Aerosol Emission Sources Research Articles

Long‐Term Changes in Salinity in the South China Sea Due To Anthropogenic Forcing

AbstractChanges in ocean salinity are essential for the stratification of the upper ocean and the regional marine ecosystem. In this study, 10 sets of large ensemble experiments and multi‐model ensembles from the Coupled Model Intercomparison Project Phase 6 (CMIP6) are used to investigate the effect of anthropogenic forcing on upper ocean salinity in the South China Sea (SCS). In most models, surface salinity increases during the historical period due to external forcing. Using the salinity budget, we find that a decrease in freshwater flux, particularly precipitation, is responsible for the increase in salinity, although horizontal advection also contributes to the change. Single forcing experiments reveal that the change in salinity in the SCS is mainly attributed to anthropogenic forcing, while the influence of natural forcing is relatively small. Anthropogenic aerosols (AAs) can decrease the dynamic and thermal components of precipitation, resulting in a considerable increase in salinity. In contrast, anthropogenic greenhouse gases (GHGs) have less effect on long‐term trend in SCS salinity because the GHG forcing leads to an increased thermal response of precipitation but a decreased dynamic response. Additionally, we use the Community Earth System Model version 1 (CESM1) to evaluate the role of different aerosol emission sources in modulating the salinity change in the SCS. The experimental results show that aerosol emissions from Asia dominate the salinity change in the SCS by changing the local Hadley circulation. In contrast, the contribution of aerosol emissions from North America and Europe (NAEU) is much smaller.

Amplified Interhemispheric Rainfall Contrast in Boreal Summer Due To Reduction in Anthropogenic Emissions Under COVID‐MIP Green Economic‐Recovery Scenarios

AbstractOur study looks at the precipitation responses to two possible future emission‐mitigation pathways, pushed by the Coronavirus Disease 2019 pandemic (COVID‐19) and achieving carbon neutrality in the mid‐21st century. We find that a simultaneous‐reduction in well‐mixed greenhouse gases (WMGHGs) and anthropogenic aerosol emissions results in an enhanced interhemispheric precipitation contrast in the 2040s by amplifying the interhemispheric thermal contrast and strengthening the meridional overturning circulation in the tropics. Reduced aerosol emissions induce generally‐increased precipitation in the Northern Hemisphere (NH) and an amplified intertropical rainfall contrast, while reduced WMGHG emissions dominate decrease in precipitation in the areas away from aerosol emission sources. Further, the above precipitation contrast will be enhanced under stronger emission‐mitigation pathways, mainly attributed to larger precipitation increases in the NH caused by reduced aerosols. More aggressive WMGHGs mitigation policies are necessary to counteract the aerosol‐induced warming in the NH, thereby mitigating the risk of regional drying or wetting due to the asymmetry in interhemispheric energy budgets.

Isolating the effect of biomass burning aerosol emissions on 20th century hydroclimate in South America and Southeast Asia

Biomass burning is a significant source of aerosol emissions in some regions and has a considerable impact on regional climate. Earth system model simulations indicate that increased biomass burning aerosol emissions contributed to statistically significant decreases in tropical precipitation over the 20th century. In this study, we use the Community Earth System Model version 1 Large Ensemble (CESM1-LENS) experiment to evaluate the mechanisms by which biomass burning aerosol contributed to decreased tropical precipitation, with a focus on South America and Southeast Asia. We analyze the all-but-one forcing simulations in which biomass burning aerosol emissions are held constant while other forcings (e.g., greenhouse gas concentrations) vary throughout the 20th century. This allows us to isolate the influence of biomass burning aerosol on processes that contribute to decreasing precipitation, including cloud microphysics, the radiative effects of absorbing aerosol particles, and alterations in regional circulation. We also show that the 20th century reduction in precipitation identified in the CESM1-LENS historical and biomass burning experiments is consistent across Coupled Model Intercomparison Project Phase 5 models with interactive aerosol schemes and the CESM2 single-forcing experiment. Our results demonstrate that higher concentrations of biomass burning aerosol increases the quantity of cloud condensation nuclei and cloud droplets, limiting cloud droplet size and precipitation formation. Additionally, absorbing aerosols (e.g., black carbon) contribute to a warmer cloud layer, which promotes cloud evaporation, increases atmospheric stability, and alters regional circulation patterns. Corresponding convectively coupled circulation responses, particularly over the tropical Andes, contribute to further reducing the flow of moisture and moisture convergence over tropical land. These results elucidate the processes that affect the water cycle in regions prone to biomass burning and inform our understanding of how future changes in aerosol emissions may impact tropical precipitation over the 21st century.

