Abstract:
Horton Plains, one of the two montane forests in Sri Lanka and habitat to many
endemic species of plants and animals, has been severely affected by forest dieback.
Past research has identified a direct link between soil pollution with Cadmium (Cd)
(through atmospheric pollution) and the phenomenon of forest dieback. As a
consequence, forest dieback is increasing proportionately to the soil pollution. As
such, it is imperative to protect Horton Plains and this study focuses on identifying
a cost-effective remediation technique to neutralize soil Cd thereby reducing forest
dieback. This experiment was conducted for a period of three months. Soil samples
were collected from Horton Plains, mainly Thotupolakanda site which showed more
than 90% severity of forest die back. The tree soil amendments used in this research
were bio char prepared using (i) rubber nut shells, (ii) rice husks and (iii) bio char
occurring naturally in Horton Plains. Along with the control treatment (only soil),
this experiment consisted of four treatments of 5 replicates. Treatments were added
to the soil samples, available Cd was extracted using standard methods in literature
and the Cd concentrations were analysed using the Atomic Absorption
Spectrophotometer (AAS). Horton Plains forest soil used for the study showed a pH
of 5.4 and a Cation Exchange Capacity (CEC) of 210 c moles kg -1. The soil was highly
rich with organic matter and the soil organic matter (SOM) content had reached
13.4%. Immobilization of Cd added to the soil was observed and it was significant
(p <0.03). However, the control treatment (only soil) has also shown its ability to
immobilize soil Cd. Thus, it appears that the presence of extraordinary level of SOM
and active natural sorbents in SOM such as humic acid and fulvic acid have masked
the effect of all the biochar treatments. The amount of Cd used for spiking the soil
was 0.1 µg and the minute quantity might have been immobilized by the SOM.
However the study proved the possibility of neutralizing Cd toxicity in the soil by
using natural sorbents and other treatments did not show that much of Cd
neutralizing
