Simulation of organic acid migration and transformation in Mangrove soils based on soil column experiments

The practice of directly applying unfermented and decomposed organic matter to plants is rare in the growth process of terrestrial plants. The organic matter content at the discharge outlet of shrimp ponds is usually high. Therefore, it is necessary to collect soil from the discharge outlet of shrimp ponds and simulate the migration and transformation pathways of organic acids and related metabolic microorganisms in soil of mangrove wetlands through laboratory soil columns and the HYDRUS-1D model. Results showed that the content of oxalic acid remained relatively stable in the soil column at different depths, citric acid settled downward along the vertical direction, the concentration of acetic acid in the depth range of 30-50 cm increased. The organic acids formed insoluble or slightly soluble precipitates in the form of organic acid calcium, the organic acids in 40-50 cm were completely neutralized on the 18th day. The abundance of acid-producing Acinetobacter Johnsonii increased during the later stages of anaerobic acidification and disappeared after the addition of Ca(OH)₂. The results of HYDRUS-1D simulation showed that the adsorption, deposition and transport of organic acids in the mangrove wetland were poor, the results of vertical infiltration modelling were in agreement with the soil column experiments.