Sources and their contribution to two water-soluble organic carbon fractions at a roadway site

Contributions of non-BB, BB, and secondary OC (SOC) to both WSOCHPI and WSOCHPO were estimated using a multiple linear regression analysis. The monthly average contribution of non-BB emissions ranged from 12.6% to 29.4% of the WSOCHPI and from 21.5% to 44.1% of the WSOCHPO, with high contributions occurring during the cold months and low contributions occurred during the warm months. BB emissions contributed more to WSOCHPI (2.7%-13.1%) than WSOCHPO (0.2%-1.1%), and the SOC contribution to both WSOC fractions was significant. SOC accounted for 57.2%-79.7% of the WSOCHPI, and for 55.3%-78.0% of the WSOCHPO, with the higher fractions occurring in summer. During the summer the high SOC contributions were consistent with high OC/EC and WSOC/OC ratios. Results of this study suggest that non-BB (“fossil”) emissions are likely an important source to WSOCHPI and WSOCHPO observed at this roadway site.