室内环境中的霾污染延迟效应研究

As a frequently occurred phenomenon in the past decade, especially in recent years, hazy weather or haze pollution has become an emergent environmental issue which is highly concerned in many scientific fields in China. Haze pollution not only raises particle concentration indoors during haze episodes by indoor-outdoor air exchange, but also worsens indoor air quality after the episodes due to its time-delay effects. When haze weather passed, the fine particles, which deposited on the walls of ventilation systems and formed dendritic structures, particularly in ducts, would resuspend into the incoming air by flow flushing and other impactions, and then enter into indoor environment. This phenomenon causes a time-dependent delay of indoor haze pollution, i.e., a relatively long-time pollution duration (with a relatively high concentration) indoors related to the haze episode. However, investigations and analyses are still lack on this problem and similar/corresponding topics..Considering the time-delay effects of haze pollution on indoor air quality, and indoor particle concentration differences between the durations of haze episode and haze free days, the main aim of the present study is to investigate the deposition, accumulation in short-time spans and resuspension of fine particles in ducts and indoor solid surfaces by employing field measurement, chamber experiment and theoretical analysis. According to the configurations and features of different surfaces, also with the concerning of the wide-range variations of particle concentration during haze episodes, particle deposition behaviors, their morphologies that adhered on duct walls, inner walls of rooms and furniture surfaces and the resuspension levels will be estimated by using theoretical analysis and experimental test. These analyses will be used to evaluate the deposition characteristics and to provide some suggestions for modifying the local configurations of the ducts, for this may lead haze particles to easily deposit on some special portions of the ducts, and then it is convenient for timely and effectively duct cleaning after haze episodes. Based on the investigations mentioned above, some important roles or strategies will be recommended for reducing the time-delay effects and time-duration of haze pollution indoors.

近几年来，霾天气已是我国常见的大气污染现象，霾污染已成为多学科共同关注的紧迫问题。霾污染不但在霾天气期间通过空气交换导致室内颗粒物浓度升高，恶化空气质量，在霾过程结束后，因室内和通风系统中短时间沉积的粒子堆积松散，受气流和人为干扰易发生再悬浮，从而导致持续时间更长的室内霾污染延迟效应。这一问题目前尚未引起重视并缺乏必要的研究。.本项目注意到延迟效应可能造成的室内空气质量问题、以及霾污染期间粒子浓度变化与正常天气下的区别，拟利用实测、实验和严格理论方法，针对霾污染期间粒子浓度高且变化大的特点，研究不同气流下，粒子在不同特性表面上短时间沉积、积累和再悬浮的机制与规律，以获知室内霾粒子污染特征，并用通风管道的局部改造来引导粒子沉积在易清理的区域，以便在霾污染结束后及时有效清除易于再悬浮的沉积粒子。通过分析，给出降低霾污染延迟效应和持续时间的依据，提出避免或有效减弱霾污染室内延迟效应的建议和原则。

过去10年来，霾天气已是我国常见的大气污染现象，霾污染已成为多学科共同关注的紧迫问题。霾污染不但在霾天气期间通过空气交换导致室内颗粒物浓度升高，恶化空气质量，在霾过程结束后，因室内和通风系统中短时间沉积的粒子堆积松散，受气流和人为干扰易发生再悬浮，从而导致持续时间更长的室内霾污染延迟效应。. 本课题注意到霾延迟效应造成的室内空气质量问题及霾污染期间室内粒子浓度变化与正常天气下的差别，考虑多机理耦合效应，即在对流、扩散和重力效应的联合作用下，通过严格求解多倾角下通风管道和建筑物墙面上缝隙内霾粒子输送和沉积的动力学方程，得到了一系列严格显式解析解，以描述通道内的霾粒子沉积与穿透。对结果的分析表明，已有的文献中的结果均为本研究在特殊情况下的简化（或近似）形式。对于室内固壁表面和风管中局部构件前后的粒子沉积，采用数值方法模拟分析了粒子的沉积与穿透效应。此外，本课题采用自编数值程序，对织物过滤器和静电净化器内的细粒子捕集进行了模拟研究，并讨论和分析了固壁表面的粒子沉积和附着的微观结构。. 为分析沿街道建筑开窗条件下的室内外空气耦合交换过程，采用三维数值方法并结合实验验证，讨论了不同建筑物布局等条件下街道峡谷和室内外空气耦合流动和污染物输送情况。为估计城市降雨对霾粒子清除引起的粒子谱变化，采用自编程序和拉格朗日法，研究了雨滴下落过程中的粒子捕集对粒子谱变化的影响。. 本课题的研究结果可用来估计霾粒子沉积和穿透特征，并为实用中对改进通风管道局部设计提供依据，并寻求降低特殊区域产生的霾污染延迟效应的途径，以提出在霾过程结束后对管道清洗和减弱霾污染室内延迟效应的建议和原则。