Variations In Anthropogenic Emissions Research Articles

Full-coverage mapping and spatiotemporal variations of ground-level ozone (O3) pollution from 2013 to 2020 across China

Ozone (O3) is an important trace and greenhouse gas in the atmosphere, posing a threat to the ecological environment and human health at the ground level. Large-scale and long-term studies of O3 pollution in China are few due to highly limited direct ground and satellite measurements. This study offers a new perspective to estimate ground-level O3 from solar radiation intensity and surface temperature by employing an extended ensemble learning of the space-time extremely randomized trees (STET) model, together with ground-based observations, remote sensing products, atmospheric reanalysis, and an emission inventory. A full-coverage (100%), high-resolution (10 km) and high-quality daily maximum 8-h average (MDA8) ground-level O3 dataset covering China (called ChinaHighO3) from 2013 to 2020 was generated. Our MDA8 O3 estimates (predictions) are reliable, with an average out-of-sample (out-of-station) coefficient of determination of 0.87 (0.80) and root-mean-square error of 17.10 (21.10) μg/m3 in China. The unique advantage of the full coverage of our dataset allowed us to accurately capture a short-term severe O3 pollution exposure event that took place from 23 April to 8 May in 2020. Also, a rapid increase and recovery of O3 concentrations associated with variations in anthropogenic emissions were seen during and after the COVID-19 lockdown, respectively. Trends in O3 concentration showed an average growth rate of 2.49 μg/m3/yr (p < 0.001) from 2013 to 2020, along with the continuous expansion of polluted areas exceeding the daily O3 standard (i.e., MDA8 O3 = 160 μg/m3). Summertime O3 concentrations and the probability of occurrence of daily O3 pollution have significantly increased since 2015, especially in the North China Plain and the main air pollution transmission belt (i.e., the “2 + 26” cities). However, a decline in both was seen in 2020, mainly due to the coordinated control of air pollution and ongoing COVID-19 effects. This carefully vetted and smoothed dataset is valuable for studies on air pollution and environmental health in China.

Investigation of aerosol black carbon over semi-urban and urban locations in south-western India

Abstract Temporal evolution of the ‘dual-spot’ 7-channel Aethalometer measured black carbon (BC) aerosols over different time scales, their potential source regions and impact of meteorology on BC mass are analyzed using observational data at Ahmednagar College (AC-Ahmednagar), Ahmednagar and Indian Institute of Tropical Meteorology, Pashan (IITM-Pashan), Pune. Results reveal well defined bimodal diurnal pattern in BC mass; one in morning (07:00-09:00 LT) and another in evening (around 20:00 LT) at both sites. This is quite consistent with seasonally changing BC mass and is the combined effects of variations in anthropogenic emissions, meteorology and associated atmospheric boundary layer (ABL) dynamics. BC mass concentration at AC-Ahmednagar and IITM-Pashan varied from 1.8 to 49.0 μg m−3 (annual mean 13.8 ± 10.4 μg m−3) and 0.7–21.6 μg m−3 (annual mean 3.9 ± 2.8 μg m−3) respectively. Annual BC cycle at AC-Ahmednagar, IITM-Pashan, Delhi and Xian (China) appears to be similar. However, BC mass at AC-Ahmednagar being of the same order to that reported at Delhi (India) and Xi'an (China), it is about 3.5 times higher than at IITM-Pashan. The present work, further, demonstrates prominent role exerted by surface temperature (T) and relative humidity (RH) in modulating BC mass. Occurrence of high ΔBC (BC370 nm – BC880 nm) and absorption Angstrom exponent (AAE) are indicative of enhanced absorption in near-UV and low-visible wavelengths attributed to the presence of biomass burning and light absorbing particulate matter. The back-trajectory cluster and concentrated weighted trajectory (CWT) analysis identifies four distinct potential BC source regions at the present receptor sites.

Distinct weekly cycles of thunderstorms and a potential connection with aerosol type in China

AbstractThis study identified distinct weekly cycles in thunderstorm activities and convection‐associated variables in two regions of China dominated by different types of aerosol during the summers of 1983–2005. In both regions, visibility has similar weekly cycle: lower on weekdays than on weekends. Barring any possible “natural” weekly cycles, the findings of the poorest and best visibility on Friday and Monday, respectively, point to the weekly variations in anthropogenic emissions. However, the phases of the thunderstorm cycles between the two regions were different. In central China, thunderstorms occurred more frequently from Saturday to Monday than on other days. The cycles were out of phase in southeast China. It is hypothesized that the phase difference is associated with aerosol type. In central China aerosol absorption is strong, which suppresses convection more on weekdays. In southeast China aerosols are less absorbing but more hygroscopic, which helps invigorate thunderstorms more on weekdays.

