Measurements of radium isotopes (224Ra and 226Ra) in water column samples collected aboard R/V Point Sur cruise PS19_05 in the Gulf of Mexico from 2018-09-01 to 2018-09-04

This dataset contains measurements of radium isotopes (224Ra and 226Ra) in water column samples collected aboard R/V Point Sur cruise PS19_05 in the Gulf of Mexico from 2018-09-01 to 2018-09-04. The dataset also includes the location, date, time, and depth of the sample collection. Water samples were collected from Niskin bottles during CTD casts both at the Megaplume site and in a transect extending both up current and down current of the hydrocarbon seep. Samples were collected at discrete depths through the water column at locations atop the hydrocarbon seep (‘At plume’), 1 km upcurrent of the plume, and 1,2,3 km downcurrent of the plume. Sample volumes varied between 10.7 and 121.9 L. Sample volumes were passed slowly over acrylic fibers impregnated with MnO2 to quantitatively sorb dissolved radium isotopes, then counted immediately on a Radium Delayed Coincidence Counter for total 224Ra (produced by Scientific Computer Instruments) and subsequently three weeks later for supported 224Ra. The difference between these measurements represents the excess 224Ra, serving as our tracer of hydrocarbons in the marine environment. The samples were later analyzed for 226Ra on a radon emanation line. The cruise documentation was provided for the R/V Point Sur cruise PS19_05, led by chief scientist Dr. Richard Peterson.