Physicochemical properties of hydrogen peroxide aerated water and its infiltration in clays

Clay soils with subsurface drip irrigation are often characterized by hypoxia. The addition of hydrogen peroxide to water to produce hydrogen peroxide oxygenated water, which is delivered to the root zone of crops via a subsurface drip irrigation system to increase soil oxygen levels, is a promising method of alleviating oxygen deprivation in the root zone. To explore the variation of dissolved oxygen concentration, oxygen transfer coefficient, surface tension coefficient, electrical conductivity and pH value with different hydrogen peroxide oxygenated water concentrations (H0-0 mg/L; H1-600 mg/L; H2-800 mg/L; and H3-1 000 mg/L), as well as the response of cumulative infiltration, depth of the wetting front and soil water content to hydrogen peroxide oxygenated water concentrations, two trials were carried out in 2021 at the State Key Laboratory of Eco-hydraulics in Northwest Arid Region at Xi'an University of Technology, China. The results of the study showed that H₂O₂ significantly increased the concentration of dissolved oxygen in water and the concentration of dissolved oxygen increased with increasing concentration of H₂O₂ added. Dissolved oxygen concentration was significantly enhanced by 52.10%, 87.11% and 126.59% in H1 to H3 treatments, respectively, as compared to the H0 treatment. The increase in H₂O₂ concentration decreased the oxygen transfer coefficient and inhibited the oxygen transfer process. Oxygen transfer coefficient was significantly increased by 65.17% in the H1 treatment as compared to the H3. The surface tension coefficient decreased significantly with increasing H₂O₂ concentration. The surface tension coefficients in H1 to H3 treatments were significantly reduced by 17.72%, 23.57% and 31.60%, respectively, compared to the H0 treatment. Electrical conductivity showed an increasing trend with increasing concentration of H2O2 addition, but the difference between H0 and H1 treatments was not significant (P>0.05). Electrical conductivity was significantly higher in H2 and H3 treatments by 6.60% and 10.42%, respectively, as compared to the H0. The change in pH showed an opposite trend to electrical conductivity, with pH showing a decreasing trend with increasing concentration of H₂O₂ added. There was a good logarithmic function relationship between dissolved oxygen concentration and surface tension coefficient, and the two could be used as a quantitative evaluation indicator of the physicochemical properties of hydrogen peroxide oxygenated water. Compared to the control, hydrogen peroxide oxygenated water facilitated the process of soil water infiltration and increased the water holding capacity of the soil. The cumulative infiltration showed a trend of increasing and then decreasing with increasing H₂O₂ addition concentration. Cumulative infiltration was significantly increased by 14.50%, 29.98% and 16.64% for H1 to H3 treatments, respectively, compared to the H0 treatment. For the same infiltration time, the depth of the wetting front showed a tendency of increasing and then decreasing with the increase of H₂O₂ addition concentration. The depth of wetted fronts was significantly increased by 7.66%, 18.84% and 13.39% in H1 to H3 treatments, respectively, compared to the H0. The soil water content was significantly increased by 8.73% and 4.23% in H2 and H3 treatments, respectively, as compared to the H0. The Philip infiltration model was able to better simulate the infiltration process of hydrogen peroxide oxygenated water, and the soil sorptivity showed a tendency of increasing and then decreasing with the increase of the added concentration of H₂O₂, with the maximum value also appeared in the treatment of 800 mg/L. There was a good quadratic polynomial relationship between the soil sorptivity and the dissolved oxygen concentration. Considering the results of the study together, the recommended concentration of 800 mg/L of H₂O₂ was the optimal concentration under the test conditions. These results could provide a scientific foundation for the practical application of hydrogen peroxide oxygenated water and a theoretical guide for the efficient regulation of soil aeration.