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 (−5.8±1.5) % yr−1 or −48 % from 2010 to 2018. We concluded that an emission change of (−5.3±0.7) % yr−1, related to changes in China of as much as −4.6 % yr−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 (PM2.5) 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 NOx and SO2, which are among the key precursors of scattering PM2.5

Composition and major sources of organic compounds of aerosol particulate matter sampled during the ACE-Asia campaign

The organic compound tracers of atmospheric particulate matter, as well as organic carbon (OC) and elemental carbon (EC), have been characterized for samples acquired during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) from Gosan, Jeju Island, Korea, from Sapporo, Japan, and from Chichi-jima Island in the western North Pacific, as well as on the National Oceanic and Atmospheric Administration R/V Ronald H. Brown. Total extracts were analyzed by gas chromatography–mass spectrometry to determine both polar and aliphatic compounds. Total particles, organic matter, and lipid and saccharide compounds were high during the Asian dust episode (early April 2001) compared to levels at other times. The organic matter can be apportioned to seven emission sources and to significant oxidationproducing secondary products during long-range transport. Terrestrial natural background compounds are vascular plant wax lipids derived from direct emission and as part of desert sand dust. Fossil fuel utilization is obvious and derives from petroleum product and coal combustion emissions. Saccharides are a major polar (water-soluble) carbonaceous fraction derived from soil resuspension (agricultural activities). Biomass-burning smoke is evident in all samples and seasons. It contributes up to 13% of the total compound mass as water-soluble constituents. Burning of refuse is another source of organic particles. Varying levels of marine-derived lipids are superimposed during aerosol transport over the ocean. Secondary oxidation products increase with increasing transport distance and time. The ACE-Asia aerosols are composed not only of desert dust but also of soil dust, smoke from biomass and refuse burning, and emissions from fossil fuel use in urban areas

Full latitudinal marine atmospheric measurements of iodine monoxide

14 pags., 7 figs., 4 tabs.Iodine compounds destroy ozone (O3) in the global troposphere and form new aerosols, thereby affecting the global radiative balance. However, few reports have described the latitudinal distribution of atmospheric iodine compounds. This work reports iodine monoxide (IO) measurements taken over unprecedented sampling areas from the Arctic to the Southern Hemisphere and spanning sea surface temperatures (SSTs) of approximately 0 to 31.5°C. The highest IO concentrations were observed over the Western Pacific warm pool (WPWP), where O3 minima were also measured. There, a negative correlation was found between O3 and IO mixing ratios at extremely low O3 concentrations. This correlation is not explained readily by the O3-dependent oceanic fluxes of photolabile inorganic iodine compounds, which is the dominant source in recent global-scale chemistry transport models representing iodine chemistry. Actually, the correlation rather implies that O3-independent pathways can be similarly important in the WPWP. The O3-independent fluxes result in a 15% greater O3 loss than that estimated for O3-dependent processes alone. The daily O3 loss rate related to iodine over the WPWP is as high as approximately 2ppbv (parts per billion by volume) despite low O3 concentrations of approximately 10ppbv, with the loss being up to 100% greater than that without iodine. This finding suggests that warming SST driven by climate change might affect the marine atmospheric chemical balance through iodine-ozone chemistry. Copyright:This study was supported by the KAKENHI (grant nos. 16KK0017 and 21H04933), and by the ArCS (Arctic Challenge for Sustainability; grant no. JPMXD1300000000) of the Ministry of Education, Culture, Sports, Science, and Technology of Japan. This study has also received funding from the European Research Council Executive Agency under the European Union’s Horizon 2020 Research and Innovation programme (grant no. ERC2016-COG 726349; CLIMAHAL). This study was also supported, in part, by funding from Fukuoka University (grant no. 197103).Peer reviewe

Endotoxemia by Porphyromonas gingivalis Injection Aggravates Non-alcoholic Fatty Liver Disease, Disrupts Glucose/Lipid Metabolism, and Alters Gut Microbiota in Mice

