This manuscript, Spatiotemporal and policy-related variations of PM_2.5 compositions and sources during 2015-2019 at multisite of a Chinese megacity, has been studied the relationship among urbanization, policy and PM_2.5 components variation in a fast-developing Chinese city. This manuscript investigated the spatiotemporal and policy-related variations of PM_2.5 components and sources via the methods of Hierarchical Cluster Analysis and PMF, etc. Meanwhile, source weighted PSCF was developed in this work. The results and method can be useful for further policy formulation in most developing and polluted countries as well as supply basic information for future epidemiological studies. I recommend the manuscript to be published after minor corrections.

Some minor corrections were as followed:

(1) Latitude and longitude should be added in Figure 1 and Figure 8.

(2) It is suggested that the coordinates of industrial factories could be added to Figure 1.

(3) Line 115: the start and end time of sampling day should be detailed.

(4) In section 2.2, 24 chemical species in PM_2.5 were analyzed and why only 22 chemical compositions were introduced into PMF.

(5) Lines 173-174:  why the time of “12 h” and “6 h” were chosen? Have you tried other time options? Such as the 24 h backward trajectories starting from the receptor site and 2 h time intervals during all sampling periods will chose.