微区界面物化过程对植物叶片和PM2.5/O3相互作用的影响机理研究

"Botanic Air Filtration" has been gaining attention as an effective, feasiable and economical solution for alleviating urban atmospheric pollution. Investigation and prediction of the interaction mechanism between leafs and air pollutants provide the theoretical basis of evaluating the purification capability of this solution. This study investigates the two sides featuring mutual supression occurred on leaf and pollutants: "purification" and "stress" by boundary-controlled micro-scale model experiments, analyzing the impact of interfacial physic-chemical processes in the microfluid of leaf surface on 1) fine particles and ozone transports in the air-leaf interface, 2) the formation of secondary organic aerosol due to oxidation of volatile organic compounds emitted from plant, and the spatial-temporal scale variations of leaf purification capability with single or multiple factors considerations, 3) the evaluation of the self-preservation and hereditary abilities of the resistance genes after suffering from stress injuries in the physiological characteristics and the resistance genes due to exposure to fine particles or ozone. On this basis, the methodology of "two-factors coupling" using the dimensionless transferring data associated with each factor model adopted in microfluid will be applied to build the meteorological factor-atmospheric pollutant-characteristic plant leaf coupling model. The model accesses the interactions between gaseous or particulate pollutants and leafs to predict the leafs' purification ability. A comprehensive evaluation methodology including purifying efficiency and stress injury will be established based on the outcome of this study.

以缓解城市大气污染为目标、辅助清除污染物的"植物过滤法"由于有效、易行和廉价等优势，越来越受到重视，而探析和预测叶片和污染物之间的相互作用机制是评价其净化能力的理论依据。本研究针对叶面和污染物之间"净化"和"胁迫"相互牵制的两面性，设计可控边界的微尺度模型实验，考虑单一或多环境因素变化的条件下：解析微区界面物化过程对细颗粒物和臭氧在"空气－叶片"交界面传输模式的影响、植物释放的挥发性有机物形成二次颗粒物过程的作用及叶片自身净化能力时空尺度的改变；并判别在暴露于细颗粒物和臭氧中对植物生理特征和抗性基因发生胁迫损伤后，其抗性基因的自保持性和遗传性;在此基础上，采用叶面微流体中各因素模型的传递数据无量纲化后两两耦合的方法，构建"气候因子-空气污染物-特征植物叶片"耦合模型，以解析气态、颗粒态污染物与植物叶面的交互作用模式及预测叶片净化能力，最终形成植物净化效率和胁迫损伤一体化考量的综合评价方法。

本项目针对利用植物净化大气细颗粒物和O3的生态法辅助大气治理问题，考虑了气候因子或污染源特征改变时，叶片微区的界面物化过程对细颗粒物和O3在“空气－叶片”交界面传输模式的影响及叶片自身净化能力时空尺度的改变，及定量化研究植物（苔藓、大叶黄杨、吊兰）净化的有效性和效率。研究表明苔藓对于净化颗粒态及气态污染物具有较好的效果，净化效果可达20%以上。在此基础上，进一步判别了植物暴露于细颗粒物和O3中造成的生理特征和抗污基因的胁迫损伤，以研究抗性基因的自保持性和遗传性，发现植物蒸腾量和气孔导度受颗粒物和O3的影响相对其他因素较小。而光合量对颗粒物和O3的作用较为敏感。叶绿素含量主要有植物种类及叶片位置决定，较短暴露时无变化，长时间暴露会产生变化。而甲基化研究发现植物在暴露后甲基化水平均升高。本项目进而构建“气候因子-空气污染物-特征植物叶片”耦合模型，以解析气态、颗粒态污染物与植物叶面的交互作用模式及预测叶片净化能力。研究成果可以形成植物净化能力和胁迫损伤一体化考量的综合评价方法，为实现因地（地理）制宜、因侯（气候）制宜、因物（污染物和植物）制宜的利用植物协助治理大气问题提供基础理论依据。