Recent Advances in Chemical Sensors for Soil Analysis: A Review

Abstract

The continuously rising interest in chemical sensors’ applications in environmental monitoring, for soil analysis in particular, is owed to the sufficient sensitivity and selectivity of these analytical devices, their low costs, their simple measurement setups, and the possibility to perform online and in-field analyses with them. In this review the recent advances in chemical sensors for soil analysis are summarized. The working principles of chemical sensors involved in soil analysis; their benefits and drawbacks; and select applications of both the single selective sensors and multisensor systems for assessments of main plant nutrition components, pollutants, and other important soil parameters (pH, moisture content, salinity, exhaled gases, etc.) of the past two decades with a focus on the last 5 years (from 2017 to 2021) are overviewed.

Optical Chemical Sensors for Soil Analysis: Possibilities and Challenges of Visualizing NH3 Concentrations as well as pH and O2 Microscale Heterogeneity

“…Using optodes to measure spatiotemporal variations in soil pH. Soil pH is a key parameter in soil fertility, as it controls redox reactions, nutrient and toxin bioavailability, and affects important biological processes 44,45 . This makes soil pH a parameter of general importance, and in-situ and constant monitoring will contribute to a better understanding of the complexity of soils.…”

“…This makes soil pH a parameter of general importance, and in-situ and constant monitoring will contribute to a better understanding of the complexity of soils. Traditionally, soil pH is assessed with conventional laboratory pH measuring methods utilizing potentiometric pH electrodes (in aqueous or mild saline extracts) 44 . While pH glass electrodes are fast and cover a wide pH range, they can only measure bulk pH in samples where the soil-to-solution ratio is changed to unnatural ratios 46 .…”

“…This way hotspots of pH changes can not be determined in a complex system such as soil. Optical sensors for pH, on the other hand, can be used in-situ, without the need of sample extraction, and can therefore unravel the spatial and temporal pH heterogeneities of soils 44 . However, both methods have their limitations regarding precise pH measurements, which come from different non-thermodynamic assumptions inherent in their modes of operation 47 .…”

Environmental Monitoring: A Comprehensive Review on Optical Waveguide and Fiber-Based Sensors

“…Electrochemical and optical sensors have seen rapid advancement in recent years [ 41 , 42 ]. Their usage is becoming simpler, and the range of potential uses is expanding, notably for measuring air quality.…”

Electronic tongue applications for wastewater and soil analysis

“…The number of manuscripts describing the application of ETs for soil analysis is much smaller than those related to the analysis of water samples ( Table 2 ). Nonetheless, there are still a few relevant applications that demonstrate the potential and advantages that the approach can offer, beyond those of sensors alone ( Nadporozhskaya et al., 2022 ). In this direction, most relevant applications are related to the monitoring of nutrients in farming (either in soil-less cultivations or in soil extracts), the quantification of different pollutants in soil extracts (e.g., heavy metals), or even the discrimination and classification of soils.…”