Humic acids can be measured spectroscopically/colorimetrically. Humic acids have an absorption peak near 470nm. Environmental DNA is used today to detect which species are present in the sample. Unfortunately, I do not know the procedure for such analyses.

Arne Andersen CAN YOU PLEASE DESCRIBE THE PROCEDURE OF COLORIMETRIC ASSAY FOR HUMIC ACID.

I measure absorption at 470 nm in an untreated water sample. It can be converted to "colour", which is the unit in which humic acids are measured in Norwegian waters. Humic acids are normally the only source of brown color in the water. I found a PDF that might be interesting, can't find the address, but here's the full title: International Journal of Advanced Biotechnology and Research (IJBR) ISSN 0976-2612, Online ISSN 2278–599X, Vol-7, Special Issue-April, 2016, pp19-23 Determination of Humic Acid by Spectrophotometric Analysis in the Soils Amanollah Javanshah1 and Asiye Saidi2 1Pistachio research center, Rafsanjan, Iran 2Barafza keshavarze Pars Company. Rafsanjan, Special Economic Zone, Rafsanjan, Iran Email: [email protected], [email protected]

Arne Andersen thank you