Factors influencing mobility and Adsorption of heavy metals
in soils. Understanding the process governing the migration
and plant availability of trace metals in soils is essential for
predicting the environmental impact of spreading metal
containing wastes on agricultural land. The adverse effect
of heavy metals is inseparably related to the soil’s ability
to adsorb and retain sub elements.
pH. The pH of the soil solution maintained at neutral to
slightly alkaline condition showed low mobility of all heavy
metals. To increase the mobility of heavy metals, the pH of
the soil solution should be lowered. The solubility of Pb in
soil solution was pH dependent, increasing as the pH was
adjusted from 6 to 3. At near neutral pH, the activity of
Pb2+ showed no clear relationship to pH and a small but
significant increase resulting from changing organic matter
content. In the near neutral pH range, higher Soil Organic
Matter (SOM) increases the Dissolved Organic Matter
(DOM), thereby promoting the formation of organo Pb
complexes and increasing Pb solubility (Sebastien Sauve,
1998). In acid soil, a mean value of 44% of the fractional
sum of Cd is associated with the exchangeable form; there
by enhance its mobility. There was about 10 times the
amount of Zn on exchange sites where the soil pH > 5.6
Cd (23%) is found in exchangeable form, implying that the
metal is relatively very mobile.