The strong atmospheric new particle formation in China’s highly polluted urban atmosphere can be potentially explained by the nucleation of sulfuric acid and amines, while it is unclear why urban atmospheres in China are enriched in amines. In urban China, human excreta are generally stored in septic tanks beneath buildings, which may release hazardous and odorous pollutants to the atmosphere through pipes on rooftops, i.e., ceiling ducts. Here for the first time, high-sensitive proton-transfer-reaction quadrupole-interface time-of-flight mass spectrometric measurements of gaseous amines emitted from the ceiling duct were performed in Shanghai. Driven by human activity, strong pulses of C2- and C3-amines emissions were persistently observed, in which a species (C3H7N) was rarely measured previously but emitted in significant quantities. Our direct source-determined emission ratios of amines to ammonia varied significantly with amine species and were systematically different from that previously assumed in models. These observations, if generalized, would call for a substantial change of urban amine emissions and modelling. A gridded amine emission inventory from the septic system was developed based on city-wide ammonia emission measurements, with important implications for future modeling studies to clarify our understanding of urban amine budgets and to better constrain their climate and air quality effects.

As the derivatives of ammonia (NH 3 ), gaseous amines are a class of organic vapors containing a basic nitrogen atom with a lone pair, where one or more hydrogen atoms are substituted by organic functional groups, for example, an alkyl or aryl group (Qiu & Zhang, 2013). Since ambient concentration of amines (typically in the range of ppt) is 1-3 orders of magnitude lower than that of ammonia (NH 3 ;Kuhn et al., 2011), this poses a significant analytical challenge for environmental monitoring (Szulejko & Kim, 2014), resulting in scarce information on the occurrence of amines in the atmosphere. For a long time, agriculture is considered as the dominant source for both ammonia (NH 3 ) and amines (Ge et al., 2011a). For example, the concentration of amines with low molecular weight (e.g., monomethylamine or MMA, dimethylamine or DMA, and trimethylamine or TMA) can reach as high as several hundreds of ppm in the vicinity of concentrated animal feeding operations . Additionally, amines can be emitted from various natural (such as ocean organisms [Altieri et al., 2016], protein degradation [Lidbury et al., 2017], and wildfire burning [Ito et al., 2015]) and anthropogenic (such as automobiles [Cadle & Mulawa, 1980], industries [Yao et al., 2016], CO 2 sequestration process [Yamada, 2021], and treatment of sewage and waste [Chang et al., 2021]) sources.Currently, there are 24 carcinogenic amines banned by global legislatures for use in industrial production (e.g., textile dyeing) (Lee & Wexler, 2013). Moreover, amines have much stronger basicity than NH 3 and are more likely

China's unprecedented lockdown to contain the spread of the novel coronavirus disease (COVID-19) in early 2020, provided a tragic natural experiment to investigate the responses of atmospheric pollution to emission reduction at regional scale. Primarily driven by primary emissions, particulate trace elements is vitally important due to their disproportionally adverse impacts on human health and ecosystem. Here 14 trace elements in PM 2.5 were selected for continuous measurement hourly in urban representative site of Shanghai, for three different phases: pre-control period (1–23 January 2020), control period (24 January-10 February 2020; overlapped with Chinese Lunar New Year holiday) and post control period (11–26 February 2020) the city's lockdown measures. The results show that all meteorological parameters (including temperature, RH, mixing layer height et al.) were generally consistent among different periods. Throughout the study period, the concentrations of most species displayed a “V-shaped” trend, suggesting significant effects by the restriction measures imposed during the lockdown period. While this is not the case for species like K, Cu and Ba, indicating their unusual origins. As a case study, the geographical origins of Cu were explored. Seven major sources, i.e., Vehicle-related emission (including road dust; indicative of Ca, Fe, Ba, Mn, Zn, Cu; accounting for 30.1%), shipping (Ni; 5.0%), coal combustion (As, Pb; 4.2%), Se and Cr industry (24.9%), nonferrous metal smelting (Au, Hg; 7.5%) and fireworks burning (K, Cu, Ba; 28.3%) were successfully pinpointed based on positive matrix factorization (PMF) analysis. Our source apportionment results also highlight fireworks burning was one of the dominant source of trace elements during the Chinese Lunar New Year holiday. It is worth noting that 56% of the total mass vehicular emissions are affiliated with non-exhaust sources (tire wear, brake wear, and road surface abrasion).

China introduced an emission control area (ECA) along the coastline of the Yangtze River Delta (YRD) region in 2016 in a bid to reduce its shipping emissions. Performed at a costal site in the YRD region from 2014 to 2018, we found a significant reduction (16–22%, p < 0.01) in vanadium concentrations, the exclusive marker for heavy fuel oil combustion, after the full-scale implementation of lower sulfur fuel change for marine ships. Another site closer to the coastline showed a larger reduction (24–30%, p < 0.01) during the corresponding period. The reduction of vanadium was consistent with an overall decrease rate of 17% in the annual SO2 concentrations of 10 sites across the region from 2016 to 2017. We thus provide a robust assessment of the positive effects of regulating shipping emissions on air quality in coastal China. The future trajectories of shipping-related emissions are also discussed.

In contrast to Europe and the U.S., human excreta in urban China are mainly stored in septic tanks beneath buildings, and the generated odors (including NH3) are released into the atmosphere through connecting pipes on the rooftops, that is, ceiling ducts. Here, we show that the levels of NH3 in ceiling ducts were 3 to 5 orders of magnitude higher than urban background concentrations. Unfortunately, urban air quality monitoring sites in China are mostly set on the roofs of various buildings. As the first attempt to investigate the influence of this overlooked NH3 source on the measurements of ambient NH3, hourly measurements of NH3 were performed on the rooftops of four buildings in Nanjing and Shanghai megacities. Although the two buildings in Nanjing are located in the same university campus (1 km apart), NH3 concentrations measured on the rooftop of a teaching building with dense ceiling ducts were on average 2.8 times higher than those of another building without ceiling ducts. In Shanghai, the exhaust vents of two ceiling ducts at a supersite were deliberately extended to a higher position and bent toward a direction downwind of our NH3 instrument. The resulting ambient NH3 concentration was 40% lower than that of another academic building without modification of its ceiling ducts. Besides, the measured NH3 peaks were consistently associated with air plumes from ceiling ducts. Realizing this strong NH3 source is important to avoid its significant influences on the measurement of NH3 and to interpret a large spatial heterogeneity of NH3 concentrations in urban China.