anna.ida3@gmail.com/2013

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

Diagram of the many possible environmental

flowpaths of humic substances

Sedimentary evolution

Diagenesis

Catagenesis

Metagenesisthe most advanced stage, where organic matter is almost

reduced to a carbonaceous residue

thermal degradation of the organic matter in sediment

generates hydrocarbons

organic matter loses mainly nitrogen, organic matter loses

mainly oxygen

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

carbohydrates

lipids

amino acids

humic acids (HA)

fulvic acids (FA)

humins

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.

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

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

Typical soil inputs

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)

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

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

Measurement

Precipitation Methods

Spectrophotometric

methods

Ash containing

measurement methods

standard approach for humic acidstandard approach for humic acid

rapid, less accurate methodrapid, less accurate method

typically only used for

measuring humic

content

Scheme for the isolation of humic substances from soil