Aqueous arsenic, oxygen, temperature, and plankton arsenic content in urban lakes in the Puget Sound lowland from September 2015 to August 2016

Angle Lake, Lake Killarney, North Lake, Steel Lake (western WA) were sampled monthly or bi-monthly from September 2015 to August 2016. Water column temperature and dissolved oxygen profiles were measured using a multi-parameter water quality probe (In-Situ smarTROLL MP) at approximately the deepest point in each lake. A peristaltic pump with acid-washed tubing was used to collect filtered (0.45 µm Geotech cartridge filter) water samples into acid-washed polypropylene bottles that were acidified with trace metal grade nitric acid (1% v/v). Phytoplankton (20-153 micron) and zooplankton (>153 micron) tow samples were filtered onto 5 µm polycarbonate membrane filters then subjected to a microwave-assisted (CEM MARS 5) total digestion protocol (modified EPA method 3015). Aqueous arsenic concentrations in water samples and plankton digestion solutions were determined by ICP-MS on an Agilent 7900 at the University of Washington Tacoma.