不同品种水稻-土壤界面邻苯二甲酸酯的环境行为及机制研究

Phthalic acid esters (PAEs) is one class of global important environmental organic pollutants and endocrine disrupting chemicals. However, until now, very few studies has been conducted to investigate the environmental behaviour of PAEs in soil-rice system. In this study, PAEs will be selected as target pollutant, and soil pot trial, rhizodox experiment as well as lysimeter experiment with 14C-labeled PAEs will be conducted, and different cultivars of rice (Oryza sativa L.) will be planted in soil spiked with PAEs. The samples of soil, plants and water will be collected at different stages of rice growth, and PAEs in the samples will be extracted and measured by gas chromatography coupled with mass spectrometry (GC/MS). The aims of this study are to investigate the environmental behaviour and fate of PAEs in soil-rice interface, particularly in rhizosphere, and to clarify the accumulation of PAEs by different cultivars of rice from the soil and its variation of cultivars (or genotypes). This study is also aimed to select a PAE high-accumulation cultivar and a PAE low-accumulation rice cultivar, and then to investigate the capacity variation of these two cultivars on root uptake of PAEs and metabolism in vivo and their control factors of the physiology and biochemistry (e.g., root activity, enzyme activity of plant). Moreover, the root exudates of rice and the enzyme activities in soil and plant will be determined, and phospholipid fatty acids (PLFAs) in soil including rhizosphere will be analysed at different periods with the aim of monitoring changes in microbial community structure. DNA isolated from soil (including rhizosphere) will be amplified and fingerprinted by using terminal restriction fragment length polymorphism (T-RFLP) and a polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) procedure. All results above will be helpful to elucidate the effects of the PAE high/low-accumulation cultivars on the environmental behaviour and bioavailability of PAEs in soil, especially in rhizosphere, and the relationship between the environmental behaviour and bioavailability and root exudates, rhizosphere microorganism, as well as soil enzyme activity. This study will reveal the mechanism of accumulation variation of PAE high and low-accumulation cultivars, and will provide scientific basis for selecting pollution- resistant (or low accumulation) rice cultivars and for bioremediation of contaminated soil.

邻苯二甲酸酯(PAEs)是一类全球性的重要环境有机污染物和内分泌干扰物。但目前国内外对土壤-水稻系统PAEs环境行为的研究几乎是空白。本项目拟以PAEs为研究对象，通过土培试验、根箱培养试验与Lysimeter试验相结合，采用气相色谱-质谱联机分析技术、同位素示踪技术和微生物分子生物学技术等研究手段，研究PAEs在水稻-土壤界面尤其是根际微域的环境行为及其机制，查明不同品种水稻对土壤中PAEs的吸收累积特征和品种差异；探讨高/低累积品种水稻根系吸收和体内代谢PAEs的能力差异及其生理生化(根系活力、植物酶活性等)控制因素；阐明高/低累积品种水稻对土壤尤其是根际微域中PAEs的环境行为和生物有效性的影响及其与根系分泌物、根际微生物、土壤酶活性等之间的关系。从而揭示高/低累积品种水稻吸收累积PAEs差异的机理，为抗污染(即低累积)水稻品种选育和土壤污染生物修复提供科学依据。

邻苯二甲酸酯(PAEs)是一类全球性的重要环境有机污染物，农业（尤其水田）土壤普遍检出高浓度PAEs。但国内外缺乏对土壤-水稻系统PAEs环境行为的研究。本项目以土壤中检出率和含量均较高的邻苯二甲酸正二丁酯(DBP)、邻苯二甲酸双(2-乙基己基)酯(DEHP)为目标化合物，采用土培、根箱培养与土柱模拟Lysimeter等试验，采用气相色谱-质谱联用检测PAEs和高通量测序技术分析土壤微生物群落，研究PAEs在水稻-土壤界面尤其是根际微域的环境行为及其机制。获得以下主要成果：. 1. 从广东省广泛种植的20个品种水稻中筛选获得了对PAEs高低累积的水稻品种。水稻对PAEs的吸收累积随水稻生长期、部位及品种而异，以成熟期最高，籽粒最低，品种间差异显著。. 2. 揭示了水稻生理生化差异是导致PAEs高/低累积差异的主要因素。PAEs主要分布在水稻体细胞壁和细胞器，低累积品种丰优丝苗可将更多PAEs滞留在根部细胞壁而减少向地上部迁移。丰优丝苗根系分泌的草酸和酒石酸比高累积品种培杂泰丰的高，前者多酚氧化酶活性比后者的高，可促进DEHP在水稻体内代谢降解。而培杂泰丰的根构型较丰优丝苗更利于其吸收PAEs。. 3. 土壤尤其是根际微域PAEs的残留形态与粒径分布及微生物特性等影响PAEs的环境行为。培杂泰丰和丰优丝苗非根际土中PAEs均高于根际土。PAEs会沿土柱向下层土壤迁移，土层及其溶液中PAEs浓度随土层深度增加而降低。土壤PAEs主要分布在细粉粒、粘土及粗腐殖酸组分，即细颗粒组分更易吸附PAEs。土壤PAEs主要以可脱附态和有机提取态为主，生物有效性相对较高。土壤酶活性自根生长室向远根际土逐渐降低；根际土壤以近根区微生物丰富度和多样性最高，培杂泰丰土壤微生物物种组成变化较丰优丝苗的显著，导致前者土壤残留PAEs较后者低。 筛选获得了8株高效降解PAEs的微生物菌株，可促进土壤DBP和DEHP降解。 . 4. 发表了8篇SCI收录论文，3篇核心期刊论文；培养了5名硕士；申请发明专利15件，获授权专利1件。