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.