scholarly journals Radical chemistry at a rural site (Wangdu) in the North China Plain: Observation and model calculations of OH, HO<sub>2</sub> and RO<sub>2</sub> radicals

2016 ◽  
Author(s):  
Zhaofeng Tan ◽  
Hendrik Fuchs ◽  
Keding Lu ◽  
Birger Bohn ◽  
Sebastian Broch ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
Rural Site ◽  
Daily Maximum ◽  
Model Calculations ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain

Abstract. A comprehensive field campaign was carried out in summer 2014 in Wangdu located in the North China Plain. A month of continuous OH, HO2 and RO2 measurements were achieved. Observations of radicals by laser induced fluorescence (LIF) technique gave daily maximum concentrations between (5–15) × 106 cm−3, (3–14) × 108 cm−3 and (3–15) × 108 cm−3 for OH, HO2 and RO2, respectively. Measured OH reactivities (inverse OH lifetimes) were 10 to 20 s−1 during daytime. A chemical box model constrained by trace-gas observations and based on a state-of-the-art chemical mechanism is used to interpret the observed radical concentrations. In general, the model can reasonably well reproduce measured radical concentrations during daytime. Like in previous field campaigns in China, modelled and measured OH concentrations agree for NO mixing ratios higher than 1 ppbv, but systematic discrepancies are observed in the afternoon for NO mixing ratios of less than 300 pptv (the model-measurement ratio is between 1.4 to 2 in this case). If additional OH recycling equivalent to 100 pptv NO is assumed, the model is also capable of reproducing the observed OH concentrations for conditions of high VOC and low NOx concentrations with good agreement in HO2 and RO2. Observed RO2 concentrations are underestimated in the morning hours by a factor of 3 to 5. This indicates that an additional chemical source of RO2 is missing in the model. The OH reactivity is also underpredicted in the early morning. Increasing VOC concentrations to match measured OH reactivity helps to reduce the discrepancy between modelled and measured RO2. The underprediction of RO2 coincides with high NO concentrations and therefore leads to a significant underestimation of the local ozone production rates determined from the peroxy radical (HO2 and RO2) reactions with NO. The underestimation corresponds to a daily integral ozone production of about 20 ppbv per day.

scholarly journals Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and model calculations of OH, HO<sub>2</sub> and RO<sub>2</sub> radicals

2017 ◽  
Vol 17 (1) ◽  
pp. 663-690 ◽  
Author(s):  
Zhaofeng Tan ◽  
Hendrik Fuchs ◽  
Keding Lu ◽  
Andreas Hofzumahaus ◽  
Birger Bohn ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Ozone Production ◽  
Rural Site ◽  
Model Calculations ◽  
Radical Chemistry ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain ◽  
Field Campaigns

Abstract. A comprehensive field campaign was carried out in summer 2014 in Wangdu, located in the North China Plain. A month of continuous OH, HO2 and RO2 measurements was achieved. Observations of radicals by the laser-induced fluorescence (LIF) technique revealed daily maximum concentrations between (5–15)  × 106 cm−3, (3–14)  × 108 cm−3 and (3–15)  × 108 cm−3 for OH, HO2 and RO2, respectively. Measured OH reactivities (inverse OH lifetime) were 10 to 20 s−1 during daytime. The chemical box model RACM 2, including the Leuven isoprene mechanism (LIM), was used to interpret the observed radical concentrations. As in previous field campaigns in China, modeled and measured OH concentrations agree for NO mixing ratios higher than 1 ppbv, but systematic discrepancies are observed in the afternoon for NO mixing ratios of less than 300 pptv (the model–measurement ratio is between 1.4 and 2 in this case). If additional OH recycling equivalent to 100 pptv NO is assumed, the model is capable of reproducing the observed OH, HO2 and RO2 concentrations for conditions of high volatile organic compound (VOC) and low NOx concentrations. For HO2, good agreement is found between modeled and observed concentrations during day and night. In the case of RO2, the agreement between model calculations and measurements is good in the late afternoon when NO concentrations are below 0.3 ppbv. A significant model underprediction of RO2 by a factor of 3 to 5 is found in the morning at NO concentrations higher than 1 ppbv, which can be explained by a missing RO2 source of 2 ppbv h−1. As a consequence, the model underpredicts the photochemical net ozone production by 20 ppbv per day, which is a significant portion of the daily integrated ozone production (110 ppbv) derived from the measured HO2 and RO2. The additional RO2 production from the photolysis of ClNO2 and missing reactivity can explain about 10 % and 20 % of the discrepancy, respectively. The underprediction of the photochemical ozone production at high NOx found in this study is consistent with the results from other field campaigns in urban environments, which underlines the need for better understanding of the peroxy radical chemistry for high NOx conditions.

