Table 4 Source groups identified for PM_2.5 components and WQS estimated weights assigned for the source groups

Weights estimated from WQS models on all 15 PM _2.5 components, sum the weights for identified source groups

G1: Heavy fuel oil combustion

V, Ni

0.0012

0.1369

0.0184

G2: Biomass burning

K

0.3682

0.2162

0.4065

G3: Crustal matter

Si, Ca

0.0099

0.1454

0.0045

G4: Non-tailpipe traffic source

Zn, Pb, Fe, Cu

0.4316

0.1012

0.1389

G5: Tailpipe traffic source^a

EC, OC

0.0780

0.1286

0.1237

G6: Secondary particles, power plants^a

SO₄²⁻, NO₃⁻, OC

0.1111

0.2717

0.3080

G7: Secondary particles, agriculture

NH4⁺

1.3×10^− 8

3.2×10^− 8

6.1×10^− 9

G8: Unclear source

Br

8.8×10^− 9

1.8×10^− 9

1.8×10^− 9

Weights estimated from WQS models on the identified source groups

G1: Heavy fuel oil combustion

V, Ni

1.4×10^− 6

0.0021

0.0002

G2: Biomass burning

K

0.4073

0.2342

0.4511

G3: Crustal matter

Si, Ca

0.0006

0.1069

0.0010

G4: Non-tailpipe traffic source

Zn, Pb, Fe, Cu

0.4472

0.0792

0.1586

G5: Tailpipe traffic source^a

EC, OC

0.1445

0.2678

0.2674

G6: Secondary particles, power plants^a

SO₄²⁻, NO₃⁻, OC

0.0004

0.3096

0.1209

G7: Secondary particles, agriculture

NH4⁺

6.7×10^− 6

0.0002

0.0006

G8: Unclear source

Br

6.9×10^− 7

6.9×10^− 10

0.0002