Black carbon aerosol has received much more attention as the most light-absorbing aerosol in recent years. The accuracy, traceability and comparability of its optical measurements, which could be realized by unified and comprehensive calibration and correction system, are essential for the estimation of emission factor, radiative forcing, and the resulting international regulations such as the United Nations Framework Convention on Climate Change. This manuscript summarizes the current optical-based methods applied in China including in-situ and filter-based methods. We detail the metrological traceability of BC optical measurement by comparing the calibration and correction methods in China, as well as BC metrology in other countries. We provide some insight into existed challenges of BC optical measurements in China and potential future direction. The significance of traceability of BC optical measurements in radiative forcing and emission estimation is emphasized. This review will improve our understanding of the traceability of BC measurement based on optical methods.

Particulate black carbon (BC) affects global warming by absorbing the solar radiation, by affecting cloud formation, and by decreasing ground albedo when deposited to snow or ice. BC has also a wide variety of adverse effects on human population health. In this article we reviewed the BC emission factors (EFs) of major anthropogenic sources, i.e. traffic (incl. marine and aviation), residential combustion, and energy production. We included BC EFs measured directly from individual sources and EFs derived from ambient measurements. Each source category was divided into sub-categories to find and demonstrate systematical trends, such as the potential influence of fuel, combustion technologies, and exhaust/flue gas cleaning systems on BC EFs. Our review highlights the importance of society level emission regulation in BC emission mitigation; a clear BC emission reduction was observed in ambient studies for road traffic as well as in direct emission measurements of diesel-powered individual vehicles. However, the BC emissions of gasoline vehicles were observed to be higher for vehicles with direct fuel injection techniques (gasoline direct injection) than for vehicles with port-fueled injection, indicating potentially negative trend in gasoline vehicle fleet BC EFs. In the case of shipping, a relatively clear correlation was seen between the engine size and BC EFs so that the fuel specific BC EFs of the largest engines were the lowest. Regarding the BC EFs from residential combustion, we observed large variation in EFs, indicating that fuel type and quality as well as combustion appliances significantly influence BC EFs. The largest data gaps were in EFs of large-scale energy production which can be seen crucial for estimating global radiative forcing potential of anthropogenic BC emissions. In addition, much more research is needed to improve global coverage of BC EFs. Furthermore, the use of existing data is complicated by different EF calculation methods, different units used in reporting and by variation of results due to different experimental setups and BC measurement methods. In general, the conducted review of BC EFs is seen to significantly improve the accuracy of future emission inventories and the evaluations of the climate, air quality, and health impacts of anthropogenic BC emissions.

Atmospheric brown carbon (BrC) is a light-absorbing component that affects radiative forcing; however, this effect requires further clarification, particularly with respect to BrC emission sources, chromophores, and optical properties. In the present study, the concentrations, optical properties, and emission factors of organic carbon (OC), water-soluble OC (WSOC), and humic-like substances (HULIS) in fine particulate matter (PM2.5) emitted from vehicles in three road tunnels ( the Wucun, Xianyue, and Wenxing tunnels in Xiamen, China) were investigated. The mass concentrations and light absorption of OC, WSOC, and HULLS were higher at the exits of each tunnel than at entrances, demonstrating that vehicle emissions were a BrC source. At each tunnel's exit, the average light absorption contributed by HULIS-BrC to water-soluble BrC (WS-BrC) and total BrC at 365 nm was higher than the corresponding carbon mass concentration contributed by HULIS (HULIS-C) to WSOC and OC, indicating that the chromophores of HULIS emitted from vehicles had a disproportionately high effect on the light absorption characteristics of BrC. The emission factors (ER) of HUUS-C and WSOC mass concentrations were highest at the Xianyue tunnel; however, the EFs of HULIS-BrC and WS-BrC light absorption were highest at the Wenxing tunnel, indicating that the chromophore composition of BrC was different among the tunnels and that the mass concentration EFs did not correspond directly to the light absorption EFs. (C) 2021 Elsevier B.V. All rights reserved.

Brown carbon (BrC), a carbonaceous aerosol which absorbs solar radiation over a broad range of wavelengths, is beginning to be seen as an important contributor to global warming. BrC absorbs both inorganic and organic pollutants, leading to serious effects on human health. We review the fundamental features of BrC, including its sources, chemical composition, optical properties and radiative forcing effects. We detail the importance of including photochemical processes related to BrC in the GEOS-Chem transport model for the estimation of aerosol radiative forcing. Calculation methods for BrC emission factors are examined, including the problems and limitations of current measurement methods. We provide some insight into existing publications and recommend areas for future research, such as further investigations into the reaction mechanisms of the aging of secondary BrC, calculations of the emission factors for BrC from different sources, the absorption of large and long-lived BrC molecules and the construction of an enhanced model for the simulation of radiative forcing. This review will improve our understanding of the climatic and environmental effects of BrC. (C) 2018 Elsevier B.V. All rights reserved.

While the vast majority of carbon emitted by wildland fires is released as CO2, CO, and CH4, wildland fire smoke is nonetheless a rich and complex mixture of gases and aerosols. Primary emissions include significant amounts of CH4 and aerosol (organic aerosol and black carbon), which are short-lived climate forcers. In addition to CO2 and short-lived climate forcers, wildland fires release CO, non-methane organic compounds (NMOC), nitrogen oxides (NOx = NO + NO2), NH3, and SO2. These species play a role in radiative forcing through their photochemical processing, which impacts atmospheric levels of CO2, CH4, tropospheric O-3, and aerosol. This paper reviews the current state of knowledge regarding the chemical composition of emissions and emission factors for fires in United States vegetation types as pertinent to radiative forcing and climate. Emission factors are critical input for the models used to estimate wildland fire greenhouse gas and aerosol emission inventories. Published by Elsevier B.V.

Black carbon (BC) is an important aerosol species because of its global and regional influence on radiative forcing and its local effects on the environment and human health. We have estimated the emissions of BC in China, where roughly one-fourth of global anthropogenic emissions is believed to originate. China's high rates of usage of coal and biofuels are primarily responsible for high BC emissions. This paper pays particular attention to the application of appropriate emission factors for China and the attenuation of these emissions where control devices are used. Nevertheless, because of the high degree of uncertainty associated with BC emission factors, we provide ranges of uncertainty for our emission estimates, which are approximately a factor of eight. In our central case, we calculate that BC emissions in China in 1995 were 1342 Gg, about 83% being generated by the residential combustion of coal and biofuels, We estimate that BC emissions could fall to 1224 Gg by 2020. This 9% decrease in BC emissions can be contrasted with the expected increase of 50% in energy use; the reduction will be obtained because of a transition to more advanced technology, including greater use of coal briquettes in place of raw coal in cities and towns. The increased use of diesel vehicles in the future will result in a greater share of the transport sector in total BC emissions. Spatially, BC emissions are predominantly distributed in an east-west swath across China's heartland, where the rural use of coal and biofuels for cooking and heating is widespread. This is in contrast Lo the emissions of most other anthropogenically derived air pollutants. which are closely tied to population and industrial centers. (C) 2001 Elsevier Science Ltd. All rights reserved.