地膜残留条件下旱区土壤邻苯二甲酸酯的累积阈值及再分配研究

Plastic film mulching is one of the common practices to increase crop yield in arid and semiarid regions. However, the wide use of plastic film has resulted in the release of phthalate esters (PAEs), which seriously threatens soil environmental quality and the safety of crop production. At present, it is urgent to clarify the mechanism and effects of residual film on the content changes and bioavailability of PAEs in soil to evaluate environment effects and pollution risks of PAEs. To address these issues, this project will focus on the release, accumulation and redistribution of PAEs from residual film in dryland soil. By means of analytical methods (such as isotope labeling, gas chromatography and mass spectrometry), incubation and batch experiments will be conducted to explore: (1) changes of the PAEs release from film plastic, the content of PAEs in soil, and microbial community structure in different conditions, and (2) the distribution and surface-binding features of PAEs in the three-phase film-soil-solution system. The aim of the project is to reveal the mechanism and maximum threshold of soil PAEs accumulation induced by plastic film residue, and the bioavailability of PAEs in polyphase system. Results of the presented project will provide insight into the environmental behavior of PAEs in the soil environment, and help to evaluate the pollution risk of PAEs on soils and crops caused by residual plastic film.

覆膜栽培是旱区农作物生产的重要模式之一，然而地膜大量残留引起邻苯二甲酸酯类（PAEs）增塑剂的释放，严重威胁土壤环境质量和作物安全生产。阐明地膜残留条件下旱区土壤PAEs的累积阈值及生物有效性，是深入揭示PAEs的环境行为及生态污染风险亟待解决的问题。本项目围绕PAEs的释放、累积及再分配过程，通过室内培养和序批试验方法，采用同位素标记与示踪、高通量测序、气相色谱与质谱联用等技术手段，研究不同老化程度地膜与旱区土壤环境互作条件下，残膜PAEs释放量、土壤PAEs累积量与微生物群落结构变化，以及PAEs在地膜-土壤-溶液三相体系中的分配及表面结合特征，揭示地膜残留条件下土壤PAEs的累积阈值及影响因素，并从多相体系中PAEs的再分配角度阐明残膜对PAEs生物有效性的影响。研究结果将为深入了解PAEs在土壤体系中的环境行为，评估残膜引发的土壤及作物PAEs污染风险提供科学依据。

覆膜栽培在我国旱区农业生产中占有重要地位，然而地膜残留引起的旱区土壤及作物邻苯二甲酸酯（PAEs）污染严重制约了该地区农业的绿色健康发展。本项目深入研究了旱区地膜残留条件下土壤PAEs动态变化规律及累积阈值，剖析了田间条件下土壤微生物的响应，探究了PAEs在地膜、土壤和溶液非均相体系中的吸附分配特征，综合评估了小麦籽粒PAEs在麸皮和面粉中的累积分布规律，结果表明：（1）地膜残留引起的土壤PAEs含量变化在一年的观测期内波动较大，在冬季和夏季出现周期性峰值，且随着塑料薄膜老化程度和残余量的增加而加剧。（2）高通量测序分析表明，残膜的加入增加了细菌群落的alpha多样性，改变了细菌群落结构，对细菌功能产生了显著干扰，残留薄膜招募了更多与塑料薄膜和PAEs降解相关的微生物群。（3）土壤及地膜对PAEs的吸附过程均可以分为快速吸附阶段、慢速吸附阶段以及平衡吸附阶段；土壤对PAEs的等温吸附曲线用Freundlich方程拟合较佳，而地膜对PAEs的吸附则用Langmuir方程拟合更佳。溶解性有机质的存在促进了土壤及地膜对PAEs的吸附，降低了PAEs在液相中的分配。（4）西北三省五点的田间试验表明，覆膜处理土壤和小麦籽粒中总PAEs的浓度显著升高，不同小麦品种中面粉和麸皮中PAEs比例存在差异。综上所述，地膜残留影响土壤微生物生态变化，引起了土壤及小麦籽粒PAEs的累积；残膜引起的土壤PAEs变化存在周期性阈值，并受到地膜残留量、老化程度的影响；在从事旱地农业生产时，小麦等作物的快速生长期应避免与土壤PAEs积累高峰重合，否则易导致PAEs在作物中累积，并通过食物链进一步危害人类健康。研究结果为指导旱地作物安全生产提供了理论依据和技术支撑。