Interfaces
are ubiquitous in the environment and many atmospheric
key processes, such as gas deposition, aerosol, and cloud formation
are, at one stage or another, strongly impacted by physical and chemical
processes occurring at interfaces. Here, the photoinduced chemistry
of an air/water interface coated with nonanoic acid—a fatty
acid surfactant we use as a proxy for chemically complex natural aqueous
surface microlayers—was investigated as a source of volatile
and semivolatile reactive organic species. The carboxylic acid coating
significantly increased the propensity of photosensitizers, chosen
to mimic those observed in real environmental waters, to partition
to the interface and enhance reactivity there. Photochemical formation
of functionalized and unsaturated compounds was systematically observed
upon irradiation of these coated surfaces. The role of a coated interface
appears to be critical in providing a concentrated medium allowing
radical–radical reactions to occur in parallel with molecular
oxygen additions. Mechanistic insights are provided from extensive
analysis of products observed in both gas and aqueous phases by online
switchable reagent ion-time of flight-mass spectrometry and by off-line
ultraperformance liquid chromatography coupled to a Q Exactive high
resolution mass spectrometer through heated electrospray ionization,
respectively.
There is increasing evidence indicating the critical role of ammonia (NH) in the formation of secondary aerosols. Therefore, high quality NH emission inventory is important for modeling particulate matter in the atmosphere. Unfortunately, without directly measured emission factors (EFs) in developing countries, using data from developed countries could result in an underestimation of these emissions. A series of newly reported EFs for China provide an opportunity to update the NH emission inventory. In addition, a recently released fuel consumption data product has allowed for a multisource, high-resolution inventory to be assembled. In this study, an improved global NH emission inventory for combustion and industrial sources with high sectorial (70 sources), spatial (0.1° × 0.1°), and temporal (monthly) resolutions was compiled for the years 1960 to 2013. The estimated emissions from transportation (1.59 Tg) sectors in 2010 was 2.2 times higher than those of previous reports. The spatial variation of the emissions was associated with population, gross domestic production, and temperature. Unlike other major air pollutants, NH emissions continue to increase, even in developed countries, which is likely caused by an increased use of biomass fuel in the residential sector. The emissions density of NH in urban areas is an order of magnitude higher than in rural areas.
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Abstract. The Atmospheric Pollution and Human Health in a Chinese
Megacity (APHH-Beijing) programme is an international collaborative project
focusing on understanding the sources, processes and health effects of air
pollution in the Beijing megacity. APHH-Beijing brings together leading China
and UK research groups, state-of-the-art infrastructure and air quality
models to work on four research themes: (1) sources and emissions of air
pollutants; (2) atmospheric processes affecting urban air pollution; (3) air
pollution exposure and health impacts; and (4) interventions and solutions.
Themes 1 and 2 are closely integrated and support Theme 3, while Themes 1–3
provide scientific data for Theme 4 to develop cost-effective air pollution
mitigation solutions. This paper provides an introduction to (i) the
rationale of the APHH-Beijing programme and (ii) the measurement and
modelling activities performed as part of it. In addition, this paper
introduces the meteorology and air quality conditions during two joint
intensive field campaigns – a core integration activity in APHH-Beijing. The
coordinated campaigns provided observations of the atmospheric chemistry and
physics at two sites: (i) the Institute of Atmospheric Physics in central
Beijing and (ii) Pinggu in rural Beijing during 10 November–10 December 2016 (winter) and 21 May–22 June 2017 (summer). The campaigns were
complemented by numerical modelling and automatic air quality and low-cost
sensor observations in the Beijing megacity. In summary, the paper provides
background information on the APHH-Beijing programme and sets the scene for
more focused papers addressing specific aspects, processes and effects of
air pollution in Beijing.
The essential roles of microglia in maintaining homeostasis in the healthy brain and contributing to neuropathology are well documented. Emerging evidence suggests that epigenetic modulation regulates microglial behavior in both physiological and pathological conditions. MicroRNAs (miRNAs) are short, non-coding epigenetic regulators that repress target gene expression mostly
via
binding to 3′-untranslated region (3′-UTR) of mRNA in a Dicer-dependent manner. Dysregulation of certain miRNAs can contribute to microglial hyper-activation, persistent neuroinflammation, and abnormal macrophage polarization in the brain. These abnormal conditions can support the pathogenesis of neurological disorders such as glioma, Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), stroke, ischemia, and spinal cord injury (SCI). However, the roles of miRNAs in microglia in health and neurological disease have not been systematically summarized. This review will first report the role of Dicer, a key endoribonulease that is responsible for most miRNA biogenesis in microglia. Second, we will focus on recent research about the function of miRNAs in activation, inflammation and polarization of microglia, respectively. In addition, potential crosstalk between microglia and glioma cells
via
miRNAs will be discussed in this part. Finally, the role of two essential miRNAs, miR-124, and miR-155, in microglia will be highlighted.
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