Senior Project Advisor

Catherine Clark

Document Type


Publication Date

Fall 2020


Chromophoric Dissolved Organic Matter, CDOM, Dissolved organic matter, DOM, dissolved organic carbon, DOC, photochemistry, Hoag's Pond, fluorescent spectroscopy, freshwater study


Dissolved organic matter (DOM) plays an important role in carbon cycling in lakes and ponds. DOM sources may vary with elevation due to vegetation differences. To examine this, optical properties of chromophoric dissolved organic matter (CDOM) were investigated between a season with heavy rainfall (wet season) and a season without much rainfall (dry season) in Hoag’s Pond, Washington, USA. This is the first study of CDOM optical properties on Hoag’s pond. Data shows that there is an increase of CDOM in Hoag’s Pond during wet season as compared to dry. Three-dimensional fluorescence excitation-emission matrices (EEM’s) showed that Hoag’s Pond contains allochthonous terrestrial humic-like peaks A and C. Fluorescence intensities were higher for wet season samples than dry season samples, indicating an increase of CDOM between seasons. Two fluorescence indices obtained from EEMs showed no statistically significant difference between dry and wet season; FI ranged from 1.28-1.3, indicating terrestrial material, and the BIX average was 0.66, indicating limited autochthonous contributions. The HIX index however was statistically significantly lower for dry season (3.46 as compared to 4.64), suggesting a higher proportion of autochthonous non-humic material during dry season. Water probe data indicates that conductivity (maximum 793μS ± 1% FS versus 1382μS ± 1% FS), total dissolved solids (maximum at 435ppm ± 1% FS versus 982ppm ± 1% FS), and salinity (maximum at 0.31ppt ± 1% FS versus 0.69 ppt ± 1% FS) values are statistically significantly higher for wet season, indicating a higher proportion of electrolytic, conductive material during wet season. The pH changes between seasons were not statistically significantly different, as the pH ranged from 6.34-7.30 ± 0.02 pH unit. These findings are consistent with increased inputs of allochthonous terrestrial material and decreased sources of autochthonous material between the transition from dry to wet season.



Subjects - Topical (LCSH)

Water--Organic compound content--Washington (State)--Bellingham; Fluorescence spectroscopy--Washington (State)--Bellingham; Photochemistry

Geographic Coverage

Bellingham (Wash.)


fieldwork (research)




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