Did the widespread haze pollution over China increase during the last decade? A satellite view from space

Widespread haze layers usually cover China like low clouds, exerting marked influence on air quality and regional climate. With recent Collection 6 MODIS Deep Blue aerosol data in 2000–2015, we analyzed the trends of regional haze pollution and the corresponding influence of atmospheric circulation in China. Satellite observations show that regional haze pollution is mainly concentrated in northern and central China. The annual frequency of regional haze in northern China nearly doubles between 2000 and 2006, increasing from 30–50 to 80–90 days. Though there is a marked decrease in annual frequency during 2007–2009 due to both reduction of anthropogenic emissions and changes of meteorological conditions, regional pollution increases slowly but steadily after 2009, and maintains at a high level of 70–90 days except for the sudden decrease in 2015. Generally, there is a large increase in the number of regional-scale haze events during the last decade. Seasonal frequency of regional haze exhibits distinct spatial and temporal variations. The increasing winter haze events reach a peak in 2014, but decrease strongly in 2015 due partly to synoptic conditions that are favorable for dispersion. Trends of summer regional haze pollution are more sensitive to changes of atmospheric circulation. Our results indicate that the frequency of regional haze events is associated not only with the strength of atmospheric circulation, but also with its direction and position, as well as variations in anthropogenic emissions.

Investigation of spatial and historical variations of air pollution around an industrial region using trace and macro elements in tree components

Several trace and macro elements (n=48) were measured in pine needle, branch, bark, tree ring, litter, and soil samples collected at 27 sites (21 industrial, 6 background) to investigate their spatial and historical variation in Aliaga industrial region in Turkey. Concentrations generally decreased with distance from the sources and the lowest ones were measured at background sites far from major sources. Spatial distribution of anthropogenic trace elements indicated that their major sources in the region are the iron-steel plants, ship-breaking activities and the petroleum refinery. Patterns of 40 elements that were detected in most of the samples were also evaluated to assess their suitability for investigation of historical variations. Observed increasing trends of several trace and macro elements (As, Cr, Fe, Mo, Ni, V, Cu, Pb, Sb, Sn, and Hg) in the tree-ring samples were representative for the variations in anthropogenic emissions and resulting atmospheric concentrations in Aliaga region. It was shown that lanthanides (La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb) could also be used for the investigation of historical variations due to specific industrial emissions (i.e., petroleum refining). Results of the present study showed that tree components, litter, and soil could be used to determine the spatial variations of atmospheric pollution in a region while tree rings could be used to assess the historical variations.

Simulation of the interannual variations of tropospheric ozone over China: Roles of variations in meteorological parameters and anthropogenic emissions

Abstract We quantify the interannual variations (IAVs) of tropospheric O3 over China for the years 2004–2012 by using the one-way nested-grid version of the global three-dimensional Goddard Earth Observing System chemical transport model (GEOS-Chem). The roles of variations in meteorological fields and anthropogenic emissions of O3 precursors are examined separately and together through sensitivity simulations. With variations in both meteorological parameters and emissions, simulated seasonal mean surface-layer O3 concentrations over North China (NC, 110–120°E, 32–42°N) exhibit the largest IAVs in June–July–August (JJA). The regionally averaged absolute percent departure from the mean (APDM) values over NC are 0.7%, 3.2%, 3.9%, and 2.1% in December–January–February (DJF), March–April–May (MAM), and September–October–November (SON), respectively. Over South China (SC, 110–120°E, 22–32°N), the IAVs of O3 are found maximum in MAM, and minimum in JJA; the APDM values are 2.7%, 3.7%, 1.4%, and 2.6% in DJF, MAM, JJA, and SON, respectively. With respect to the IAVs of O3 over the Sichuan Basin (SCB, 102–110°E, 27–33°N), the APDM values are simulated to be 2.7–3.8% throughout the year. The IAVs in surface-layer O3 by variations in meteorological fields are simulated to be larger than those by variations in anthropogenic emissions throughout the year in NC and SC except for JJA in SC. The relatively more important role of variations in anthropogenic emissions is simulated in SCB in all seasons. Process analyses are performed to identify key meteorological parameters that influence the IAVs of O3 over NC, SC, and SCB. Over all of these regions, variations in winds are found to have the largest impact on the IAVs of O3, followed by those in temperature and specific humidity. Considering that the APDM values represent the IAVs averaged over 2004–2012, the magnitudes of IAVs of O3 for specific years can be more significant than the numbers reported here. Our results have important implications for the effectiveness of short-term air quality control strategies in China.

