Austin Elena, Novosselov Igor, Seto Edmund, Yost Michael G
Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, United States of America.
Department of Mechanical Engineering, University of Washington, Seattle, WA, United States of America.
PLoS One. 2015 Sep 14;10(9):e0137789. doi: 10.1371/journal.pone.0137789. eCollection 2015.
Finely resolved PM2.5 exposure measurements at the level of individual participants or over a targeted geographic area can be challenging due to the cost, size and weight of the monitoring equipment. We propose re-purposing the low-cost, portable and lightweight Shinyei PPD42NS particle counter as a particle counting device. Previous field deployment of this sensor suggests that it captures trends in ambient PM2.5 concentrations, but important characteristics of the sensor response have yet to be determined. Laboratory testing was undertaken in order to characterize performance.
The Shinyei sensors, in-line with a TSI Aerosol Particle Sizer (APS) model 3321, tracked particle decay within an aerosol exposure chamber. Test atmospheres were composed of monodisperse polystyrene spheres with diameters of 0.75, 1, 2 3 and 6 um as well as a polydisperse atmosphere of ASHRAE test dust #1.
Two-minute block averages of the sensor response provide a measurement with low random error, within sensor, for particles in the 0.75-6μm range with a limit of detection of 1 μg/m3. The response slope of the sensors is idiomatic, and each sensor requires a unique response curve. A linear model captures the sensor response for concentrations below 50 μg/m3 and for concentrations above 50 μg/m3 a non-linear function captures the response and saturates at 800 μg/m3. The Limit of Detection (LOD) is 1 μg/m3. The response time is on the order of minutes, making it appropriate for tracking short-term changes in concentration.
When paired with prior evaluation, these sensors are appropriate for use as ambient particle counters for low and medium concentrations of respirable particles (< 100 ug/m3). Multiple sensors deployed over a spatial grid would provide valuable spatio-temporal variability in PM2.5 and could be used to validate exposure models. When paired with GPS tracking, these devices have the potential to provide time and space resolved exposure measurements for a large number of participants, thus increasing the power of a study.
由于监测设备的成本、尺寸和重量，在个体参与者层面或目标地理区域进行高分辨率的细颗粒物（PM2.5）暴露测量具有挑战性。我们提议将低成本、便携式且轻便的新怡PPD42NS颗粒计数器重新用作颗粒计数设备。此前该传感器在实地的部署表明它能捕捉环境PM2.5浓度的趋势，但传感器响应的重要特性尚未确定。因此进行了实验室测试以表征其性能。
将新怡传感器与TSI气溶胶粒径分析仪（APS）型号3321串联，在气溶胶暴露室内追踪颗粒衰减。测试环境由直径为0.75、1、2、3和6微米的单分散聚苯乙烯球体以及ASHRAE测试粉尘#1的多分散大气组成。
传感器响应的两分钟分组平均值对于0.75 - 6微米范围内的颗粒提供了低随机误差的测量，检测限为1微克/立方米。传感器的响应斜率是独特的，每个传感器都需要一条独特的响应曲线。线性模型可捕捉浓度低于50微克/立方米时的传感器响应，对于浓度高于50微克/立方米的情况，非线性函数可捕捉响应并在800微克/立方米时达到饱和。检测限为1微克/立方米。响应时间在数分钟量级，适合追踪浓度的短期变化。
当与先前的评估相结合时，这些传感器适用于作为低中浓度可吸入颗粒物（< 100微克/立方米）的环境颗粒计数器。在空间网格上部署多个传感器将提供PM2.5有价值的时空变异性，并可用于验证暴露模型。当与全球定位系统（GPS）跟踪相结合时，这些设备有潜力为大量参与者提供时间和空间分辨的暴露测量，从而提高研究的效能。
