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. 2014 Apr 22;9(4):e95734. doi: 10.1371/journal.pone.0095734

Table 2. Descriptive statistics and spatial differences for the 10 VOCs (µg/m3) monitored at the four local-source dominated sites in the study.

N Mean SD Min Med Max p-valuea MultipleComparisonb N Mean SD Min Med Max p-valuea MultipleComparisonb
Acetylene Styrene
Background 69 0.52 0.35 0.02 0.43 1.76 <.0001 A Background 69 0.07 0.06 0.02 0.04 0.34 <.0001 A
Commercial 45 1.76 1.72 0.34 1.16 8.22 B Commercial 45 0.28 0.24 0.02 0.21 0.98 B
Industrial 45 1.20 1.10 0.20 0.97 6.89 B Industrial 45 0.16 0.11 0.02 0.13 0.60 C
Mobile 50 1.41 1.27 0.27 1.11 6.72 B Mobile 50 0.17 0.11 0.02 0.13 0.60 B C
Benzene Toluene
Background 69 0.52 0.22 0.22 0.48 1.19 <.0001 A Background 69 0.71 0.54 0.19 0.53 3.17 <.0001 A
Commercial 45 1.81 1.15 0.54 1.44 6.52 B Commercial 45 7.98 6.06 1.06 6.37 32.4 B
Industrial 45 1.11 0.68 0.35 0.90 4.16 C Industrial 45 6.46 4.94 0.45 5.47 25.6 B
Mobile 50 1.36 0.82 0.35 1.21 4.99 B C Mobile 50 8.06 6.60 0.87 6.49 31.4 B
DCM m,p-Xylene
Background 69 0.33 0.25 0.03 0.28 1.60 <.0001 A Background 69 0.30 0.21 0.04 0.26 1.13 <.0001 A
Commercial 45 1.15 1.26 0.17 0.80 7.18 B Commercial 45 4.62 6.99 0.43 2.39 40.9 B
Industrial 45 1.31 1.46 0.17 0.70 6.34 B Industrial 45 1.51 1.28 0.17 1.35 7.17 C
Mobile 50 1.14 1.28 0.24 0.71 6.83 B Mobile 50 1.45 1.09 0.26 1.24 6.82 C
EB o-Xylene
Background 69 0.14 0.08 0.04 0.13 0.43 <.0001 A Background 69 0.13 0.08 0.01 0.13 0.43 <.0001 A
Commercial 45 1.28 1.50 0.17 0.83 9.04 B Commercial 45 1.20 1.19 0.17 0.87 6.65 B
Industrial 45 0.53 0.38 0.09 0.48 2.22 C Industrial 45 0.55 0.42 0.09 0.48 2.48 C
Mobile 50 0.54 0.34 0.13 0.48 2.17 C Mobile 50 0.57 0.40 0.13 0.48 2.56 C
MEK p-DCB
Background 69 1.08 1.22 0.07 0.91 8.09 <.0001 A Background 69 0.04 0.04 0.02 0.02 0.24 <.0001 A
Commercial 45 2.76 2.11 0.07 2.27 10.0 B Commercial 31 0.47 0.24 0.12 0.42 1.39 B
Industrial 45 2.77 3.06 0.07 1.77 14.0 B Industrial 45 0.34 0.20 0.02 0.30 1.02 C
Mobile 50 1.41 1.09 0.07 1.03 4.72 A Mobile 50 0.30 0.17 0.06 0.27 0.78 C
a

Differences within the four sampling sites were conducted using the Kruskal-Wallis test and pairwise multiple comparison tests (Wilcoxon rank-sum test) were followed, if the difference was significant (p<0.05).

b

Different letters mean significant differences (p<0.0083) among the four monitoring sites.

Abbreviation in the table: DCM: Dichloromethane, EB: Ethylbenzene, MEK: Methyl Ethyl Ketone, p-DCB: p-Dichlorobenzene.