Small (1-53 µm) and large (>53 µm) marine particles were sampled on all three cruises using in situ pumps (WTS-LV, standard, 8 L min⁻¹; McLane Research Laboratories, East Falmouth); water was passed sequentially through 53 μm pore-size nylon mesh and 1 μm pore-size quartz microfiber (QMA) filters with 142 mm diameter using a mini-MULVFS filter holder (Bishop et al., 2012). On the spring cruise, one pump was equipped with a pump head and motor with a maximum flow rate of 30 L min⁻¹, and high volume samples of particles >53 µm were collected. The large particles collected on the nylon mesh were sonicated and concentrated into a pre-combusted 47 mm QMA filter.
Marine particles were collected in two size fractions, small particles in combusted quartz filters (1-53 μm) and large particles in a nylon mesh (> 53 μm) using in situ McLane pumps during the three research cruises.
The marine particles were analyzed for total Hg concentrations by acid assisted microwave digestions and aliquots were analyzed by cold vapor atomic fluorescence spectrophotometry.
For THg isotope determination samples were combusted in a two-stage combustion furnace and Hg(0) g was trapped in a 1% KMnO4 solution. The 1% KMnO4 solution was analyzed for Hg stable isotope composition using a multiple collector inductively coupled plasma mass spectrometer.
All the methods are detailed in Motta et al., (2019).
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