Critical Role of Secondary Organic Aerosol in Urban Atmospheric Visibility Improvement Identified by Machine Learning

Understanding the relationship between atmospheric visibility and aerosol emission sources and identifying the key drivers of visibility have significant implications for the radiative forcing of aerosol. In this work, we combined the positive matrix factorization (PMF) model and machine learning (ML) models (the extreme gradient boosting model (XGBoost) and the Shapely additive explanations model (SHAP)) to identify the key drivers of visibility improvement based on long-term observations of visibility and PM2.5 composition in Shenzhen, China. From 2014 to 2021, the annual average levels of visibility increased from 17.2 to 27.0 km, which is tightly associated with the decreasing year by year PM2.5 concentrations. ML models, with distinct advantages in dealing with nonlinear relationships, revealed that secondary organic aerosol (SOA) is the major driver determining visibility, which is inconsistent with inorganic salts being the major driver identified by the widely used traditional linear method. Visibility improvement in Shenzhen was also found primarily driven by a decrease in SOA, highlighting that SOA in PM2.5 plays a critical role in radiative balance. This is the first study to investigate source impacts on atmospheric visibility using novel ML models, reflecting the great potential of ML methods in air pollution data analysis.

Annual cycle of hygroscopic properties and mixing state of the suburban aerosol in Athens, Greece

Abstract. The hygroscopic properties of atmospheric aerosol were investigated at a suburban environment in Athens, Greece, from August 2016 to July 2017. The growth factor distribution probability density function (GF-PDF) and mixing state were determined with a hygroscopicity tandem differential mobility analyser (HTDMA). Four dry particle sizes (D0) were selected to be analysed in terms of their hygroscopic properties at 90 % relative humidity. The annual mean GFs for D0 = 30, 50, 80 and 250 nm were found to be equal to 1.28, 1.11, 1.13 and 1.22, respectively. The hygroscopic growth spectra were divided into two distinct hygroscopic ranges: a non- and/or slightly hygroscopic mode (GF < 1.12) and a moderately hygroscopic mode (GF > 1.12), which are representative of a suburban environment influenced by local/urban emissions and background aerosol. The standard deviation σ of the GF-PDF was employed as a measure of the mixing state of ambient aerosol. The 30 nm particles were mostly internally mixed, whereas larger particles were found to be externally mixed, either with a distinct bimodal structure or with partly overlapping modes. Cluster analysis on the hourly dry number size distributions was performed to identify the link between aerosol hygroscopicity and aerosol emission sources and formation processes. The size distributions were classified into five groups, with the “mixed urban and regional background” aerosol (67 %) and the “fresh traffic-related particles” from the neighbourhood urban area (15 %) accounting for more than 80 % of the results. The hygroscopic properties for 50 and 80 nm were found to be similar in all cases, indicating particles of similar nature and origin across these sizes. This was also confirmed through the modal analysis of the average number size distributions for each cluster; the 50 and 80 nm particles were found to belong to the same Aitken mode in most cases. The 250 nm particles (i.e. accumulation mode) were generally more hygroscopic than Aitken particles but less hygroscopic than the 30 nm particles (nuclei mode).

Prevention of the Combined Cytotoxic Effect of Selenium and Copper Oxide Nanoparticles in the Animal Experiment

