A new portable open-path instrument for ambient NH_(3) and on-road emission measurements

Increased attentions to vehicle emission of NH_(3)have been paid since it is generally regarded as an important source in urban areas.Here,we developed a movable instrument based on Differential Optical Absorption Spectroscopy(DOAS)principle for detecting on-road NH_(3),which can avoid the losses in the sampling process attributed to the non-sampling methods.For this mobile DOAS,the temporal resolution,detection limit and relative error for NH_(3)were 1 min,2.29 ppbv and 4.57%±2.44%,respectively.By employed to the on-road measurements along the arterial highway in Shanghai,the spatial distributions of NH_(3)and NO were obtained,and their dependence of traffic and road conditions were studied.The slopes of linear regression between NH_(3)and NO were 0.40,0.02 and 0.07 on the Middle Ring Road,Outer Ring Road and Chongming Island Ring Road.It indicates that light gasoline vehicles(LGVs)were found to be the main contributor to NH_(3)emissions,while heavy-duty diesel vehicles(HDVs)mainly emitted NO.Based on the measured NH_(3)in the tunnel,the mileagebased NH_(3)emission factor per vehicle was estimated to be 17.9±6.3 mg/km.The reported open-path instrument can be broadly used in on-road pollutant monitoring or vehicle emissions,and the measurements can reveal the real situation of emission characteristics,even find the abnormal operations of vehicle catalyst system.

A review of Space-Air-Ground integrated remote sensing techniques for atmospheric monitoring

Currently,the three-dimensional(3D)distribution and characteristics of air pollution cannot be understood based on the application of any single atmospheric monitoring technology.Long-term,high-precision and large-scale 3D atmospheric monitoring might become practical by combining heterogeneous modern technologies;for this purpose,the SpaceAir-Ground integrated system is a promising concept.In this system,optical remote sensing technologies employing fixed or mobile platforms are used as the main means for groundbased observations.Tethered balloons,unmanned aerial vehicles(UAV)and airborne platforms serve as the air-based observation segment.The final part,satellite remote sensing,corresponds to space-based observations.Aside from obtaining the 3D distribution of air pollution,research on emission estimation and pollution mechanisms has been extensively implemented based on the strengths of this system or some portion of it.Moreover,further research on the fusion of multi-source data,optimization of inversion algorithms,and coupling with atmospheric models is of great importance to the realization of this system.

MAX-DOAS observation in the midlatitude marine boundary layer: Influences of typhoon forced air mass

As a passive remote sensing technique,MAX-DOAS method was widely used to investigate the vertical profiles of aerosol and trace gases in the lower troposphere.However,the measurements for midlatitude marine boundary layer are rarely reported,especially during the storm weather system.In this study,the MAX-DOAS was used to retrieve the aerosol,HCHO and NO_(2) vertical distribution at Huaniao Island of East China Sea in summer 2018,during which a strong tropical cyclone developed and passed through the measurement site.The observed aerosol optical depth(AOD),HCHO-and NO_(2)-VCDs(Vertical Column Density)were in the range of 0.19-0.97,(2.57-12.27)×10^(15) molec/cm^(2),(1.24-4.71)×10^(15) molec/cm^(2),which is much higher than remote ocean area due to the short distance to continent.The vertically resolved aerosol extinction coefficient(AEC),HCHO and NO_(2) presented the decline trend with the increase of height.After the typhoon passing through,the distribution of high levels of aerosol and HCHO stretched to about 1 kmand the abundances of the bottom layer were found as double higher than before,reaching 0.51 km^(−1) and 2.44 ppbv,while NO_(2) was still constrained within about 300 m with 2.59 ppbv in the bottom layer.The impacts of typhoon process forced air mass were also observed at the suburban site in Shanghai in view of both the aerosol extinction and chemical components.The different changes on air quality associated with typhoon and its mechanism in two different environments:coastal island and coastal city are worthy of further investigation as it frequent occurred in East Asia during summer and fall.