| Semi-volatile PAHs are major pollutants of urban air, mostly regionally transported and
reaching remote environments[1]. Some semi-volatile PAHs are carcinogenic. About 22% of
global PAHs emissions are in China.
The transport and sinks (atmospheric reactions, deposition) of semi-volatile PAHs in East
Asia are studied using a modified version of the Weather Research and Forecasting model
coupled with chemistry (WRF/Chem [2]). For this purpose, PAHs’ gas and particulate phase
chemical reactions and dry and wet deposition processes are included. We use emissions
of 2008 [3] which include technical combustion processes (coal, oil, gas, waste
and biomass) and open fires and apply diurnal time functions as those of black
carbon.
The model was run for phenanthrene (3-ring PAH, p = 1.5x10-2 Pa at 298 K) and
benzo(a)pyrene (5-ring PAH, p = 7x10-7 Pa) for July 2013 with hourly output and 27 km
horizontal grid spacing. The comparison of model predicted phenanthrene concentrations
with measurements at a rural site near Beijing (own data, unpublished) validates the model’s
ability to simulate diurnal variations of gaseous PAHs. The model’s performance is better in
simulating day time than night time gaseous PAHs. The concentrations of PAHs
had experienced significant diurnal variations in rural and remote areas of China.
Elevated concentration levels of 40-60 ng m-3 for phenanthrene and 1-10 ng m-3 for
benzo(a)pyrene are predicted in Shanxi, Guizhou, the North China Plain, the Sichuan
Basin and Chongqing metropolitan areas due to the high emission densities at those
locations.
References
[1] Keyte, I.J., Harrison, R.M., and Lammel, G., 2013: Chemical reactivity and
long-range transport potential of polycyclic aromatic hydrocarbons – a review, Chem. Soc.
Rev., 42, 9333-9391.
[2] Grell, G.A, Peckham, S.E, Schmitz, R, McKeen, S.A, Frost, G, Skamarock, W.C, and
Eder, B., 2005: Fully coupled online chemistry within the WRF model, Atmos. Environ., 39,
6957–6975.
[3] Shen, H. Z., Huang, Y., Wang, R., Zhu, D., Li, W., Shen, G. F., Wang, B., Zhang, Y.
Y., Chen, Y. C., Lu, Y., Chen, H., Li, T. C., Sun, K., Li, B. G., Liu, W. X., Liu, J. F., and
Tao, S., 2013: Global atmospheric emissions of polycyclic aromatic hydrocarbons
from 1960 to 2008 and future predictions, Environ. Sci. Technol., 47, 6415-6424. |