Background: Copper ore processing plants are the emission sources of aerosols having a complex chemical composition. The aerosol components polluting both the workplace air and the ambient air of the adjacent populated areas include selenium, copper, and nanoparticles of these metal oxides. Objective: To evaluate the combined cytotoxic effect of selenium and copper oxide nanoparticles following the administration of a bioprophylactic complex. Materials and methods: The exposure to cytotoxic chemicals was modeled on outbred female rats by a single intratracheal injection of a suspension of selenium and copper oxide nanoparticles at a concentration of 0.25 g/L, obtained by laser ablation. Cytological and biochemical parameters of the bronchoalveolar lavage fluid (BALF) were measured 24 hours after the exposure. A specially developed bioprophylactic complex was administered to a part of the experimental animals with feed and drink during a month prior to the injection. Results: A single intratracheal instillation of the suspension of SeO and CuO nanoparticles altered BALF cytological and biochemical parameters, thus indicating their pronounced cytotoxic effect. In the group of the exposed rats administered a preliminary course of biological prophylaxis, we observed a decrease in the absolute number of neutrophils and the neutrophil to alveolar macrophage ratio, which is an indirect indicator of the cytotoxic effect, and the activity of aspartate aminotransferase in the bronchoalveolar lavage fluid. Conclusion: The science-based and experimentally tested complex of bioprotectors can attenuate a combined cytotoxic health effect of the exposure to selenium and copper oxide nanoparticles.

The Impact of COVID-19 Lockdowns on Satellite-Observed Aerosol Optical Thickness over the Surrounding Coastal Oceanic Areas of Megacities in the Coastal Zone

Nearly 40 years of aerosol optical thickness (AOT) climate data record (CDR) derived from NOAA operational satellite Advanced Very High Resolution Radiometer (AVHRR) observation over the global oceans is used to study the AOT changes due to the COVID-19 lockdown over the surrounding coastal oceanic areas of 18 megacities in the coast zone (MCCZ). The AOT difference between the annual mean AOT values of 2020 with COVID-19 lockdown and 2019 without the lockdown along with the 2020 AOT annual anomaly are used to effectively identify the AOT changes that are a result of the lockdown. We found that for most of the 18 MCCZ, the COVID-19 lockdowns implemented to contain the spread of the coronavirus resulted in a decrease between 1% and 30% in AOT due to reduced anthropogenic emissions associated with the lockdowns. However, the AOT long-term trend and other aerosol interannual variations due to favorable or unfavorable meteorological conditions may mask AOT changes due to the lockdown effect in some MCCZ. Different seasonal variations of aerosol amount in 2020 relative to 2019 due to other natural aerosol emission sources not influenced by the lockdown, such as dust storms and natural biomass burning and smoke, may also conceal a limited reduction in the annual mean AOT due to the lockdown in MCCZ with relatively loose lockdown. This study indicates that the use of long-term satellite observation is helpful for studying and monitoring the aerosol changes due to the emission reduction associated with the COVID-19 lockdown in the surrounding coastal oceanic areas of MCCZ, which will benefit the future development of the mitigation strategy for air pollution and emissions in megacities.

Abundance and fractional solubility of phosphorus and trace metals in combustion ash and desert dust: Implications for bioavailability and reactivity

Aerosol phosphorus (P) and trace metals derived from natural processes and anthropogenic emissions have considerable impacts on ocean ecosystems, human health, and atmospheric processes. However, the abundance and fractional solubility of P and trace metals in combustion ash and desert dust, which are two of the largest emission sources of aerosols, are still not well understood. In this study, the abundance and fractional solubility of P and trace metals in seven coal fly ash samples, two municipal waste fly ash samples, and three desert dust samples were experimentally examined. It was found that the abundance of aluminum (Al) in combustion ash was comparable or even higher than that in desert dust, and, therefore, care should be taken when using Al as a tracer of desert dust. The abundance and fractional solubility of P were higher in combustion ash, with a soluble P content ~4–6 times higher than that of the desert dust, indicating that combustion ash could be an important source of bioavailable P in the atmosphere. Except for Mn, the abundance and fractional solubility of other heavy metals were higher in the combustion ash compared to the desert dust, indicating the potential importance of combustion ash in ocean ecosystems, human health, and atmospheric processes. In contrast, both the abundance and solubility of Mn were highest in the desert dust, indicating a potentially important source of soluble Mn in the atmosphere. The fractional solubilities of P and trace metals are significantly affected by acidity and ions in the extraction solutions, and it is suggested that a buffer solution can better represent the acidity of the aqueous system in the true atmospheric environment. The results of this study improve our understanding of the sources of bioavailable and reactive P and trace metals in ambient aerosols.

