PARAGON 1 - KM2112 - Nitrogen In Situ Measurements

This dataset contains measurements of in situ nitrogen concentrations collected during the PARAGON 1 expedition (KM2112) in the North Pacific Subtropical Gyre. Measurements come from daily collections of whole seawater at 150 m using trace metal clean techniques. Samples for measurements of nitrogen concentrations were collected by subsampling 250 mL aliquots of whole seawater into high density polyethylene bottles and freezing upright at -20°C until analysis onshore. Nitrate plus nitrite (NO₃⁻ + NO₂⁻) concentrations were measured colorimetrically using segmented flow on a SEAL Autoanalyzer III with a high resolution detector as described by Foreman et al. (2019). Total nitrogen concentrations were measured similarly, following overnight UV oxidation of the sample according to Foreman et al. (2019). NO₂⁻ concentrations were measured using the high sensitivity chemiluminescent method described by Dore and Karl (1996) and Foreman et al. (2016). Ammonium (NH₄⁺) concentrations were determined using the high sensitivity fluorometric method of Holmes et al. (1999). For each analysis, reported values are the average of technical duplicate measurements from each sample. Timestamp is in UTC.