scholarly journals Variations of O<sub>3</sub> and CO in summertime at a rural site near Beijing

2008 ◽  
Vol 8 (21) ◽  
pp. 6355-6363 ◽  
Author(s):  
Y. Wang ◽  
M. B. McElroy ◽  
J. W. Munger ◽  
J. Hao ◽  
H. Ma ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Rural Site ◽  
Mixing Ratio ◽  
Efficient Manner ◽  
Strong Negative Correlation ◽  
Cloud Optical Depth ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain

Abstract. Large intra-season differences in mixing ratios of CO and O3 were detected at Miyun, a rural site north of Beijing, in summer 2006. Despite an increase in mean daytime mixing ratio of CO from 500 ppbv in June to 700 ppbv in July, mean daytime O3 dropped from 67 ppbv in June to 50 ppbv in July and August. The observed changes in CO and O3 are attributed to the influence of the summer monsoonal circulation that develops over the North China Plain in July. Photochemical production of O3 is reduced as a consequence of increased cloudiness during July and August, as indicated by the strong negative correlation observed between O3 and satellite observations of cloud optical depth, with cloudiness having little effect on CO. The analysis suggests a strategy for emission controls that could be implemented in an economically efficient manner to minimize the frequency of high levels of O3 during summer in Beijing.

scholarly journals Observation of atmospheric peroxides during Wangdu Campaign 2014 at a rural site in the North China Plain

2016 ◽  
Vol 16 (17) ◽  
pp. 10985-11000 ◽  
Author(s):  
Yin Wang ◽  
Zhongming Chen ◽  
Qinqin Wu ◽  
Hao Liang ◽  
Liubin Huang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
North China Plain ◽  
North China ◽  
Chemical Mechanism ◽  
Rural Site ◽  
Direct Production ◽  
The North ◽  
The North China Plain ◽  
The Impact ◽  
Haze Days

Abstract. Measurements of atmospheric peroxides were made during Wangdu Campaign 2014 at Wangdu, a rural site in the North China Plain (NCP) in summer 2014. The predominant peroxides were detected to be hydrogen peroxide (H2O2), methyl hydroperoxide (MHP) and peroxyacetic acid (PAA). The observed H2O2 reached up to 11.3 ppbv, which was the highest value compared with previous observations in China at summer time. A box model simulation based on the Master Chemical Mechanism and constrained by the simultaneous observations of physical parameters and chemical species was performed to explore the chemical budget of atmospheric peroxides. Photochemical oxidation of alkenes was found to be the major secondary formation pathway of atmospheric peroxides, while contributions from alkanes and aromatics were of minor importance. The comparison of modeled and measured peroxide concentrations revealed an underestimation during biomass burning events and an overestimation on haze days, which were ascribed to the direct production of peroxides from biomass burning and the heterogeneous uptake of peroxides by aerosols, respectively. The strengths of the primary emissions from biomass burning were on the same order of the known secondary production rates of atmospheric peroxides during the biomass burning events. The heterogeneous process on aerosol particles was suggested to be the predominant sink for atmospheric peroxides. The atmospheric lifetime of peroxides on haze days in summer in the NCP was about 2–3 h, which is in good agreement with the laboratory studies. Further comprehensive investigations are necessary to better understand the impact of biomass burning and heterogeneous uptake on the concentration of peroxides in the atmosphere.

scholarly journals Observation of atmospheric peroxides during Wangdu Campaign 2014 at a rural site in the North China Plain

2016 ◽  
Author(s):  
Yin Wang ◽  
Zhongming Chen ◽  
Qinqin Wu ◽  
Hao Liang ◽  
Liubin Huang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
North China Plain ◽  
North China ◽  
Chemical Mechanism ◽  
Rural Site ◽  
Direct Production ◽  
The North ◽  
The North China Plain ◽  
The Impact ◽  
Haze Days

