scholarly journals Sources of nitrous acid (HONO) in the upper boundary layer and lower free troposphere of the North China Plain: insights from the Mount Tai Observatory

2020 ◽  
Vol 20 (20) ◽  
pp. 12115-12131
Author(s):  
Ying Jiang ◽  
Likun Xue ◽  
Rongrong Gu ◽  
Mengwei Jia ◽  
Yingnan Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrous Acid ◽  
North China Plain ◽  
North China ◽  
High Elevation ◽  
Free Troposphere ◽  
Radical Chemistry ◽  
The North ◽  
The North China Plain ◽  
Upper Boundary

Abstract. Nitrous acid (HONO) is a significant precursor of atmospheric “detergent” OH radicals and plays a vital role in tropospheric chemistry. The current knowledge about daytime HONO sources is incomplete, and its impact on the tropospheric radical chemistry has not been fully quantified. Existing observational studies of HONO were mostly conducted at the surface, with few efforts focusing on the high-elevation atmosphere. In order to better understand the characteristics and sources of HONO in the upper boundary layer and lower free troposphere, two intensive field observations were carried out at the summit of Mt. Tai (1534 m a.s.l.), the peak of the North China Plain (NCP), in winter 2017 and spring 2018. HONO showed moderate concentration levels (average ± standard deviation: 0.15±0.15 and 0.13±0.15 ppbv), with maximum values of 1.14 and 3.23 ppbv in winter and spring, respectively. Diurnal variation patterns with broad noontime maxima and lower nighttime concentrations were observed during both campaigns, which is distinct from most of the previous studies at the ground level. The Lagrangian particle dispersion model (LPDM, WRF-FLEXPART v3.3) simulations indicated the combined effects of the planetary boundary layer evolution and valley breeze on the daytime HONO peak. A photostationary state (PSS) analysis suggested a strong unknown daytime HONO source with production rates of 0.45±0.25 ppb h−1 in winter and 0.64±0.49 ppb h−1 in spring. Correlation analysis supported the important role of photo-enhanced heterogeneous conversion of NO2 to HONO on the aerosol surface at this high-elevation site. HONO photolysis is the predominant primary source of OH radical and plays a major role in the radical chemistry at Mt. Tai. The model only considering a homogenous HONO source predicted much lower levels of the HOx radicals and atmospheric oxidation capacity than the model constrained with measured HONO data. This study sheds light on the characteristics, sources, chemistry, and impacts of HONO in the upper boundary layer and lower free troposphere in the NCP region.

scholarly journals Sources of nitrous acid (HONO) in the upper boundary layer and lower free troposphere of North China Plain: insights from the Mount Tai Observatory

2020 ◽  
Author(s):  
Ying Jiang ◽  
Likun Xue ◽  
Rongrong Gu ◽  
Mengwei Jia ◽  
Yingnan Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrous Acid ◽  
North China Plain ◽  
North China ◽  
High Elevation ◽  
Tropospheric Chemistry ◽  
Oh Radicals ◽  
Free Troposphere ◽  
Radical Chemistry ◽  
Upper Boundary

Abstract. Nitrous acid (HONO) is a significant precursor of atmospheric detergent OH radicals, and plays a vital role in tropospheric chemistry. The current knowledge about the daytime HONO sources is incomplete, and its impact on the tropospheric radical chemistry has not been fully quantified. Existing observational studies of HONO were mostly conducted at surface, with few efforts focusing on the high-elevation atmospheres. In order to better understand the characteristics and sources of HONO in the upper boundary layer and lower free troposphere, two intensive field observations were carried out at the summit of Mt. Tai (1534 m a.s.l.), the peak of the North China Plain, in winter 2017 and spring 2018. HONO showed moderate concentration levels (0.15 ± 0.15 and 0.13 ± 0.15 ppbv), with maximum values of 1.14 and 3.23 ppbv in winter and spring, respectively. Diurnal variation patterns with a broad noontime maximum and lower nighttime concentrations were observed during both campaigns, which is distinct from most of the previous studies at the ground level. The WRF-FLEXPART simulations indicated the combined effects of the planetary boundary layer evolution and valley breeze on the daytime HONO peak. A photostationary state (PSS) analysis suggested the strong unknown daytime HONO source with production rates of 0.45 ± 0.25 ppb/h in winter and 0.64 ± 0.49 ppb/h in spring. Correlation analysis supported the important role of photo-enhanced heterogeneous conversion of NO2 to HONO on the aerosol surface at this high-elevation site. HONO photolysis is the predominant primary source of OH radical and plays a major role in the radical chemistry at Mt. Tai. The model only considering homogenous HONO source would largely underestimate the HOx radical levels and atmospheric oxidation capacity in the high-altitude atmosphere. This study shed light on the characteristics, sources, chemistry, and impacts of HONO in the upper boundary layer and lower free troposphere in the NCP region.

scholarly journals Relationships between the planetary boundary layer height and surface pollutants derived from lidar observations over China

2018 ◽  
Author(s):  
Tianning Su ◽  
Zhanqing Li ◽  
Ralph Kahn
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Negative Correlation ◽  
North China Plain ◽  
North China ◽  
Planetary Boundary Layer Height ◽  
Layer Height ◽  
Boundary Layer Height ◽  
The North ◽  
The North China Plain

Abstract. The frequent occurrence of severe air pollution episodes in China has raised great concerns with the public and scientific communities. Planetary boundary layer height (PBLH) is a key factor in the vertical mixing and dilution of near-surface pollutants. However, the relationship between PBLH and surface pollutants, especially particulate matter (PM) concentration, across the whole of China, is not yet well understood. We investigate this issue at ~ 1500 surface stations using PBLH derived from space-borne and ground-based lidar, and discuss the influence of topography and meteorological variables on the PBLH-PM relationship. A generally negative correlation is observed between PM and the PBLH, albeit varying greatly in magnitude with location and season. Correlations are much weaker over the highlands than plains regions, which may be associated with lower pollution levels and mountain breezes. The influence of horizontal transport on surface PM is considered as well, manifested as a negative correlation between surface PM and wind speed over the whole nation. Strong wind with clean upwind sources plays a dominant role in removing pollutants, and leads to weak PBLH-PM correlation. A ventilation rate is introduced to jointly consider horizontal and vertical dispersion, which has the largest impact on surface pollutant accumulation over the North China Plain. Aerosol absorption feedbacks also appear to affect the PBLH-PM relationship, as revealed via comparing air pollution in Beijing and Hong Kong. Absorbing aerosols in high concentrations likely contribute to the significant PBLH-PM correlation over the North China Plain (e.g., during winter). As major precursor emissions for secondary aerosols, sulfur dioxide, nitrogen dioxide, and carbon monoxide have similar negative responses to increased PBLH, whereas ozone is positively correlated with PBLH over most regions, which may be caused by heterogeneous reactions and photolysis rates.

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