Abstract:
The application of pesticides has played an indispensable role in agriculture for centuries. Profenofos
is an organophosphorus pesticide, extensively applied for insect control in agriculture.
It poses health risks and disrupts beneficial microorganisms and insects, causing ecological imbalance.
Consequently, environment-friendly and sustainable remediation techniques should
be developed for pesticide detoxification. This study examines the use of Gliricidia sepium
biochar (GSB) as a carrier material to immobilise a Profenofos-degrading bacterium, Bacillus
megaterium, for the remediation of Profenofos-contaminated soil. Uncontaminated soils from
a 0-20 cm depth were collected from a hillside dense forest in Samanalawewa reservoir area,
Imbulpe, Sabaragamuwa Province. Three experimental setups were conducted to evaluate the
growth, shelf life, and pesticide degradation potential of the B. megaterium immobilized Gliricidia
sepium biochar (BM-GSB). Bacterial cultures were grown to an Optical Density (OD) of
1.0 at a wavelength of 600 nm, harvested, and immobilised onto biochar (1% w/v). The growth
of B. megaterium was evaluated by colony counting on agar plates and OD measurements of
solutions containing BM-GSB powder over successive days. The contaminated soil was prepared
by spiking 1.0 kg of sterilised soil with 200 ppm Profenofos pesticide solution. A batch
incubation experiment with four treatments was conducted, containing 50.00 g of soil samples.
They are unamended soil (control), Profenofos-contaminated soil, Profenofos-contaminated
soil amended with GSB, and Profenofos-contaminated soil amended with BM-GSB. Residual
Profenofos content was extracted and analysed via GC-MS. SEM imaging was performed
to observe bacterial adherence to the biochar surface. The shelf-life of B. megaterium on GSB
was 37 days, with high initial colony growth followed by a noticeable decline over time. The
pesticide degradation was evaluated using GC-MS. In the presence of GSB biochar, 70.97%
Profenofos reduction was achieved. A 37.83% reduction was observed when introducing the
BM-GSB. The SEM analysis confirmed the successful immobilisation of B. on GSB was 37
days, with high initial colony growth followed by a noticeable decline over time. The pesticide
degradation was evaluated using GC-MS. In the presence of GSB biochar, 70.97% Profenofos
reduction was achieved. A 37.83% reduction was observed when introducing the BM-GSB. The
SEM analysis confirmed the successful immobilisation of B.megaterium on GSB. The findings
suggest that BM-GSB was an effective, eco-friendly material for reducing Profenofos residues
in agricultural soils, offering a sustainable approach to soil detoxification.