Comparison of the impacts due to biomass burning, anthropogenic, and biogenic aerosol emissions on the mature phase of an urban heavy precipitation event over the Pearl River Delta

The study is aimed to discuss the differences in the aerosol impacts on the precipitation in mature phase due to three different aerosol emission sources, the biomass burning emission (BB), the anthropogenic emission (AE), and the biogenic emission (BE). Four simulations were conducted using WRF-Chem version 4.1.2 on the heavy urban precipitation event over the Pearl River Delta (PRD) region, which occurred on 21 February 2019, with 0800–0900 UTC 21 February as the mature phase. The inclusion of aerosol emissions improved the simulation performance on the temporal variations of the precipitation event and the peak precipitation. BB, AE, and BE contributed to the aerosol loading by around 6.8%, 88.1%, and 5.1%, respectively; and weakened the precipitation 28.0%, 31.0%, and 14.1%, respectively. The BE impact occurred the latest during the developing phase. The weakening effect was mainly over the convective precipitation. The aerosol indirect effect of BE strengthened the stratiform precipitation. The weakened convective precipitation was contributed by the weakened cloud microphysical processes above the zero-isotherm line. The BB impact induced the smallest change in cloud microphysical latent heating and weakened the precipitation more likely via its aerosol direct effect. The AE impact was the largest in precipitation, convection, and the cloud microphysical latent heating.

Volcanic Aerosol Impacts on Hawai‘i Island Rainfall

AbstractIn recent decades, a significant rainfall decline over the island of Hawai‘i has been noted, with many hypothesizing that the drying is associated with the volcanic aerosols emitted from the Kīlauea volcano. While it is clear that volcanic emissions can create hazardous air quality for Hawaiian communities, the impacts on rainfall are less clear. Here we investigate the impact of volcanic aerosol emissions on Hawai‘i Island rainfall. Based on observed daily rainfall and SO2 emissions, it is found that days with high SO2 emissions have on average 8 mm day−1 less rainfall downstream of the Kīlauea volcano. Sensitivity studies with varying volcanic aerosol emission sources from the Kīlauea vent locations have also been conducted by the Weather Research and Forecasting (WRF) Model in order to examine the detailed physical processes. Consistent with SO2 air quality observations, it is found that the diurnal change in aerosol number concentration is strongly dependent on the diurnal variation of local circulations. The added aerosols are lofted into the orographic convection where they modify the microphysical properties of the warm clouds by increasing the cloud droplet number concentration, decreasing the cloud droplet size, increasing cloud water content, and enhancing cloud evaporation. The volcanic aerosols also delay precipitation production and modify the spatial distribution of rainfall on the downstream mountainside. The modification of precipitation on an island has far-reaching consequences. For this reason, we work to quantify the sensitivity of the orographic precipitation to volcanic aerosols and move beyond hypothesized relationships to work toward understanding the underlying problem.

High resolution aerosol optical depth retrieval over urban areas from Landsat-8 OLI images

The satellite-retrieved aerosol optical depth (AOD) provides unique estimation of aerosol loading across a continuous space. However, current AOD products with a relatively coarse resolution (≥1 km) can hardly capture the details in urban areas with large spatial AOD gradients. To address this issue, here we developed a novel retrieval algorithm for retrieving AOD with extra fine spatial resolution (30 m) from Landsat-8 satellite OLI images. In the algorithm, the three land surface reflectance (LSR) estimation schemes and four aerosol types are adopted to improve the retrieval accuracy. The algorithm is applied on Beijing and Wuhan city in China during 2014–2019. Results suggest that the retrieved AOD with the new algorithm exhibits good agreement with the ground-based measured AOD (R2 = 0.920), and 81.63% of the AODs fall within the expected error line with a root-mean-square error of 0.112. Moreover, the high-resolution AOD products also successfully identified polluted sources and discrepancy of aerosol loading over different land cover types in two megacities in China, implying its great potential on detecting fine aerosol emission sources over the complex urban area. Such improvement of the new algorithm for retrieving 30 m AOD developed in this study demonstrates its substantial potentials in supporting further studies of air pollution management and human exposure at extra-fine spatial scale.

