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2 Have you ever heard HUMUS?? A brown to black complex variable of carbon containing compounds as possessing cellular organization in the form of plant and animal bodies Derived from plant and animal detritus changes through biochemical processes

3 Diagram of the many possible environmental flowpaths of humic substances

4 organic matter loses mainly nitrogen, organic matter loses mainly oxygen Diagenesis Sedimentary evolution Catagenesis thermal degradation of the organic matter in sediment generates hydrocarbons Metagenesis the most advanced stage, where organic matter is almost reduced to a carbonaceous residue

5 The major organic elements in sedimentary humic substances are carbon, hydrogen, oxygen, nitrogen, and sulfur Terestrial Humus Low alifatic structure High lignin Marine Humus High alifatic structure Low lignin

6 carbohydrates lipids amino acids humic acids (HA) fulvic acids (FA) humins

7 Organic matter which change : lignin, sulfonat, tannin, pectin, polisakarida Create humus substances with large molecul weight Humus is the major soil organic matter component, making up 65% to 75% of the total Humus assumes an important role as a fertility component of all soils, far in excess of the percentage contribution it makes to the total soil mass.

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9 the fraction of humic substances that is soluble in water under all ph conditions remains in solution after removal of humic acid by acidification light yellow to yellow-brown in color the fraction of humic substances that is not soluble in water under acidic conditions (ph < 2) but is soluble at higher ph values can be extracted from soil by various reagents and which is insoluble in dilute acid the major extractable component of soil humic substances dark brown to black in color the fraction of humic substances that is not soluble in water at any ph value and in alkali black in color

10 Comprise a mixture of weak aliphatic and aromatic organic acids Not soluble in water under acid conditions but are soluble in water under alkaline conditions Consist of that fraction of humic substances that are precipitated from aqueous solution when the ph is decreased below 2 Readily form salts with inorganic trace mineral elements

11 Typical soil inputs

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13 A mixture of weak aliphatic and aromatic organic acids which are soluble in water at all ph conditions (acidic, neutral and alkaline) Smaller than humic acids (HAs), with molecular weights which range from approximately 1,000 to 10,000 Have an oxygen content twice that of humic acids (HAs), many carboxyl (-COOH) and hydroxyl (-COH) groups Much more chemically reactive : the exchange capacity is more than double that of humic acids (HAs)

14 The ratio of fulvic acid to humic acid decreases with the burial depth of a sediment Fulvic acid seems to result principally from the oxidation of organic matter The formation of fulvic acid decreases with burial depth, because there is no more oxygen in the sediment The fraction already present in the sediment is eliminated from the sediment by solubilization in the pore water or mineralization by bacteria

15 Fraction of humic substances which are not soluble in alkali (high ph) and are not soluble in acid (low ph) Not soluble in water at any ph Humins present within the soil is the most resistant to decomposition (slow to breakdown) of all the humic substances To improve the soils water holding capacity, to improve soil structure, to maintain soil stability

16 Measurement standard approach for humic acid Precipitation Methods Ash containing measurement methods rapid, less accurate method Spectrophoto metric methods typically only used for measuring humic content

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18 Scheme for the isolation of humic substances from soil

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