A Temperature Compensated Smart Nitrate- Sensor for Agricultural Industry
Abstract:
Extended research on the design and development of a smart nitrate sensor for monitoring nitrate concentration in surface and groundwater, are reported in this paper. The developed portable sensing system consists of a planar interdigital sensor, associated electronics, instrumentation and Electrochemical Impedance Spectroscopy (EIS) based analysis. The system is capable of measuring nitrate concentrations in the range of 0.01 to 0.5 mg/L in ground and surface water. This study extends our earlier work by including a temperature compensation capacity within the sensor. WiFi-based Internet of Things (IoT) has been included making it a connected sensing system. The system is capable of sending data directly to an IoT-based web server, which will be useful to develop distributed monitoring systems in the future. The developed system has the potential to monitor the impact of industrial, agricultural or urban activity on water quality, in real-time.
Existing system:
The spectrophotometric method is commonly used to detect nitrate-nitrogen NO3-N) in water using specific chemical reagents .In other research, vanadium has been utilized for the reduction of nitrate ions by acidic Griess reaction. Other detection ethods include ion chromatography , palladium nanostructures ,planar electrode sensors, ion selective electrodes , and optical fiber sensors. In situ detection of nitrate in soil moisture using impedance spectroscopy, have also been reported . The objective of this research is to extend our earlier work to develop a low-cost, in-situ real-time monitoring system based on the planar interdigital sensor. The purpose is to achieve continuous assessment of nitrate-N in water to improve our understanding and measurement of seasonal and annual losses of nitrate to waterways. The earlier reported system provided good accuracy under a controlled environment. However, the ambient temperature under field conditions vary considerably. Therefore, the performance of the developed system suffered due to temperature fluctuations. Therefore, a compensation of the effect of temperature was required in the current system.
Proposed system:
The main contributions of this paper are 1. the use of a temperature compensated inter digital capacitive sensor to measure nitrate at low concentrations and 2. The development of a low-cost (the estimated amount of the whole system’s cost is less than $100 USD) sensing system for continuous nitrate measurement which links to an IoT-based cloud server through an integrated WiFi connection. The experimental development, evaluation and validation of the systems performance are explained. The IoT [30] offers promising solutions to transform the operation and role of existing industrial technologies. IoT is already having an impact in the areas of agriculture, food processing, environmental monitoring, security surveillance and others [31]. The proposed Arduino Yun has integrated WiFi which can provide instant connectivity to the Internet. The last experiment was done to demonstrate the usefulness of the temperature compensation in the developed system. The temperature of the sample water was maintained at 30°C. The concentration of nitrate was measured by the developed sensing system and laboratory spectrophotometric method.
Conclusion:
Further to our earlier work, a temperature compensated interdigital capacitive sensor has been developed in the current study to measure nitrate at low concentrations. A portable, novel sensing system has been developed that could be used on-site as a stand-alone device, as well as IoT-based remote monitoring smart sensor node, to measure nitrate concentration in surface and ground water. Electrochemical Impedance Spectroscopy was employed to detect and display nitrate concentrations, by evaluating the impedance change read by the interdigital transducer immersed in the surface water samples. The test samples were evaluated by commercial equipment (LCR meter) and the designed system. These results were also validated using standard laboratory techniques to assess nitrate concentrations in water samples. The designed system showed a good linear relationship between the measured nitrate concentrations (ranged from 0.01 to 0.5 mg/L) to those measured by the commercial equipment in the collected water samples. However, the current system has the potential to be used to estimate nitrate concentrations in water samples, in real-time. The system can upload the measured nitrate data on a website based on IoT. This system could be used to integrate water quality monitoring sites within farms, or between streams, rivers, and lakes. For the in-situ installation, a robust box containing the whole system would need to be installed at the monitoring site.
References:
[1] H. Di and K. Cameron, “How does the application of different nitrification inhibitors affect nitrous oxide emissions and nitrate leaching from cow urine in grazed pastures?,” Soil Use and Management, vol. 28, pp. 54-61, 2012.
[2] J. Dymond, A.-G. Ausseil, R. Parfitt, A. Herzig, and R. McDowell, “Nitrate and phosphorus leaching in New Zealand: a national perspective,” New Zealand Journal of Agricultural Research, vol. 56, pp. 49-59, 2013.
[3] L. Kellman and C. Hillaire-Marcel, “Evaluation of nitrogen isotopes as indicators of nitrate contamination sources in an agricultural watershed,” Agriculture, ecosystems & environment, vol. 95, pp. 87-102, 2003.
[4] P. J. Thorburn, J. S. Biggs, K. L. Weier, and B. A. Keating, “Nitrate in groundwaters of intensive agricultural areas in coastal Northeastern Australia,” Agriculture, ecosystems & environment, vol. 94, pp. 49-58, 2003.
[5] DairyNZ. (2013, 27/02/2017). Nutrient management on your dairy farm. Available: https://www.dairynz.co.nz/media/757901/nutrient_management_on_your_dairy_farm.pdf
[6] C. O. R. WATERS, “Water quality and chemistry in running waters.”
[7] A. Ghani, K. Müller, M. Dodd, and A. Mackay, “Dissolved organic matter leaching in some contrasting New Zealand pasture soils,” European Journal of Soil Science, vol. 61, pp. 525-538, 2010.
[8] W. H. Organization. (2017, 27/02/2017). Water-related diseases. Available: http://www.who.int/water_sanitation_health/diseases-risks/diseases/methaemoglob/en/
[9] E. P. Agency. (2017, 27/02/2017). Ground Water and Drinking Water. Available: https://www.epa.gov/ground-water-and-drinking-water/table-regulated-drinking-water-contaminants
[10] B. Narayana and K. Sunil, “A spectrophotometric method for the determination of nitrite and nitrate,” Eurasian Journal of Analytical Chemistry, vol. 4, pp. 204-214, 2009.