设施化农业区包气带孔隙介质中赤霉素运移机理的研究

Gibberellin is a plant hormone that can be secreted from the plant, it is also a plant growth regulating agent that can be synthetized. Gibberellin can affect the human endocrine system due to its molecular structure is very similar to the steroid hormones in human body. As the high strength and excessive using of the plant growth regulating agent such as gibberellin in agriculture, a lot of food safety and environmental health problems of plant growth regulating agent had been reported, such as the hormone bean sprout event and the watermelon splitting event. Moreover, high concentration of gibberellin that exceeding the maximum residue limits of the developed countries had also been detected in eight kinds of fruit and vegetables (i.e. bean sprouts and grapes). At the same time, as a new type of micro-toxic pesticides, excessive residue of gibberellin from agriculture area is mainly hosted in porous media in the vadose zone and continuing enter into groundwater, and make a high threat to the groundwater safety. However, no research relating to the gibberellin transporting in vadose zone and groundwater at the agricultural area has been found, especially at the facility agricultural area. Therefore, based on the characterization of facility agriculture, the adsorption and desorption of gibberellin in the vadose zone media is investigated, and factors that affect the adsorption and desorption of gibberellin in vadose zone media are analyzed, and the influence of high-strength fertilizer and pesticide using on the migration of gibberellin in the vadose zone media during the intermittent irrigation process at the facility agriculture area is also considered. Finally, the migration mechanism of gibberellin in the vadose zone media can be efficiently understood basis on this kinetics and thermodynamics research.

赤霉素是植物体内分泌的一种植物激素，也是一种可以人工合成的植物生长调节剂，其分子结构与人体内类固醇激素相似，可影响人体内分泌系统。在我国赤霉素等植物生长调节剂的高强度、过量使用已导致众多食品安全与人体健康问题，如激素毒豆芽和西瓜裂瓜事件；同时，研究者在市售黄豆芽、葡萄等8种果蔬中也检测到超过发达国家最高残留限值的赤霉素。作为一种新型微毒农药，过量的赤霉素会主要赋存在包气带孔隙介质中并进入地下水，进一步威胁地下水安全，而目前尚无关于赤霉素在农业区特别是设施化农业区包气带孔隙介质及地下水中运移的研究。本研究将依据设施化农业区特点，研究赤霉素在不同类型包气带介质中的吸附、解吸；分析影响赤霉素在典型包气带介质中吸附解吸的因素；探索设施化农业区间歇性灌溉过程中高强度化肥和农药的使用对赤霉素在典型包气带介质中迁移的影响；从动力学和热力学的角度掌握赤霉素的包气带孔隙介质中的运移规律。

通过本项目的研究，建立了一种同时检测地下水中GA3及草甘膦的测试方法，并建立了GA3的液相色谱测试方法，且测试过程不受地下水中常见离子和共存农药草甘膦的影响，并能同时测定出内酯环异构化的GA3（Iso-GA3）、赤霉烯酸（GEA）和内酯环异构化的羟基GA3等降解产物。随后，采集并检测了具有长期GA3施用历史的（>3年）设施农业区表层土壤（0-25 cm）中的GA3，但均未检测到GA3。.通过不同类型矿物对GA3吸附解吸研究发现，相比于蒙脱土、高岭土两种硅酸盐类矿物以及针铁矿、赤铁矿和水铁矿三种铁氧化物，水铁矿对GA3在包气带中的迁移转化起了重要作用。同时，GA3在GSS 7广东徐闻玄武岩砖红壤，GSS 8陕西洛川黄土，GSS 11辽河平原土壤，GSS 12新疆土壤，GSS 13华北平原土壤，GBW07410黑龙江的黑土六种标准土壤上的吸附均不显著（<0.002 mg/g），且目前研究结果表明只有静电引力可以促进吸附，地下水中常见离子和腐殖酸均不能促进吸附。.采集具有长期GA3施用历史的（>3年）表层土壤（0-25 cm），研究GA3在包气带介质中的衰减过程，发现高温灭菌后土壤对GA3有少量吸附，吸附量为0.03-0.05 mg/g。同时，实际土壤均能促进GA3的水解，30天内的水解过程均符合准一级动力学模型，水解速率为0.04680-0.0479 d-1。.通过研究GA3的衰减过程发现，GA3在大多数矿物及土壤中吸附解吸过程并不突出，影响其在环境中迁移的主要因素是水解作用和生物降解。在包气带GA3迁移过程中，62天内GA3衰减率可达~90%，符合准一级动力学。GA3在0-30天内衰减速率较大，30天后衰减速率略降低。过酸（pH=2.0）及过碱（pH=9.5）条件下GA3的水解作用促进了其衰减，同时GA3的生物降解也可以促进其衰减。