Question

Describe two spectroscopic techniques used to differentiate the source of DOM (allochthonous vs. autochthonous) in water samples.

Answer 1

DOM is a heterogenous mixture of allochthonous and autochthonous organic compounds. The DOM influences water quality, redox processes, carbon cycling, transport of contaminants inthe aquatic ecosystem. To differentiate the allochthonous and autochthonous organic compounds from DOM, the folowing spectroscopic techniques can be used -

1. Excitation emission matrix Fluorescence (EEM) -

It is used to delineate the origin and metabolism of allochthonous and autochthonous DOM in marine ecosystems (such as found in Sundarban Mangrove). Allochthonous DOM are humic like fluorophores and autochthonous DOM are protein like fluorophores. The two fluorophores overlaps in EEM, resulting in complexity, that can be simplified by Parallel factor analysis.

2. UV Absorbance -

The bulk DOM aromaticity depends on Specific UV absorbance (SUVA). SUVA is the UV absorbance of the water sample at a given wavelength which is normalized for Dissolved organic carbon concentration. With the SUVA data, the chemical composition of DOM can be obtained.