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

The short-lived radionuclide 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 Th in seawater and suggests areas of further improvements. The standard Th protocol method consists of scavenging Th from seawater via a MnO precipitate, beta counting, and using chemical recoveries determined by adding 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 Th method.