Analysis of Thorium (Th) and Uranium (U) in radioactive wastewater sample in accordance with American Public Health Association (APHA) 3125 method

Abstract

The main issue with thorium (Th) and uranium (U) in radioactive wastewater is the potential of these elements to contaminate the water bodies. The unregulated radioactive wastewater release can affect the ecosystem and potentially harm aquatic life. Therefore, there is a need to establish the analysis of Th and U using standard method to obtain better sensitivity and good confidence in the final report. In this study, the determination of uranium and thorium was employed using the American Public Health Association (APHA) method 3125 standard method. The method performance and method detection level (MDL) samples for APHA 3125 were prepared in the deionized water and digested using hot block (APHA 3030E) and microwave digester (APHA 3030K). The quantification of 238U, 235U and 232Th in the method performance and MDL samples was performed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). From the results, the method performance samples for both digestion methods were in accordance with the APHA requirement. The MDL obtained from APHA 3030E for 232Th, 238U, and 235U were 5, 7, and 8 μg L−1 respectively. Meanwhile, the MDL obtained from the microwave digester for 232Th, 238U, and 235U, and were 2, 3, and 3 μg L−1 respectively. The APHA 3030K digestion technique gives lower and better detection limit compared to the APHA 3030E technique. Based on APHA 3030K MDL, 232Th was detected in the radioactive wastewater sample while 238U and 235U were less than MDL. Meanwhile, for APHA 3030E, all elements were below MDL. This study will enhance the detection of uranium and thorium in the radioactive wastewater sample towards better environmental monitoring programs at the national and global levels.