Degradation of Monocrotophos in Sandy Loam Soil by Aspergillus sp

Abstract

The present study premeditated to explore and compare the potential of Aspergillus sp. to degrade monocrotophos in soil. Two different strains of Aspergillus sp. viz Aspergillus niger JQ660373 and Aspergillus flavus, were tested under anaerobic conditions for their monocrotophos (150 μg Kg) degrading ability in sandy loam soil for a period of 30 days. The water-holding capacity was maintained at 60% and samples were incubated at 25 ± 4 °C. After regular time interval of 5 days, the samples were collected and estimated for residual monocrotophos concentration. Residual monocrotophos was extracted with ethyl acetate and estimated by spectrophotometric method at 254nm. The degradation of monocrotophos in soil was observed to be rapid and followed first order kinetics. A 99% of applied pesticide was degraded within 30 days of incubation. It was found that Aspergillus niger was more efficient for the degradation of monocrotophos than Aspergillus flavus. The half life of monocrotophos for Aspergillus niger and Aspergillus flavus was found to be 7.35 and 9.23 days, respectively. Degradation process was assessed by HPTLC and FTIR analysis. These revealed reduction in the peak of standard monocrotophos as a measure of hydrolytic cleavage of vinyl bond with the formation of inorganic phosphates and release of carbon dioxide and ammonia. It could be concluded from the study that these two fungal strains had the ability to degrade monocrotophos in soil. doi: 10.5829/idosi.ijee.2015.06.01.10 Monocrotophos (MCP) is a broad-spectrum organophosphorus (OP) insecticide and acaricide, developed by Ciba-Geigy (now Novartis) and was first registered in 1965. MCP is widely used for agricultural and household purposes; it works systemically as multipurpose agrochemicals pesticides [4]. It is characterized by a P–O–C linkage and amide bond and is a perilous chemical especially for conditions of use in developing countries [5]. It has been barred due to its acute toxicity against beneficial and non-target insects such as honey bees [6, 7], fish [8] birds and mammals [9]. However, its usage for the control of major insect pests in agriculture has been continued in developing countries like India, primarily due to lack of alternative replacements [10]. Use of temporary suspension of pyrethroid insecticide resulted in the development of high resistance to pests [11]. This ultimately led to reliance on cheap insecticides such as MCP for control of pests in agriculture. It is surprising to know that MCP had a lion’s share (one-third) of total sales of pesticides in 1996 alone in India. Despite of its indiscriminative and wide usage, only limited number of studies were undertaken to find its impact on agroecosystem under tropical conditions. Although it has short-life on different agricultural crops [12-16] and in soil [17] but frequent exposure to pests developed moderate insecticide resistance in them [18]. But still nervous system of different pests as well as humans and soil ecology is adversely affected by this perilous chemical. In view of all these facts degradation Please cite this article as: R. Jain, V. Garg, 2015. Degradation of Monocrotophos in Sandy Loam Soil by Aspergillus sp., Iranica Journal of Energy and Environment, 6 (1): 56-62. *Corresponding Author: Rachna Jain. E-mail: rachna11587@gmail.com INTRODUCTION Soil is a complex matrix containing different component viz. chemical, physical and biological. They undergo constant changes due to environmental factors and anthropogenic management [1-3]. Therefore, it is best known as the sink of pesticide residues. Iranica Journal of Energy and Environment 6(1): 56-62, 2015