Biomonitoring the spatial and historical variations of persistent organic pollutants (POPs) in an industrial region.

Several persistent organic pollutants (POPs) like polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polybrominated diphenyl ethers (PBDEs) were measured in needle, branch, bark, and tree ring samples in pine samples collected at 27 sites (21 industrial, 6 background) in Aliaga industrial region in Turkey. Soil, litter, and air samples were also collected to investigate the relationships between the air and soil, litter, and tree components. Concentrations decreased with distance from the sources and the lowest ones were measured at background sites. The spatial distribution of POPs indicated that the major sources in the region are the iron-steel, ship-breaking, petrochemical plants and the petroleum refinery. Significant correlations between the air concentrations and, soil, litter, and tree components indicated the interaction of these compartments with air. Observed increasing trends of POPs in the tree-ring samples were representative for the variations in anthropogenic emissions and resulting atmospheric concentrations in Aliaga region. These results indicated that tree components, litter and soil could be used to determine the spatial variations while tree rings could be used to investigate the historical trends of atmospheric POPs in a region. POP amounts (mg/ha) stored in different tree components, litter, and soil were also inventoried. Among the tree components, generally, the highest amounts were stored in the stem followed by needles. For the overall inventory, the highest amounts were stored in soil for PCNs, PBDEs, and PCBs while highest PAH amounts were stored in trees, indicating that in addition to soil, vegetation is also an important reservoir for POPs.

Decadal trend and interannual variation of outflow of aerosols from East Asia: Roles of variations in meteorological parameters and emissions

We apply a global three-dimensional Goddard Earth Observing System (GEOS) chemical transport model (GEOS-Chem) to quantify the decadal trend and interannual variation of aerosol outflow from East Asia. Simulations of aerosols are performed for years 1986–2006, driven by the NASA/GEOS-4 assimilated meteorological fields. The impacts of variations in meteorological parameters and emissions are imposed separately and together by numerical experiments. With variations in both meteorological parameters and anthropogenic emissions, simulated annual outflow of PM2.5 (sum of sulfate, nitrate, ammonium, black carbon, and organic carbon) from East Asia increased by 6.0 Tg (or 53%) over years 1986–2006, in which the outflow fluxes of sulfate, nitrate, and ammonium aerosols had the largest contributions with decadal trends of +1.2, +0.8, and +0.7 Tg decade−1, respectively. Simulated outflow fluxes of aerosols also exhibited large interannual variations; the absolute percent departure from the mean (APDM) values of the annual outflow fluxes of sulfate, nitrate, ammonium, black carbon, organic carbon, and PM2.5 were 5.9%, 7.9%, 5.4%, 5.8%, 4.2%, and 5.2%, respectively, as variations in both meteorological parameters and anthropogenic emissions were considered. Model sensitivity studies show that, for outflow fluxes of aerosols from East Asia, the decadal trends were driven by variations in anthropogenic emissions whereas the interannual variations were dominated by variations in meteorological parameters. The increases in anthropogenic emissions alone explained about 86% of the decadal trend in outflow of PM2.5. Although variations in meteorological parameters can influence the interannual variations in aerosol outflow by changing both aerosol concentrations over East Asia and zonal winds, the latter is identified to be the key factor because of the high positive correlation coefficient between the annual outflow flux of PM2.5 and zonal wind at 700 hPa (the altitude with the maximum outflow fluxes) for years 1986–2006.

Simulation of the interannual variations of aerosols in China: role of variations in meteorological parameters