Ice Nucleation Activity of Alpine Bioaerosol Emitted in Vicinity of a Birch Forest

In alpine environments, many plants, bacteria, and fungi contain ice nuclei (IN) that control freezing events, providing survival benefits. Once airborne, IN could trigger ice nucleation in cloud droplets, influencing the radiation budget and the hydrological cycle. To estimate the atmospheric relevance of alpine IN, investigations near emission sources are inevitable. In this study, we collected 14 aerosol samples over three days in August 2019 at a single site in the Austrian Alps, close to a forest of silver birches, which are known to release IN from their surface. Samples were taken during and after rainfall, as possible trigger of aerosol emission by an impactor and impinger at the ground level. In addition, we collected aerosol samples above the canopy using a rotary wing drone. Samples were analyzed for ice nucleation activity, and bioaerosols were characterized based on morphology and auto-fluorescence using microscopic techniques. We found high concentrations of IN below the canopy, with a freezing behavior similar to birch extracts. Sampled particles showed auto-fluorescent characteristics and the morphology strongly suggested the presence of cellular material. Moreover, some particles appeared to be coated with an organic film. To our knowledge, this is the first investigation of aerosol emission sources in alpine vegetation with a focus on birches.

Seasonal heterogeneity in aerosol optical properties over the subtropical humid region of northern India

First-ever measurements and study of aerosol optical properties from a subtropical humid region of the eastern part of the central Indo-Gangetic Plain (IGP), Gorakhpur (26.75°N, 83.38°E, 85 m amsl) is presented. Four years, March 2014–February 2018, of columnar aerosol optical measurements, using a Multi-wavelength solar radiometer (MWR), are analyzed to examine temporal and seasonal heterogeneity in aerosol optical properties, and to ascertain aerosol types over the study region along with their seasonal contribution. Average columnar aerosol optical depth at 500 nm (AOD500) is 0.65 ± 0.27, with highest seasonal mean (0.73 ± 0.30) during pre-monsoon (PM) and lowest seasonal mean (0.59 ± 0.25) during monsoon (M) season. During PM season, more than 50% of AOD500 values are greater than 0.7 indicating high aerosol loading over the study region. Large variability in Ångström exponent (α) and atmospheric turbidity (β) from 0.12 to 2.26 and 0.05 to 1.34, with mean value of 0.92 ± 0.27 and 0.37 ± 0.14, respectively, indicates heterogeneous aerosol emission sources and turbid atmosphere over the study region. Higher α (>1) during post-monsoon (PoM) and winter (W) seasons indicate predominance of fine mode aerosols whereas lower α (<0.7) during PM season indicate prevalence of coarser mode aerosols over the study region. Aerosols of urban/industrial and biomass burning origins (UB) have maximum contribution during PoM (71.4%) and W (56.2%) seasons, while more than 25% of mixed type (MT) aerosols are observed throughout the study period with maximum contribution observed during M (63%) season. AOD retrieved from MWR and that from MODerate-resolution Imaging Spectroradiometer (MODIS) compare reasonably well with a correlation coefficient of 0.66.

Light Absorption by Organic Aerosol Emissions Rivals That of Black Carbon from Residential Biomass Fuels in South Asia

Solid-biomass-fuel residential cookstoves are the largest source of aerosol emissions in the Indian subcontinent. For assessing radiative forcing due to this pollutant source, laboratory-generated ...

Biomass burning and urban emission impacts in the Andes Cordillera region based on in situ measurements from the Chacaltaya observatory, Bolivia (5240 m a.s.l.)

