Dissolved aluminum (Al) and manganese (Mn) and total dissolvable Al and Mn from surface water samples collected during three cruises in 2010 in the northern Gulf of Alaska

Water samples were collected along a transect during three cruises in 2010 (7-9 April, 5-7 May, and 27-29 July) in the northern Gulf of Alaska, from the mouth of the Copper River to about 50 km past the shelf break. Surface samples were collected by underway pumping using Teflon-lined tubing, using a method modified from Vink et al. (2000). Filtered dissolved metal surface samples were collected using a 0.45 µm in-line Acropore filter under N₂ pressure. Water samples were processed in the shipboard clean lab within three hours of collection. Dissolved samples were filtered using acid-washed 0.45 µm Pall-Supor filters. All samples were acidified to pH 1.8 using Seastar grade HCl within 3 days and stored for 5 years before analysis.

Filtered samples were analyzed for dissolved Al and unfiltered samples were analyzed for total dissolvable Al using Flow Injection Analysis (Resing and Measures 1994) using fluorescent detection of lumogallion. Filtered samples were analyzed for dissolved Mn and unfiltered samples were analyzed for total dissolvable Mn according to the method of Resing and Mottl (1992), which uses spectroscopic detection of leuchomalachite green.