Organic tracers are useful for investigating the sources of carbonaceous aerosols but there are still no adequate studies in China. To obtain insights into the diurnal variations, properties, and the influence of regional emission controls on carbonaceous aerosols in Beijing, day-/nighttime PM₂.₅ samples were collected before (Oct. 15th – Nov. 2nd) and during (Nov. 3rd – Nov. 12th) the 2014 Asia-Pacific Economic Cooperation (APEC) summit. Eleven organic compound classes were analysed using gas chromatography/mass spectrometry (GC/MS). In addition, the stable carbon isotope ratios (δ¹³CTC) of total carbon (TC) were detected using an elemental analyser/isotope ratio mass spectrometry (EA/irMS). Most of the organic compounds were more abundant during the night than in the daytime, and their concentrations generally decreased during the APEC. These features were associated with the strict regional emission controls and meteorological conditions. The day/night variations of δ¹³CTC were smaller during the APEC than those before the APEC the summit, suggesting that regionally transported aerosols are potentially played an important role in the loading of organic aerosols in Beijing before the APEC summit. The source apportionment based on the organic tracers suggested that biomass burning, plastic and microbial emissions, and fossil fuel combustion were important sources of organic aerosols in Beijing. Furthermore, a similar contribution of biomass burning to OC before and during the APEC suggests biomass burning was a persistent contributor to PM₂.₅ in Beijing and its surroundings.

Currently the land use and land use change (LULUC) emits 1.3 ± 0.5 Pg carbon (C) year⁻¹, equivalent to 8% of the global annual emissions. The objectives of this study were to quantify (1) the impact of LULUC on greenhouse gas (GHG) emissions in a subtropical region and (2) the role of conservation agriculture to mitigate GHG emissions promoting ecosystem services. We developed a detailed IPCC Tier 2 GHG inventory for the Campos Gerais region of southern Brazil that has large cropland area under long-term conservation agriculture with high crop yields. The inventory accounted for historical and current emissions from fossil fuel combustion, LULUC and other minor sources. We used Century model to simulate the adoption of conservation best management practices, to all croplands in the region from 2017 to 2117. Our results showed historical (1930–2017) GHG emissions of 412 Tg C, in which LULUC contributes 91% (376 ± 130 Tg C), the uncertainties ranged between 13 and 36%. Between 1930 and 1985 LULUC was a major source of GHG emission, however from 1985 to 2015 fossil fuel combustion became the primary source of GHG emission. Forestry sequestered 52 ± 24 Tg C in 0.6 Mha in a period of 47 years (1.8 Tg C Mha⁻¹ year⁻¹) and no-till sequestered 30.4 ± 24 Tg C in 2 Mha in a period of 32 years (0.5 Tg C Mha⁻¹ year⁻¹) being the principal GHG mitigating activities in the study area. The model predictions showed that best management practices have the potential to mitigate 13 years of regional emissions (330 Tg C in 100 years) or 105 years of agriculture, forestry and livestock emissions (40 Tg C in 100 years) making the agriculture sector a net carbon (C) sink and promoting ecosystem services.

Humic-like substances (HULIS) are a class of high molecular weight, light-absorbing compounds that are highly related to brown carbon (BrC). In this study, the sources and compositions of HULIS isolated from fine particles collected in Beijing, China during the 2014 Asia-Pacific Economic Cooperation (APEC) summit were characterized based on carbon isotope (¹³C and ¹⁴C) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses, respectively. HULIS were the main light-absorbing components of water-soluble organic carbon (WSOC), accounting for 80.2 ± 6.1% of the WSOC absorption capacity at 365 nm. The carbon isotope data showed that HULIS had a lower non-fossil contribution (53 ± 4%) and were less enriched with ¹³C (−24.2 ± 0.6‰) relative to non-HULIS (62 ± 8% and −20.8 ± 0.3‰, respectively). The higher relative intensity fraction of sulfur-containing compounds in HULIS before and after APEC was attributed to higher sulfur dioxide levels emitted from fossil fuel combustion, whereas the higher fraction of nitrogen-containing compounds during APEC may have been due to the relatively greater contribution of non-fossil compounds or the influence of nitrate radical chemistry. The results of investigating the relationships among the sources, elemental compositions, and optical properties of HULIS demonstrated that the light absorption of HULIS appeared to increase with increasing unsaturation degree, but decrease with increasing oxidation level. The unsaturation of HULIS was affected by both sources and aging level.

