Atmospheric Brown Carbon (BrC) with strong wavelength-dependence light-absorption ability can significantly affect radiative forcing. Highly resolved emission inventories with lower uncertainties are important premise and essential in scientifically evaluating impacts of emissions on air quality, human health and climate change. This study developed a bottom-up inventory of primary BrC from combustion sources in China from 1960 to 2016 with a spatial resolution at 0.1 degrees x 0.1 degrees, based on compiled emission factors and detailed activity data. The primary BrC emission in China was about 593 Gg (500-735 Gg as interquartile range) in 2016, contributing to 7% (5%-8%) of a previously estimated global total BrC emission. Residential fuel combustion was the largest source of primary BrC in China, with the contribution of 67% as the national average but ranging from 25% to 99% among different provincial regions. Significant spatial disparities were also observed in the relative shares of different fuel types. Coal combustion contribution varied from 8% to 99% across different regions. Heilongjiang and North China Plain had high emissions of primary BrC. Generally, on the national scale, spatial distribution of BrC emission density per area was aligned with the population distribution. Primary BrC emission from combustion sources in China have been declined since a peak of similar to 1300 Gg in 1980, but the temporal trends were distinct in different sectors. The high-resolution inventory developed here enables radiative forcing simulations in future atmospheric models so as to promote better understanding of carbonaceous aerosol impacts in the Earth's climate system and to develop strategies achieving co-benefits of human health protection and climate change.

Brown carbon (BrC), known as light-absorbing organic aerosol in the near-ultraviolet (UV) and short visible region, plays a significant role in the global and regional climate change. A detailed understanding of the spectral optical properties of BrC is beneficial for reducing the uncertainty in radiative forcing calculation. In this work, the spectral properties of primary BrC were investigated by using a four-wavelength broadband cavity-enhanced albedometer with central wavelengths at 365, 405, 532 and 660 nm. The BrC samples were generated by the pyrolysis of three types of wood. During the pyrolysis process, the measured average single scattering albedo (SSA) at 365 nm was about 0.66 to 0.86, where the average absorption angstrom ngstrom exponent (AAE) was between 5.8 and 7.8, and the average extinction angstrom ngstrom exponent (EAE) was within 2.1 to 3.5. The full spectral measurement of SSA (300-700 nm) was realized by an optical retrieval method and the retrieved SSA spectrum was directly applied to evaluate aerosol direct radiative forcing (DRF) efficiency. The DRF efficiency over ground of various primary BrC emissions increased from 5.3 % to 68 % as compared to the non-absorbing organic aerosol assumption. A decrease of about 35 % in SSA would cause the DRF efficiency over ground to change from cooling effect to warming effect (from -0.33 W/m2 to +0.15 W/m2) in the near-UV band (365-405 nm). The DRF efficiency over ground of strongly absorptive primary BrC (lower SSA) contributed 66 % more than weakly absorptive primary BrC (higher SSA). These findings proved the importance of broadband spectral properties of BrC, which are substantial for radiative forcing evaluation of BrC and should be considered in global climate models.

India is currently the second-largest emitter of black carbon (BC) in the world, with emissions projected to rise steadily in the coming decades. In view of the large variations associated with BC emission inventories in this region, model outputs of BC mass and radiative forcing (RF) need to be validated against long-term regionally representative atmospheric measurements. Such measurements are highly scattered spatially as well as temporally in India, and a systematic evaluation of BC data is non-existent so far. To address this issue, we present here a comprehensive review of BC measurements in India from a survey of > 140 studies spanning 2002-2018. In addition to summarizing baseline BC levels in urban, semi-urban, rural and remote locations, we report impacts of anomalous environmental and/or emission conditions, e.g., truck/general strikes, firework events, fog/haze episodes, large-scale biomass burning events, etc. We also present a discussion on major BC sources and climate impacts (in terms of direct RF) in major land-use categories, mitigation strategies currently employed on a national scale, and recent advances in measuring brown carbon (BrC) in India. We identify key areas for improvement, such as - i) the need for long-term BC monitoring networks, especially in regions where estimated emissions are high but measurement coverage is low; ii) the general lack of understanding, despite some recent reports, of BC aerosol mixing states, aging and direct climate effects in the Indian context; iii) the need to shift from qualitative approaches of BC source apportionment to robust quantitative measures; and iv) the prospects for coupled chemical-optical characterization of BrC for a better understanding of its sources and climate effects. We list potential research directions for the scientific community to address these knowledge gaps. We also believe that this review will be beneficial to policymakers for prioritizing BC mitigation efforts.

The impact of Brown Carbon (BrC) to aerosol light absorption has been paid more attention recently and there are a large number of studies showing that the influence of BrC on radiative forcing should not be ignored. BrC also acts as an important component of haze pollution which is occurring frequently in Wuhan, China. Therefore, it is essential to estimate their optical properties, composition, and mass concentration. Considering most haze pollution happens during the coldest time, we retrieved BrC columnar content during winter in Wuhan for the first time. Our method bases on the fact that BrC showed the strong spectral dependence on UV-light absorption. Using this method, we found that BrC makes up the small proportions of total aerosol volume (less than 10%). In the winter of 2011, we retrieved the daily-averaged columnar- integrated mass concentration of BrC on clear day is 4.353 mg/m(2) while that of haze day is 12.750 mg/m(2). According to the sensitivity study, we found that the results highly relied on the assumed aerosol refractive index. To reduce the uncertainty of this approach, we need to gain a better understanding of the temporal variability of the radiation absorbing components of these aerosols in the future.