Yuanhang Zhang

Peking University, Peping, Beijing, China

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Publications (106)327.58 Total impact

  • Run Liu · Shaw Chen Liu · Chein-Jung Shiu · Jun Li · Yuanhang Zhang
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    ABSTRACT: Trends in precipitation are critical to water resources. Considerable uncertainty remains concerning the trends of regional precipitation in response to global warming and their controlling mechanisms. Here, we use an interannual difference method to derive trends of regional precipitation from GPCP (Global Precipitation Climatology Project) data and MERRA (Modern- Era Retrospective Analysis for Research and Applications) reanalysis in the near-global domain of 60°S–60°N during a major global warming period of 1979–2013. We find that trends of regional annual precipitation are primarily driven by changes in the top 30% heavy precipitation events, which in turn are controlled by changes in precipitable water in response to global warming, i.e., by thermodynamic processes. Significant drying trends are found in most parts of the U.S. and eastern Canada, the Middle East, and eastern South America, while significant increases in precipitation occur in northern Australia, southern Africa, western India and western China. In addition, as the climate warms there are extensive enhancements and expansions of the three major tropical precipitation centers–the Maritime Continent, Central America, and tropical Africa–leading to the observed widening of Hadley cells and a significant strengthening of the global hydrological cycle.
    No preview · Article · Feb 2016 · Advances in Atmospheric Sciences
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    Jun Li · Run Liu · Shaw Chen Liu · Chein-Jung Shiu · Jingli Wang · Yuanhang Zhang
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    ABSTRACT: A new method has been developed to retrieve aerosol optical depth (AOD) from sunshine duration (SSD). Retrieved AODs from SSD at the six stations in northern China in 2003–2005 agree reasonably well with AODs retrieved from Moderate Resolution Imaging Spectroradiometer observations near the six stations. Values and trends in AOD retrieved from SSD in Beijing and Tianjin in the period 1961–2005 also agree with those retrieved from solar radiation and visibility. These agreements allow the retrieval of credible upper and lower limits for anthropogenic AODs from SSD at the six stations during 1961–2005. The trends in anthropogenic AODs are approximately a factor of 3 to 5 lower than the trends in emissions of gas-phase precursors of aerosols in 1973–2005, implying a significant sublinear relationship between the level of aerosols and emissions of their gas phase precursors. This finding has important implications for formulating a control strategy for PM2.5 or haze pollution in northern China.
    Full-text · Article · Jan 2016 · Geophysical Research Letters
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    ABSTRACT: In his comments, Wang cites a number of works to dispute the conclusion in our previous work, which attributes the observed decreases/increases in light/heavy precipitation in eastern China primarily to global warming rather than the regional aerosol effect. However, most of the cited works (admittedly, including our previous work), employ correlation analysis, which has little bearing on the cause–effect relationship. Theoretical analyses and/or modeling studies are needed to ascertain the cause–effect relationship. We argue that theoretical analyses and modeling results show that global warming is the primary cause of the widely observed phenomena of suppression of light precipitation and enhancement of heavy precipitation across the globe, including in eastern China.
    No preview · Article · Oct 2015 · Advances in Atmospheric Sciences
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    Mengmeng Li · Yu Song · Mingxu Liu · Huan Yao · Xin Huang · Xuesong Wang · Yuanhang Zhang
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    ABSTRACT: The decadal variations in emissions of high-reactivity biogenic volatile organics (BVOCs), as a result of land-cover changes, could significantly impact ozone (O-3) production. In this study, the Weather Research and Forecasting/Chemistry (WRF/Chem) modelling system, coupled with dynamic vegetation data sets derived from Moderate Resolution Imaging Spectroradiometer (MODIS, 2001-2012) and Advanced Very High Resolution Radiometer (AVHRR, early 1990s) measurements, were used to investigate the impacts of land-cover changes on natural emissions, and consequently O-3 production, in the Pearl River Delta (PRD) region of southern China over the past two decades. Model results indicate that BVOC emissions were highly dependent on forest area. The total BVOC emissions in the modelling domain increased by a factor of two due to afforestation since the early 1990s, declined slowly (-5.8% yr(-1)) until 2006 and then increased continuously (+ 9.1% yr(-1)) to 2012. The decadal variations in BVOC emissions have complex implications for summer O-3 production in PRD, depending on the chemical regimes and prevailing winds. The impacts on O-3 production were most sensitive in downwind areas, and it was found that the large increase in BVOC emissions during 2006-2012 tended to reduce surface O-3 concentrations by 1.6-2.5 ppb in rural regions, but caused an increment of O-3 peaks by up to 2.0-6.0 ppb in VOC-limited urban areas (e.g., Guangzhou, Foshan and Zhongshan). The opposite was true in the period 2001-2006, when the reduced BVOC emissions resulted in 1.3-4.0 ppb increases in daytime O-3 concentrations over northern rural regions. Impact of the two-fold increase in BVOC emissions since the early 1990s to 2006 was a 0.9-4.6 ppb increment in surface O-3 concentrations over the downwind areas. This study suggests that the potential impacts on ozone chemistry should be considered in long-term land-use planning and air-quality management.
