# Rapid reduction in black carbon emissions from China: evidence from 2009–2019 observations on Fukue Island, Japan

A long-term, robust observational record of atmospheric black carbon (BC) concentrations at Fukue Island for 2009–2019 was produced by unifying the data from a continuous soot monitoring system (COSMOS) and a Multi-Angle Absorption Photometer (MAAP). This record was then used to analyze emission trends from China. We identified a rapid reduction in BC concentrations of (inline-formula $M1inlinescrollmathml-normal 5.8±normal 1.5$ 52pt10ptsvg-formulamathimgd70a8256f19fe625208fe448ee91f5f5 acp-20-6339-2020-ie00001.svg52pt10ptacp-20-6339-2020-ie00001.png ) % yrinline-formula−1 or inline-formula−48 % from 2010 to 2018. We concluded that an emission change of (inline-formula $M4inlinescrollmathml-normal 5.3±normal 0.7$ 52pt10ptsvg-formulamathimgb445b2738e7c78aa305360cfda995925 acp-20-6339-2020-ie00002.svg52pt10ptacp-20-6339-2020-ie00002.png ) % yrinline-formula−1, related to changes in China of as much as inline-formula−4.6 % yrinline-formula−1, was the main underlying driver. This evaluation was made after correcting for the interannual meteorological variability (IAV) by using the regional atmospheric chemistry model simulations from the Weather Research and Forecasting (WRF) and Community Multiscale Air Quality (CMAQ) models (collectively WRF/CMAQ) with the constant emissions. This resolves the current fundamental disagreements about the sign of the BC emissions trend from China over the past decade as assessed from bottom-up emission inventories. Our analysis supports inventories reflecting the governmental clean air actions after 2010 (e.g., MEIC1.3, ECLIPSE versions 5a and 6b, and the Regional Emission inventory in ASia (REAS) version 3.1) and recommends revisions to those that do not (e.g., Community Emissions Data System – CEDS). Our estimated emission trends were fairly uniform across seasons but diverse among air mass origins. Stronger BC reductions, accompanied by a reduction in carbon monoxide (CO) emissions, occurred in regions of south-central East China, while weaker BC reductions occurred in north-central East China and northeastern China. Prior to 2017, the BC and CO emissions trends were both unexpectedly positive in northeastern China during winter months, which possibly influenced the climate at higher latitudes. The pace of the estimated emissions reduction over China surpasses the Shared Socioeconomic Pathways (SSPs with reference to SSP1, specifically) scenarios for 2015–2030, which suggests highly successful emission control policies. At Fukue Island, the BC fraction of fine particulate matter (PMinline-formula2.5) also steadily decreased over the last decade. This suggests that reductions in BC emissions started without significant delay when compared to other pollutants such as inline-formulaNOx and inline-formulaSO2, which are among the key precursors of scattering PMinline-formula2.5.

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Kanaya, Yugo / Yamaji, Kazuyo / Miyakawa, Takuma / et al: Rapid reduction in black carbon emissions from China: evidence from 2009–2019 observations on Fukue Island, Japan. 2020. Copernicus Publications.

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