L1 /
17
CH3041
SOIL FULVIC ACIDS
• Humic matter is dark brown, acidic and refractory (resists biodegradation) material.
• t½ soils 500yr (t½ river 20yr)
• Fulvic acids make up
25-75% of the organic fraction of
soils.
• FAs play a major role in the transport
and
deposition of Fe, Al and other metals in the soil. The FA ligands complex with Fe3+ and Al3+ allowing ¯ movement through the soil.
deposition of Fe, Al and other metals in the soil. The FA ligands complex with Fe3+ and Al3+ allowing ¯ movement through the soil.
• As the ligands in
the Fe, Al complexes are oxidised on their downward movement the metals are deposited as oxyhydroxides – typically
in the B horizon. (BIF formation)
•Coprecipitation of other
metals then occurs