    Preview · Article · Sep 2015 · Tellus B
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    ABSTRACT: Significant increases of heavy precipitation and decreases of light precipitation have been reported over widespread regions of the globe. Global warming and effects of anthropogenic aerosols have both been proposed as possible causes of these changes. We examine data from urban and rural meteorological stations in eastern China (1955–2011) and compare them with Global Precipitation Climatology Project (GPCP) data (1979–2007) and reanalysis data in various latitude zones to study changes in precipitation extremes. Significant decreases in light precipitation and increases in heavy precipitation are found at both rural and urban stations, as well as low latitudes over the ocean, while total precipitation shows little change. Characteristics of these changes and changes in the equatorial zone and other latitudes suggest that global warming rather than aerosol effects is the primary cause of the changes. In eastern China, increases of annual total dry days (28 days) and ≥10 consecutive dry days (36%) are due to the decrease in light precipitation days, thereby establishing a causal link among global warming, changes in precipitation extremes, and higher meteorological risk of floods and droughts. Further, results derived from the GPCP data and reanalysis data suggest that the causal link exists over widespread regions of the globe.
    No preview · Article · Aug 2015 · Advances in Atmospheric Sciences
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    ABSTRACT: Size-resolved aerosol samples were collected by MOUDI in four seasons in 2007 in Beijing. The PM10 and PM1.8 mass concentrations were 166.0±120.5 and 91.6±69.7μg/m(3), respectively, throughout the measurement, with seasonal variation: nearly two times higher in autumn than in summer and spring. Serious fine particle pollution occurred in winter with the PM1.8/PM10 ratio of 0.63, which was higher than other seasons. The size distribution of PM showed obvious seasonal and diurnal variation, with a smaller fine mode peak in spring and in the daytime. OM (organic matter=1.6×OC (organic carbon)) and SIA (secondary inorganic aerosol) were major components of fine particles, while OM, SIA and Ca(2+) were major components in coarse particles. Moreover, secondary components, mainly SOA (secondary organic aerosol) and SIA, accounted for 46%-96% of each size bin in fine particles, which meant that secondary pollution existed all year. Sulfates and nitrates, primarily in the form of (NH4)2SO4, NH4NO3, CaSO4, Na2SO4 and K2SO4, calculated by the model ISORROPIA II, were major components of the solid phase in fine particles. The PM concentration and size distribution were similar in the four seasons on non-haze days, while large differences occurred on haze days, which indicated seasonal variation of PM concentration and size distribution were dominated by haze days. The SIA concentrations and fractions of nearly all size bins were higher on haze days than on non-haze days, which was attributed to heterogeneous aqueous reactions on haze days in the four seasons. Copyright © 2015. Published by Elsevier B.V.
