Shi Jingjin, Chen Fei'er, Cai Yunfei, Fan Shichen, Cai Jing, Chen Renjie, Kan Haidong, Lu Yihan, Zhao Zhuohui
Department of Environmental Health, School of Public Health, Fudan University, Shanghai 200032, China.
International Peace Maternity and Child Health Hospital of China Welfare Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
PLoS One. 2017 Nov 9;12(11):e0185700. doi: 10.1371/journal.pone.0185700. eCollection 2017.
Portable direct-reading instruments by light-scattering method are increasingly used in airborne fine particulate matter (PM2.5) monitoring. However, there are limited calibration studies on such instruments by applying the gravimetric method as reference method in field tests.
An 8-month sampling was performed and 96 pairs of PM2.5 data by both the gravimetric method and the simultaneous light-scattering real-time monitoring (QT-50) were obtained from July, 2015 to February, 2016 in Shanghai. Temperature and relative humidity (RH) were recorded. Mann-Whitney U nonparametric test and Spearman correlation were used to investigate the differences between the two measurements. Multiple linear regression (MLR) model was applied to set up the calibration model for the light-scattering device.
The average PM2.5 concentration (median) was 48.1μg/m3 (min-max 10.4-95.8μg/m3) by the gravimetric method and 58.1μg/m3 (19.2-315.9μg/m3) by the light-scattering method, respectively. By time trend analyses, they were significantly correlated with each other (Spearman correlation coefficient 0.889, P<0.01). By MLR, the calibration model for the light-scattering instrument was Y(calibrated) = 57.45 + 0.47 × X(the QT - 50 measurements) - 0.53 × RH - 0.41 × Temp with both RH and temperature adjusted. The 10-fold cross-validation R2 and the root mean squared error of the calibration model were 0.79 and 11.43 μg/m3, respectively.
Light-scattering measurements of PM2.5 by QT-50 instrument overestimated the concentration levels and were affected by temperature and RH. The calibration model for QT-50 instrument was firstly set up against the gravimetric method with temperature and RH adjusted.
采用光散射法的便携式直读仪器在空气中细颗粒物（PM2.5）监测中应用越来越广泛。然而，在现场测试中，以重量法作为参考方法对这类仪器进行校准的研究有限。
于2015年7月至2016年2月在上海进行了为期8个月的采样，获得了96对分别采用重量法和同步光散射实时监测（QT - 50）得到的PM2.5数据。记录了温度和相对湿度（RH）。采用曼 - 惠特尼U非参数检验和斯皮尔曼相关性分析来研究两种测量方法之间的差异。应用多元线性回归（MLR）模型建立光散射设备的校准模型。
重量法测得的PM2.5平均浓度（中位数）为48.1μg/m³（最小值 - 最大值10.4 - 95.8μg/m³），光散射法测得的为58.1μg/m³（19.2 - 315.9μg/m³）。通过时间趋势分析，二者显著相关（斯皮尔曼相关系数0.889，P<0.01）。通过MLR，光散射仪器的校准模型为Y（校准后） = 57.45 + 0.47×X（QT - 50测量值） - 0.53×RH - 0.41×温度，同时对RH和温度进行了校正。校准模型的10倍交叉验证R²和均方根误差分别为0.79和11.43μg/m³。
QT - 50仪器对PM2.5的光散射测量高估了浓度水平，且受温度和RH影响。首次建立了针对重量法并对温度和RH进行校正的QT - 50仪器校准模型。