Abstract. Measurements of atmospheric peroxides were made during Wangdu Campaign 2014 at Wangdu, a rural site in the North China Plain (NCP) in summer 2014. The predominant peroxides were detected to be hydrogen peroxide (H2O2), methyl hydroperoxide (MHP) and peroxyacetic acid (PAA). The observed H2O2 reached up to 11.3 ppbv, which was the highest value compared with previous observations in China at summer time. A box model simulation based on the Master Chemical Mechanism and constrained by the simultaneous observations of physical parameters and chemical species was performed to explore the chemical budget of atmospheric peroxides. Photochemical oxidation of alkenes was found to be the major secondary formation pathway of atmospheric peroxides, while contributions from alkanes and aromatics were of minor importance. The comparison of modelled and measured peroxide concentrations revealed an underestimation during biomass burning events and an overestimation on haze days, which were ascribed to the direct production of peroxides from biomass burning and the heterogeneous uptake of peroxides by aerosols, respectively. The strengths of the primary emissions from biomass burning were on the same order of the known secondary production rates of atmospheric peroxides during the biomass burning events. The heterogeneous process on aerosol particles was suggested to be the predominant sink for atmospheric peroxides. The atmospheric lifetime of peroxides on haze days in summer in the NCP was about 2–3 hours, which is in good agreement with the laboratory studies. Further comprehensive investigations are necessary to better understand the impact of biomass burning and heterogeneous uptake on the concentration of peroxides in the atmosphere.

scholarly journals Aerosol vertical mass flux measurements during heavy aerosol pollution episodes at a rural site and an urban site in the Beijing area of the North China Plain

2019 ◽  
Vol 19 (20) ◽  
pp. 12857-12874 ◽  
Author(s):  
Renmin Yuan ◽  
Xiaoye Zhang ◽  
Hao Liu ◽  
Yu Gui ◽  
Bohao Shao ◽  
...  
Keyword(s):  
Mass Flux ◽  
North China Plain ◽  
North China ◽  
Rural Site ◽  
Urban Site ◽  
The North ◽  
The North China Plain ◽  
Aerosol Pollution ◽  
The Mean ◽  
Pollution Episodes

Abstract. Due to excessive anthropogenic emissions, heavy aerosol pollution episodes (HPEs) often occur during winter in the Beijing–Tianjin–Hebei (BTH) area of the North China Plain. Extensive observational studies have been carried out to understand the causes of HPEs; however, few measurements of vertical aerosol fluxes exist, despite them being the key to understanding vertical aerosol mixing, specifically during weak turbulence stages in HPEs. In the winter of 2016 and the spring of 2017 aerosol vertical mass fluxes were measured by combining large aperture scintillometer (LAS) observations, surface PM2.5 and PM10 mass concentrations, and meteorological observations, including temperature, relative humidity (RH), and visibility, at a rural site in Gucheng (GC), Hebei Province, and an urban site at the Chinese Academy of Meteorological Sciences (CAMS) in Beijing located 100 km to the northeast. These are based on the light propagation theory and surface-layer similarity theory. The near-ground aerosol mass flux was generally lower in winter than in spring and weaker in rural GC than in urban Beijing. This finding provides direct observational evidence for a weakened turbulence intensity and low vertical aerosol fluxes in winter and polluted areas such as GC. The HPEs included a transport stage (TS), an accumulative stage (AS), and a removal stage (RS). During the HPEs from 25 to 31 January 2017, in Beijing, the mean mass flux decreased by 51 % from 0.0049 mg m−2 s−1 in RSs to 0.0024 mg m−2 s−1 in the TSs. During the ASs, the mean mass flux decreased further to 0.00087 mg m−2 s−1, accounting for approximately one-third of the flux in the TSs. A similar reduction from the TSs to ASs was observed in the HPE from 16 to 22 December 2016 in GC. It can be seen that from the TS to the AS, the aerosol vertical turbulent flux decreased, but the aerosol particle concentration within the surface layer increased, and it is inferred that in addition to the contribution of regional transport from upwind areas during the TS, suppression of vertical turbulence mixing confining aerosols to a shallow boundary layer increased accumulation.

scholarly journals Measurement report: Variations in surface SO<sub>2</sub> and NO<sub>x</sub> mixing ratios from 2004 to 2016 at a background site in the North China Plain

2022 ◽  
Author(s):  
Xueli Liu ◽  
Liang Ran ◽  
Weili Lin ◽  
Xiaobin Xu ◽  
Zhiqiang Ma ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Diurnal Variations ◽  
Nox Emission ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain ◽  
Regional Background ◽  
Long Term Trends

