Critical Review of Methods to Estimate PM_2.5 Concentrations within Specified Research Region

Obtaining PM_2.5 data for the entirety of a research region underlies the study of the relationship between PM_2.5 and human spatiotemporal activity. A professional sampler with a filter membrane is used to measure accurate values of PM_2.5 at single points in space. However, there are numerous PM_2.5 sampling and monitoring facilities that rely on data from only representative points, and which cannot measure the data for the whole region of research interest. This provides the motivation for researching the methods of estimation of particulate matter in areas having fewer monitors at a special scale, an approach now attracting considerable academic interest. The aim of this study is to (1) reclassify and particularize the most frequently used approaches for estimating the PM_2.5 concentrations covering an entire research region; (2) list improvements to and integrations of traditional methods and their applications; and (3) compare existing approaches to PM_2.5 estimation on the basis of accuracy and applicability.