Objective: To develop a new accurate method for continuous measurement of personal exposure to fine particulate matter( PM_(2. 5) ) by integrating the advantage of both light scattering and gravimetric method.
Methods: The PM_(2. 5) concentrations were measured by both light scattering and gravimetric method simultaneously. The ratio of time-weighted average concentrations from gravimetric method to the responding values from light scattering method was calculated as coefficient of correction and used to calibrate the real-time PM_(2. 5) concentrations from light scattering method.
Results: The limit of detections( LOD) for 3, 10, 30 and 60 min time-weighted average concentrations of PM_(2. 5) were 4. 6, 4. 0, 3. 9 and 3. 7 μg/m~3, respectively. The precision( relativestandard deviation, RSD) was from 2. 1% to 9. 5%. The 30 min time-weighted average concentrations from this method were highly related to the results from TEOM method which was considered as reference method( Pearson r = 0. 934, P < 0. 001, n = 233), and no significantly bias between these two methods was detected by paired t test( P =0. 957). Zero drift was detected for 3 out of 10 devices with drift values in the range of- 5-- 3 μg/m~3 in the experiment of continuous 24 h monitoring conducted in the lab. And zero shift was also investigated in 7. 5%( 31 /412) field monitoring events, but most of the values shifted were within the range of- 3- 3 μg/m~3. The direction and scale of zero shift were not influenced by PM_(2. 5) concentrations.
Conclusion: The developed method in this study that combines the advantages of both light-scattering and gravimetric method is validated to measure real-time concentrations of personal exposure to PM_(2. 5) .
Keywords: PM2. 5; continuous monitoring; gravimatric method; light scattering method; personal exposure.