Abstract. Strict air pollution control strategies have been implemented in recent decades in the North China Plain (NCP), previously one of the most polluted regions in the world, and have resulted in considerable changes in emissions of air pollutants. However, little is so far known about the long-term trends of the regional background level of NOx and SO2, along with the increase and decrease processes of regional emissions. In this study, the seasonal and diurnal variations of NOx and SO2 as well as their long-term trends at a regional background station in the NCP were characterized from 2004 to 2016. On average, SO2 and NOx mixing ratios were 5.7 ± 8.4 ppb and 14.2 ± 12.4 ppb, respectively. The seasonal variations in SO2 and NOx mixing ratios showed a similar pattern with a peak in winter and a valley in summer. However, the diurnal variations in SO2 and NOx mixing ratios greatly differed for all seasons, indicating different sources for SO2 and NOx. Overall, the annual mean SO2 exhibited a significant decreasing trend of ‒6.1 % yr−1 (R = −0.84, P < 0.01) from 2004 to 2016, which is very close to −6.3 % yr−1 of the annual SO2 emission in Beijing, and a greater decreasing trend of −7.4 % yr−1 (R = −0.95, P < 0.01) from 2008 to 2016. The annual mean of NOx showed a fluctuating rise of +3.4 % yr−1 (R = 0.38, P = 0.40) from 2005 to 2010, reaching the peak value (16.9 ppb) in 2010, and then exhibited an extremely significant fluctuating downward trend of −4.5 % yr−1 (R = 0.95, P < 0.01) from 2010 to 2016. After 2010, the annual mean NOx mixing ratios correlated significantly (R = 0.94, P < 0.01) with the annual NOx emission in North China. The decreasing rate (−4.8 % yr−1, R = −0.92, P < 0.01) of the annual mean NOx mixing ratios from 2011 to 2016 at SDZ are lower than the one (−8.8 % yr−1, R = −0.94, P < 0.01) for the annual NOx emission in the NCP and (−9.0 % yr−1, R = −0.96, P < 0.01) in Beijing. It indicated that surface NOx mixing ratios at SDZ had weaker influence than SO2 by the emission reduction in Beijing and its surrounding areas in the NCP. The increase in the amount of motor vehicles led to an increase in traffic emissions for NOx. This study supported conclusions from previous studies that the measures taken for controlling NOx and SO2 in the NCP in the past decades were generally successful. However, NOx emission control should be strengthened in the future.

scholarly journals Study on the Change Characteristics of and Population Exposure to Heatwave Events on the North China Plain

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Long-Fei Zhan ◽  
Yanjun Wang ◽  
Hemin Sun ◽  
Jianqing Zhai ◽  
Mingjin Zhan
Keyword(s):  
North China Plain ◽  
North China ◽  
Climatic Factors ◽  
Demographic Data ◽  
Population Exposure ◽  
Central Position ◽  
Daily Maximum ◽  
The North ◽  
The North China Plain ◽  
The Impact

In accordance with the China Meteorological Administration definition, this study considered a weather process with a maximum surface temperature of ≥35°C for more than three consecutive days as a heatwave event. Based on a dataset of daily maximum temperatures from meteorological stations on the North China Plain, including ordinary and national basic/reference surface stations, the intensity-area-duration method was used to analyze the spatiotemporal distribution characteristics of heatwave events on the North China Plain (1961–2017). Moreover, based on demographic data from the Statistical Yearbook and Greenhouse Gas Initiative (GGI) Population Scenario Database of the Austrian Institute for International Applied Systems Analysis (IIASA), population exposure to heatwave events was also studied. The results showed that the frequency, intensity, and area of impact of heatwave events on the North China Plain initially decreased (becoming weaker and less extensive) and then increased (becoming stronger and more extensive). Similarly, the trend of population exposure to heatwave events initially decreased and then increased, and the central position of exposure initially moved southward and then returned northward. Population exposure in the eastern Taihang Mountains was found significantly higher than in the western Taihang Mountains. In relation to the change of population exposure to heatwave events on the North China Plain, the influence of climatic factors was found dominant with an absolute contribution rate of >75%. Except for 2011–2017, increase in population also increased the exposure to heatwaves, particularly in the first half of the study period. Interaction between climatic and population factors generally had less impact on population exposure than either climatic factors or population factors alone. This study demonstrated a method for assessing the impact of heatwave events on population exposure, which could form a scientific basis for the development of government policy regarding adaption to climate change.

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