Table 1.

Air quality in Ningxia Province in 2018.

Index	Monthly average concentrations of major monitored pollutants (μg/m3)
	SO2 (x1)	NO2 (x2)	PM10 (x3)	PM2.5 (x4)	O3 (x5)
January			93	46
February	40	27	86	40	104
March	30	32	167	55	129
April	18	27	159	47	141
May	14	23	150	45	162
June	14	24	74	26	178
July	9	17	81	29	160
August	10	20	56	25	150
September	13	27	65	26	129
October	19	37	87	39	112
November	27	43	155	57	83
December	32	37	141	50	76