ICMGP - Conference Presentation

Abstract Information :

Reactive gaseous mercury (RGHg) and particulate mercury (HgP) measurements over the marine boundary layer (MBL) has been investigated in many oceans, such as the North Atlantic, Arctic and Antarctic. RGHg was measured by either the KCl-coated denuder, as deployed in the Tekran instrument, or with cation exchange membranes (CEM). HgP was measured by either quartz wool-filled tube, as deployed in the Tekran instrument, or a regular quartz microfiber filter (QMA) for aerosol collection. Several recent studies have raised concerns on the suitability of the denuder for capturing RGHg. Also, HgP measured by the Tekran instrument can only measure the small size HgP group (< 10 ?m) and this leaves a knowledge gap of HgP characteristics for larger aerosols (sea salt). Therefore, we compared RGHg and HgP concentrations measured by the KCl-coated denuder/CEM and glass filter tube/QMA, respectively, on two cruises, which were the Pacific GEOTRACES GP15 cruise (from 18 September to November 24, 2018, between Alaska and Tahiti along 152øW) and an Arctic cruise (from May 20 to June 14, 2021, transiting from the Bering Sea into the Chukchi Sea, entering the ice edge around 70øN). In addition, methylated Hg (MeHg) was measured on the HgP collected by the QMA. For both cruises, RGHg was measured by the two approaches but with a low-volume sampler in the Pacific and high-volume sampler in the Arctic. However, HgP was measured by two approaches only during the Arctic cruise. Results will be discussed in terms of the comparison of RGHg and HgP measured by different approaches on the Pacific or Arctic cruises, and the influence of flow rate, and physical/chemical factors on the atmospheric RGHg and HgP. Additionally, the importance of MeHg in HgP, which varied with latitude, as a MeHg source to surface ocean by wet/dry deposition will be discussed.