Many risk factors related to the development of non-alcoholic fatty liver disease (NAFLD) have been proposed, including the most well-known of diabetes and obesity as well as periodontitis. As periodontal pathogenic bacteria produce endotoxins, periodontal treatment can result in endotoxemia. The aim of this study was to investigate the effects of intravenous, sonicated Porphyromonas gingivalis (Pg) injection on glucose/lipid metabolism, liver steatosis, and gut microbiota in mice. Endotoxemia was induced in C57BL/6J mice (8 weeks old) by intravenous injection of sonicated Pg; Pg was deactivated but its endotoxin remained. The mice were fed a high-fat diet and administered sonicated Pg (HFPg) or saline (HFco) injections for 12 weeks. Liver steatosis, glucose metabolism, and gene expression in the liver were evaluated. 16S rRNA gene sequencing with metagenome prediction was performed on the gut microbiota. Compared to HFco mice, HFPg mice exhibited impaired glucose tolerance and insulin resistance along with increased liver steatosis. Liver microarray analysis demonstrated that 1278 genes were differentially expressed between HFco and HFPg mice. Gene set enrichment analysis showed that fatty acid metabolism, hypoxia, and TNFα signaling via NFκB gene sets were enriched in HFPg mice. Although sonicated Pg did not directly reach the gut, it changed the gut microbiota and decreased bacterial diversity in HFPg mice. Metagenome prediction in the gut microbiota showed enriched citrate cycle and carbon fixation pathways in prokaryotes. Overall, intravenous injection of sonicated Pg caused impaired glucose tolerance, insulin resistance, and liver steatosis in mice fed high-fat diets. Thus, blood infusion of Pg contributes to NAFLD and alters the gut microbiota

Secondary aerosol formation promotes water uptake by organic-rich wildfire haze particles in equatorial Asia

The diameter growth factor (GF) of 100nm haze particles at 85% relative humidity (RH) and their chemical characteristics were simultaneously monitored at Singapore in October 2015 during a pervasive wildfire haze episode that was caused by peatland burning in Indonesia. Non-refractory submicron particles (NR-PM1) were dominated by organics (OA; approximating 77.1% in total mass), whereas sulfate was the most abundant inorganic constituent (11.7% on average). A statistical analysis of the organic mass spectra showed that most organics (36.0% of NR-PM1 mass) were highly oxygenated. Diurnal variations of GF, number fractions of more hygroscopic mode particles, mass fractions of sulfate, and mass fractions of oxygenated organics (OOA) synchronized well, peaking during the day. The mean hygroscopicity parameter (κ) of the haze particles was 0.189±0.087, and the mean κ values of organics were 0.157±0.108 (κorg, bulk organics) and 0.266±0.184 (κOOA, OOA), demonstrating the important roles of both sulfate and highly oxygenated organics in the hygroscopic growth of organics-dominated wildfire haze particles. κorg correlated with the water-soluble organic fraction insignificantly, but it positively correlated with f44 (fraction of the ion fragment at m∕z44 in total organics) (R=0.070), implying the oxygenation degree of organics could be more critical for the water uptake of organic compounds. These results further suggest the importance of sulfate and secondary organic aerosol formation in promoting the hygroscopic growth of wildfire haze particles. Further detailed size-resolved as well as molecular-level chemical information about organics is necessary for the profound exploration of water uptake by wildfire haze particles in equatorial Asia.NRF (Natl Research Foundation, S’pore)Published versio

Composition and major sources of organic compounds of aerosol particulate matter sampled during the ACE-Asia campaign

The organic compound tracers of atmospheric particulate matter, as well as organic carbon (OC) and elemental carbon (EC), have been characterized for samples acquired during the ACEAsia campaign from Gosan, Jeju Island, Korea; Sapporo, Japan, and Chichi-jima Island in the western North Pacific, as well as on the NOAA R/V Ronald H. Brown. Total extracts were analyzed by GC-MS to determine both polar and aliphatic compounds. Total particles, organic matter and lipid and saccharide compounds were high during the Asian dust episode (early April 2001) compared to levels at other times. The organic matter can be apportioned to seven emission sources and to significant oxidation producing secondary products during long-range transport. Terrestrial natural background compounds are vascular plant wax lipids derived from direct emission and as part of desert sand dust. Fossil fuel utilization is obvious and derives from petroleum product and coal combustion emissions. Saccharides are a major polar (water-soluble) carbonaceous fraction derived from soil resuspension (agricultural activities). Biomass burning smoke is evident in all samples and seasons. It contributes up to 13% of the total compound mass as water-soluble constituents. Burning of refuse is another source of organic particles. Varying levels of marine-derived lipids are superimposed during aerosol transport over the ocean. Secondary oxidation products increase with increasing transport distance and time. The ACEAsia aerosols are comprised not only of desert dust, but also of soil dust, smoke from biomass and refuse burning, and emissions from fossil fuels use in urban areas

