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Core principle and industry application of soil redox potential analyzer
Date: 2025-09-16Read: 0
Soil redox potential meterEh meter is a professional equipment for monitoring the redox status (electron gain and loss ability) of soil. By measuring the relative activity (potential value, unit mV) of oxidants and reducing agents in soil, it reveals key information on soil microbial activity, nutrient availability, and pollution level. It is widely used in agriculture, environmental science, and pollution remediation fields.
1、 Core principle:
The oxidation-reduction potential (Eh) reflects the trend of electron transfer in soil solution - when oxidants (such as oxygen, high valent iron Fe ³ ⁺) dominate in soil, the Eh value is relatively high (usually>400mV, aerobic environment); When reducing agents such as hydrogen sulfide H ₂ S and low valent iron Fe ² ⁺ are dominant, the Eh value is low (usually<200mV, anaerobic environment). The instrument is based on electrochemical principles and consists of a primary cell composed of a platinum electrode (working electrode) and a reference electrode (such as a saturated calomel electrode or a silver chloride electrode): the platinum electrode surface undergoes redox reactions (exchanging electrons with electron donors/acceptors in the soil), and the reference electrode provides a stable reference. The potential difference between the two (after temperature compensation) is the Eh value (measurement range is usually -400mV to+1000mV).
The key parameters are influenced by soil moisture content, aeration, and microbial activity - for example, flooded soil (aeration difference) can produce a large amount of reducing substances (such as CH ₄, H ₂ S) due to anaerobic decomposition of organic matter, and the Eh value can be reduced to below -300mV; Dry and loose dryland soil (with sufficient oxygen) often has an Eh value higher than 600mV. For every 10 ℃ increase in temperature, the Eh value increases by about 10-30mV (which needs to be compensated and corrected by built-in temperature sensors).
2、 Industry applications:
• Agricultural planting: In rice fields, the Eh value needs to be maintained at 100-200mV (micro reducing environment) to promote the absorption of iron, manganese and other elements by rice roots (hypoxia induces the formation of iron film on the root surface, protecting the roots from heavy metal toxicity); If the Eh value is too high (>400mV), it will cause nitrogen to exist in the form of nitrate nitrogen (easily leached), and Eh needs to be reduced through drainage or the application of organic fertilizer. In dryland farmland, when the Eh value is>300mV, the availability of phosphorus in the soil (as insoluble iron/aluminum phosphate) is low, and Eh can be adjusted to 200-300mV through deep plowing or lime application to release available phosphorus.
Environmental monitoring: In the soil around wetlands and lakes, Eh value is a key indicator for determining the risk of eutrophication in water bodies. A low Eh value (<100mV) indicates strong anaerobic decomposition of organic matter, which may release large amounts of ammonia nitrogen and hydrogen sulfide, deteriorating water quality; Around the landfill site, Eh value monitoring can track the range of soil pollution caused by leachate (Eh values in polluted areas are usually<-200mV, accompanied by hydrogen sulfide odor).
Pollution remediation: In the remediation of heavy metal contaminated soil (such as cadmium and lead), adjusting the Eh value to change the form of heavy metals - for example, increasing the Eh value of acidic mine drainage contaminated soil from -100mV (reduced state, heavy metals exist in ionic state, easy migration) to 300mV (oxidized state, heavy metals form insoluble hydroxide or sulfide precipitates), reducing its bioavailability; In organic polluted sites (such as petroleum hydrocarbons), aerobic microbial activity is strong when Eh value>400mV, which can accelerate pollutant degradation (increase remediation efficiency by more than 50%).
Soil redox potential meterBy quantifying the "electronic ecology" of soil, it provides a scientific basis for optimizing agricultural production, environmental risk warning, and pollution control, and is an "electronic probe" for soil health management.