Analytical Concerns in the Analysis of Gross Alpha-Beta in Wastewaters

Collaborative Efforts to Improve Environmental Monitoring - Session 2
Oral Presentation

Prepared by M. Alpizar
General Dynamics Information Technology, 6361 Walker Lane, Ste 300, Alexandria, Virginia, 22310, United States


Contact Information: mirna.alpizar@gdit.com; 703-485-2588

ABSTRACT

Radioactivity from naturally occurring and anthropogenic sources is present throughout the environment. The level of activity present in different water bodies is dependent on their geological characteristics, climate, and releases from wastewater treatment plants as well as from nuclear power plants. Under the Clean Water Act, a discharger may be required to monitor radioactivity levels in effluents prior to any discharge into the environment. Methods promulgated by EPA for the analysis of gross alpha and gross beta radioactivity have mainly focused on drinking water matrices; however, the methods also have been promulgated for use in wastewater testing. The main sample preparation approaches used in the promulgated methods are evaporation and coprecipitation. The evaporation methods have the main drawback of limiting the analysis to samples containing less than 500 mg of dissolved solids, as well as having interferences caused by the composition of salts within the sample. The coprecipitation method bypasses the challenge with the dissolved solids, but it does not account for attenuation, or the variation of weights in the presence of suspended solids, and it only allows for the analysis of gross alpha isotopes. Other issues include finding the appropriate isotopes for efficiency calibration, exclusion of volatile isotopes, and the cross-talk factor. In order to resolve some of these issues, new methods have been developed that use liquid scintillation counting instead of gas proportional counting; however, there are still concerns related to the use of liquid scintillation counting that have not been fully addressed in the new methods. In this presentation, we will discuss those emerging concerns and possible solutions to the analytical interferences related to the analysis of gross alpha and beta in wastewaters.