The Measurement of [35]S Retention in Incinerator Ash

The two main objectives of this study were to measure quantitatively the retention of [35]S in residual incinerator ash and to determine the optimal ash sampling method for use at NIEHS. In pursuing these objectives, 12 test burns with known activity and 6 control burns were performed using a dual chamber, starved-air, pathological waste incinerator. The two variables examined for their affects on the retention efficiency of [35]S in the ash were the type of vial incinerated (glass vs. polyethylene) and the chemical form of [35]S (methionine vs. sulfate). The three sample forms tested were ash taken directly from the incinerator, ash ground in a jar mill grinder and extraction fluid obtained using EPA's Extraction Procedure and Toxicity Test Method 1310. Samples from all 18 burns were counted using a liquid scintillation counter and a gas flow proportional counter. Because the data collected on the rough ash were considered to be biased and inconsistent, they were not used for any calculations of retention or mass reduction. A statistically significant difference in the mean [35]S retention was found between the methionine and sulfate forms of [35]s. The mean retention efficiency, considering both detectors and the ground ash and extract fluid sampling methods, for sulfate was 10.54% and for methionine was 1.51%. Ash from burns containing polyethylene and glass vials had a mean retention efficiency of 8.22% which was significantly higher than the 3.84% for burns with polyethylene vials only. It was concluded that until further research is done on the extraction procedure it is best for NIEHS to use the gas flow proportional counter and ground ash for routine sample counting to eliminate problems resulting from ash settling and quench associated with the liquid scintillation counter.Master of Science in Public Healt