. The Chinese government launched the Air Pollution Prevention and
Control Action Plan in 2013, and various stringent measures have since been
implemented, which have resulted in significant decreases in emissions and
ambient concentrations of primary pollutants such as SO2 , NOx , and
particulate matter (PM). However, surface ozone ( O3 ) concentrations
have still been increasing in urban areas across the country. In a previous
analysis, we examined in detail the roles of meteorological variation during
2013–2017 in the summertime surface O3 trend in various regions of
China. In this study, we evaluated the effect of changes in multi-pollutant
emissions from anthropogenic activities on O3 levels during the same
period by using an up-to-date regional chemical transport model (WRF-CMAQ)
driven by an interannual anthropogenic emission inventory. The Community Multiscale Air
Quality (CMAQ) model
was improved with regard to heterogeneous reactions of reactive gases on
aerosol surfaces, which led to better model performance in reproducing the
ambient concentrations of those gases. The model simulations showed that the
maximum daily 8  h average (MDA8) O3 mixing ratio in urban areas
increased by 0.46 ppbv per year ( ppbv a−1 ) ( p=0.001 ) from 2013 to
2017. In contrast, a slight decrease in MDA8 O3 by 0.17  ppbv a−1 
( p=0.005 ) in rural areas was predicted, mainly attributable to the
 NOx emission reduction. The effects of changes in individual pollutant
emissions on O3 were also simulated. The reduction of NOx emission
increased the O3 levels in urban areas due to the nonlinear
 NOx and volatile organic compound (VOC) chemistry and decreasing aerosol
effects; the slight increase in VOC emissions enhanced the O3 levels;
the reduction of PM emissions increased the O3 levels by enhancing the
photolysis rates and reducing the loss of reactive gases on aerosol
surfaces; and the reduction of SO2 emissions resulted in a drastic
decrease in sulfate concentrations, which increased O3 through aerosol
effects. In contrast to the unfavorable effect of the above changes in
pollutant emissions on efforts to reduce surface O3 , the reduction of
CO emissions did help to decrease the O3 level in recent years. The
dominant cause of increasing O3 due to changes in anthropogenic
emissions varied geographically. In Beijing, NOx and PM emission
reductions were the two largest causes of the O3 increase; in Shanghai,
the reduction of NOx and increase in VOC emissions were the two major
causes; in Guangzhou, NOx reduction was the primary cause; in
Chengdu, the PM and SO2 emission decreases contributed most to the
 O3 increase. Regarding the effects of decreasing concentrations of
aerosols, the drop in heterogeneous uptake of reactive gases – mainly
 HO2 and O3 – was found to be more important than the increase in
photolysis rates. The adverse effect of the reductions of NOx ,
 SO2 , and PM emissions on O3 abatement in Beijing, Shanghai,
Guangzhou, and Chengdu would have been avoided if the anthropogenic VOCs
emission had been reduced by 24 %, 23 %, 20 %, and 16 %,
respectively, from 2013 to 2017. Our analysis revealed that the NOx 
reduction in recent years has helped to contain the total O3 production
in China. However, to reduce O3 levels in major urban and industrial
areas, VOC emission controls should be added to the current
 NOx - SO2 -PM policy.

/pdf/worsening-urban-ozone-pollution-in-china-from-2013-to-2017-1eyai0ich9.pdf

Worsening urban ozone pollution in China from 2013 to 2017 – Part 2: The effects of emission changes and implications for multi-pollutant control

Biogenic organosulfates (OSs) are important markers of secondary organic aerosol (SOA) formation involving cross reactions of biogenic precursors (terpenoids) with anthropogenic pollutants. Until now, there has been rare information about biogenic OSs in the air of highly polluted areas. In this study, fine particle (PM2.5) samples were separately collected in daytime and nighttime from summer to fall 2010 at a site in the central Pearl River Delta (PRD), South China. Pinene-derived nitrooxy-organosulfates (pNOSs) and isoprene-derived OSs (iOSs) were quantified using a liquid chromatograph (LC) coupled with a tandem mass spectrometer (MS/MS) operated in negative electrospray ionization (ESI) mode. The pNOSs with MW 295 exhibited higher levels in fall (151 ± 86.9 ng m–3) than summer (52.4 ± 34.0 ng m–3), probably owing to the elevated levels of NOx and sulfate in fall when air masses mainly passed through city clusters in the PRD and biomass burning was enhanced. In contrast to observations elsewhere where...

