Table 2.

Summary of PM_1.0 species mass concentrations and other relevant environmental parameters and chemical ratios for different periods of the year (MJ = May–June; JAS = July–September; N = November; DJ = December–January) in Tucson between July 2012 and June 2013. The chemical ratios are on a molar basis.

	MJ (n = 19)	JAS (n = 28)	N (n = 5)	DJ (n = 16)
WVMR (g kg−1)	6.2	12.6	4.1	3.3
RH (%)	22	51	35	46
T (°C)	29.8	29.4	17.2	9.6
NDVI	0.22	0.40	0.29	0.23
WS (m s−1)	3.2	2.3	1.7	2.3
WD (°)	150	160	158	162
DMA (ng m−3)	15.6	20.5	12.4	9.3
${\mathrm{SO}}_4^{2-}$ (μg m−3)	1.26	1.35	0.93	0.48
${\mathrm{NO}}_3^{-}$ (μg m−3)	0.56	0.28	0.46	0.52
${\mathrm{NH}}_4^{+}$ (μg m−3)	0.26	0.29	0.24	0.17
MSA (ng m−3)	8.83	4.86	2.66	1.94
${\mathrm{NH}}_4^{+}$:${\mathrm{SO}}_4^{2-}$	1.10	1.20	1.38	1.88
DMA:${\mathrm{NH}}_4^{+}$	0.02	0.03	0.02	0.02