    No preview · Article · Apr 2015 · Journal of Environmental Sciences
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    ABSTRACT: In recent years, fine particulate matter (PM) pollution and visibility degradation have become severe air quality issues in China. In this study, PM2.5 pollution over the Pearl River Delta (PRD) region during January, April, August, and November 2009 was simulated using the Community Multiscale Air Quality (CMAQ) model. An in-depth diagnostic analysis, focused on November 2009, was also conducted to reveal the patterns of sulfate and nitrate distribution, and to identify the main factors that influence the formation of sulfate and nitrate under typical meteorological conditions. The CMAQ model reasonably reproduced the observed concentrations, but showed better performance for January and November than it did for April and August, for which there was light-moderate underestimation of SO2, NOx, O3, PM10, and PM2.5 concentrations, and slight overestimation of daily 8-hr maximum concentrations of O3. Utilizing a sulfate tracking technique, it was found that on nearly 20 days in November 2009, characterized by northeasterly winds, cross-boundary transport contributed to >75% of the total sulfate budget, while local gas phase oxidation and primary emissions averaged 10% and 8%, respectively. Aqueous sulfate typically contributed less than 1% of the total sulfate budget, except when the winds were directed from the sea and high humidity favored aqueous oxidation, and the percentage contribution reached up to 46%. NH3 was generally sufficient to fully neutralize H2SO4; however, the formation of nitrate over the PRD was limited by the availability of NH3.
    No preview · Article · Apr 2015 · Atmospheric Environment
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    ABSTRACT: It is not known whether exposure to air pollutants causes systemic oxidative stress in children. We investigated the association between exposure to air pollution and biomarkers of oxidative stress in relation to a governmental air quality intervention implemented during the 2008 Beijing Olympic Games. We studied 36 schoolchildren during 5 time periods before and during the Olympic Games in Beijing (June 2007-September 2008). The oxidative stress biomarkers 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and malondialdehyde were measured in urine samples collected daily during each period. Generalized estimating equations were used to examine the relationship between repeated biomarker measurements and ambient air pollutant levels. During the Olympic intervention period, substantial reductions in air pollution (-19% to -72%), urinary 8-oxodG concentrations (-37.4%; 95% confidence interval: -53.5, -15.7), and urinary malondialdehyde concentrations (-25.3%; 95% confidence interval: -34.3, -15.1) were found. Malondialdehyde and 8-oxodG were significantly associated with concentrations of black carbon, fine particulate matter with an aerodynamic with diameter less than 2.5 μm, sulfur dioxide, nitrogen dioxide, and carbon monoxide. Biomarker changes per each interquartile-range increase in pollutants were largest at lag 0 or lag 1. In a 2-pollutant model, the most robust associations were for black carbon. These findings suggest that exposure to black carbon leads to systemic oxidative stress in children. © The Author 2015. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
    Full-text · Article · Mar 2015 · American Journal of Epidemiology
  • Tingting Han · Xingang Liu · Yuanhang Zhang · Yu Qu · Limin Zeng · Min Hu · Tong Zhu
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    ABSTRACT: A field experiment from 18 August to 8 September 2006 in Beijing, China, was carried out. A hazy day was defined as visibility<l0km and RH (relative humidity)<90%. Four haze episodes, which accounted for ~60% of the time during the whole campaign, were characterized by increases of SNA (sulfate, nitrate, and ammonium) and SOA (secondary organic aerosol) concentrations. The average values with standard deviation of SO4(2-), NO3(-), NH4(+) and SOA were 49.8 (±31.6), 31.4 (±22.3), 25.8 (±16.6) and 8.9 (±4.1)μg/m(3), respectively, during the haze episodes, which were 4.3, 3.4, 4.1, and 1.7 times those in the non-haze days. The SO4(2-), NO3(-), NH4(+), and SOA accounted for 15.8%, 8.8%, 7.3%, and 6.0% of the total mass concentration of PM10 during the non-haze days. The respective contributions of SNA species to PM10 rose to about 27.2%, 15.9%, and 13.9% during the haze days, while the contributions of SOA maintained the same level with a slight decrease to about 4.9%. The observed mass concentrations of SNA and SOA increased with the increase of PM10 mass concentration, however, the rate of increase of SNA was much faster than that of the SOA. The SOR (sulfur oxidation ratio) and NOR (nitrogen oxidation ratio) increased from non-haze days to hazy days, and increased with the increase of RH. High concentrations of aerosols and water vapor favored the conversion of SO2 to SO4(2-) and NO2 to NO3(-), which accelerated the accumulation of the aerosols and resulted in the formation of haze in Beijing. Copyright © 2015. Published by Elsevier B.V.
