Summertime Urban Ammonia Emissions May Be Substantially Underestimated in Beijing, China.

Ammonia (NH) is critical to the nitrogen cycle and PM formation, yet a great deal of uncertainty exists in its urban emission quantifications. Model-underestimated NH concentrations have been reported for cities, yet few studies have provided an explanation. Here, we explore reasons for severe WRF-Chem model underestimations of NH concentrations in Beijing in August 2018, including simulated gas-particle partitioning, meteorology, regional transport, and emissions, using spatially refined (3 km resolution) NH emission estimates in the agricultural sector for Beijing-Tianjin-Hebei and in the traffic sector for Beijing.

[Characteristics of BTEX and Health Risk Assessment During Typical Pollution Episodes in Summer and Winter in Tianjin Urban Area].

Real-time BTEX(including benzene, toluene, ethylbenzene, -, -, and -xylenes) were measured continuously in Tianjin urban site in July 2019 and January 2020 using a Syntech Spectras GC955 analyzer. The BTEX concentration levels, composition, and evolutionary mechanisms during typical pollution episodes were investigated. The potential sources of BTEX were analyzed qualitatively using the diagnostic ratios method.

[Characteristics of Two Pollution Episodes Before and After City Heating in Beijing from February to March of 2019].

The characteristics of meteorological conditions and pollutant concentrations were analyzed based on two pollution episodes before and after city heating in Beijing during February to March of 2019. The backward trajectory and WRF-CAMx models were used to analyze the evolution of pollutants before and after city heating, and the influences of meteorological conditions, regional transport, and secondary transformation on the episodes were discussed. There was little difference in the average (PM) between February 21-24 (episode 1) and March 18-20 (episode 2), with concentrations of 100.

[Impact of atmospheric pollutants transport pathways on aerosol optical properties at Shangdianzi background station].

The impact of transport pathways on aerosol properties at Shangdianzi (SDZ) background station was analyzed using the back trajectory analysis method with the observation of PM2.5 concentration and aerosol scattering coefficients ( σ(sp)) during 2005-2010. The results showed that the pollutant level at SDZ was influenced by both the direction and motion state of air masses.

[Meteorological mechanism for the formation of a serious pollution case in Beijing in the background of northerly flow at upper levels].

There is a kind of serious air pollution case occurring in the situation of northerly flow at the levels above 850 hPa in Beijing area. Meteorological data, NCEP reanalysis data and PM2.5 concentration survey were used to analyze the roles of meteorological mechanism in this kind of air pollution case.

[Effect of weather condition on the aerosol scattering property at Shangdianzi].

A study on the effect of weather condition on the aerosol scattering property has been carried out using one year measurement data sets of aerosol scattering coefficient (ASC) and meteorological parameters at Shangdianzi (SDZ). The results showed that the ASC was highest in haze-fog day with 608.4 Mm(-1) and higher in fog day with 500.