Results of Porewater Oxidation Trials to Determine Dissolved Total Hg at Younger Lagoon Reserve, Santa Cruz California, USA (2019-2023)

This “Porewater-Oxidation” dataset was prepared to accompany the publication "Improved Total Mercury Analysis in High C and S Estuarine Porewaters using Longer Oxidation Times", Calvin et al., in prep. The overlying water and porewater analyzed to produce the data provided here was collected at the University of California Natural Reserve System’s Younger Lagoon Reserve, doi: (10.21973/N3894D). Sampling sites included Beach Zone (BZ; 36.949380 N, -122.067624 W), at the southern edge of the lagoon, characterized by sandy sediment and a close connection to the ocean and East Fork (EF; 36.951483 N, -122.066275 W), at the northern boundary of the lagoon, characterized by organic-rich, clay sediment and spatial proximity to agricultural sites. Sampling events took place in December 2019, April 2020, October 2020, and September 2023. This dataset contains porewater dissolved total mercury (HgT) concentrations accompanied by porewater acid volatile sulfide (AVS) concentrations. Other characteristics of overlying and porewater from the same sampling dates also include: pH, oxygen saturation, temperature, and salinity. The dataset provided here reports the HgT concentrations that resulted from oxidative digestion trials comparing EPA Method 1631e to a heated water bath and extended oxidation time (14-day and 21-24-day) room temperature digestions. The investigation was designed to reveal conditions that would best oxidize ligands while minimizing the reagent blank and was conducted with a range (0.25-5% v/v) of bromine monochloride (BrCl) concentrations. A 24-day digestion allowed more HgT to be detected compared to a 14-day digestion or a heated water bath.