Review of the analysis of 234 Th in small volume (2–4 L) seawater samples: improvements and recommendations

The short-lived radionuclide 234 Th is widely used to study particle scavenging and transport from the upper ocean to deeper waters. This manuscript optimizes, reviews and validates the collection, processing and analyses of total 234 Th in seawater and suggests areas of further improvements. The standard 234 Th protocol method consists of scavenging 234 Th from seawater via a MnO 2 precipitate, beta counting, and using chemical recoveries determined by adding 230 Th. The revised protocol decreases sample volumes to 2 L, shortens wait times between steps, and simplifies the chemical recovery process, expanding the ability to more rapidly and safely apply the 234 Th method.