Thorium determination in seawater by inductively coupled plasma mass spectrometry: Method development and oceanographic applications

Thorium isotopes in the ocean (including radiogenic isotopes and terrigenous-derived 232Th) serve as key tracers for studying land-derived material transport. While high-sensitivity and high-resolution inductively coupled plasma mass spectrometry (ICP-MS) has become the mainstream technique for seawater thorium isotope analysis, its application faces three major challenges: complex pretreatment purification procedures, varying sample volume requirements, and significant instrument memory effects. This review systematically summarizes the technical difficulties and solutions in ICP-MS-based thorium isotope detection and examines its oceanographic applications in quantifying dust inputs and tracing water mass mixing, thereby providing critical data for assessing marine carbon pump efficiency.