Due to its dependence on fossil fuel combustion, emissions from the marine transport sector can significantly contribute to air pollution. This work aims to evaluate the impact of maritime transport emissions on air quality in Portugal using a numerical air quality modelling approach, with high-resolution emission data. Emissions from the European TNO inventory were compiled and pre-processed at hourly and high spatial (∼3 × 3 km²) resolutions. Scenarios with and without these maritime emissions were then simulated with the WRF-CHIMERE modelling system, extensively tested and validated for Portugal domain, in order to evaluate their impact on air quality. A simulation was performed for one year (2016) and the resulting differences were analysed in terms of spatial distribution, time series and deltas. The main deltas for NO₂ and PM10 are located over international shipping routes and major ports, while O₃ concentrations are impacted in a larger area. The modelling results also indicate that shipping emissions are responsible for deltas in the concentration of NO₂ higher than 20% over specific urban areas located in the west coast of Portugal, and less than 5% for PM10. For O₃ the relative contribution is low (around 2%) but this contribution is also observed at locations more than 50 km from the coast.

The sources of aerosol ammonium (NH4+) are of interest because of the potential of NH4+ to impact the Earth's radiative balance, as well as human health and biological diversity. Isotopic source apportionment of aerosol NH4+ is challenging in the urban atmosphere, which has excess ammonia (NH3) and where nitrogen isotopic fractionation commonly occurs. Based on year-round isotopic measurements in urban Beijing, we show the source dependence of the isotopic abundance of aerosol NH4+, with isotopically light (−33.8‰) and heavy (0 to +12.0‰) NH4+ associated with strong northerly winds and sustained southerly winds, respectively. On an annual basis, 37–52% of the initial NH3 concentrations in urban Beijing arises from fossil fuel emissions, which are episodically enhanced by air mass stagnation preceding the passage of cold fronts. These results provide strong evidence for the contribution of non-agricultural sources to NH3 in urban regions and suggest that priority should be given to controlling these emissions for haze regulation. This study presents a carefully executed application of existing stable nitrogen isotope measurement and mass-balance techniques to a very important problem: understanding source contributions to atmospheric NH3 in Beijing. This question is crucial to informing environmental policy on reducing particulate matter concentrations, which are some of the highest in the world. However, the isotopic source attribution results presented here still involve a number of uncertain assumptions and they are limited by the incomplete set of chemical and isotopic measurements of gas NH3 and aerosol NH4+. Further field work and lab experiments are required to adequately characterize endmember isotopic signatures and the subsequent isotopic fractionation process under different air pollution and meteorological conditions.

Particulate matter with a diameter of 10 μm or less (PM10) using receptor modelling was determined at an urban (La Linea, LL) and an industrial area (Puente Mayorga, PMY) in Southern Spain with samples collected during 2005–2014. The concentrations of PM10 had been decreasing at both sites in three distinctive periods: 1) the initial PM10 levels approached or exceeded the Spain and EU PM10 annual guidelines of 40 μg/m3 during 2005–2007 at LL and 2005–2009 at PMY; 2) then PM10 dropped by 25%–∼30 μg/m3 during 2008–2011 at LL and during 2010–2011 at PMY; 3) since 2012, the PM10 concentrations gradually decreased to <30 μg/m3. Chemical compositions of PM10 revealed the important contributions of water soluble ions (sulfate, nitrate, ammonium, and chloride), carbonaceous aerosols, and other major elements. These PM components generally showed a decrease trend, in accord with the trend of PM10 reduction. A PMF model identified seven sources to PM10 contributions. Secondary sulfate, soil/urban/construction dust, and secondary nitrate showed significantly decreasing trends with reduction of 40–60% comparing to the initial levels. The road traffic contribution decreased by 14% from the first to third period. However, sea salt, oil combustion, and industrial metallurgical process had relative stable contributions. These source contribution changes are reasonably governed by the PM emission abatement actions implemented during the past decade, as well as the financial crisis, that accounted for a significant decrease of PM pollution in Southern Spain.We identified that the mitigation efforts on industry, fossil fuel combustion, and urban transportation during the past decade were successful for air quality improvement in a highly industrialized area in Southern Spain.

