节水模式驱动的根际效应对水稻累积PAHs的影响机理研究

Polycyclic aromatic hydrocarbons (PAHs) is a common organic risk pollutants in paddy fields, most of them and their derivatives have carcinogenicity on human. In recent years, the residual quantity of them in rice in parts of our country has threaten the safety of agricultural products and caused concern. Water-saving irrigation is an economic and efficient paddy field management mode, it has wide application prospect in water shortage area. But the effect of rhizosphere effect induced by water saving mode on the accumulation of PAHs in rice is seldom reported at home and abroad, and the influence mechanism is unclear. The preliminary field survey of applicant shows that the water-saving treatment can reduce the residual risk of PAHs in paddy fields and rice, but the impact mechanism needs further simulation validation. In view of the characteristics of dry-wet alternate, oxidation reduction potential changeable in the rice growth duration and the regulation function of different water-saving mode on the microorganism and biological habitat in rice rhizosphere and non-rhizosphere, we plan to use the Lysimeter, 13C stable isotope tracer, in situ micro domain habitat observation, risk material trace detection and tracking, PLFA-SIP microbial fingerprint identification technology, to study the impact mechanism of rice rhizosphere effect driven by different water-saving mode on the quantitative transmission of PAHs from paddy field to rice on the molecular level, and identify the master key factors impacted on the residual quantity of PAHs in agricultural products, and to provide support for the paddy PAHs pollution prevention and agricultural product safety.

多环芳烃（PAHs）是稻田常见的有机风险物，大部分种类及其衍生物具致癌性。近年，其在我国部分地区稻米中的残留量已威胁到农产品安全并受到关注。节水灌溉是一种经济、高效的稻田管理模式，在水资源紧缺地区颇具前景；但节水模式下的根际效应及其对水稻累积PAHs的影响，国内外尚少有报道，影响机理尚不明确。申请人前期野外调查显示，节水处理可降低稻田及水稻中PAHs的残留和风险，但影响机理尚需进一步模拟论证。本项目针对水稻生育期干湿交替、氧化还原电位多变等特征，利用不同节水模式对稻田根际微生物-生境的调控作用，综合利用根箱、Lysimeter、13C稳定同位素示踪、生境原位观测、磷脂脂肪酸-稳定同位素探针等技术，从分子水平认知不同节水调控驱动下的根际效应对PAHs在稻田及水稻中定量传输的影响机理，识别影响PAHs在农产品中赋存的主控关键因子，为高产、节水与生态安全的水稻节水模式提出及农产品安全提供支撑。

多环芳烃（PAHs）是稻田常见的有机风险物，大部分种类及其衍生物具致癌性。近年，其在我国部分地区稻米中的残留量已威胁到农产品安全并受到关注。节水灌溉是一种经济、高效的稻田管理模式，在水资源紧缺地区颇具前景；但节水模式下的根际效应及其对水稻累积PAHs的影响，国内外尚少有报道，影响机理尚不明确。本项目针对水稻生育期干湿交替、氧化还原电位多变等特征，利用不同节水模式对稻田根际微生物-生境的调控作用，综合利用根箱、Lysimeter、同位素示踪、生境原位观测、高通量测序等技术，从分子水平认知不同节水调控驱动下的根际效应对PAHs在稻田及水稻中定量传输的影响机理。研究发现，浅湿控灌和半旱节水相对于常规淹灌和湿润灌溉可以加速土壤中PAHs的消解，且菲的消减率大于芘。水稻的存在促进了菲和芘的消减（菲提高到134%，芘提高到237%）；随着水稻生长，土壤中的菲和芘有上层和向下层迁移的趋势，非根际向近根际迁移的趋势，且根际土壤远远低于近根际和非根际土壤，很好地证明了根际效应的存在。湿润灌溉和浅湿控灌组水稻的总穗数、每穗粒数和千粒重及根系质量均较高，常规灌溉和半旱节水较少。浅湿控灌节水模式相对于常规淹灌籽实对菲和芘的富集分别可降低40%和47%左右，印证了前期野外试验结果，节水模式不利于菲和芘向籽实中的迁移累积，即水稻节水灌溉处理可明显降低PAHs在水稻籽实中的残留风险，有利于食品安全的控制，可大大降低稻米的食品风险。这可能与节水模式下较高的土面蒸发和植物蒸腾效应，以及较高的根际脲酶、过氧化氢酶和多酚氧化酶、漆酶和双加氧酶活性和高丰度的可降解PAHs的鞘氨醇单胞菌属、酸杆菌属、芽单胞菌属、酸杆菌属、新鞘氨醇单胞菌属、假单胞菌属等菌种有关。本研究成果可为高产、节水与生态安全的水稻灌溉模式提出及农产品安全提供支撑。