Characteristics and change of ammonia at the rural, urban, and remote sites in China

Zhaoyang Meng1, Yu Song2, Xuhui Cai3, Yuchong Miao4, Xingying Zhang5, Hong Geng6, Xichao Zhang7, Hongshen Zhang8, Hongbing Cheng9, Ting Zhang10 and Shasha Yin11

As the most dominant alkaline trace gas in the atmosphere, NH3 plays a very critical role in the chemical cycle of nitrogen and in aerosol formation processes. In order to better understand temporal and spatial differences in NH3 concentrations in differences regions in China, we present about two years (March 2017 to December 2018) of NH3 measurements from sixteen urban, rural, and remote sites in China. The measurements were made on daily and 5-day basis using passive samplers under careful quality control.

The observed concentrations show very large geographical differences. The highest NH3 concentration was observed at Linqing of Shangdong province in eastern China, about 4.8 times higher than that at Meixian of Guangdong in southeast China. The observed levels of NH3 are compared with the emission data from Multi-resolution Emission Inventory for China, previous passive sampling data, and the satellite measurements. On the whole, the geographical distributions or relative levels of observed NH3 concentrations agree with those of emissions. However, the comparison results indicate that NH3 emission around Longfengshan of Heilongjiang province in northeast China seem to be underestimated in existing inventories.

The NH3 levels in this study are 1.9-4.5 folds higher than those observed during 2007-2008 at remote and regional background sites in Qinghai-Tibetan Plateau, North China Plain, Yangtze River Delta and northeast China, suggesting an increase in NH3 levels in these regions in China. The higher NH3 concentrations was found at urban site such as Zhengzhou of Henan in central China, reflecting the mix of the strong influence of the vehicles, industrial emissions in the vicinity and agricultural emissions from the suburban areas.

At most sites, the concentrations of NH3 peaked in warmer seasons, which is consistent with the seasonal changes of NH3 sources. The meteorological conditions such as temperature and precipitation have the important impacts on the spatial and seasonal distribution of ammonia.

The ground measurements of NH3 in 2017 are compared with NH3 columns retrieved by the Infrared Atmospheric Sounding Interferometer (IASI) satellite. The comparisons between ground and satellite measurements suggest that in most cases, the IASI NH3 columns capture the geographical differences in the ground NH3 and correlate fairly well to ground measurements of NH3 at ten of the sixteen sites.

 

1Chinese Academy of Meteorological Sciences, mengzy@cma.gov.cn
2Peking University, songyu@pku.edu.cn
3Peking University, songyu@pku.edu.cn
4Chinese Academy of Meteorological Sciences, songyu@pku.edu.cn
5National Satellite Meteorological Center of CMA, songyu@pku.edu.cn
6Shanxi University, songyu@pku.edu.cn
7Peking University, songyu@pku.edu.cn
8Peking University, songyu@pku.edu.cn
9Chinese Academy of Meteorological Sciences, songyu@pku.edu.cn
10Chinese Academy of Sciences, songyu@pku.edu.cn
11Zhengzhou University, songyu@pku.edu.cn