Data Package Metadata   View Summary

WATER COLUMN SAMPLING: We collected water samples for total and soluble Fe and Mn concentrations from Falling Creek Reservoir (FCR) and Beaverdam Reservoir (BVR) approximately fortnightly from March-April, weekly from May-October, and monthly from November-February. Water samples were collected at the deepest site of each reservoir using a 4-L Van Dorn sampler (Wildlife Supply Company, Yulee, FL). In FCR, water samples were collected at specified depths ranging from 0.1 m to 9.8 m. Additional water samples were collected from the primary inflow tributary. In BVR, water samples were collected at specified depths ranging from 0.1 m to 12.0 m. After collection, we poured raw water samples directly from the Van Dorn sampler into sample bottles for total metal analyses and we syringe-filtered water using 0.45 micron nylon filters into bottles for soluble metal analyses. All samples were preserved using trace metal grade nitric acid to pH less than 2.

SAMPLING TIMES: Most sampling occurred between the hours of 9:00 and 15:00. Some sampling occurred outside of these hours, including some overnight sampling; these instances are noted by the actual sampling time within the DateTime column. Samples with no exact sampling time recorded are reported as 12:00 in the DateTime column and flagged with a '1' in the Flag_DateTime column.

CHEMICAL ANALYSIS: In 2014-2015, samples were analyzed for Fe and Mn using an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS; Thermo Electron X-Series) following APHA Standard Method 3125-B (American Public Health Association et al., 1998). Detection limits for Fe and Mn were 0.0008 mg/L and 0.0005 mg/L, respectively, in 2014 and 0.0012 mg/L and 0.00007 mg/L, respectively, in 2015. In 2016-2019, samples were analyzed for Fe and Mn using an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) using a Spectro ARCOS SOP (Side-On Plasma interface) instrument using methods similar to EPA 200.7 (EPA, 1994). Detection limits for Fe and Mn were 0.004 mg/L and 0.001 mg/L, respectively. Starting in 2020, samples were analyzed for Fe and Mn using an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS; Thermo Electron iCAP-RQ) following APHA Standard Method 3125-B (American Public Health Association et al., 1998). Detection limits for Fe and Mn were 0.0004 mg/L and 0.00003 mg/L, respectively. The minimum reporting levels for Fe and Mn were 0.005 mg/L and 0.0001 mg/L, respectively. We used the minimum reporting levels as the lower threshold for data in 2020. Values that were below the minimum detection limit (for 2014-2019) or minimum reporting level (for 2020) were set to the value of the minimum detection limit or minimum reporting level. Negative values were set to 0.

REFERENCES: American Public Health Association (APHA), American Water Works Association, Water Environment Federation, 1998. Standard Methods for the Examination of Water and Wastewater, 20th ed. American Public Health Association, Washington, DC.

Environmental Protection Agency (EPA) (1994), Method 200.7: Determination of Metals and Trace Elements in Water and Waste by Inductively Coupled Plasma-Atomic Emission Spectrometry, Revision 4.4, May 1994, Environmental Monitoring Systems Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH 45268, T.D. Martin, C.A. Brockhoff, J.T. Creed and EMMC Methods Work Group