Chemistry of Orange and Reference Streams in Northwestern Alaska

Stream water quality parameters (temperature, specific conductivity, pH, and dissolved oxygen) were measured in situ using a YSI Professional Plus multi-parameter instrument. All probes were regularly calibrated following standard methods.

Samples were collected in the field using a peristaltic pump. Silicon tubing (size 15) was connected to a Geotech 2 peristaltic pump to collect water samples, approximately 25-50 cm below the stream surface in a well-mixed location. Four samples were collected, one unfiltered whole water sample for metals, and three samples filtered with a Geotech disposable capsule filter (0.45 micrometer pore size). Filtered samples were analyzed for sulfate, dissolved metals, and stable isotopes of water.

All samples were measured by B. Poulin and T. Evinger at the University of California Davis. Inorganic sulfate was quantified using ion chromatography on a Metrohm IC, Metrosep A Supp 7 Column, and Metrosep A Supp 5 Guard Column following standard methods (Brinton, et al., 2016). Calibration and quality control standards were purchased from Inorganic Ventures Lab Inc. For unfiltered raw acidified samples, samples were digested in the laboratory by acidifying to 3 percent volume/volume with Omni-Trace nitric acid, heating for 8 hours at 65 degrees Celsius in Teflon vessels, and filtering. Digested raw acidified samples and filtered acidified samples were analyzed for metal content by inductively coupled plasma- mass spectrometry (Thermo-Fisher iCAP-RQ ICP-MS) following standard methods (Garbarino and Taylor, 1979). Calibration standards were purchased from Inorganic Ventures Lab Inc. (IV-Stock-50) and the National Institute of Standards and Technology (NIST 1643f, IV-ICPMS-71A).