Abstract. We used the nested grid version of the global three-dimensional Goddard Earth Observing System chemical transport model (GEOS-Chem) to examine the interannual variations (IAVs) of aerosols over heavily polluted regions in China for years 2004–2012. The role of variations in meteorological parameters was quantified by a simulation with fixed anthropogenic emissions at year 2006 levels and changes in meteorological parameters over 2004–2012. Simulated PM2.5 (particles with a diameter of 2.5 μm or less) aerosol concentrations exhibited large IAVs in North China (NC; 32–42° N, 110–120° E), with regionally averaged absolute percent departure from the mean (APDM) values of 17, 14, 14, and 11% in December-January-February (DJF), March-April-May (MAM), June-July-August (JJA), and September-October-November (SON), respectively. Over South China (SC; 22–32° N, 110–120° E), the IAVs in PM2.5 were found to be the largest in JJA, with the regional mean APDM values of 14% in JJA and of about 9% in other seasons. The concentrations of PM2.5 over the Sichuan Basin (SCB; 27–33° N, 102–110° E) were simulated to have the smallest IAVs among the polluted regions examined in this work, with APDM values of 8–9% in all seasons. All aerosol species (sulfate, nitrate, ammonium, black carbon, and organic carbon) were simulated to have the largest IAVs over NC in DJF, corresponding to the large variations in meteorological parameters over NC in this season. Process analyses were performed to identify the key meteorological parameters that determined the IAVs of different aerosol species in different regions. While the variations in temperature and specific humidity, which influenced the gas-phase formation of sulfate, jointly determined the IAVs of sulfate over NC in both DJF and JJA, wind (or convergence of wind) in DJF and precipitation in JJA were the dominant meteorological factors to influence IAVs of sulfate over SC and the SCB. The IAVs in temperature and specific humidity influenced gas-to-aerosol partitioning, which were the major factors that led to the IAVs of nitrate aerosol in China. The IAVs in wind and precipitation were found to drive the IAVs of organic carbon aerosol. We also compared the IAVs of aerosols simulated with variations in meteorological parameters alone with those simulated with variations in anthropogenic emissions alone; the variations in meteorological fields were found to dominate the IAVs of aerosols in northern and southern China over 2004–2012. Considering that the IAVs in meteorological fields are mainly associated with natural variability in the climate system, the IAVs in aerosol concentrations driven by meteorological parameters have important implications for the effectiveness of short-term air quality control strategies in China.

Effect of the strengthened western Pacific subtropical high on summer visibility decrease over eastern China since 1973

Daily visibility (Vis) data from 354 meteorological stations are used to evaluate the seasonal Vis trends over China from 1973 to 2009, which show that Vis decline is most distinct over eastern China in summer, with a trend of −1.4 km per decade or −34% in the 37 years. This rapid decline of summertime Vis is found to be partially associated with the intensification and westward extension of the western Pacific subtropical high (WPSH) that has occurred in recent years. Such a change in the strength and breadth of WPSH has resulted in more days with stable, hot, and humid weather, which is favorable for Vis decrease. Analysis through decomposing the trend of Vis into contributions respectively from days with and without WPSH‐type meteorological conditions further shows that the intensification of WPSH leads to more episodes of Vis impairment and amplifies the effect of increased aerosol and precursor emissions on the summertime Vis decline in eastern China. Consequently, the difference of Vis between summer and winter follows a declining trend, although the Vis level in winter is still lower than that in summer. The result of this study underscores the importance of considering not only the variation of anthropogenic emissions, but also the change of climate and synoptic systems in the prediction and regulation of air quality and visibility.

Simulation of contribution of continental anthropogenic sources to variations in the CO2 concentration during winter period on Hateruma Island

Data of continuous CO2 observations in the zone affected by pollutants emitted on the territory of China are analyzed using the method for simulating the CO2 transport with the help of a combination of grid based and Lagrangian particle dispersion models of atmospheric pollutant transport, taking into account the data on surface fluxes of carbon dioxide of anthropogenic, biospheric, and oceanic origins. The results of the model calculations are compared with observations at the Hateruma station, Japan, and demonstrated good correspondence. We analyzed how emissions from pollution sources located on the territory of China affect the simulated time series. Calculations are performed with and without accounting for emissions on the territory of China; they showed that anthropogenic emissions on the territory of China are the main contributors to CO2 variations at the observation site during winter period. The fact that regional anthropogenic emissions predominate in the observed signal indicates that the data from the Hateruma station can be effectively used for transport simulation in the region and for solution of inverse problems on interannual variations in anthropogenic emissions of CO2 and other gases.

Dynamics of a closed low-parameter compartment model of the global carbon cycle

A closed dynamic compartment model of the global carbon cycle and its modifications with a small number of external parameters, which are constructed on the basis of data on the current and preindustrial carbon fluxes and reserves in reservoirs, are studied. The first possible controlling parameter is the amount of anthropogenic CO2 emission into the atmosphere. Closure in substance allows a decrease in the dimensionality of dynamic models and yields another variable parameter—the system’s total mass, whose change reflects the level of uncertainty in the knowledge of the amount of reserves. The calibration of unsaturated fluxes in each of the models is based on an algorithm developed earlier for local ecosystems, and the measured differences between the fluxes opposite in sign for several times are used to calculate the coefficients of saturated fluxes. The model’s modifications make it possible to estimate the degree to which the oceanic active layer may be involved in rapid exchange with the atmosphere and to introduce the factor of land use as an additional anthropogenic effect. The time trajectories of carbon reserves in reservoirs are calculated until 2100 under variations in anthropogenic emissions in accordance with the IPCC basic scenarios until 2100 for the basic model and its modifications.

