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Browsing by Author "Brezonik, Patrick L"

Now showing 1 - 3 of 3
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    Combined UMN-MPCA 2014-2017 lake data on Secchi depth, CDOM, Chlorophyll and total suspended solids
    (2019-01-15) Brezonik, Patrick L; Hozalski, Raymond M.; Finlay, Jacques C; brezonik@umn.edu; Brezonik, Patrick L; University of Minnesota Water Quality by Remote Sensing Group
    This file contains approximately 1460 records on four water quality variables measured on near-surface water samples of lakes in Minnesota (primarily) and also in Wisconsin and Michigan collected by our research group from 2014 to 2017 and similar data collected by the Minnesota Pollution Control Agency in its annual lake water quality assessment program from 2015 to 2017. The variables are Secchi depth (SD), colored dissolved organic matter (CDOM) measured as the Napierian light absorption coefficient at 440 nm, chlorophyll-a, and total suspended solids concentrations. The database was used for a published paper to analyze the effects of CDOM on SD and show that high CDOM levels limit light penetration and thus SD in colored lakes.
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    Effect of dissolved iron on CDOM and other optical properties for dissolved organic matter in lakes and rivers of the Upper Great Lakes states
    (2019-01-23) Brezonik, Patrick L; Finlay, Jacques C; Hozalski, Raymond M; brezonik@umn.edu; Brezonik, Patrick L
    These files contain the raw field and lab data collected during sampling of lakes and a few rivers in 2014-2016 to evaluate the importance of dissolved iron concentrations in affecting apparent levels of colored dissolved organic matter (CDOM), as measured spectrophotometrically by light absorption coefficient at 440 nm, a(440), with additional sampling in 2018 for more specific purposes. Approximately 450 sets of measurements were made on 280 lakes/rivers during the field seasons of 2014-2016, with most of the sampling in two ecoregions of Minnesota -- the Northern Lakes and Forests (NLF) and the North Central Hardwood Forests (NCHF). Additional samples collected in these two ecoregions in neighboring Wisconsin and Michigan in 2016 and in the Northern Minnesota Wetlands (NMW) ecoregion of Minnesota also are in the database. Data collected in 2018 included depth profiles of a(440), iron, dissolved organic carbon (DOC), and basic water quality parameters on three NLF lakes and samples on about 20 colored lakes and rivers to evaluate the importance of particulate iron as a component of total iron. Experimental data for addition of dissolved iron (Fe(III)) to six lakes also is included.
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    Reflectance spectra and related water quality and color data from 325 Minnesota and Wisconsin lakes and rivers
    (2023-01-23) Olmanson, Leif G; Burket, Martha; Brezonik, Patrick L; olman002@umn.edu; Olmanson, Leif G
    This data set contains in situ reflectance spectra measured on 325 lakes and a few rivers broadly across the states of Minnesota and Wisconsin. The spectra were measured at the water surface at 1-nm intervals over the wavelength range 400-900 nm and are called "hyperspectra." Associated data include site identifications, key optical water quality variables measured on samples collected at the time of the reflectance measurements, two quantitative metrics of water color, dominant wavelength and hue angle, calculated from the hyperspectra, and values of the same two water-color metrics computed from simulated data for three satellite sensors (Sentinel-2 MSI, Sentinel-3 OLCI, and Landsat 8 OLI) derived from the hyperspectra using two published algorithms. The computed results are used to compare the reliability of the two published algorithms relative to the results obtained directly from the hyperspectra, which are considered to be the "true" values of dominant wavelength and hue angle metrics. In addition, the data set includes MATLAB code used in the computations.