Long-range transport of ozone, carbon monoxide, and acidic trace gases at Oki Island, Japan, during PEM-WEST B / PEACAMPOT B campaign

Ground based measurements of ozone, CO, HNO3, SO2, HCl, and formic acid were carried out at Oki, a remote island site in the Sea of Japan, during Feburuary 26 to March 16, 1994, as the Pacific Exploratory Mission in the Western Pacific / Perturbation by East Asian Continental Air Mass to the Pacific Oceanic Troposphere (PEM-West B / PEACAMPOT B) campaign. According to trajectory analysis, the air mass reaching Oki was classified into four groups: northerly, northwesterly, west-northwesterly, and westerly flows. Clear dependence of gas concentrations on flow direction of air mass was found for all species studied. Lowest concentrations were observed in the northerly airflow originating from the Bering Sea. The mean concentrations of ozone and CO in northerly flow were 37.6±1.9 and 157±7 ppbv, respectively. The mean values of HNO3, SO2, HCl, and formic acid in the northerly flow were 34±10, 41±5, 107±23, and 54±81 pptv, respectively. The highest concentrations of all species were observed in the westerly flow passing through a lower boundary layer over the Yellow Sea and South Korean Peninsula. The mean concentrations of ozone and CO in the westerly flow were 45.9±4.0 and 292±44 ppbv, respectively. The mean values of HNO3, SO2, HCl, and formic acid in the westerly flow were 137±37, 2075±1307, 515±214, and 264±183 pptv, respectively. Clear seasonal variation of the background concentrations of ozone and CO were identified by comparison with the data from the PEM-West A /PEACAMPOT A campaign conducted in the fall. In contrast to other species, strong diurnal variation of formic acid with a daytime maximum was observed. The possibility of photochemical formation of formic acid from HCHO and the HO2 radical is discussed

Mass concentrations of black carbon measured by four instruments in the middle of Central East China in June 2006

Mass concentrations of black carbon (BC) were determined in June 2006 at the top of Mount Tai (36.26° N, 117.11° E, 1534 m a.s.l.), located in the middle of Central East China, using four different instruments: a multi-angle absorption photometer (5012 MAAP, Thermo), a particle soot absorption photometer (PSAP, Radiance Research), an ECOC semi-continuous analyzer (Sunset Laboratory) and an Aethalometer (AE-21, Magee Scientific). High correlation coefficients (<i>R</i><sup>2</sup>>0.88) were obtained between the measurements of the BC mass concentrations made using the different instruments. From the range of the slopes of the linear least-square fittings, we concluded that BC concentrations regionally-representative of the area were measured in a range with a maximum-to-minimum ratio of 1.5 (an exception was that the BC (PM<sub>2.5</sub>) concentrations derived from MAAP were ~2 times higher than the optical measurements (PM<sub>2.5</sub>) derived from the ECOC analyzer). While this range is significant, it is still sufficiently narrow to better constrain the large and highly uncertain emission rate of BC from Central East China. In detail, two optical instruments (the MAAP and the PSAP equipped with a heated inlet 400°C) tended to give higher concentrations than the thermal EC concentrations observed by the ECOC analyzer. The ratios of optical BC to thermal EC showed a positive correlation with the OC/EC ratio reported by the ECOC analyzer, suggesting two explanations. One is that the optical instruments overestimated BC concentrations in spite of careful cancellation of the scattering effect in the MAAP instrument and the expected evaporation of volatile species by heating the inlet of the PSAP instrument. The other is that the determined split points between OC and EC were too late when a large amount of OC underwent charring during the analysis, resulting in an underestimation of EC by the ECOC analyzer. High ratios of optical BC to thermal EC were recorded when the NO<sub>x</sub>/NO<sub>y</sub> ratio was low, implying the coating of the particles became thicker in an aged air mass and thus resulted in the optical instruments overestimating BC concentrations because of the lensing effect