Abstract. This study documents and analyses a 4-year continuous record of aerosol optical properties measured at the Global Atmosphere Watch (GAW) station of Chacaltaya (CHC; 5240 m a.s.l.), in Bolivia. Records of particle light scattering and particle light absorption coefficients are used to investigate how the high Andean Cordillera is affected by both long-range transport and by the fast-growing agglomeration of La Paz–El Alto, located approximately 20 km away and 1.5 km below the sampling site. The extended multi-year record allows us to study the properties of aerosol particles for different air mass types, during wet and dry seasons, also covering periods when the site was affected by biomass burning in the Bolivian lowlands and the Amazon Basin. The absorption, scattering, and extinction coefficients (median annual values of 0.74, 12.14, and 12.96 Mm−1 respectively) show a clear seasonal variation with low values during the wet season (0.57, 7.94, and 8.68 Mm−1 respectively) and higher values during the dry season (0.80, 11.23, and 14.51 Mm−1 respectively). The record is driven by variability at both seasonal and diurnal scales. At a diurnal scale, all records of intensive and extensive aerosol properties show a pronounced variation (daytime maximum, night-time minimum), as a result of the dynamic and convective effects. The particle light absorption, scattering, and extinction coefficients are on average 1.94, 1.49, and 1.55 times higher respectively in the turbulent thermally driven conditions than the more stable conditions, due to more efficient transport from the boundary layer. Retrieved intensive optical properties are significantly different from one season to the other, reflecting the changing aerosol emission sources of aerosol at a larger scale. Using the wavelength dependence of aerosol particle optical properties, we discriminated between contributions from natural (mainly mineral dust) and anthropogenic (mainly biomass burning and urban transport or industries) emissions according to seasons and local circulation. The main sources influencing measurements at CHC are from the urban area of La Paz–El Alto in the Altiplano and from regional biomass burning in the Amazon Basin. Results show a 28 % to 80 % increase in the extinction coefficients during the biomass burning season with respect to the dry season, which is observed in both tropospheric dynamic conditions. From this analysis, long-term observations at CHC provide the first direct evidence of the impact of biomass burning emissions of the Amazon Basin and urban emissions from the La Paz area on atmospheric optical properties at a remote site all the way to the free troposphere.

Year-round records of bulk aerosol composition over the Zhongshan Station, Coastal East Antarctica

To characterize ionic composition and trace elements in the coastal Antarctic, more than 100 bulk aerosol samples were collected at the Chinese Zhongshan Station from February 2005 to November 2008. Major water-soluble species, including Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3−, SO42−, and methane sulfonic acid (MSA), were analyzed by ion chromatography (IC). Trace metals, including Al, V, Cr, Fe, Cu, Zn, and Pb, were measured by inductively coupled plasma mass spectrometry (ICP-MS). Results showed that sea salt was the major component in aerosols at the Zhongshan Station in coastal East Antarctica. Sea salt ions Na+, Mg2+, Ca2+, and Cl− exhibited the maximum concentration in March, and the highest average concentration in September. NH4+, NO3−, SO42−, and MSA exhibited obvious seasonal variations, with higher concentrations in austral summer than in austral winter. During the 4-year observations, the highest aerosol composition loading was showed in 2008, and the high variation and average concentrations of trace metals appeared in January. Based on high NH4+/(Cl− + NO3− + 2 × SO42−) molar ratios, atmospheric aerosol was not that acidic in the austral summer. Sulfate depletion was found by the low SO42−/Na+ ratio in samples collected in the austral winter, especially from May to October. Enrichment factor (EF) and multivariate statistical analysis were utilized to explore potential emission sources of aerosols over the Zhongshan station. Na+, Cl−, K+, Mg2+, and Ca2+ were mainly from sea salt sources, and Al, Fe, Cu, Cr, Pb, and V were mainly from crustal and anthropogenic pollution sources, while S-cycle compounds non-sea-salt sulfate (nss-SO42−) and MSA originated from marine biogenic emissions.

Monitoring the industrial sources of aerosol in Cubatao, Brazil, using a scanning elastic lidar and a lidar doppler

Field campaigns with a scanning multiwavelength elastic lidar coupled with a Doppler system to monitor industrial atmospheric aerosol emissions were carried out, with the objective of monitoring aerosol emission sources and plume dispersion. Since the technique provides information on the spatial and temporal distribution of aerosol concentration, the implementation of a systematic monitoring procedure is proposed as a valuable tool in air quality monitoring applied to regions of interest.

