脱硫石膏+纳米零价铁协同改良滩涂盐碱地的机理研究

Internal desalination mechanism is the core of the scientific problem to explore efficient and rapid development and utilization of saline-alkali soil in tidal flats. Desulfurization gypsum, as desulphurization byproduct of power plant, has been successfully used to improve saline-alkali soil by sodium calcium exchange function with low price and extensive, nano zero-valent iron causes wide public concern for diluting salt water by adsorption-desorption. In order to explore the synergy desulfurization mechanism of desulfurization gypsum and nano zero-valent iron, adsorption experiment, penetrant testing of Ca2+/Fe0 and ion migration transformation experiment under single and combined application of desulfurization gypsum and nano zero-valent iron are operated, the related indicators in soil and leachate and characterization of soil structure is analyzed, then isothermal adsorption curve is fitted to simulate adsorption, and UNSATCHEM model simulate the process, including the movement of basic cations in soil solution, adsorption-exchange between basic cations in soil colloid and soil solution, to explore synergetic desalination mechanism of desulfurization gypsum and nano zero-valent iron. The pot experiment and soil column experiment are operated to verify the synergy improvement effect of desulfurization gypsum and nano zero-valent iron on saline-alkali soil.

环境材料改良土壤盐碱化的内在机理是探索高效快速滩涂盐碱地修复与利用途径的核心科学问题。脱硫石膏作为电厂脱硫副产物来源广泛、价格低廉，通过钙钠交换作用改良滩涂盐碱地已有成功的研究和应用；纳米零价铁则通过吸附-解吸作用淡化盐渍水引起广泛关注。本项目选用脱硫石膏和纳米零价铁通过单施和配施组合处理开展等温吸附和吸附动力学、Ca2+/Fe0穿透及离子迁移转化试验研究，分析土壤、淋溶液含盐量、Na+等盐离子组分、pH等盐碱指标并进行土壤表征结构分析，结合动力学方程拟合吸附等温曲线和UNSATCHEM模型模拟土壤Na+等离子吸附、迁移转化过程，以明确脱硫石膏和纳米零价铁单施和配施下对Na+吸附和迁移转化规律，并进一步通过盆栽试验和土柱试验验证脱硫石膏+纳米零价铁协同改良滩涂盐碱地的效果，试图探索脱硫石膏与纳米零价铁协同脱盐机理。

探究高效快速持续改良滩涂盐碱土的机理是实现滩涂盐碱地开发和利用的核心科学问题。本项目选用脱硫石膏和纳米零价铁通过单施和配施开展吸附试验、离子迁移转化试验，分析土壤、淋溶液相关指标，并进行土壤表征结构分析，结合动力学方程拟合吸附曲线，探究脱硫石膏和纳米零价铁对滩涂盐碱土Na+吸附和迁移转化的规律，揭示了脱硫石膏+纳米零价铁对滩涂盐碱土壤代换性Na+吸附动力学特征，脱硫石膏和脱硫石膏复合纳米零价铁的吸附解吸土壤代换性Na+在5 min内完成，脱硫石膏与土壤的钙钠置换机制是影响土壤代换性Na+解吸的主要因素。揭示了脱硫石膏+纳米零价铁对滩涂盐碱土降Na的机理，短期内，纳米零价铁能够减少土壤颗粒和溶液Na，降低盐害，但因导致土壤颗粒粘结，孔隙度受影响，淋洗掉Na减少；而脱硫石膏能够持续释放Ca2+，通过钙钠置换降低土壤颗粒和溶液可溶性Na。并通过盆栽试验和土柱试验验证脱硫石膏+纳米零价铁协同改良滩涂盐碱地的效果，明确了脱硫石膏+纳米零价铁对滩涂盐碱地的脱盐效应和机理，脱硫石膏+纳米零价铁抑制Na+对植物的胁迫作用，增加植物的出苗率和生物量。XRD分析表明相比于脱硫石膏，纳米零价铁会增加土壤晶格内的Na。