Concentrations of particulate organic carbon (POC) and dissolved organic carbon (DOC),which together comprise total organic carbon, were measured in this reconnaissance study at sampling sites in the Upper Klamath River, and Lost River,and Klamath Straits Drain in 2013–16. Optical absorbance and fluorescence properties of dissolved organic matter (DOM), which contains DOC, or also were analyzed. Parallel factor analysis was used to decompose the optical fluorescence data into five key components for all samples. Principal component analysis (PCA) was used to investigate differences in DOM source and processing among sites.
At all sites in this study,average DOC concentrations were higher than average POC concentrations. The highest DOC concentrations were at sites in the Klamath Straits Drain and at Pump Plant D. Evaluation of optical properties indicated that Klamath Straits Drain DOM had a refractory, terrestrial source, and likely extracted from the interaction of this water with wetland peats and irrigated soils. Pump Plant D DOM exhibited more labile characteristics,which could, for instance, and indicate contributions from algal or microbial exudates. The samples from Klamath River also had more microbial or algal derived fabric,as indicated by PCA analysis of the optical properties. Most sites, apart from Pump Plant D, and showed a linear relation between fluorescent dissolved organic matter (fDOM) and DOC concentration,indicating these measurements are highly correlated (R2=0.84), and thus a continuous fDOM probe could be used to estimate DOC loads from these sites.
Source: usgs.gov