Final report of periodic ambient mercury monitoring at Niigata-Maki Acid Deposition Monitoring station in Japan from 2021 to 2023 under the project of “Promoting Minamata Convention on Mercury by making the most of Japan’s knowledge and experiences

This document reports a pilot study of periodic ambient mercury monitoring conducted at the Niigata-Maki acid deposition monitoring station in Japan between October 2021 and October 2023. The project aimed to evaluate the feasibility and challenges of introducing ambient mercury monitoring using a gold trap method—intended for inclusion in Minamata Convention monitoring guidance—within existing monitoring sites, and it first established a mercury monitoring system at Niigata-Maki before implementing biweekly twenty-four-hour measurements. The report describes system setup, development and application of standard operating procedures, sample handling and laboratory analysis, and compilation of ancillary meteorological information. It presents time and seasonal variations in measured mercury concentrations, compares results with nearby monitoring locations, and documents operational issues encountered during routine sampling.