    No preview · Article · Mar 2015 · Journal of Environmental Sciences
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    ABSTRACT: The north and east Pearl River Delta (PRD) is usually a clean, upwind area in autumn. Serious ozone pollution there in mid-late October 2008 was first discovered and then analyzed. Trajectory analysis, process analysis, ozone source apportionment technology, and sensitivity analysis were used to study this episode. Under the influence of a weak south wind, the precursors emitted in Guangzhou and Foshan were transported to the north and northeast PRD and formed ozone there, which resulted in high ozone concentration (>100 ppb). As the wind direction later transited to northerly, the precursors in the northeast PRD that originated from the central and west PRD were transported to the south, and caused severe ozone pollution in the southeast PRD. The ozone contributed by chemical processes reached >20 ppb/h in Jinguowan. More than 40 ppb ozone was contributed by the precursor emission in the central and west PRD during the episode. The ozone concentration was highly sensitive to the precursor emission in the PRD region in the high-ozone situations. This episode showed the complexity of regional pollution in the PRD. When the PRD is controlled by a low air pressure system and then cold air moves from northern China to the south, the risk of ozone pollution in the north and southeast PRD increases.
    Full-text · Article · Mar 2015 · Atmospheric Environment
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    ABSTRACT: Marine aerosols over the East China Seas are heavily polluted by continental sources. During the Chinese Comprehensive Ocean Experiment in November 2012, size and mass spectra of individual atmospheric particles in the size range from 0.2 to 2.0μm were measured on board by a single particle aerosol mass spectrometer (SPAMS). The average hourly particle number (PN) was around 4560±3240 in the South Yellow Sea (SYS), 2900±3970 in the North Yellow Sea (NYS), and 1700±2220 in the Bohai Sea (BS). PN in NYS and BS varied greatly over 3 orders of magnitude, while that in SYS varied slightly. The size distributions were fitted with two log-normal modes. Accumulation mode dominated in NYS and BS, especially during episodic periods. Coarse mode particles played an important role in SYS. Particles were classified using an adaptive resonance theory based neural network algorithm (ART-2a). Six particle types were identified with secondary-containing, aged sea-salt, soot-like, biomass burning, fresh sea-salt, and lead-containing particles accounting for 32%, 21%, 18%, 16%, 4%, and 3% of total PN, respectively. Aerosols in BS were relatively enriched in particles from anthropogenic sources compared to SYS, probably due to emissions from more developed upwind regions and indicating stronger influence of continental outflow on marine environment. Variation of source types depended mainly on origins of transported air masses. This study examined rapid changes in PN, size distribution and source types of fine particles in marine atmospheres. It also demonstrated the effectiveness of high-time-resolution source apportionment by ART-2a. Copyright © 2015. Published by Elsevier B.V.
    Full-text · Article · Jan 2015 · Journal of Environmental Sciences
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    Wei Lü · Jinfeng Li · Xuesong Wang · Yuanhang Zhang
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    ABSTRACT: The Community Multiscale Air Quality (CMAQ) model was applied to simulate the seasonal characteristics of temporal⁃spatial distribution and transport patterns for major ambient air pollutants. The impact of long⁃range transport on the regional air quality in the Pearl River Delta was analyzed in combination with other methods. The simulation results indicated higher NO2 , SO2 , PM10 and PM2.5 concentrations in autumn and winter but lower levels in spring and summer as well as peak O3 concentrations in autumn. The results using zero⁃emission perturbation method showed that long⁃range transport contributed to ambient NO2 , SO2 , PM10 and PM2.5 concentrations by 2.6%, 13.9%, 24.2% and 28.1%, respectively, at 15 regional monitoring sites. Long⁃range transport was more significant in autumn and winter than spring and summer. The 72⁃h back trajectory clustering analysis revealed four kinds of air masses that affected air quality at Wanqingsha, a regional representative monitoring site, including coastal air mass, continental air mass, regional circulated air mass and marine air mass, according to their origin. The highly polluted periods with concentrations of major pollutants greater than 150 μg·m-3 were often correlated with the transport of short⁃range coastal air mass, short⁃range continental air mass and regional circulated air mass. Four⁃dimensional flux calculation indicated that NO2 transport pathways outside Guangdong Province could not extend to the Pearl River Delta, thus NO2 in the Pearl River Delta could only be attributed to emissions inside Guangdong Province. High fluxes of SO2 and PM2.5 could be transported from Fujian Province or Jiangxi Province to the Pearl River Delta under the control of coastal air mass or continental air mass. It could be concluded that region⁃wide and collaborative efforts are important to effectively control air pollution in the Pearl River Delta. Different control measures should be applied for different ambient pollutants, taking regional background meteorological conditions into consideration.
