For detailed water sampling protocols see the Arctic LTER Land-Water group protocol book accessible from the Land-Water main page on the Arctic LTER web page or at http://www-personal.umich.edu/~gwk and clicking on the protocol link at the bottom of the page. A brief method is provided below.

In general water samples from soils, streams, and lakes are filtered in the field and kept cold and dark or preserved until analysis. Water samples for DOC are collected in acid-washed opaque polyethylene bottles, kept dark and cool until they are filtered through Whatman GF/F filters (nominal pore size 0.6 microns), then acidified to pH<4 with trace-metal grade 6N HCl (~ 1 microliter of acid per 1 milliliter of sample). Samples are then stored in the dark at ~4 deg C until analysis at the University of Michigan on a Shimadzu TOC-5000 with a high-temperature, platinum-catalyzed combustion to CO2 and infrared detection.

Missing values (not sampled or analyzed) are represented by a period " . " in the dataset.
Field and Lab Methods & Protocols

http://ecosystems.mbl.edu/arc/landwater/lw_protocols.html
http://arc-lter.ecosystems.mbl.edu/landwater/lw_protocols