Table 1.

Mean concentrations of PM_2.5 and its chemical components between weekends and workdays.

	Lockdown periods			The pre-epidemic era			The post-epidemic era
	Workdays	Weekends	Diff (%)	Workdays	Weekends	Diff (%)	Workdays	Weekends	Diff (%)
Al	3201.76	3520.65	10	3434.61	3350.59	−3	2983.68	2927.51	−1
Ca	116.25	364.26	213	340.36	320.02	−6	162.61	160.82	−2
Fe	167.92	367.73	119	525.82	496.72	−6	347.03	353.02	−1
Si	492.66	1347.38	174	737.65	665.17	−10	571.90	578.53	2
S	2846.04	1646.29	−42	2213.86	2094.98	−5	1626.38	1656.12	1
K	845.03	814.34	−4	664.79	647.90	−3	439.36	436.02	2
Cr	2.19	1.84	−16	3.77	3.35	−11	1.97	2.12	−1
Mn	8.13	13.72	69	27.91	26.80	−4	22.91	23.52	7
Ni	0.74	1.20	63	1.35	1.27	−6	0.97	0.92	3
Cu	82.22	89.81	9	39.35	37.14	−6	36.11	34.62	−5
Zn	39.03	32.75	−16	105.70	99.99	−5	81.43	82.62	−4
As	5.34	3.51	−34	7.44	6.67	−10	3.69	3.69	1
Se	1.88	1.26	−33	1.78	1.69	−5	1.27	1.25	0
Ag	3.81	4.18	10	3.80	3.70	−2	3.08	2.95	−2
Cd	7.55	7.79	3	8.54	8.38	−2	6.80	6.96	−4
Ba	16.63	27.42	65	35.18	35.44	1	20.40	20.36	2
Au	1.96	2.33	18	2.46	2.47	1	0.61	0.62	−0
Hg	1.73	2.19	27	2.44	2.41	−1	0.52	0.51	2
Pb	17.02	12.58	−26	16.24	15.09	−7	18.19	18.01	−0
NO₃⁻	27.40	19.78	−28	3.27	3.19	−2	5.55	5.68	2
NH₄⁺	8.38	9.64	15	2.81	2.79	−1	3.91	4.06	4
SO₄2⁻	7.28	4.46	−39	3.34	3.17	−5	3.70	3.75	1
Na⁺	0.18	0.17	−5	0.11	0.11	−3	0.12	0.12	1
K⁺	0.84	0.65	−23	0.16	0.15	−4	0.27	0.28	3
Mg2⁺	0.29	0.24	−17	0.08	0.09	8	0.08	0.09	2
Ca2⁺	0.62	0.67	8	0.04	0.03	−19	0.81	0.82	1
Cl⁻	1.24	1.17	−6	0.29	0.28	−3	0.36	0.36	−0

(“Diff” indicates the relative changes over weekends compared to weekdays deduced from the GAM model. Unit: ng·m⁻³ for trace elements and μg·m⁻³ for water-soluble ions).