In 2015, a controversial bicycle lane was installed on Paulista Avenue –a thoroughfare in the heart of the megacity of São Paulo with a high rate of motorised vehicles. For the first time, on-bicycle air pollution concentrations were assessed along this lane using black carbon (BC) as an indicator of fossil fuel combustion. We measured BC concentrations with a hand-held microaethalometer at a high temporal resolution, enabling the capture of fine spatial gradients along the route. Although this new link expanded the city's cycling network, our pioneering study showed that BC concentrations were large (mean 8.5 μg m⁻³) with extreme values reaching 24.0 μg m⁻³, comparable to concentrations found in many megacities. In agreement with other studies, we observed that concentrations decreased about 1.6 times on a section of the bicycle lane running through a calmer neighbourhood, which could indicate the potential to safeguard the health of cyclists by installing lanes with greater separation from main roads, such as Paulista Avenue. This pilot work paves the way to more detailed studies aiming to map out the spatial distribution of other traffic-related pollutants across the city's 458-km long bicycle network.

The distribution, sources and potential ecological risk of priority polycyclic aromatic hydrocarbons (PAHs) in sediment from the Amazon River Estuary (Macapá and Santana, Amapá, Northern Brazil) were investigated. The total PAHs concentration (∑PAH) ranged from 22.2 to 158.9 ng g−1 dw (mean value 49.4 ng g−1 dw). PAHs levels in the study area were relatively low than those in nearby areas and other coastal zones worldwide, and could be considered as baseline for PAHs in Amazonic sediments. PAHs ratios and the statistical analysis showed that fossil fuel and biomass combustions, primarily from local sources, were the dominant PAHs origins. The potential ecological risk was assessed on the basis of the sediment quality guidelines, and it was found that PAHs in the sediments of the Amazon River Estuary do not cause adverse effects on living organisms; however, the abundance of naphthalene and the presence of dibenzo[a,h]anthracene and benzo[a]pyrene deserve more attention.

This study was conducted from October 2015 to March 2017, with the aim of providing the first data on the fluxes and sources of wet and dry deposition of trace elements (TEs) in Daya Bay, South China Sea. Wet deposition flux of TEs was always preponderant and orders of magnitude higher than that of dry deposition owing to the high rainfall frequency in Daya Bay. The total deposition fluxes of TEs in the target area were higher than in most places worldwide, but at a moderate level within China. Wet deposition was highest in summer and lowest in winter, whereas dry deposition showed an opposite seasonal trend. The main sources of TEs in wet deposition were seasalt/dust, fossil fuel combustion, and crustal sources, and in dry deposition, they were dust/metallurgic, fossil fuel, petrochemical industry and crustal sources.

The capacities of fatty esters and commercial biodiesel (i.e., mixture of fatty esters with fossil diesel) for solubilizing polycyclic aromatic hydrocarbons (PAHs) were investigated and were attributed to the property of fatty esters forming aggregates and internally accommodating such compounds. Different systems formed by solely fatty esters and commercial biodiesel were investigated to study the effect of the structure of fatty esters on the solubility of PAHs. In the presence of ethyl oleate, the solubility of naphthalene increased by 23 ± 1.3%, that of phenanthrene by 1.4 ± 0.7%, and those of anthracene and pyrene by 1.1 ± 0.6%. The maximum solubility values of PAHs indicated that fatty esters exerted a positive effect on solubility in the same way as a surfactant (ionic and neutral). In the presence of a mixture of fatty esters, the maximum concentration of naphthalene solubilized was 105.5 ± 2.5 mg/L, a 3.7-fold increase compared to its solubility in water. The same behavior was observed for other compounds like pyrene and phenanthrene. However, they were dissolved in different proportions due to the different physico-chemical properties and chemical structure of each compound. Considering the presence of PAHs in fossil diesel, the potential of fatty esters was assessed when mixed with fossil diesel, commercial available as biodiesel, which showed increase in the solubility of PAHs in the aqueous phase. In the absence of fatty esters, when only fossil diesel was present, the maximum concentrations of naphthalene and phenanthrene were 136.3 ± 3.9 and 1.28 ± 0.07 μg/L, respectively, while the maximum values in the presence of a blend of fossil diesel and biodiesel were 437.6 ± 16.7 and 26.8 ± 4.5 μg/L for naphthalene and phenanthrene, respectively. Therefore, it was reasonable to affirm that fatty esters interfered in the solubilities of PAHs, which might be associated with the formation of aggregates.