Design and Testing of an Electrochemical Trace Pesticide Assessment System in Soil Run-Off
Authors: Dhamu Vikram Narayanan , Muthukumar Sriram , Prasad Shalini 
Published: July 2022

Despite recent efforts and breakthroughs in the development of environmental biosensors, one particular vital component of the environment has been probed comparatively much more sparsely-namely, the soil ecosystem that directly and indirectly affects the agricultural health and throughput as well as ecosystem balance. One specific problem that is understudied is the application of pesticides in crops and other plants often finds its way seeping into soil in a large manner and there exists a leaching effect at the soil and ground water sources. This causes long-term effects that is deteriorating for environmental as well as human health- due to soil and ground water contamination that further causes dampening of food production and safety as well as causing acute and chronic diseases in the human body. The potential for a sensor system that detects in-field: the levels of pesticide residue in soil run-off is immense and would be beneficial to understand its negative effect on food security and food safety by inhibiting soil microbial activity and therefore impacting crop throughput and food quality. This field deployable sensor probe would help promote responsible agricultural practices and curb overapplication of harmful agents to the soil. Electrochemistry proves to be a viable choice of application for such a sensor to track pesticides in soil samples due to its feasibility for in-situ analysis used as well as solving for the ASSURED criteria as given by the World Health Organization (WHO), wherein it denotes- Affordable, Sensitive, Specific, User-friendly, Rapid, and robust, Equipment-free and Deliverable to end-users. The proposed system would have to utilize minimally complex sensor modification/functionalization and no pre-processing of samples. Hence citing all these factors and requirements, in this work- we present a highly intuitive electroanalytical sensor approach towards rapid, on-demand screening of 2 commonly used pesticides in this proof-of-feasibility study- Glyphosate and Atrazine in soil run-off which have a half-life of 47 days and 60-75 days respectively. By studying the levels of soil contaminant residues at the field site-the sensor acts as a screening instrument for soil pollution levels. The proposed sensor functions based on affinity biosensing mechanism driven via thiol-crosslinker and antibody receptors that holistically behaves as a recognition immunoassay stack that is specific and sensitive to track test pesticide analytes with a detection limit of 0.19 ng/mL or parts per billion (ppb) range for glyphosate and 0.15 pg/mL or parts per trillion (ppt) range for atrazine. Then, this developed sensor is integrated further to create a pesticide sensing ecosystem by means of a front-end field-deployable smart device with post-hoc Machine Learning (ML) assisted classification (LOW-MID-HIGH levels of pesticide) and thereby, a universal pesticide screening analytical device is designed and fabricated for pesticide assessment in real soil run-off samples.

Figure 1