    Full-text · Article · Jan 2015 · Huanjing Kexue Xuebao / Acta Scientiae Circumstantiae
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    Full-text · Article · Jan 2015 · Chinese Journal
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    Jie Li · Huabin Dong · Limin Zeng · Yuanhang Zhang · Min Shao · Zifa Wang · Yele Sun · Pingqing Fu
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    ABSTRACT: Nitrate and its precursor (gaseous HNO3) in China are generally overestimated by current chemical transport models in comparison to in-situ observations. In this study, we used an observation-based box model and in-situ measurements at a rural site in southern China to investigate possible missing sinks of nitrate. We found that a heterogeneous reaction of HNO3 to NOx on soot can better balance the NOx/HNO3 chemistry in models and improve model performance with regard to nitrate, particularly where an additional HONO source (the heterogeneous reaction of NO2 on soot) is incorporated into current models. Through a series of sensitivity simulations, the uptake coefficients of heterogeneous reactions were suggested to be 3.0 × 10−3 and 1 × 10−4 for HNO3 and HONO over southern China in fall, respectively. A 3-D simulation with the suggested uptake coefficients further confirmed that heterogeneous reactions significantly decreased the nitrate concentrations (PNO3) in southern China, by up to 10 μg m−3 (50%-80% of simulated PNO3) in polluted regions (e.g., the Yangtze River). In contrast to nitrate and HNO3, NOx concentrations in China were enhanced, which partly explained the underestimation of NO2 in current models compared to satellite observations.
    Full-text · Article · Jan 2015 · Scientific online letters on the atmosphere: SOLA
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    Yuanhang Zhang · Jinfeng Li
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    ABSTRACT: 与PM2.5相比,臭氧污染更具隐蔽性,即使是晴朗的蓝天,也可能存在臭氧浓度超标问题。如果臭氧不能得到有效控制,PM2.5的治理工作就会事倍功半,或者在一定程度上加剧PM2.5污染。
    Full-text · Article · Dec 2014
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    ABSTRACT: Size-resolved aerosols were continuously collected by a Nano Sampler for 13 days at an urban site in Beijing during winter 2012 to measure the chemical composition of ambient aerosol particles. Data collected by the Nano Sampler and an ACSM (Aerodyne Aerosol Chemical Speciation Monitor) were compared. Between the data sets, similar trends and strong correlations were observed, demonstrating the validity of the Nano Sampler. PM10 and PM2.5 concentrations during the measurement were 150.5 ± 96.0 μg/m3 (mean ± standard variation) and 106.9 ± 71.6 μg/m3, respectively. The PM2.5/PM10 ratio was 0.70 ± 0.10, indicating that PM2.5 dominated PM10. The aerosol size distributions showed that three size bins of 0.5–1, 1–2.5 and 2.5–10 μm contributed 21.8%, 23.3% and 26.0% to the total mass concentration (TMC), respectively. OM (organic matter) and SIA (secondary ionic aerosol, mainly SO42 −, NO3− and NH4+) were major components of PM2.5. Secondary compounds (SIA and secondary organic carbon) accounted for half of TMC (about 49.8%) in PM2.5, and suggested that secondary aerosols significantly contributed to the serious particulate matter pollution observed in winter. Coal burning, biomass combustion, vehicle emissions and SIA were found to be the main sources of PM2.5. Mass concentrations of water-soluble ions and undetected materials, as well as their fractions in TMC, strikingly increased with deteriorating particle pollution conditions, while OM and EC (elemental carbon) exhibited different variations, with mass concentrations slightly increasing but fractions in TMC decreasing.
