Natural organic matter (NOM)
"Natural organic matter (NOM) is the generic term for a mixture of organic, slightly water-soluble components. The most general route for NOM in soil, sediments, and natural waters are humic substances that contribute to the brownish-yellowish color of natural waters. The composting activities of microbes on dead plant tissues, dead organisms, and excrement of living organisms produce these humic substances. NOM mostly consists of humic (humic acid (HA) and fulvic acid (FA)) and nonhumic fractions, which are carbohydrates, amino acids, and proteins." (Darko, B., 2014)
Darko, B., and Sharma, V. K. Advances made in understanding of ferrate (VI) with natural organic matter in water. 2014. Water Reclamation and Sustainability.