An uncertainty quantification of PM2.5 emissions from residential wood combustion in Italy

Residential wood combustion from fireplaces and wood stoves represents a major source of aerosol emissions which can cause severe air quality deterioration, pose a serious threat to human health and climate change. Moreover, the emission estimates from this source have a high degree of uncertainty that in many emission inventories has not yet been assessed. This paper represents a first attempt to quantify the PM2.5 emission uncertainty from residential wood combustion in Italy. A bootstrap simulation analysis has been performed considering the data from the two most updated national surveys on wood consumption. The bootstrap simulations have been carried out both on a national and on a regional level varying wood consumption and emission factors of the different appliance type considered, but keeping constant their distribution in the whole national territory. The influence of the two resulting emission datasets on PM2.5 concentrations in Italy has been investigated with the MINNI model. The results show that the mean of PM2.5 total emissions for Italy is circa 120 kt, from a minimum of 97 kt to a maximum of 146 kt (−18.9%, +21.5% on the mean value). Moreover, a significant variation of annual average PM2.5 concentrations, with values higher than 10 μg/m3 in the most polluted areas, is shown by model results. The distribution influence of the different appliance types has been explored with a sensitivity test in the Veneto Region. This test reveals the importance of emission factors and technology share as the most important parameters influencing the uncertainty analysis.

Aerosol climate change effects on land ecosystem services.

A coupled global aerosol-carbon-climate model is applied to assess the impacts of aerosol physical climate change on the land ecosystem services gross primary productivity (GPP) and net primary productivity (NPP) in the 1996-2005 period. Aerosol impacts are quantified on an annual mean basis relative to the hypothetical aerosol-free world in 1996-2005, the global climate state in the absence of the historical rise in aerosol pollution. We examine the separate and combined roles of fast feedbacks associated with the land and slow feedbacks associated with the ocean. We consider all fossil fuel, biofuel and biomass burning aerosol emission sources as anthropogenic. The effective radiative forcing for aerosol-radiation interactions is -0.44 W m-2 and aerosol-cloud interactions is -1.64 W m-2. Aerosols cool and dry the global climate system by -0.8 °C and -0.08 mm per day relative to the aerosol-free world. Without aerosol pollution, human-induced global warming since the preindustrial would have already exceeded the 1.5 °C aspirational limit set in the Paris Agreement by the 1996-2005 decade. Aerosol climate impacts on the global average land ecosystem services are small due to large opposite sign effects in the tropical and boreal biomes. Aerosol slow feedbacks associated with the ocean strongly dominate impacts in the Amazon and North American Boreal. Aerosol cooling of the Amazon by -1.2 °C drives NPP increases of 8% or +0.76 ± 0.61 PgC per year, a 5-10 times larger impact than estimates of diffuse radiation fertilization by biomass burning aerosol in this region. The North American Boreal suffers GPP and NPP decreases of 35% due to aerosol-induced cooling and drying (-1.6 °C, -0.14 mm per day). Aerosol-land feedbacks play a larger role in the eastern US and Central Africa. Our study identifies an eco-climate teleconnection in the polluted earth system: the rise of the northern hemisphere mid-latitude reflective aerosol pollution layer causes long range cooling that protects Amazon NPP by 8% and suppresses boreal NPP by 35%.

Characterization and Cytotoxicity of PM

Background: The potential impact of municipal solid waste incineration (MSWI), which is an anthropogenic source of aerosol emissions, is of great public health concern. This study investigated the characterization and cytotoxic effects of ambient ultrafine particles (PM<0.2), fine particles (PM0.2–2.5) and coarse particles (PM2.5–10) collected around a municipal solid waste incineration (MSWI) plant in the Pudong district of Shanghai. Methods: Mass concentrations of trace elements in particulate matter (PM) samples were determined using ICP-MS (Inductively Coupled Plasma Mass Spectrometry). The cytotoxicity of sampled atmospheric PM was evaluated by cell viability and reactive oxygen species (ROS) levels in A549 cells. Result: The mass percentage of PM0.2–2.5 accounted for 72.91% of the total mass of PM. Crustal metals (Mg, Al, and Ti) were abundant in the coarse particles, while the anthropogenic elements (V, Ni, Cu, Zn, Cd, and Pb) were dominant in the fine particles. The enrichment factors of Zn, Cd and Pb in the fine and ultrafine particles were extremely high (>100). The cytotoxicity of the size-resolved particles was in the order of coarse particles < fine particles < ultrafine particles. Conclusions: Fine particles dominated the MSWI ambient particles. Emissions from the MSWI could bring contamination of anthropogenic elements (Zn, Cd and Pb) into ambient environment. The PM around the MSWI plant displayed an additive toxic effect, and the ultrafine and fine particles possessed higher biological toxicity than the coarse particles.