Organosulfates from Pinene and Isoprene over the Pearl River Delta, South China: Seasonal Variation and Implication in Formation Mechanisms

 Nocturnal reactive nitrogen compounds play an important role in regional air
pollution Here we present the measurements of dinitrogen pentoxide
( N2O5 ) associated with nitryl chloride ( ClNO2 ) and particulate
nitrate ( p NO 3 - ) at a suburban site of Beijing in the summer of 2016
High levels of N2O5 and ClNO2 were observed in the
outflow of the urban Beijing air masses, with 1  min average maxima of 937 and 2900  pptv ,
respectively The N2O5 uptake coefficients,
 γ , and ClNO2 yield, f , were experimentally determined
from the observed parameters The N2O5 uptake coefficient ranged
from 0012 to 0055, with an average of 0034  ±  0018, which is in the
upper range of previous field studies reported in North America and Europe
but is a moderate value in the North China Plain (NCP), which reflects
efficient N2O5 heterogeneous processes in Beijing The
 ClNO2 yield exhibited high variability, with a range of 050 to
unity and an average of 073  ±  025 The concentration of the nitrate
radical ( NO3 ) was calculated assuming that the thermal equilibrium
between NO3 and N2O5 was maintained In
 NOx -rich air masses, the oxidation of nocturnal biogenic
volatile organic compounds (BVOCs) was dominated by NO3 rather than
 O3  The production rate of organic nitrate (ON) via NO3 +  BVOCs was
significant, with an average of 010  ±  007  ppbv h−1  We highlight
the importance of NO3 oxidation of VOCs in the formation of ON and
subsequent secondary organic aerosols in summer in Beijing

/pdf/efficient-n-2-o-5-uptake-and-no-3-oxidation-in-the-outflow-20qhjg2mmn.pdf

Efficient N 2 O 5 uptake and NO 3 oxidation in the outflow of urban Beijing

Observation of NO3 radicals over Shanghai, China

. Mobile passive differential optical absorption spectroscopy measurements of SO2 and NO2 were performed in the Guangzhou eastern area (GEA) during the Guangzhou Asian Games 2010 from November 2010 to December 2010. The observations were carried out between 10:00 to 13:00 (local time, i.e., during daylight). Spatial and temporal distributions of SO2 and NO2 in this area were obtained and emission sources were determined using wind field data. The NO2 vertical column densities were found to agree with Ozone Monitoring Instrument values. The correlation coefficient (referred to as R2) was 0.88 after cloud filtering within a specific ground pixel. During the Guangzhou Asian Games and Asian Paralympics (Para) Games, the SO2 and NOx emissions in the area were quantified using averaged wind speed and wind direction. For times outside the games the average SO2 emission was estimated to be 9.50 ± 0.90 tons per hour and the average NOx emission was estimated to be 5.87 ± 3.46 tons per hour. During the phases of the Asian and Asian Para Games, the SO2 and NOx emissions were reduced by 53.50% and 43.50%, respectively, compared to the usual condition. We also investigated the influence of GEA on Guangzhou University Town, the main venue located northwest of the GEA, and found that SO2 concentrations here were about tripled by emissions from the GEA.

/pdf/observations-of-so-2-and-no-2-by-mobile-doas-in-the-1ghek35bog.pdf

Observations of SO 2 and NO 2 by mobile DOAS in the Guangzhou eastern area during the Asian Games 2010

From July 4 to 11, 2006 at Back Garden site (23°28'86”N; 113°02'91”E), nighttime nitrate radical (NO3) was measured with a long path differential optical absorption spectroscopy (DOAS) during an intensive field campaign in the Pearl River Delta of China. The NO3 concentration in polluted air masses varied from 3.6 to 82.5 ppt with an average level of 21.8 ± 1.8 ppt. NO3 at these levels can play a significant role in oxidation of volatile organic compounds (VOCs). The calculated production rate of nitrate radical ranged from 8 × 10^5 to 2.98 × 10^7 cm^(-3) s^(-1), while its lifetimes spanned from between just several seconds to 650 seconds, with an average of 89 seconds. N2O5 levels were calculated with the average of 620 ± 93 ppt during this campaign. The possible scavenging processes for the nitrate radical were obtained by using a statistical analysis of the correlation between NO3 and NO levels, NO3 concentration and its production rate, and the NO3 lifetime and NO2 levels, respectively. Results showed that the direct losses were of importance at Back Garden in summer Pearl River Delta, China.

/pdf/observation-of-nitrate-radical-in-the-nocturnal-boundary-2c49cmxy0f.pdf

Observation of Nitrate Radical in the Nocturnal Boundary Layer During a Summer Field Campaign in Pearl River Delta, China

. We present an improved incoherent broadband cavity-enhanced
absorption spectroscopy (IBBCEAS) system based on an iterative retrieval
algorithm for the simultaneous detection of atmospheric nitrous acid (HONO) and
nitrogen dioxide ( NO2 ). The conventional IBBCEAS retrieval algorithm
depends on the absolute change in the light intensity, which requires high light source stability and the stable transmission of the light intensity of all
optical components. The new algorithm has an iterative module to obtain the
effective absorption optical path length, and the concentrations of
HONO and NO2 are then determined by differential optical absorption
spectroscopy (DOAS) retrieval; thus, the method is insensitive to the fluctuation in the
absolute light intensity. The robustness of the system is verified by
simulating the influence of the relative change in the light intensity on the
spectral retrieval results. The effect of nitrogen purging in front of the
cavity mirrors on shortening the actual cavity length was measured and
corrected using NO2 gas samples. Allan deviation analysis was
conducted to determine the system stability, and it indicated that the detection limits
( 2σ ) of HONO and NO2 are 0.08 and 0.14 ppbv at an
integration time of 60 s respectively. Furthermore, Kalman filtering was
used to improve the measurement precision of the system. The measurement
precision at an integration time of 3 s can be improved
4.5-fold by applying Kalman filtering, which is equivalent to the
measurement precision at an integration time of 60 s without applying Kalman
filtering. The atmospheric HONO and NO2 concentrations were observed by the IBBCEAS
system based on an iterative algorithm and were compared with values measured by
conventional IBBCEAS.

