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Concentrations (µg m−3) of total carbon (TC), organic carbon (OC) and elemental carbon (EC), F14C of OC and EC, δ13C (‰) of OC desorbed at different temperatures (200 °C, 350 °C and 550 °C), δ13C of EC, as well as source apportionment results of OC and EC at Qinghai Lake.&nbsp

Nitrated aromatic compounds (NACs) are a group of key chromophores for brown carbon (light-absorbing organic carbon, i.e., BrC) aerosol, which affects radiative forcing. The chemical composition and sources of NACs and their contributions to BrC absorption, however, are still not well understood. In this study, PM2:5-bound NACs in Xi'an, Northwest China, were investigated for 112 daily PM2:5 filter samples from 2015 to 2016. Both the total concentrations and contributions from individual species of NACs show distinct seasonal variations. The seasonally averaged concentrations of NACs are 2.1 (spring), 1.1 (summer), 12.9 (fall), and 56 ngm3 (winter). Thereinto, 4-nitrophenol is the major NAC component in spring (58 %). The concentrations of 5-nitrosalicylic acid and 4-nitrophenol dominate in summer (70 %), and the concentrations of 4-nitrocatechol and 4-nitrophenol dominate in fall (58 %) and winter (55 %). The NAC species show different seasonal patterns in concentrations, indicating differences in emissions and formation pathways. Source apportionment results using positive matrix factorization (PMF) further show large seasonal differences in the sources of NACs. Specifically, in summer, NACs were highly influenced by secondary formation and vehicle emissions (80 %), while in winter, biomass burning and coal combustion contributed the most (75 %). Furthermore, the light absorption contributions of NACs to BrC are wavelength-dependent and vary greatly by season, with maximum contributions at 330 nm in winter and fall and 320 nm in summer and spring. The differences in the contribution to light absorption are associated with the higher mass fractions of 4-nitrocatechol (max D345 nm) and 4-nitrophenol (max D310 nm) in fall and winter, 4-nitrophenol in spring, and 5-nitrosalicylic acid (max D315 nm) and 4-nitrophenol in summer. The mean contributions of NACs to BrC light absorption at a wavelength of 365 nm in different seasons are 0.14% (spring), 0.09% (summer), 0.36% (fall), and 0.91% (winter), which are about 6-9 times higher than their mass fractional contributions of carbon in total organic carbon. Our results indicate that the composition and sources of NACs have profound impacts on the BrC light absorption.

Sources of particulate organic carbon (OC) with different volatility have rarely been investigated despite the significant importance for better understanding of the atmospheric processes of organic aerosols. In this study we develop a radiocarbon (14C) based approach for source apportionment of more volatile OC (mvOC) and apply to ambient aerosol samples collected in winter in six Chinese megacities. mvOC is isolated by desorbing organic carbon from the filter samples in He at 200 °C in a custom-made aerosol combustion system for 14C analysis. Evaluation of this new isolation method shows that the isolated mvOC amount agrees very well with the OC1 fraction (also desorbed at 200 °C in He) measured by a thermal optical analyzer using the EUSAAR_2 protocol. The mvOC, OC and elemental carbon (EC) of thirteen combined PM2.5 samples in six Chinese cities are analyzed for 14C to investigate their sources and formation mechanisms. The relative contribution of fossil sources to mvOC is 59 ± 11 %, consistently larger than the contribution to OC (48 ± 16 %) and smaller than that to EC (73 ± 9 %), despite large differences in fossil contributions in different cities. The average difference in the fossil fractions between mvOC and OC is 13 % (7 %–25 %; range), similar to that between mvOC and EC (13 %; 4 %–25 %). SOC concentrations and sources are modelled based on the 14C-apportioned OC and EC, and compared with concentrations and sources of mvOC. SOC concentrations (15.4 ± 9.0 μg m-3) are consistently higher than those of mvOC (3.3 ± 2.2 μg m-3), indicating that only a fraction of SOC is accounted for by the more volatile carbon fraction desorbed at 200 °C. The fossil fraction in SOC is 43 % (10 %–70 %), lower than that in mvOC (59 %; 45 %–78 %). Correlation between mvOC and SOC from non-fossil sources (mvOCnf vs. SOCnf) and from fossil sources (mvOCfossil vs. SOCfossil) are examined to further explore sources and formation processes of mvOC and SOC.

Sources of organic carbon (OC) and elemental carbon (EC) in Xi'an, China, are investigated based on 1-year radiocarbon and stable carbon isotope measurements. The radiocarbon results demonstrate that EC is dominated by fossil sources throughout the year, with a mean contribution of 83 +/- 5% (7 +/- 2 mu gm(-3)). The remaining 17 +/- 5% (1.5 +/- 1 mu gm(-3)) is attributed to biomass burning, with a higher contribution in the winter (similar to 24 %) compared to the summer (similar to 14 %). Stable carbon isotopes of EC (delta C-13(EC)) are enriched in winter (-23.2 +/- 0.4 %) and depleted in summer (-25.9 +/- 0.5 %), indicating the influence of coal combustion in winter and liquid fossil fuel combustion in summer. By combining radiocarbon and stable carbon signatures, relative contributions from coal combustion and liquid fossil fuel combustion are estimated to be 45% (median; 29 %-58 %, interquartile range) and 31% (18 %-46 %) in winter, respectively, whereas in other seasons more than one half of EC is from liquid fossil combustion. In contrast with EC, the contribution of non-fossil sources to OC is much larger, with an annual average of 54 +/- 8% (12 +/- 10 mu gm(-3)). Clear seasonal variations are seen in OC concentrations both from fossil and non-fossil sources, with maxima in winter and minima in summer because of unfavorable meteorological conditions coupled with enhanced fossil and non-fossil activities in winter, mainly biomass burning and domestic coal burning. delta C-13(OC) exhibited similar values to delta C-13(EC), and showed strong correlations (r(2) = 0.90) in summer and autumn, indicating similar source mixtures with EC. In spring, delta C-13(OC) is depleted (1.1 %-2.4 %) compared to delta C-13(EC), indicating the importance of secondary formation of OC (e.g., from volatile organic compound precursors) in addition to primary sources. Modeled mass concentrations and source contributions of primary OC are compared to the measured mass and source contributions. There is strong evidence that both secondary formation and photochemical loss processes influence the final OC concentrations.