    No preview · Article · Aug 2014 · Journal of Environmental Sciences
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    ABSTRACT: The removal of trace gases from the troposphere is, in most cases, initialized by reactions with hydroxyl radicals, and the products of these reactions are eventually deposited on the Earth's surface. The concentration of these hydroxyl radicals is therefore a measure of atmospheric self-cleansing. In theory, hydroxyl-radical concentrations can be enhanced by the recycling of some of the reaction products. The only known efficient recycling process involves nitrogen oxide and leads to production of ozone, yet observations in regions with high hydrocarbon and low nitrogen oxide concentrations show substantially elevated hydroxyl-radical concentrations, up to ten times higher than expected. If we normalize observed hydroxyl-radical concentrations to the maximum achievable in model calculations with variable nitrogen oxide concentrations, this photochemical coordinate system uncovers a common feature in almost all of these observations: even in the presence of inadequate amounts of nitrogen oxides, hydroxyl-radical concentrations are enhanced to the theoretical maximum obtainable at very much higher nitrogen oxide concentrations. This means that this important part of the self-cleansing capability of the atmosphere is working at maximum efficiency even in regions with a high burden of biogenic hydrocarbons and low nitrogen oxide concentration. Since these processes do not involve nitrogen oxides, tropospheric ozone production is greatly reduced compared with the expectation from current theory.
    No preview · Article · Jul 2014 · Nature Geoscience
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    ABSTRACT: Nitrous acid (HONO), as a primary precursor of OH radicals, has been considered one of the most important nitrogen-containing species in the atmosphere. Up to 30% of primary OH radical production is attributed to the photolysis of HONO. However, the major HONO formation mechanisms are still under discussion. During the Campaigns of Air Quality Research in Beijing and Surrounding Region (CAREBeijing2006) campaign, comprehensive measurements were carried out in the megacity Beijing, where the chemical budget of HONO was fully constrained. The average diurnal HONO concentration varied from 0.33 to 1.2 ppbv. The net OH production rate from HONO, P OH(HONO)net, was on average (from 05:00 to 19:00 h) 7.1 × 106 molecule/(cm3 s), 2.7 times higher than from O3 photolysis. This production rate demonstrates the important role of HONO in the atmospheric chemistry of megacity Beijing. An unknown HONO source (P unknown) with an average of 7.3 × 106 molecule/(cm3 s) was derived from the budget analysis during daytime. P unknown provided four times more HONO than the reaction of NO with OH did. The diurnal variation of P unknown showed an apparent photo-enhanced feature with a maximum around 12:00 h, which was consistent with previous studies at forest and rural sites. Laboratory studies proposed new mechanisms to recruit NO2 and J(NO2) in order to explain a photo-enhancement of of P unknown. In this study, these mechanisms were validated against the observation-constraint P unknown. The reaction of exited NO2 accounted for only 6% of P unknown, and P unknown poorly correlated with [NO2] (R = 0.26) and J(NO2)[NO2] (R = 0.35). These results challenged the role of NO2 as a major precursor of the missing HONO source.
    Full-text · Article · Jul 2014 · Science China-Chemistry
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    Full-text · Dataset · Apr 2014
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    Jinfeng Li · Keding Lu · Wei Lv · Jun Li · Liuju Zhong · Yubo Ou · Duohong Chen · Xin Huang · Yuanhang Zhang
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    ABSTRACT: Based on the observation by a Regional Air Quality Monitoring Network including 16 monitoring stations, temporal and spatial variations of ozone (O3), NO2 and total oxidant (Ox) were analyzed by both linear regression and cluster analysis. A fast increase of regional O3 concentrations of 0.86 ppbV/yr was found for the annual averaged values from 2006 to 2011 in Guangdong, China. Such fast O3 increase is accompanied by a correspondingly fast NOx reduction as indicated by a fast NO2 reduction rate of 0.61 ppbV/yr. Based on a cluster analysis, the monitoring stations were classified into two major categories – rural stations (non-urban) and suburban/urban stations. The O3 concentrations at rural stations were relatively conserved while those at suburban/urban stations showed a fast increase rate of 2.0 ppbV/yr accompanied by a NO2 reduction rate of 1.2 ppbV/yr. Moreover, a rapid increase of the averaged O3 concentrations in springtime (13%/yr referred to 2006 level) was observed, which may result from the increase of solar duration, reduction of precipitation in Guangdong and transport from Eastern Central China. Application of smog production algorithm showed that the photochemical O3 production is mainly volatile organic compounds (VOC)-controlled. However, the photochemical O3 production is sensitive to both NOx and VOC for O3 pollution episode. Accordingly, it is expected that a combined NOx and VOC reduction will be helpful for the reduction of the O3 pollution episodes in Pearl River Delta while stringent VOC emission control is in general required for the regional O3 pollution control.
    Full-text · Article · Mar 2014