High secondary aerosol contribution to particulate pollution during haze events in China

Toxicity of aged gasoline exhaust particles to normal and diseased airway epithelia

Particulate matter (PM) pollution is a leading cause of premature death, particularly in those with pre-existing lung disease. A causative link between particle properties and adverse health effects remains unestablished mainly due to complex and variable physico-chemical PM parameters. Controlled laboratory experiments are required. Generating atmospherically realistic aerosols and performing cell-exposure studies at relevant particle-doses are challenging. Here we examine gasoline-exhaust particle toxicity from a Euro-5 passenger car in a uniquely realistic exposure scenario, combining a smog chamber simulating atmospheric ageing, an aerosol enrichment system varying particle number concentration independent of particle chemistry, and an aerosol deposition chamber physiologically delivering particles on air-liquid interface (ALI) cultures reproducing normal and susceptible health status. Gasoline-exhaust is an important PM source with largely unknown health effects. We investigated acute responses of fully-differentiated normal, distressed (antibiotics-treated) normal, and cystic fibrosis human bronchial epithelia (HBE), and a proliferating, single-cell type bronchial epithelial cell-line (BEAS-2B). We show that a single, short-term exposure to realistic doses of atmospherically-aged gasoline-exhaust particles impairs epithelial key-defence mechanisms, rendering it more vulnerable to subsequent hazards. We establish dose-response curves at realistic particle-concentration levels. Significant differences between cell models suggest the use of fully-differentiated HBE is most appropriate in future toxicity studies.

Integrated reactive nitrogen budgets and future trends in China

Reactive nitrogen (Nr) plays a central role in food production, and at the same time it can be an important pollutant with substantial effects on air and water quality, biological diversity, and human health. China now creates far more Nr than any other country. We developed a budget for Nr in China in 1980 and 2010, in which we evaluated the natural and anthropogenic creation of Nr, losses of Nr, and transfers among 14 subsystems within China. Our analyses demonstrated that a tripling of anthropogenic Nr creation was associated with an even more rapid increase in Nr fluxes to the atmosphere and hydrosphere, contributing to intense and increasing threats to human health, the sustainability of croplands, and the environment of China and its environs. Under a business as usual scenario, anthropogenic Nr creation in 2050 would more than double compared with 2010 levels, whereas a scenario that combined reasonable changes in diet, N use efficiency, and N recycling could reduce N losses and anthropogenic Nr creation in 2050 to 52% and 64% of 2010 levels, respectively. Achieving reductions in Nr creation (while simultaneously increasing food production and offsetting imports of animal feed) will require much more in addition to good science, but it is useful to know that there are pathways by which both food security and health/environmental protection could be enhanced simultaneously.

Radiocarbon-based impact assessment of open biomass burning on regional carbonaceous aerosols in North China

Samples of total suspended particulates (TSPs) and fine particulate matter (PM2.5) were collected from 29th May to 1st July, 2013 at a regional background site in Bohai Rim, North China. Mass concentrations of particulate matter and carbonaceous species showed a total of 50% and 97% of the measured TSP and PM2.5 levels exceeded the first grade national standard of China, respectively. Daily concentrations of organic carbon (OC) and elemental carbon (EC) were detected 7.3 and 2.5 μg m(-3) in TSP and 5.2 and 2.0 μg m(-3) in PM2.5, which accounted 5.8% and 2.0% of TSP while 5.6% and 2.2% for PM2.5, respectively. The concentrations of OC, EC, TSP and PM2.5 were observed higher in the day time than those in the night time. The observations were associated with the emission variations from anthropogenic activities. Two merged samples representing from south and north source areas were selected for radiocarbon analysis. The radiocarbon measurements showed 74% of water-insoluble OC (WINSOC) and 59% of EC in PM2.5 derived from biomass burning and biogenic sources when the air masses were from south region, and 63% and 48% for the air masses from north, respectively. Combined with backward trajectories and daily burned area, open burning of agricultural wastes was found to be predominating, which was confirmed by the potential source contribution function (PSCF).

