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    Enhancing the Understanding of Soil Nitrogen Fate Using a 3D-Electrospray Sensor Roll Casted with a Thin-Layer Hydrogel

    Year: 2022

    Journal: Environ. Sci. Technol., Volume 56, APR 19, page 4905–4914

    Authors: Fan, Yingzheng; Wang, Xingyu; Qian, Xin; Dixit, Anand; Herman, Brianna; Lei, Yu; McCutcheon, Jeffrey; Li, Baikun

    Organizations: National Science Foundation (NSF) Environmental Engineering Program GOALI Project [1706343]; NSF Signal in the soil (SitS) Project [1935599]; NSF Civil, Mechanical and Manufacturing Innovation (CMMI) Project [2001544]; Connecticut SPARK Program; Infiltrator Water Technologies Co

    Keywords: solid-state ion-selective membrane sensors; polyacrylamide hydrogel; soil nitrogen fate; continuous monitoring; 3D electrospray; soil-based denoising data processing algorithm

    Accurate and continuous monitoring of soil nitrogen is critical for determining its fate and providing early warning for swift soil nutrient management. However, the accuracy of existing electrochemical sensors is hurdled by the immobility of targeted ions, ion adsorption to soil particles, and sensor reading noise and drifting over time. In this study, polyacrylamide hydrogel with a thickness of 0.45 mu m was coated on the surface of solid-state ion-selective membrane (S-ISM) sensors to absorb water contained in soil and, consequently, enhance the accuracy (R-2 > 0.98) and stability (drifting < 0.3 mV/h) of these sensors monitoring ammonium (NH4+) and nitrate (NO3-) ions in soil. An ion transport model was built to simulate the long-term NH4+ dynamic process (R-2 > 0.7) by considering the soil adsorption process and soil complexity. Furthermore, a soil-based denoising data processing algorithm (SDDPA) was developed based on the unique features of soil sensors including the nonlinear mass transfer and ion diffusion on the heterogeneous sensor-hydrogel-soil interface. The 14 day tests using real- world soil demonstrated the effectiveness of S-DDPA to eliminate false signals and retrieve the actual soil nitrogen information for accurate (error: <2 mg/L) and continuous monitoring.
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