Measurement of dissolved organic matter fluorescence in aquatic environments: an interlaboratory comparison.
The fluorescent properties of dissolved organic matter (DOM) are often studied in order to infer DOM characteristics in aquatic environments, including source, quantity, composition, and behavior. While a potentially powerful technique, a single widely implemented standard method for correcting and presenting fluorescence measurements is lacking, leading to difficulties when comparing data collected by different research groups. This paper reports on a large-scale interlaboratory comparison in which natural samples and well-characterized fluorophores were analyzed in 20 laboratories in the U.S., Europe, and Australia. Shortcomings were evident in several areas, including data quality-assurance, the accuracy of spectral correction factors used to correct EEMs, and the treatment of optically dense samples. Data corrected by participants according to individual laboratory procedures were more variable than when corrected under a standard protocol. Wavelength dependency in measurement precision and accuracy were observed within and between instruments, even in corrected data. In an effort to reduce future occurrences of similar problems, algorithms for correcting and calibrating EEMs are described in detail, and MATLAB scripts for implementing the study's protocol are provided. Combined with the recent expansion of spectral fluorescence standards, this approach will serve to increase the intercomparability of DOM fluorescence studies.
School of Civil and Environmental Engineering, The University of New South Wales, Sydney, New South Wales 2052, Australia. krm@unsw.edu.au
Kathleen R
KR
Murphy
Kenna D
KD
Butler
Robert G M
RG
Spencer
Colin A
CA
Stedmon
Jennifer R
JR
Boehme
George R
GR
Aiken
D004784:Environmental Monitoring / Q000379:methods*; D005453:Fluorescence; D005618:Fresh Water / Q000737:chemistry*; D007753:Laboratories; D015588:Observer Variation; D009930:Organic Chemicals / Q000032:analysis* / Q000737:chemistry / Q000592:standards; D013050:Spectrometry, Fluorescence; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry / Q000592:standards
D009930:Organic Chemicals; D014874:Water Pollutants, Chemical