Dataset: PUMP CASTS

McLane WTS-LV08 in situ pumps were deployed on the CTD wire. Depth of deployment was determined by monitoring the depth of the CTD package and the wire interval let out between the CTD package & each pump. Pumps were pre-programmed to pump for a certain time interval, and were only retrieved once the time interval had completely passed.

Pumps were deployed with filters placed on “mini-MULVFS” filter holders (see Bishop et al., 2012, L&O Methods and Lam and Morris U.S. patent US 20130298702 A1), which contain 3 sequential filtering platforms for 142-mm diameter filters. When 2 filter pore sizes were used, the smaller pore size filter was placed against a lower frit on the filter holder, and the larger pore size filter was placed on the middle tier. When 3 filter pore sizes were used, all 3 filtering platforms were used, with the largest pore size filter on the top, and the smallest on the bottom frit. On a few occasions where 4 filter pore sizes were used, the two smallest filter pore size were placed together on the bottom platform (frit backing). Filters placed on the middle or top platform in all cases were placed with an additional backing mesh of 150 µm Nitex to maintain material integrity of the filter during flow.

After removal from water, filter holders were detached from pump, carried to an interior lab, and drained gently via vacuum filtration. Filters were removed under laminar flow hood. Samples intended for mercury and thorium analyses were treated using trace-metal clean techniques.