Black carbon (BC) aerosol plays an important role in the Earth's radiative balance. An intensive measurement campaign was conducted at Xi'an, China, from December 2012 to January 2013 to investigate the sources and physicochemical characteristics of refractory BC (rBC) and its direct radiative forcing at the surface. The overall average rBC concentration for the campaign was 8.0 ± 7.1 µg m−3. Source apportionment based on positive matrix factorization showed that traffic was the dominant rBC source (46.0%), followed by coal burning (33.9%) and biomass burning (20.1%). The rBC mass size distributions were monomodal and lognormal with larger mass median diameters for coal burning source (215 nm) compared with the traffic source (189 nm). Coal burning rBC was more strongly associated with sulfate than traffic rBC, suggesting a higher cloud condensation nuclei activity. The slope of a robust linear regression between rBC and carbon monoxide (CO) for all samples was 5.9 µg m−3 ppm−1, and the slope for the coal burning source (4.5 µg m−3 ppm−1) was larger than that for the traffic source (2.7 µg m−3 ppm−1). The net rBC emission during winter of 2009 was estimated to be 4.5 Gg based on the relationship between rBC and CO. A Tropospheric Ultraviolet and Visible radiation model showed that the average daytime value for the clear-sky direct radiative forcing due to rBC from 23 December 2012 to 31 January 2013 was −47.7 ± 28.9 W m−2, which amounted to an average of 45.7% of the total surface atmospheric aerosol forcing.

MOS Current-Mode Logic (MCML) is usually used for high-speed applications. In this paper, the design method of the low-power high-speed MOS MCML is addressed. The layout implementations of MCML basic gates are presented at a NCSU FreePDK 45nm technology. The post-layout simulations are carried out. For normal supply voltage, the MCML basic gates can save more energy and have better performance than the traditional CMOS counterparts at 1GHz or higher operation frequencies. Scaling down the supply voltage of MCML circuits is investigated. The results show that the power consumption of MCML circuits can be reduced by lowering the supply voltage with a little performance degrading.

This paper presents the design of a 485-Serial Network Architecture in an Intelligent Uptown. Based on it, a Management Service system, is proposed for remote data collecting and terminal control. There are many functions in this management service system functions including intelligent meter remote-reading, the security precaution, estate management, etc. Here, we introduce the whole architecture of the system, and present the design of two main modules, communication engine and the management platform. In particular, we also give the detailed analysis on the multithreading technology in the communications engine and management platform modules.

Reactive oxygen species (ROS) are believed to contribute to the adverse health effects of aerosols. This may happen by inhaled particle-bound (exogenic) ROS (PBROS) or by ROS formed within the respiratory tract by certain aerosol components (endogenic ROS). We investigated the chemical composition of aerosols and their exogenic ROS content at the two contrasting locations Beijing (China) and Bern (Switzerland). We apportioned the ambient organic aerosol to different sources and attributed the observed water-soluble PB-ROS to them. The oxygenated organic aerosol (OOA, a proxy for secondary organic aerosol, SOA) explained the highest fraction of the exogenic ROS concentration variance at both locations. We also characterized primary and secondary aerosol emissions generated from different biogenic and anthropogenic sources in smog chamber experiments. The exogenic PB-ROS content in the OOA from these emission sources was comparable to that in the ambient measurements. Our results imply that SOA from gaseous precursors of different anthropogenic emission sources is a crucial source of water-soluble PB-ROS and should be additionally considered in toxicological and epidemiological studies in an adequate way besides primary emissions. The importance of PB-ROS may be connected to the seasonal trends in health effects of PM reported by epidemiological studies, with elevated incidences of adverse effects in warmer seasons, which are accompanied by moreintense atmospheric oxidation processes.

Reactive oxygen species (ROS) are believed to contribute to the adverse health effects of aerosols. This may happen by inhaled particle-bound (exogenic) ROS (PB-ROS) or by ROS formed within the respiratory tract by certain aerosol components (endogenic ROS). We investigated the chemical composition of aerosols and their exogenic ROS content at the two contrasting locations Beijing (China) and Bern (Switzerland). We apportioned the ambient organic aerosol to different sources and attributed the observed water-soluble PB-ROS to them. The oxygenated organic aerosol (OOA, a proxy for secondary organic aerosol, SOA) explained the highest fraction of the exogenic ROS concentration variance at both locations. We also characterized primary and secondary aerosol emissions generated from different biogenic and anthropogenic sources in smog chamber experiments. The exogenic PB-ROS content in the OOA from these emission sources was comparable to that in the ambient measurements. Our results imply that SOA from gaseous precursors of different anthropogenic emission sources is a crucial source of water-soluble PB-ROS and should be additionally considered in toxicological and epidemiological studies in an adequate way besides primary emissions. The importance of PB-ROS may be connected to the seasonal trends in health effects of PM reported by epidemiological studies, with elevated incidences of adverse effects in warmer seasons, which are accompanied by more-intense atmospheric oxidation processes., Atmospheric Chemistry and Physics, 19 (23), ISSN:1680-7375, ISSN:1680-7367