Regenerable fluorescent nanosensors for monitoring and recovering metal ions based on photoactivatable monolayer self-assembly and host-guest interactions

Efficient detection, removal, and recovery of heavy metal ions from aqueous environments represents a technologically challenging and ecologically urgent question in the face of increasing metal-related pollution and poisoning across the globe. Although small-molecule and entrapment-based nanoparticle sensors have been extensively explored for metal detection, neither of these extant strategies satisfies the critical needs for high-performance sensors that are inexpensive, efficient, and recyclable. Here we first report the development of a regenerable fluorescent nanosensor system for the selective and sensitive detection of multiple heavy metal ions, based on light-switchable monolayer self-assembly and host-guest interactions. The system exploits photocontrolled inclusion and exclusion responses of an α-cyclodextrin (CD)-containing surface conjugated with photoisomerizable azobenzene as a supramolecular system that undergoes reversible assembly and disassembly. The metal nanosensors can be facilely fabricated and photochemically switched between three chemically distinct entities, each having an excellent capacity for selective detecting specific metal ions (namely, Cu(2+), Fe(3+), Hg(2+)) in a chemical system and in assays on actual water samples with interfering contaminants.

Characterization of fine particulate matter in ambient air by combining TEM and multiple spectroscopic techniques--NMR, FTIR and Raman spectroscopy

This paper reports a systematic study of the microstructures and spectroscopic characteristics of PM2.5 and its potential sources in Beijing by combining transmission electron microscopy and multiple spectroscopic techniques: nuclear magnetic resonance, Fourier transform infrared and Raman spectroscopy. TEM images showed that dominant components of PM2.5 are airborne organic substances with many trace metal elements which are associated with combustion sources. NMR spectra precisely determined the percentage of carbonaceous speciation in both PM2.5 (with spatial and temporal distribution) and its potential sources, and distinguished the similarities and differences among them. In FTIR spectra, a remarkable peak at 1390 cm(-1) that appeared only in PM2.5 samples was attributed to NH4NO3, representing the occurrence of secondary processes. Raman spectra revealed certain inorganic compounds including sulfate and nitrate ions. Based on the analysis of the decomposition of Raman spectra, spectral parameters provided structural information and helped to find potential sources of PM2.5. In the space of carbon aromaticity index and ID1/IG, PM2.5 points followed a linear distribution which may also be useful in source tracing. The result shows that the combined non-destructive methods are efficient to trace the sources of PM2.5.

Regionally-varying combustion sources of the January 2013 severe haze events over eastern China

Thick haze plagued northeastern China in January 2013, strongly affecting both regional climate and human respiratory health. Here, we present dual carbon isotope constrained (Δ(14)C and δ(13)C) source apportionment for combustion-derived black carbon aerosol (BC) for three key hotspot regions (megacities): North China Plain (NCP, Beijing), the Yangtze River Delta (YRD, Shanghai), and the Pearl River Delta (PRD, Guangzhou) for January 2013. BC, here quantified as elemental carbon (EC), is one of the most health-detrimental components of PM2.5 and a strong climate warming agent. The results show that these severe haze events were equally affected (∼ 30%) by biomass combustion in all three regions, whereas the sources of the dominant fossil fuel component was dramatically different between north and south. In the NCP region, coal combustion accounted for 66% (46-74%, 95% C.I.) of the EC, whereas, in the YRD and PRD regions, liquid fossil fuel combustion (e.g., traffic) stood for 46% (18-66%) and 58% (38-68%), respectively. Taken together, these findings suggest the need for a regionally-specific description of BC sources in climate models and regionally-tailored mitigation to combat severe air pollution events in East Asia.

