Seasonal variation and potential source regions of PM2.5-bound PAHs in the megacity Beijing, China: Impact of regional transport

 Measurements of gaseous elemental mercury (GEM), other air pollutants, including SO2 ,
 NOx , O3 , PM25 , and CO, and meteorological
conditions were carried out at Chongming Island in East China from 1 March
2014 to 31 December 2016 During the sampling period, GEM
concentrations significantly decreased from 268  ±  107 ng m −3 in
2014 (March to December) to 160  ±  056 ng m −3 in 2016 (March to
December) Monthly mean GEM concentration showed a significant decrease, at
a rate of - 060 ± 008  ng m −3  yr −1 ( R2=064 ,
 p  < 001 significance level) Combining the analysis of the potential
source contribution function (PSCF), principle component analysis (PCA), and
the emission inventory, we found that the Yangtze River Delta (YRD) region was the
dominant source region of GEM in Chongming Island and the main source
industries included coal-fired power plants, coal-fired industrial boilers,
and cement clinker production We further quantified the effect of emission
change on the air Hg concentration variations at Chongming Island through a
coupled method of trajectory clusters and air Hg concentrations It was
found that the reduction of domestic emissions was the main driver of GEM
decline in Chongming Island, accounting for 70 % of the total decline The
results indicated that air pollution control policies targeting SO2 ,
 NOx , and particulate matter reductions had significant co-benefits on
GEM

/pdf/recent-decrease-trend-of-atmospheric-mercury-concentrations-1yiuj37iii.pdf

Recent decrease trend of atmospheric mercury concentrations in East China: the influence of anthropogenic emissions

Evolution of the vertical structure of air pollutants during winter heavy pollution episodes: The role of regional transport and potential sources

Concentrations and gas-particle partitioning of atmospheric reactive mercury at an urban site in Beijing, China.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018JD028350

Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

. Long-term continuous measurements of speciated atmospheric mercury were conducted from July 2013 to June 2014 in Hefei, a midlatitude inland city in eastern central China that experiences frequent haze pollution. The mean concentrations (±standard deviation) of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) were 3.95 ± 1.93 ng m−3, 2.49 ± 2.41 and 23.3 ± 90.8 pg m−3, respectively, on non-haze days, and 4.74 ± 1.62 ng m−3, 4.32 ± 8.36 and 60.2 ± 131.4 pg m−3, respectively, on haze days. Potential source contribution function (PSCF) analysis suggested that atmospheric mercury pollution on haze days was caused primarily by local emissions, instead of via long-range transport. The poorer mixing conditions on haze days also favored the accumulation of atmospheric mercury. Compared to GEM and GOM, PBM was especially sensitive to haze pollution. The mean PBM concentration on haze days was 2.5 times that on non-haze days due to elevated concentrations of particulate matter. PBM also showed a clear seasonal trend; its concentration was the highest in fall and winter, decreased rapidly in spring and was the lowest in summer, following the same order in the frequency of haze days in different seasons. On both non-haze and haze days, GOM concentrations remained low at night, but increased rapidly just before sunrise, which could be due to diurnal variation in air exchange between the boundary layer and free troposphere. However, non-haze and haze days showed different trends in daytime GEM and GOM concentrations. On non-haze days, GEM and GOM declined synchronously through the afternoon, probably due to the retreat of the free tropospheric air as the height of the atmospheric boundary layer increases. In contrast, on haze days, GOM and GEM showed opposite trends with the highest GOM and lowest GEM observed in the afternoon, suggesting the occurrence of photochemical oxidation. This is supported by simple box-model calculations, which showed that oxidation of GEM to GOM does occur and that the transport of free tropospheric GOM alone is not large enough to account for the observed increase in daytime GOM. Our results further postulate that NO2 aggregation with the HgOH intermediate may be a potential mechanism for the enhanced production of GOM during daytime.

/pdf/speciated-atmospheric-mercury-on-haze-and-non-haze-days-in-4tlaqcaxua.pdf

Speciated atmospheric mercury on haze and non-haze days in an inland city in China

The invention relates to a method for acquiring a complex refractive index of urban aerosol on the basis of various ground-based remote sensing technologies. The method comprises the following steps of: acquiring the extinction coefficient and the scattering extinction ratio of the aerosol through an inverse algorithm by virtue of Raman laser radar echo signals, and integrating the extinction coefficient of a certain route to acquire the optical thickness of the aerosol on the route; continuously correcting the extinction coefficient and the scattering extinction ratio by performing iterative alignment on an aerosol optical thickness of a whole atmospheric layer acquired via a sun photometer and the aerosol optical thickness acquired via a laser radar according to a Monte Carlo principle; then acquiring the particle size distribution of the aerosol via a particle spectrometer; and finally, acquiring the complex refractive index of the urban aerosol according to a mie-scattering model by virtue of the known scattering extinction ratio of the aerosol and the particle size distribution of the aerosol. According to the invention, the complex refractive index of the urban aerosol is acquired by the Raman laser radar, the sun photometer and the particle spectrometer, and the method has the advantages of small error, high discriminability and high universality.

Method for acquiring complex refractive index of urban aerosol on basis of various ground-based remote sensing technologies

The invention discloses a method and a device for emitting and receiving symmetrically-distributed light beams of laser radar. A system adopts the method for independently emitting and receiving the light beams with a plurality of wavelengths, thereby eliminating an effect on a measurement result caused by different divergent angles and refractive indexes of the laser beams with the different wavelengths, independently realizing the calculation of the overlap coefficient of the system under the different laser wavelengths, developing the real coaxiality or completely parallel optical axes of receiving and emitting optical systems, ensuring data comparability and providing the method for the further development and practical application of the laser radar. The independent emission of the light beams with the different laser wavelengths in the system can be debugged under a visible software interface, so that an ordinary operator can finish the operation and maintenance of the system without the help of a precise measuring instrument or special technical personnel.

Method and device for emitting and receiving symmetrically-distributed light beams of laser radar

The utility model leads received optical signals to be directly input into a detection optical splitter system, and multi-wavelength and multi-channel optical signal measurement can be directly completed by the detection optical splitter system which is processed by optical calibration A whole beam-splitting path and a detector component are sealed inside a closed shell, thus avoiding complicatedoptical calibration and interference of stray light, reducing the attenuation loss of the optical signals, and realizing compactness and reliability of the laser radar beam-splitting path and the detection system, furthermore, the optical path is simple and easy for a detection channel to expand; therefore, the utility model can be used for splitting and detecting of various laser radar optical signals, especially for detecting multi-wavelength and multi-channel weak optical signals The system greatly simplifies the structure of a light split and detection system, improves the sensitivity ofdetection and realizes effective measurement of signals

Yunsheng Dong

Papers

Speciated atmospheric mercury on haze and non-haze days in an inland city in China

Method for acquiring complex refractive index of urban aerosol on basis of various ground-based remote sensing technologies

Method and device for emitting and receiving symmetrically-distributed light beams of laser radar

Laser radar multi-channel detection optical splitter system