铁锰氧化物改性生物炭材料对土壤PAEs生物有效性的调控及其机制

Phthalic acid ester (PAEs) contaminated soil exists widely in China and is difficult to be remedied. It is well established that applied biochar based modified material have ability to decrease bioavailability of PAEs and PAEs content of wheat. Our pervious experiments showed that manganese (iron) oxide impregnated biochar composite had good effect on the removal of PAEs in aqueous solution. However, until now, the investigations on remediation for PAEs contaminated farmland soil using composite of biochar and ferric-manganese oxide is fairly insufficient. Furthermore, the reaction mechanism of PAEs on the surface of composite is unclear and its effects on the bioavailability are also unconfirmed. In this study, the adsorption experiments, soil cultures and pot experiments are conducted simultaneously combined with the advanced instruments as, Q-TOF-MS, HPLC-MS, microscopic infrared spectral, X ray photoelectron spectroscopy, and high-throughput sequencing technologies. The main objectives of the current study are to investigate: 1) the sorption/oxidation characteristics of PAEs on the surface of ferric-manganese oxide materials; 2) the effect of ferric-manganese oxide on soil micro-ecology; 3) regulative effect and mechanism of ferric-manganese oxide on the bioavailability of PAEs in the farmland soil. This project not only can provide new knowledge to application of biochar based modified material in PAEs-polluted soils, but also provide new ideas of preventing PAEs invasion into the food chain.

邻苯二甲酸酯（PAEs）在我国农田土壤中广泛存在且污染程度、强度日益加重。施用生物炭基修复材料是降低农田PAEs生物有效性、减少其在小麦籽粒中累积的有效途径之一。前期实验表明，锰（铁）氧化物改性生物炭材料对水溶液中PAEs具有较好的去除效果，但其在土壤中与PAEs相互作用机制尚待明确。据此，本项目以铁锰氧化物改性生物炭材料为试材，以北方棕壤、潮土为试验土壤，采用等温吸附，室内培养与盆栽试验相结合的方法，利用Q-TOF-MS，显微红外光谱，X射线光电子能谱扫描等先进分析手段，结合固相萃取和高通量测序技术，研究铁锰氧化物改性生物炭材料在土壤中与PAEs相互作用机制，探讨其对小麦根际土壤微生态环境的影响，揭示其对土壤PAEs生物有效性的调控效果差异及机理。本项目的实施既为生物炭基修复材料在PAEs污染农田上合理施用提供思路，又为屏蔽PAEs进入食物链保障小麦品质安全提供科学依据。

PAEs作为一类农田土壤中广泛存在的有机污染物，已经对植物生长以及人健康体产生潜在影响。本项目以玉米秸秆生物炭（BC）为原料，采用浸渍法制备出铁锰氧化物改性生物炭（FMBC），研究了FMBC对DBP/DEHP的吸附/氧化作用机理，探讨了FMBC对棕壤/潮土中PAEs生物有效性调控机制及其与PAEs交互作用对土壤微生态环境的影响。研究结果表明：.（1）FMBC对DBP和DEHP的饱和吸附量分别是BC的1.54倍和3.98倍，由物理和化学吸附共同主导。其中，FMBC对DBP的吸附过程为单层均匀吸附，对DEHP的吸附为多层吸附位点和非均相吸附。DEHP吸附在FMBC上的吸附机制涉及分配作用、氧化和氢键作用。此外，低pH和高浓度NO3-有利于FMBC对PAEs的吸附，而高浓度的PO42-和砷对DBP的吸附存在抑制作用。.（2）FMBC的施用降低了小麦根、茎叶和籽粒对PAEs的吸收和蓄积，促进了PAEs污染土壤上小麦的光合作用，使DBP（DEHP）污染潮土和棕壤上小麦籽粒增产高达248%（209%）和243%（186%）。孕穗期小麦叶片中与淀粉和蛋白质合成相关酶的活性显著提高，从而导致小麦籽粒支链淀粉、直链淀粉和可溶性蛋白含量明显增加。此外，矿质元素（Fe、Mn、K和Ca）和部分氨基酸含量显著增加，表明其品质得到明显改善。.（3）FMBC的施用明显增加了潮土和棕壤对DBP（DEHP）的固持能力，增幅为37.3-87.9%（41.3-91.5%）和16.2-97.7%（44.1-95.1%），且与生物炭材料施用量呈显著正相关关系。FMBC对PAEs的固持能力优于BC，这归因于其具有更大的表面积、更多的孔隙结构和表面官能团。.（4）FMBC的添加明显增加了小麦根际土壤pH、有机质、碱解氮、有效磷和速效钾含量以及土壤多酚氧化酶、蛋白酶、脲酶、β-葡萄糖苷酶和脱氢酶等的活性，对两种土壤中细菌多样性和丰富度无明显影响，提高了Bacillus 和Pseudomonas等PAEs降解菌的相对丰度。分子对接的结果证实，DBP和DEHP能通过氢键、范德华力、π-π T型等化学键稳定在Pseudomonas分泌的羧酸酯酶的活性位点，酶的丝氨酸残基的存在有助于实现降解过程。