DISTRIBUTION OF ZINC TOXICITY LEVELS IN SURFACE WATERS ACROSS WASHINGTON STATE

Since the mid-1800’s, extensive mining projects have riddled the state of Washington contaminating freshwaters with large concentrations of toxic waste. Recent studies have suggested that local water hardness can decrease toxicity levels of heavy metals including Cu and Zn. The purpose of this study was to investigate the distribution of Zn toxicity levels in surface waters across Washington. In 2018, the Washington Department of Fish and Wildlife collected 648 water samples from 100 waterbodies across the state during the Early Detection Zebra/Quagga Mussel Monitoring program. Samples were analyzed for Ca, Mg and Zn concentrations using an ICP-OES at Eastern Washington University. Ca and Mg concentrations ranged from 0.2 – 267.8 mg/L and 0.02 – 919.2 mg/L, respectively. Sample hardness was calculated as [CaCO₃] = 2.50[Ca]+4.1[Mg]. Further, acute and critical Zn toxicity levels were calculated based on CaCO₃ levels according to EPA guidelines. Approximately 25% of the samples exhibited Zn concentrations greater than critical toxicity levels. High levels of dissolved metals, including Zn, in surface waters have been linked to the decline in native fish populations such as the white sturgeon in the Upper Columbia River. Therefore, the large percent of toxic samples collected in Washington is especially concerning and likely poses an immanent threat to local ecosystems.