Table 2.

Mean concentrations of water-soluble species (μg m⁻³) between 14 March and 18 May over the period 2015–2020.

	PM1						PM10
	2015	2016	2017	2018	2019	2020	2015	2016	2017	2018	2019	2020
Cl−	0.28	0.29	0.21	0.11	0.09	─	0.82	0.61	0.98	0.69	1.04	0.33
NO3−	0.96	1.22	0.30	0.21	0.32	0.10	2.71	2.58	2.34	1.71	2.04	0.94
SO42−	1.51	1.72	1.28	1.30	1.26	0.88	2.13	2.14	2.38	2.11	1.91	1.22
C2O42−	0.11	0.13	0.07	0.07	0.08	0.07	0.19	0.17	0.15	0.14	0.15	0.12
Na+	0.18	0.19	0.12	0.08	0.11	─	0.64	0.75	0.98	0.74	1.09	0.55
NH4+	0.76	1.00	0.49	0.41	0.45	0.39	0.68	0.88	0.42	0.39	0.42	0.22
K+	0.14	0.11	0.16	0.13	0.11	0.07	0.16	0.13	0.27	0.19	0.18	0.08
Mg2+	0.03	0.04	0.02	0.02	0.03	0.01	0.13	0.14	0.15	0.11	0.18	0.08
Ca2+	0.39	0.53	0.26	0.40	0.44	0.11	1.29	1.23	1.49	1.43	1.29	0.48

*Data on sodium and chloride for 2020 are not included since most concentrations were below the detection limit.