Influence of pH on fluorescent dissolved organic matter photo-degradation

Stephen A Timko; Michael Gonsior; William J Cooper

doi:10.1016/j.watres.2015.08.047

Influence of pH on fluorescent dissolved organic matter photo-degradation

Water Res. 2015 Nov 15:85:266-74. doi: 10.1016/j.watres.2015.08.047. Epub 2015 Aug 28.

Authors

Stephen A Timko¹, Michael Gonsior², William J Cooper³

Affiliations

¹ Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175, USA. Electronic address: stimko@uci.edu.
² University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, 146 Williams Street, Solomons, MD 20688, USA. Electronic address: gonsior@umces.edu.
³ Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175, USA. Electronic address: wcooper@uci.edu.

PMID: 26342180
DOI: 10.1016/j.watres.2015.08.047

Abstract

A novel semi-continuous excitation emission matrix (EEM) fluorescence and absorbance monitoring system has been developed. Full EEMs were collected simultaneously with absorbance spectra every 20 min during 24 h solar-simulated irradiation experiments, and the kinetic change of fluorescence of Suwannee River natural organic matter IHSS standard material (SRNOM) at various pH values was investigated. Parallel factor analysis (PARAFAC) was then used to isolate the photo-labile and pH-influenced fluorescent components of SRNOM. Kinetic analysis showed increasing rates of fluorescence loss with increasing pH. This has significant implications for the photo-degradation of dissolved natural organic matter during estuarine mixing, when large increases of pH are common. The influence of pH on fluorescence and photo-degradation kinetics emphasizes the need for pH to be monitored and accurately controlled during laboratory experiments. It is also highly recommended that when constructing PARAFAC models or monitoring changes in fluorescence data between samples of different origins, that the pH be held constant to remove any potential artifacts or misinterpretation of data.

Keywords: Absorbance; Dissolved organic matter; Excitation emission matrix fluorescence; PARAFAC; Photochemistry; pH dependency.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Environmental Monitoring / methods*
Fresh Water / chemistry
Humic Substances / radiation effects*
Hydrogen-Ion Concentration
Kinetics
Photolysis*
Rivers
Spectrometry, Fluorescence / methods*
Water Pollutants, Chemical / radiation effects*

Substances

Humic Substances
Water Pollutants, Chemical