A multiyear assessment of air quality benefits from China's emerging shale gas revolution: Urumqi as a case study

China is seeking to unlock its shale gas in order to curb its notorious urban air pollution, but robust assessment of the impact on PM2.5 pollution of replacing coal with natural gas for winter heating is lacking. Here, using a whole-city heating energy shift opportunity offered by substantial reductions in coal combustion during the heating periods in Urumqi, northwest China, we conducted a four-year study to reveal the impact of replacing coal with natural gas on the mass concentrations and chemical components of PM2.5. We found a significant decline in PM2.5, major soluble ions and metal elements in PM2.5 in January of 2013 and 2014 compared with the same periods in 2012 and 2011, reflecting the positive effects on air quality of using natural gas as a heating fuel throughout the city. This occurred following complete replacement with natural gas for heating energy in October 2012. The weather conditions during winter did not show any significant variation over the four years of the study. Our results indicate that China and other developing nations will benefit greatly from a change in energy source, that is, increasing the contribution of either natural gas or shale gas to total energy consumption with a concomitant reduction in coal consumption.

Occurrence, gas/particle partitioning and carcinogenic risk of polycyclic aromatic hydrocarbons and their oxygen and nitrogen containing derivatives in Xi'an, central China

29 parent- and alkyl-polycyclic aromatic hydrocarbons (PAHs), 15 oxygenated-PAHs (OPAHs), 11 nitrated-PAHs (NPAHs) and 4 azaarenes (AZAs) in both the gaseous and particulate phases, as well as the particulate-bound carbon fractions (organic carbon, elemental carbon, char, and soot) in ambient air sampled in March and September 2012 from an urban site in Xi'an, central China were extracted and analyzed. The average concentrations (gaseous+particulate) of ∑29PAHs, ∑15OPAHs, ∑11NPAHs and ∑4AZAs were 1267.0 ± 307.5, 113.8 ± 46.1, 11.8 ± 4.8 and 26.5 ± 11.8 ng m(-3) in March and 784.7 ± 165.1, 67.2 ± 9.8, 9.0 ± 1.5 and 21.6 ± 5.1 ng m(-3) in September, respectively. Concentrations of ∑29PAHs, ∑15OPAHs and ∑11NPAHs in particulates were significantly correlated with those of the carbon fractions (OC, EC, char and soot). Both absorption into organic matter in particles and adsorption onto the surface of particles were important for PAHs and OPAHs in both sampling periods, with more absorption occurring in September, while absorption was always the most important process for NPAHs. The total carcinogenic risk of PAHs plus the NPAHs was higher in March. Gaseous compounds, which were not considered in most previous studies, contributed 29 to 44% of the total health risk in March and September, respectively.

The promotion effect of isolated potassium atoms with hybridized orbitals in catalytic oxidation

The promotion effect of isolated potassium atoms in catalytic oxidation was investigated by studying their geometric and electronic structures.

Cerium promotion on the hydrocarbon resistance of a Cu-SAPO-34 NH3-SCR monolith catalyst

Ce was introduced to promote the HC resistance of Cu-SAPO-34, and a series of CuCe-xcatalysts with various content of Ce were prepared by a wet co-impregnation method.

Low temperature catalytic oxidation of volatile organic compounds: a review

Volatile organic compounds (VOCs) are toxic and recognized as one of the major contributors to air pollution.

Evidence of aerosols as a media for rapid daytime HONO production over China

Current knowledge of daytime HONO sources remains incomplete. A large missing daytime HONO source has been found in many places around the world, including polluted regions in China. Conventional understanding and recent studies attributed this missing source mainly to ground surface processes or gas-phase chemistry, while assuming aerosols to be an insignificant media for HONO production. We analyze in situ observations of HONO and its precursors at an urban site in Beijing, China, and report an apparent dependence of the missing HONO source strength on aerosol surface area and solar ultraviolet radiation. Based on extensive correlation analysis and process-modeling, we propose that the rapid daytime HONO production in Beijing can be explained by enhanced hydrolytic disproportionation of NO2 on aqueous aerosol surfaces due to catalysis by dicarboxylic acid anions. The combination of high abundance of NO2, aromatic hydrocarbons, and aerosols over broad regions in China likely leads to elevated HONO levels, rapid OH production, and enhanced oxidizing capacity on a regional basis. Our findings call for attention to aerosols as a media for daytime heterogeneous HONO production in polluted regions like Beijing. This study also highlights the complex and uncertain heterogeneous chemistry in China, which merits future efforts of reconciling regional modeling and laboratory experiments, in order to understand and mitigate the regional particulate and O3 pollutions over China.