Abstract:
Forest dieback in the Upper Montane Rain Forest in Sri Lanka, Horton Plains, has by
now grown out of control resulting in a disastrous environmental problem in the
country. Horton Plains may be the most important forest resource in the country in
terms of its service offered as the major water catchment and the biodiversity hot
spot. Soil pollution by Pb has been identified as one of the major reasons for the
forest dieback in Horton Plains. This study focuses on finding a cost-effective
solution to remediate the contaminated soils in Horton Plains. The efficacy of three
(3) natural geo-sorbents made from plant materials were used to assess the
immobilization of soil Pb. Soil samples collected from the worst affected area with
100% forest dieback, Thotupolakanda in Horton Plains, were used for the
laboratory trial. Three types of biochar materials, i.e. (a) Rubber Nut Shell (RNB) (b)
Rice Husk (RBH) and (c) Naturally developed Biochar (HPB) in Horton Plains, were
used to study the immobilization capacity of them with Pb in contaminated soils.
Soils were spiked with standard Pb, treated with biochar and left for incubation at
room temperature for 14 weeks. Soil pH and the Cation Exchange Capacity (CEC)
were recorded as 5.4 and 210 c mols kg-1 respectively. Soil organic matter (SOM)
content was extraordinarily high at 13.4%. Soluble Pb in each treatment was
analyzed in the Atomic Absorption Spectrophotometer (AAS). Before adding
treatments, the content of Pb in all the biochar types used for the study was analyzed
and was undetectable. It was evident that the Pb immobilization capacity of RBH
was the highest followed by RNB (P< 0.0001). HPB was proven to be ineffective in
immobilizing soil Pb. HPB collected from Horton Plains have not been made under
controlled pyrolysis process and cannot even be considered as biochar. Thus, RBH
appears to be a cost-effective material to remediate Pb contaminated soils in Horton
Plains
