommendations for results from all 236 samples in this study. The following section contains a narrative discussion of results and recommendations by sample type and method. These narrative recommendations are reflected in Tables A 1 through A5. MP&M Sulfide Method Evaluation 2 March 21, 2002

3 value well below the capabilities of either Method or SM Therefore, SCC recommends that the detected value by Method be used. For Sample 60779, the result of 10.7 mg/l by Method is above the detection limit of 4 mg/l reported for the other two methods. This sample was also collected in Episode, but at a different sampling point than the other 8 samples with detected results by all three methods. While the possibility of interferences with Method cannot be ruled out from the data for this one sample, SCC recommends that this result be used as reported, consistent with our recommendations to use the Method results for other effluent samples with disparate results. Influent Sample Results and Recommendations As shown in Table 1, sulfide was detected in 22 influent samples by one or more of the three methods. Sulfide was detected by all three methods in only three of these samples. This result is consistent with the expectation that influent samples present a greater analytical challenge than the effluent samples for all three of the methods. The results for the three samples that had detects in all three methods, do not show a consistent pattern among the three methods (e.g., Method yielded much lower results for two of the three samples, and a higher result for the third sample). Two of the three samples were collected from the same sampling point on different days, and show consistent results within each of the methods (e.g., both results are higher than the SM 4500-S' 2 (E) results, which are higher than the results). SCC recommends that the mean of the three results be employed. Of the 22 influent samples in which sulfide was detected, 8 samples had sulfide detected by Method only. As with the effluent samples, the Method results may be due to interferences and SCC recommends that the detection limits from Method be employed in any further assessment of these results. Of the 22 influent samples in which sulfide was detected, 4 samples had sulfide detected by Method and SM 4500-S'2 (E), with non-detects by Method Here again, because of the possibility of interferences with Method 376.1, and to a lesser extent SM 4500-S' 2 (E), SCC recommends using the non-detects by Method Of the 22 influent samples in which sulfide was detected, 4 samples had sulfide detected by SM 4500-S'2 (E) only. The detected levels were 1-3 mg/l, only slightly above the reported detection limit for Method (1 mg/l). The Method detection limit for 3 of these 4 samples is 0.1 mg/l, with a detection limit at 1 mg/l for the fourth sample. Due to possible interferences with SM 4500 especially near the detection limits, SCC recommends using the non-detect results by Method 376.2, since they have the lower detection limits. Of the 22 influent samples in which sulfide was detected, 1 sample had sulfide detected by Method at 3 mg/l and by Method at 0.12 mg/l, with a non-detect by SM 4500-S' 2 (E). Due to possible interferences with the Method result especially near the method detection limit and because the Method result is lower than the SM 4500 detection limit, SCC recommends that the Method result be used. Of the 22 influent samples in which sulfide was detected, 2 samples had detected results by Method that were five times lower than the detection limits for Method and SM 4500-S' 2 Since the Method results are well below the capabilities of the other two methods, SCC recommends that the Method results be used. (E). MP&M Sulfide Method Evaluation 4 March 21, 2002

4 Summary of SCC Recommendations by Sample Attachment 1 The following tables summarize SCC recommendations regarding the post-proposal MP&M samples analyzed for total sulfide by MCAWW Methods and 376.2, and SM 4500-S -2 (E). All values shown are in units of mg/l. These tables also are available in an Excel file. Table Al. Recommended Detection Limits for Effluent Non-Detects Episode Sample M376.2 Detlimit SM 4500-S'2 (E) Detlimit MP&M Sulfide Method Evaluation 6 March 21, 2002

5 Table Al. Recommended Detection Limits for Effluent Non-Detects Episode Sample M376.2 Detlimit SM 4500-S -= (E) Detlimit Table A2. Recommended Detection Limits for Influent Non-Detects Episode 6455 Sample M376.2Detlimit SM 4500-S'2 (E) Detlimit MP&M Sulfide Method Evaluation 8 March 21, 2002

6 Table A3. Recommended Detection Limits for Unit Process Non-Detects Episode 6455 Sample M376.1Detlimit M376.2Detlimit SM 4500-S'2 (E) Detlimit MP&M Sulfide Method Evaluation 10 March 21, 2002

7 Table A4. Recommended Values for Samples with Detects by All 3 Methods Recommended Values for Effluent Detects Episode Sample M M SM4500 E Mean Recommended Values for Influent Detects Episode Sample M376.1 M376.2 SM4500 E Mean Recommended Values for Unit Process Detects Episode Sample M376.1 M376.2 SM4500 E Mean MP&M Sulfide Method Evaluation 1 2 March 21, 2002