Inner filter correction of dissolved organic matter fluorescence

Abstract

The fluorescence of dissolved organic matter (DOM) is suppressed by a phenomenon of self‐quenching known as the inner filter effect (IFE). Despite widespread use of fluorescence to characterize DOM in surface waters, the advantages and constraints of IFE correction are poorly defined. We assessed the effectiveness of a commonly used absorbance‐based approach (ABA), and a recently proposed controlled dilution approach (CDA) to correct for IFE. Linearity between corrected fluorescence and total absorbance (ATotal; the sum of absorbance at excitation and emission wavelengths) across the full excitation‐emission matrix (EEM) in dilution series of four samples indicated both ABA and CDA were effective to an absorbance of at least 1.5 in a 1 cm cell, regardless of wavelength positioning. In regions of the EEMs where signal to background noise (S/N) was low, CDA correction resulted in more variability than ABA correction. From the ABA algorithm, the onset of significant IFE (>5%) occurs when absorbance exceeds 0.042. In these cases, IFE correction is required, which was the case for the vast majority (97%) of lakes in a nationwide survey (n= 554). For highly absorbing samples, undesirably large dilution factors would be necessary to reduce absorbance below 0.042. For rare EEMs with ATotal > 1.5 (3.0% of the lakes in the Swedish survey), a 2‐fold dilution is recommended followed by ABA or CDA correction. This study shows that for the vast majority of natural DOM samples the most commonly applied ABA algorithm provides adequate correction without prior dilution.

Decoupling of dissolved organic matter patterns between stream and riparian groundwater in a headwater forested catchment

“…A Milli-Q blank was subtracted from each sample to eliminate Raman scattering, sampling blanks were included to assess for leaching of DOM during the sampling procedure. We followed the procedure in Kothawala et al (2013) for inner filter correction. Briefly, Vis absorbance spectra (200-800 nm) were obtained in a Shimadzu UV-1700 spectrophotometer, using 1cm quartz cuvette.…”

Calibration, standardization, and quantitative analysis of multidimensional fluorescence (MDF) measurements on complex mixtures (IUPAC Technical Report)

“…Sample dilution is relatively easy to implement, but it adds a sample handling penalty (which is a source of error) that may not always be appropriate for the application. The mathematical correction approach (detailed below) is appropriate for some samples where the optical density is not too high, A < 1.5 [24]. The final option of essentially doing nothing (detailed below) and including IFE in the EEM/SFS analysis is also a valid option in applications where sample handling should be minimized.…”

Catchment tracers reveal discharge, recharge and sources of groundwater-borne pollutants in a novel lake modelling approach

“…Prior to PARAFAC analysis, fluorescence data was processed in R (3.3.1) using the eemR (0.1.3) package. Blank values were subtracted following the documentation provided in the eemR package removing Raman and Rayleigh scattering (Bahram et al, 2006;Lakowicz, 2006;Zepp et al, 2004) the data were then Raman normalized (Lawaetz and Stedmon, 2009) and lastly corrected for inner filter effect (Kothawala et al, 2013) before being exported to Matlab (2015b). In Matlab the fluorescence data was combined with a larger dataset (>1000 fluorescent samples originating from 120…”