An analytical method for 14C in environmental water based on a wet-oxidation process

Abstract

An analytical method for 14C in environmental water based on a wet-oxidation process was developed. The method can be used to determine the activity concentrations of organic and inorganic 14C in environmental water, or total 14C, including in drinking water, surface water, rainwater and seawater. The wet-oxidation of the organic component allows the conversion of organic carbon to an inorganic form, and the extraction of the inorganic 14C can be achieved by acidification and nitrogen purging. Environmental water with a volume of 20 L can be used for the wet-oxidation and extraction, and a detection limit of about 0.02 Bq/g(C) can be achieved for water with carbon content above 15 mg(C)/L, obviously lower than the natural level of 14C in the environment. The collected carbon is sufficient for measurement with a low level liquid scintillation counter (LSC) for typical samples. Extraction or recovery experiments for inorganic carbon and organic carbon from typical materials, including analytical reagents of organic benzoquinone, sucrose, glutamic acid, nicotinic acid, humic acid, ethane diol, et cetera., were conducted with excellent results based on measurement on a total organic carbon analyzer and LSC. The recovery rate for inorganic carbon ranged tween 98.7%–99.0% with a mean of 98.9(±0.1)%, for organic carbon recovery ranged between 93.8% and 100.0% with a mean of 97.1(±2.6)%. Verification and an uncertainty budget of the method are also presented for a representative environmental water. The method is appropriate for 14C analysis in environmental water, and can be applied also to the analysis of liquid effluent from nuclear facilities.