Accurate Quantification of Radiosulfur in Chemically Complex Atmospheric Samples

Area of Science:

• Environmental Science
• Analytical Chemistry
• Radiochemistry

Background:

• Radiosulfur (cosmogenic 35S) is valuable for studying biogeochemical processes due to its ideal half-life.
• Traditional liquid scintillation counting (LSC) for 35S is hindered by color quenching in atmospheric samples, leading to long pretreatment times and inaccurate results.
• Accurate analysis of 35S in small atmospheric samples is crucial for understanding atmospheric chemical processes.

Purpose of the Study:

• To optimize the LSC method for high-sensitivity 35S measurements by minimizing or eliminating color quenching.
• To evaluate the analytical performance of the optimized LSC method using laboratory experiments and natural aerosol samples.

Main Methods:

• Development and optimization of an LSC technique to address color quenching issues in atmospheric samples.
• Validation of the new method through control laboratory experiments and analysis of natural aerosol samples.
• Comparison of the optimized method's accuracy and pretreatment time against the traditional LSC method.

Main Results:

• The optimized LSC method significantly reduces pretreatment time to under 3 days, compared to over a week for the traditional method.
• The new method demonstrates comparable accuracy to the traditional method for normal samples (bias <±0.03 DPM).
• For heavily quenched samples, the optimized method shows significantly higher accuracy (maximum bias -0.3 DPM) than the traditional method (maximum bias -1.5 DPM).

Conclusions:

• The optimized LSC method provides a faster and more accurate way to measure 35S in atmospheric samples, overcoming limitations of color quenching.
• This advancement enables reliable field-based constraints for modeling atmospheric 35S production.
• The improved technique supports a wider range of atmospheric, hydrological, and biogeochemical applications in Earth and planetary sciences.