Abstract
This study evaluated the bioremediation of atrazine herbicide contaminated agricultural soil under different bioremediation strategies using indigenous Pseudomonas aeruginosa, Bacillus subtilis and Aspergillus niger as bioaugmentation agents and poultry droppings as biostimulation agent. The results showed that bioaugmentation with Pseudomonas aeruginosa, bioaugmentation with Bacillus subtilis, bioaugmentation with Aspergillus niger, bioaugmentation with bacterial-fungal consortium (Pseudomonas aeruginosa, Bacillus subtilis and Aspergillus niger) , biostimulation with poultry droppings, and combined biougmentation and biostimulation (Pseudomonas aeruginosa, Bacillus subtilis, Aspergillus niger and poultry droppings) resulted in maximum atrazine biodegradation of about 97%, 95%, 84%, 99%, 100% and 100%, respectively. The kinetics of atrazine biodegradation in the soil were modelled using first-order kinetic model and the biodegradation half-life estimated. The first order kinetic model adequately described the kinetics of atrazine biodegradation in soil under the different bioremediation strategies. The rate constants ( k1 ) of atrazine biodegradation in soil subjected to bioaugmentations with Pseudomonas aeruginosa, Bacillus subtilis, Aspergillus niger, and bacterial-fungal consortium ranges between 0.059 day-1 and 0.191 day-1 while for that subjected to natural bioattenuation, biostimulation and combined bioaugmentation and biostimulation are 0.026 day-1, 0.164 day- 1 and 0.279 day-1, respectively. The half-life ( 2 t1/ ) of atrazine biodegradation in soil under natural bioattenuation was obtained to be 26.7 days. This was reduced to between 2.5 and 11.7 days under the application of bioaugmentation, biostimulation and combined bioaugmentation and biostimulation strategies. The bioremediation efficiencies of the different bioremediation strategies in influencing atrazine biodegradation or removal is of the following order: Combined bioaugmentation and biostimulation > Bioaugmentation with bacterial-fungal consortium > Biostimulation with poultry droppings > Bioaugmentation with Pseudomonas aeruginosa > Bioaugmentation with Bacillus subtilis > Bioaugmentation with Aspergillus niger > Natural bioattenuation. Keywords : Atrazine; Bioaugmentation; Bioremediation; Biostimulation
Highlights
This study evaluated the bioremediation of atrazine herbicide contaminated agricultural soil under different bioremediation strategies using indigenous Pseudomonas aeruginosa, Bacillus subtilis and Aspergillus niger as bioaugmentation agents and poultry droppings as biostimulation agent
It is observed that the percentage atrazine biodegradation was relatively rapid within the first 15 days of remediation in all the soil subjected to bioaugmentation with Pseudomonas aeruginosa, bioaugmentation with Bacillus subtilis, bioaugmentation with Aspergillus niger, biostimulation with poultry droppings, bioaugmentation with bacterial-fungal consortium and combined bioaugmentation and biostimulation and rapidly continued up to day 30 when compared to that of the soil under natural bioattenuation
At the end of day 30, the atrazine concentration reduced from 50,000 mg/kg to 1,451±240, 2,450±350, 8,000±470, 480±40, 0 and 0 mg/kg corresponding to 97.1%, 95.1%, 84%, 100%, 99% and 100% reduction in atrazine contaminated soil subjected to bioaugmentation with Pseudomonas aeruginosa, bioaugmentation with Bacillus subtilis, bioaugmentation with Aspergillus niger, biostimulation with poultry droppings, bioaugmentation with bacterial-fungal consortium, and combined bioaugmentation and biostimulation, respectively
Summary
This study evaluated the bioremediation of atrazine herbicide contaminated agricultural soil under different bioremediation strategies using indigenous Pseudomonas aeruginosa, Bacillus subtilis and Aspergillus niger as bioaugmentation agents and poultry droppings as biostimulation agent. The bioremediation efficiencies of the different bioremediation strategies in influencing atrazine biodegradation or removal is of the following order: Combined bioaugmentation and biostimulation > Bioaugmentation with bacterial-fungal consortium > Biostimulation with poultry droppings > Bioaugmentation with Pseudomonas aeruginosa > Bioaugmentation with Bacillus subtilis > Bioaugmentation with Aspergillus niger > Natural bioattenuation. One of the most widely used herbicides in agriculture is atrazine (2chloro-4-ethylamino-6-isopropylamino-1,3,5triazine) (Ackerman, 2007; El-Bestawy et al, 2014; Cao et al, 2018) It is a non-polar, non-volatile and low soluble compound (El-Bestawy et al, 2014). This study aimed to experimentally investigate and evaluate the bioremediation of atrazine contaminated agricultural soil under different bioremediation strategies of bioaugmentation, biostimulation, bioaugmentation coupled with biostimulation (i.e. combined bioaugmentation and biostimulation), and natural bioattenuation
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