Dissolved and particulate Ba concentrations and Ba isotopic compositions (δ138Ba) were determined from two shelf-slope transects at 12 degree S and 14 degree S in the Peruvian upwelling zone. Samples were collected during cruises M136 and M138 in April and June 2017 using trace metal-clean GO-FLO bottles (profiles) and a towed-fish sampler (surface samples). Dissolved samples were filtered through 0.2 μm polyethersulfone (PES) filters (profiles) or AcropackTM capsule filters (Pall®; 0.8/0.2 μm; surface samples) into acid-cleaned low-density polyethylene (LDPE) bottles. Particulate samples were collected on the PES filters. These data are used to evaluate the partitioning of Ba isotopes between the dissolved and particulate phases.

<0.001 = below detection limitBottom depths shallower than the deepest CTD sample, likely due to the slight movement of vessel during sampling.Concentration units of pmol/L and nmol/L for pBa and other particulate metal elements were converted to pmol/kg and nmol/kg using potential density of individual sample, respectively.All seawater samples for nutrients were collected from Go-Flo bottles, except for station 56 whose nutrient samples were collected form Niskin bottle.