CAREER: Investigation of Laser-Induced Breakdown Spectroscopy for Analysis of Airborne Particulate Matter

最近和即将出台的关于颗粒物(PM)的联邦空气污染法规要求开发连续的排放监测仪来测量空气中颗粒物的大小和组成。激光诱导击穿光谱(LIBS)是一种很有前途的实时测量100 nm-10 nm尺寸范围内主要是无机气溶胶颗粒的尺寸和组成的方法。这些纳米颗粒已被证明与一系列重大的健康影响有关，包括肺功能下降、哮喘发病率增加、肺组织和结构改变、住院人数增加和过早死亡。在LIBS中，利用高能脉冲激光在样品介质中产生火花或击穿。最近在焚烧炉和热处理装置上进行的这项技术的现场试验表明，LIBS测量很好地跟踪了排放的趋势，可以捕获抽取式、积分型采样器无法观测到的瞬时事件。由于联合颗粒物组成和大小的可能性，LIBS对于源解析也很有吸引力，也就是通过成分指纹来确定空气中特定颗粒物的来源。该建议的主要目标是：1)了解颗粒基质、气体基质以及等离子体尺寸和温度对LIBS测量的联合影响，2)确定使用LIBS测量颗粒的上下限，以及不同颗粒尺寸的最佳激光功率、最佳火花尺寸和温度、以及最佳探测器门延迟和宽度的变化，3)模拟由前两个目标实现的典型颗粒组成的颗粒/等离子体相互作用，4)进行环境气溶胶的实时、准确、全光谱LIBS测量，在前三个目标的推动下，职业发展计划包括了涉及高中生、高中教师和大学生的强有力的教育内容。研究表明，在有前途的年轻理科学生中，一些人的流失是因为人们认为当前的科学问题与主导高中/大学早期的基础科学课程之间缺乏联系。拟议的教育计划包括创建互动的、基于网络的教学工具，使用来自常见大气现象的插图，如光化学烟雾、臭氧空洞、酸雨和空气中气溶胶粒子的迁移，教授与实际问题相关的基本科学概念。对教学感兴趣的马里兰大学工程和理科本科生将被招募，以协助当地高中的AP化学和AP环境科学教师制定课程和计算机/网络编程，为AP课程开发互动学习单元。人们希望这些努力能促进有前途的高中生保持学习科学的动力，而一些有教学天赋的大学生可能会有一段有益的经历，激发人们对科学教育的兴趣。我们计划将教育计划与研究计划联系起来，在项目的第四年和第五年将LIBS单元引入学校，作为气溶胶课程模块的一部分进行环境气溶胶测量。

Recent and pending Federal air pollution regulations for particulate matter (PM) require the development of continuous emissions monitors to measure the size and composition of airborne particles. Laser-induced breakdown spectroscopy (LIBS) is a promising method for real-time measurement of joint size and composition of primarily inorganic airborne aerosol particles in the size range 100 nm - 10 nm. These nanoparticles have been shown to be linked to a series of significant health effects, including decreased lung function, increased incidence of asthma, alterations in lung tissue and structure, increased hospital admissions, and premature death. In LIBS, a high-energy pulsed laser is utilized to create a spark, or breakdown, in the sample media. Recent field trials of this technique on incinerators and thermal treatment units show that LIBS measurements follow trends of emissions well and can capture transient events that are not observed by extractive, integrating type samplers. Due to the possibility of joint particle composition and sizing, LIBS also is attractive forsource apportionment, that is, determination of the source of particular particles in an airshed by compositional fingerprinting. The primary objectives of the proposal are:1) to understand the joint influences of the particle matrix, of the gas matrix, and of plasma size and temperature on the LIBS measurement,2) to determine the upper and lower size limits for particle measurements using LIBS, and the variation in optimal laser power, optimum spark size and temperature, and optimum detector gate delay and width for various particle sizes,3) to model the particle / plasma interaction for typical particle compositions, as enabled by the previous two objectives,4) to perform real-time, accurate, full-spectrum LIBS measurements of ambient aerosol, as enabled by the previous three objectives.The career development plan includes a strong educational component involving both high school students, high school teachers, and college students. It is suggested that some of the attrition among promising young science students is due to a perceived lack of connection between current scientific problems and the basic science classes that dominate high school / early college years. The proposed educational plan involves the creation of interactive, web-based teaching tools that use illustrations from familiar atmospheric phenomena such as photochemical smog, the ozone hole, acid rain, and migration of airborne aerosol particles to teach basic science concepts linked to real problems. Undergraduate engineering and science students from the University of Maryland with an interest in teaching would be recruited to assist AP Chemistry and AP Environmental Science teachers from local high schools in curriculum development and computer/web programming to develop interactive learning modules for the AP classes. It is hoped that these efforts promote promising high school students to remain motivated to study science, while some college students with a teaching aptitude may have a rewarding experience that stimulates interest in science education. We plan to tie the education plan with the research plan by bringing the LIBS unit to schools to make ambient aerosol measurements as part of an aerosol curriculum module in the 4th and 5th years of the project.