更好地表征PM2.5(空气动力学直径小于或等于2.5μm的颗粒)物种的毒性差异的研究努力通常受到地面监测器的稀疏或不存在的覆盖的阻碍。NASA的Terra卫星上的多角度成像光谱辐射计(MISR)是提供气溶胶形状信息的少数卫星气溶胶传感器之一,全球范围内的规模和灭绝时间长,可用于估计2000年以来的PM2.5形态浓度。目前,MISR仅为其整个任务提供17.6公里的产品,每9天覆盖一次全球,对于空气污染健康影响研究和捕获PM2.5形态的局部空间变异性来说,这有点太粗糙了。在这项研究中,使用具有气象变量和地理指标的MISR原型4.4km分辨率气溶胶数据开发了广义相加模型(GAMs),预测PM2.5硫酸盐的地面浓度,硝酸盐,2001年至2015年南加州的有机碳(OC)和元素碳(EC)的日水平。GAM能够解释66%,62%,硫酸盐PM2.5日变异性的55%和58%,硝酸盐,整个研究期间的OC和EC浓度,分别。预测的浓度捕获了洛杉矶市区和其他县的四种PM2.5物种的大区域模式和精细梯度,以及在中央山谷。这项研究是首次尝试使用MISR原型4.4公里分辨率的AOD(气溶胶光学深度)组件数据来预测PM2.5硫酸盐,硝酸盐,分区域尺度的OC和EC浓度。尽管时间采样频率低,我们的分析表明,MISR4.4km分数AOD提供了一种有希望的方法来捕获PM2.5形态的空间热点和长期时间趋势,了解空气质量控制的有效性,并允许我们估计的PM2.5形态数据与流行病学研究中的人口普查道或邮政编码等常见空间单位相关联。当将来有更多的MISR4.4km数据可用时,需要在其他地区验证此建模策略。
Research efforts to better characterize the differential toxicity of PM2.5 (particles with aerodynamic diameters less than or equal to 2.5 μm) speciation are often hindered by the sparse or non-existent coverage of ground monitors. The Multi-angle Imaging SpectroRadiometer (MISR) aboard NASA\'s Terra satellite is one of few satellite aerosol sensors providing information of aerosol shape, size and extinction globally for a long and continuous period that can be used to estimate PM2.5 speciation concentrations since year 2000. Currently, MISR only provides a 17.6 km product for its entire mission with global coverage every 9 days, a bit too coarse for air pollution health effects research and to capture local spatial variability of PM2.5 speciation. In this study, generalized additive models (GAMs) were developed using MISR prototype 4.4 km-resolution aerosol data with meteorological variables and geographical indicators, to predict ground-level concentrations of PM2.5 sulfate, nitrate, organic carbon (OC) and elemental carbon (EC) in Southern California between 2001 and 2015 at the daily level. The GAMs are able to explain 66%, 62%, 55% and 58% of the daily variability in PM2.5 sulfate, nitrate, OC and EC concentrations during the whole study period, respectively. Predicted concentrations capture large regional patterns as well as fine gradients of the four PM2.5 species in urban areas of Los Angeles and other counties, as well as in the Central Valley. This study is the first attempt to use MISR prototype 4.4 km-resolution AOD (aerosol optical depth) components data to predict PM2.5 sulfate, nitrate, OC and EC concentrations at the sub-regional scale. In spite of its low temporal sampling frequency, our analysis suggests that the MISR 4.4 km fractional AODs provide a promising way to capture the spatial hotspots and long-term temporal trends of PM2.5 speciation, understand the effectiveness of air quality controls, and allow our estimated PM2.5 speciation data to be linked with common spatial units such as census tract or zip code in epidemiological studies. This modeling strategy needs to be validated in other regions when more MISR 4.4 km data becoming available in the future.