/pdf/simultaneous-detection-of-atmospheric-hono-and-no-2-3hdfu6y4rg.pdf

Simultaneous detection of atmospheric HONO and NO 2 utilising an IBBCEAS system based on an iterative algorithm

The invention relates to an LED (light emitting diode) light source with a stable radiation spectrum and a control device thereof. The LED light source comprises an LED chip, an aluminium baseplate, aluminium heat radiation fins, a temperature sensor, a semiconductor refrigerating piece and a fan, wherein the LED chip is welded on the LED aluminium baseplate, the aluminium baseplate and the aluminum heat radiation fin are closely pasted through heat conduction silica gel, and a hole is punched on the aluminium heat radiation fin; the temperature sensor is inserted in the hole, a temperature sensor guideline is leaded out so as to seal the hole through the heat conduction silica gel, the heat conduction silica gel is used for pasting the other surface of one aluminum cooling fin on the semiconductor refrigerating piece, and the other surface of the semiconductor refrigerating piece is mutually pasted with the other aluminium heat radiation fin which is provided with a fan; and the LED light control device takes a singlechip as a control core, the semiconductor refrigerating piece is adopted as a temperature-controlling element, a constant current source circuit which is composed ofa current negative feedback provides working current for the semiconductor refrigerating piece, and the output current of the constant current source is controlled by the voltage output by a result control D/A (digital to analog) transducer after PID (proportion integration differentiation) operation by the singlechip. The LED light source provided by the invention is used for an open light path dusty gas spectrographic detection system, and provides the stable spectrum for the concentration inversion of a measuring system.

LED (light emitting diode) light source with stable radiation spectrum and control device thereof

The invention relates to a light path online calibration type cavity enhanced atmosphere trace gas detection system. The system comprises a light source, a light source driving device, non-spherical lenses, a filter, diaphragms, an optical cavity, a one-divided-two type optical fiber bundle, a light attenuation signal detection device, a light spectrum detector, and the like. Lights emitted from the light source firstly pass through a non-spherical lens to be collimated, are coupled, then enter the optical cavity formed by two mirrors with high reflectivity, and are emitted back and forth a plurality of times inside the cavity so as to provide a absorption light path increasing effect. The lights transmitted from the other side of the optical cavity are focused on an incidence end surface of a one-divided-two type optical fiber bundle through a non-spherical lens. One emergence end of the one-divided-two type optical fiber bundle is connected with the light attenuation signal detection device, and the other emergence end of the one-divided-two type optical fiber bundle is connected with the light spectrum detector. The light source has two driving modes of narrow pulse and constant current, wherein the narrow pulse driving mode is used for light attenuation signal measuring so as to determine the absorption light path during gas measuring, the constant current driving mode is used for absorption light spectrum measuring to obtain the column concentration of the trace gas in the measured atmosphere, and the concentration value of the measured gas can be obtained according to both measurement results.

Light path online calibration type cavity enhanced atmosphere trace gas detection system

The invention discloses a DOAS measurement system by means of polarizing beam splitting. The DOAS measurement system comprises a lambda/4 wave wafer, a polarizing beam splitting piece, a parabolic mirror primary mirror, a corner mirror, an optical fiber, a power source device and a spectrograph detector. By means of the characteristics of the polarizing beam splitting piece, due to the fact that a signal carrying an absorbing spectrum passes through the lambda/4 wave wafer for two times, the polarizing state will change, and the signal will be reflected to the receiving optical fiber by the polarizing beam splitting piece; due to the fact that a telescope stray light signal which does not carry the absorbing spectrum and is not in atmospheric transmission does not pass through the lambda/4 wave wafer, the polarizing state does not change, and the signal passes through the polarizing beam splitting piece and will not be reflected to the receiving optical fiber by the polarizing beam splitting piece. Compared with an existing light-path receiving and transmitting integrated DOAS measurement system, the DOAS measurement system can reduce the proportion of stray light inside a telescope and scattered light in the atmospheric background in the measurement signals, also improve the signal to noise ratio of DOAS measurement on the premise that the lighting effect is ensured, and improve the detection precision of the DOAS.

Wenqing Liu

Papers

Observation of Nitrate Radical in the Nocturnal Boundary Layer During a Summer Field Campaign in Pearl River Delta, China

Simultaneous detection of atmospheric HONO and NO 2 utilising an IBBCEAS system based on an iterative algorithm

LED (light emitting diode) light source with stable radiation spectrum and control device thereof

Light path online calibration type cavity enhanced atmosphere trace gas detection system

DOAS measurement system by means of polarizing beam splitting