Intercalibration studies of short-lived thorium-234 in the water column and marine particles

Intercomparision of 234 Th measurements in both water and particulate samples was carried out between 15 laboratories worldwide, as a part of GEOTRACES inter-calibration program. Particulate samples from four dif ferent stations namely BATS (both shallow and deep) and shelf station (shallow) in Atlantic and SAFE (both shallow and deep) and Santa Barbara station (shallow) in Pacific were used in the effort. Particulate intercali bration results indicate good agreement between all the participating labs with data from all labs falling with in the 95% confidence interval around the mean for most instances. Filter type experiments indicate no signif icant differences in 234 Th activities between filter types and pore sizes (0.2‐0.8 µm). The only exception are the