Colored dissolved organic matter

Spectral line

Quantum mechanics

Phytoplankton

Organic matter

Materials science

Absorption (acoustics)

Spectral slope

Soil water

Physics

Organic chemistry

Astronomy

Environmental chemistry

Fluorescence

Environmental science

Soil science

Composite material

Analytical Chemistry (journal)

Chemistry

Dissolved organic carbon

Humus

Nutrient

Isotope

The Science of The Total Environment

The present study demonstrates that the ratio of fluorescence integration of peak C to peak T (IC:IT) can be used as an indicator tracing the compositional dynamics of chromophoric dissolved organic matter (CDOM). CDOM absorption and fluorescence spectroscopy and stable isotope δ13C were determined on a seasonal basis in seventeen Chinese inland waters as well as in a series of mixing and photodegradation experiments in the lab. A strong positive linear correlation was recorded between IC:IT and the ratio of terrestrial humic-like C1 to tryptophan-like C4 (C1:C4) derived by parallel factor analysis. The r2 for the linear fitting between IC:IT and C1:C4 (r2=0.80) was notably higher than between C1:C4 and other indices tested, including the ratio of CDOM absorption at 250nm to 365nm, i.e. a(250):a(365) (r2=0.09), spectral slope (S275-295) (r2=0.26), spectral slope ratio (SR) (r2=0.31), the humification index (HIX) (r2=0.47), the recent autochthonous biological contribution index (BIX) (r2=0.27), and a fluorescence index (FI370) (r2=0.07). IC:IT exhibited larger variability than the remaining six indices and a closer correlation with stable isotope δ13C than that observed for a(250):a(365), S275-295, SR, FI370, and BIX during field campaigns. Confirming our field observations, significant correlations were recorded between IC:IT and the remaining six indices, and IC:IT also demonstrated notably larger variability than the six other indices during our wastewater addition experiment. Compared with HIX, eutrophic water addition and photobleaching substantially decreased IC:IT but had no pronounced effect on a(250):a(365), S275-297, SR, FI370, and BIX, further suggesting that IC:IT is the most efficient indicator of the CDOM compositional dynamics.

Fluorescence peak integration ratio IC:IT as a new potential indicator tracing the compositional changes in chromophoric dissolved organic matter