Routine Estimation of Dissolved Organic Matter Sources Using Fluorescence Data and Linear Least Squares

Source identification of dissolved organicmatter (DOM)in surface waters using fluorescence is achieved using a simple andrapid linear regression method. Dissolved organic matter (DOM) isan important component of thebiogeochemistry and ecosystem function of streams and rivers. Unlikeinorganic nitrogen nutrients, organic nitrogen (DON) nutrients canvary considerably depending on the contributions of various sources.The properties of DOM in natural waters have been measured using fluorescencespectroscopy, which is inexpensive compared to more sophisticatedchemical analysis and is fast enough to enable its use in routinewater quality monitoring. However, estimating the contributions ofDOM sources to surface waters from fluorescence data in a similarlyefficient manner remains an area of active research. In this study,we develop a simple linear regression method for estimating the relativeamounts of DOM sources in a stream or river sample. The regressionestimates are more accurate than those of previous approaches andare orders of magnitude faster to compute. Codes and data to implementthe method are provided for a variety of computing environments tofacilitate use for water quality and research applications.