Evaluation of the linear mixing model in fluorescence spectroscopy

TL;DR

This study assesses the validity of the linear mixing model in fluorescence spectroscopy of dissolved organic matter, finding it effective for high-fluorescence components but less reliable for low-fluorescence ones.

Contribution

It provides a statistical evaluation of the linear mixing hypothesis in fluorescence spectroscopy, highlighting its strengths and limitations for different endmember fluorescence levels.

Findings

Linear mixing model accurately recovers high-fluorescence endmember abundances.

Low-fluorescence endmember estimates show high variability.

No strong statistical evidence against linear mixing for high-fluorescence data.

Abstract

Analyses of spectral data often assume a linear mixing hypothesis, which states that the spectrum of a mixed substance is approximately the mixture of the individual spectra of its constituent parts. We evaluate this hypothesis in the context of dissolved organic matter (DOM) fluorescence spectroscopy for endmember abundance recovery from mixtures of three different DOM endmembers. We quantify two key sources of experimental variation, and statistically evaluate the linear mixing hypotheses in the context of this variation. We find that there is not strong statistical evidence against this hypothesis for high-fluorescence readings, and that true abundances of high-fluorescence endmembers are accurately recovered from the excitation-emission fluorescence spectra of mixed samples using linear methods. However, abundances of a low-fluorescence endmember are less well-estimated, in that the abundance coefficient estimates exhibit a high degree of variability across replicate experiments.