Water preparation methods of dissolved organic fraction determination for C-14 AMS measurements

The determination of ¹⁴C in dissolved inorganic carbon (DIC) fraction has important task in nuclear environmental monitoring and water base protection. The aim of my research is to develop a preparation method for the ¹⁴C determination of dissolved organic carbon (DOC) and to develop sample preparation of total carbon containing both organic and inorganic fractions. In practice, the measurement of dissolved inorganic carbon (DIC) ¹⁴C is of essencial importance for example in environmental studies, as the amount of DIC is usually more than 100 times the amount of DOC and there is an easy, rapid preparation method. However, it is often difficult to interpret water dating and water residence time by measurement of dissolved inorganic fraction, because DIC dissolved in water can come from several sources: deep CO₂ uptake and bedrock dissolution, not only from the surface biogenic environment at the time of seepage. Therefore, the measurement of dissolved organic carbon (DOC) component gets more importance around nuclear facilities because of its efficiency in detection of anthropogenic effect. To this aim, preparation methods have been developed that are suitable to determine the specific ¹⁴C activity concentration of the total dissolved carbon (TD¹⁴C) as well as of the dissolved organic form (non-purgeable organic fraction). The measurement of ¹⁴C in organic form is a difficult task, the amount of material is usually very small (only a few µg) and samples are difficult to handle furthermore the necessary sample volume usually is more than 500 mL. One of the solutions for DO¹⁴C sample preparation is an application of wet oxidation method. In this case the organic components are oxidized by acid and CO₂ is extracted. This type of sample preparation technique is basically very sensitive about modern and fossil carbon contamination. However, the method has the additional disadvantage of high chemical demand (hence the contamination introduced) and a complicated and long sample preparation process. These disadvantages can be overcome by testing the total dissolved fraction ¹⁴C, which contains both fraction: inorganic and organic forms. Sample preparation can be performed in a significantly shorter time and at lower cost and can be used effectively alongside DI¹⁴C for the detection and monitoring of organic forms, for example in environmental monitoring of nuclear facilities. By determining DI¹⁴C and TD¹⁴C and carbon concentrations, DO¹⁴C can be estimated with a good approximation (±10% rel. error).

 

,,Prepared with the professional support of the Doctoral Student Scholarship Program of the Co-operative Doctoral Program of the Ministry of Innovation and Technology financed from the National Research, Development and Innovation Fund.”

The research was supported by the European Union and the State of Hungary, co-financed by the European Regional Development Fund in the project of GINOP-2.3.4-15-2020-00007 “INTERACT”.