TITLE:
Mitigating Cadmium (Cd) Toxicity in Montane Forest Soils Using Biochar: Laboratory Trial for Soils from Horton Plains, Sri Lanka
AUTHORS:
Ranmalee Bandara, Priyantha Indralal Yapa, Rasanjali de Silva, Kasun Lakmini, Niluka Ranasinghe, Mahina Senevirathne
KEYWORDS:
Forest Dieback, Soil Amendments, Cadmium, Biochar, Natural Geosorbents
JOURNAL NAME:
Open Journal of Soil Science,
Vol.11 No.10,
October
26,
2021
ABSTRACT: Horton Plains (HP), 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) and the phenomenon of forest dieback. As a consequence, forest dieback is increasing proportionately to the soil pollution. Hence, this study focuses on identifying a cost-effective remediation technique to neutralize soil Cd, and thereby reducing forest dieback. Soil samples were collected from HP, mainly Thotupolakanda site which shows more than 90% severity of forest die back, and bulked together. The soil was high (13.4) in organic matter and low (5.42) in pH, and three soil amendments were tested in this research as; bio char prepared using 1) rubber nut shells, 2) rice husk, and 3) dead wood from HP. Each sample was spiked with 20 ml of 5 ppm (parts per million) Cd solution, and four treatments a) soil + rubber-nut shell biochar (T1), b) soil + rice husk biochar (T2), c) soil + wood-from-HP biochar (T3), and d) soil only (T4), with five (05) replicates, were setup. During the first eight weeks after the application of treatments, it was observed that T1 showed the best performance, by showing a consistent trend in reducing the available soil Cd, with T2 following closely. The interesting observation was that the natural forest soil (T4) was also able to buffer the loading of Cd. At the close of the experiment, it was observed that the available soil Cd goes almost to zero, in less than 24 months.