Multi-model ensemble simulations of tropospheric NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; compared with GOME retrievals for the year 2000

Abstract. We present a systematic comparison of tropospheric NO2 from 17 global atmospheric chemistry models with three state-of-the-art retrievals from the Global Ozone Monitoring Experiment (GOME) for the year 2000. The models used constant anthropogenic emissions from IIASA/EDGAR3.2 and monthly emissions from biomass burning based on the 1997–2002 average carbon emissions from the Global Fire Emissions Database (GFED). Model output is analyzed at 10:30 local time, close to the overpass time of the ERS-2 satellite, and collocated with the measurements to account for sampling biases due to incomplete spatiotemporal coverage of the instrument. We assessed the importance of different contributions to the sampling bias: correlations on seasonal time scale give rise to a positive bias of 30–50% in the retrieved annual means over regions dominated by emissions from biomass burning. Over the industrial regions of the eastern United States, Europe and eastern China the retrieved annual means have a negative bias with significant contributions (between –25% and +10% of the NO2 column) resulting from correlations on time scales from a day to a month. We present global maps of modeled and retrieved annual mean NO2 column densities, together with the corresponding ensemble means and standard deviations for models and retrievals. The spatial correlation between the individual models and retrievals are high, typically in the range 0.81–0.93 after smoothing the data to a common resolution. On average the models underestimate the retrievals in industrial regions, especially over eastern China and over the Highveld region of South Africa, and overestimate the retrievals in regions dominated by biomass burning during the dry season. The discrepancy over South America south of the Amazon disappears when we use the GFED emissions specific to the year 2000. The seasonal cycle is analyzed in detail for eight different continental regions. Over regions dominated by biomass burning, the timing of the seasonal cycle is generally well reproduced by the models. However, over Central Africa south of the Equator the models peak one to two months earlier than the retrievals. We further evaluate a recent proposal to reduce the NOx emission factors for savanna fires by 40% and find that this leads to an improvement of the amplitude of the seasonal cycle over the biomass burning regions of Northern and Central Africa. In these regions the models tend to underestimate the retrievals during the wet season, suggesting that the soil emissions are higher than assumed in the models. In general, the discrepancies between models and retrievals cannot be explained by a priori profile assumptions made in the retrievals, neither by diurnal variations in anthropogenic emissions, which lead to a marginal reduction of the NO2 abundance at 10:30 local time (by 2.5–4.1% over Europe). Overall, there are significant differences among the various models and, in particular, among the three retrievals. The discrepancies among the retrievals (10–50% in the annual mean over polluted regions) indicate that the previously estimated retrieval uncertainties have a large systematic component. Our findings imply that top-down estimations of NOx emissions from satellite retrievals of tropospheric NO2 are strongly dependent on the choice of model and retrieval.

Isotopic evidence of pollutant lead sources in Northwestern France

Ratios of stable lead isotopes ( 204Pb, 206Pb, 207Pb, 208Pb) are used to characterize both spatial and temporal variations in anthropogenic emissions of industrial lead aerosols to the atmosphere of northwestern France. Differences in isotopic compositions of aerosols collected from a rural area (Wimereux) in the Nord-Pas de Calais region along the English Channel in 1982–1983 ( 206Pb/ 207Pb=1.108±0.005) and 1994 ( 206Pb/ 207Pb=1.148±0.003) are paralleled by similar variations in urban aerosols within France during the same period (e.g., 206Pb/ 207Pb=1.115±0.008 from 1981–1989 and 1.143±0.006 from 1992–1995). These results correlate well with recent findings in the Mediterranean basin (Alleman, 1997) where this radiogenicity increase is clearly associated with industrial sources other than leaded gasoline that has remained relatively constant during its phasing out ( 206Pb/ 207Pb=1.08–1.11). Here we used archived data, air mass trajectories and aerosol diameters combined with isotopic signatures to confirm this trend at a regional scale. Indeed, the main industrial signatures from lead smelting ( 206Pb/ 207Pb=1.133±0.001) and steel metallurgy ( 206Pb/ 207Pb=1.196±0.015) in northwestern France appear more radiogenic than that of leaded gasoline. The shift in isotopic compositions also conform with the systematic change in the mean size (diameter) of aerosols at Wimereux, which ranged from 0.30 to 0.61 μm in 1982–1984 and from 0.70 to 0.89 μm in 1994.