Size distribution and chemical composition of marine aerosols: A compilation and review

Some 30 years of physical and chemical marine aerosol data are reviewed to derive global-size distribution parameters and inorganic particle composition on a coarse 15°×15° grid. There are large gaps in geographical and seasonal coverage and chemical and physical aerosol characterisation. About 28% of the grid cells contain physical data while there are compositional data in some 60% of the cells. The size distribution data were parametrized in terms of 2 submicrometer log-normal distributions. The sparseness of the data did not allow zonal differentiation of the distributions. By segregating the chemical data according to the major aerosol sources, sea salt, dimethylsulfide, crustal material, combustion processes and other anthropogenic sources, much information on mass concentrations and contribution of natural and anthropogenic sources to the marine aerosol can be gleaned from the data base. There are significant meridional differences in the contributions of the different sources to the marine aerosol. Very clearly, we see though that the global marine surface atmosphere is polluted by anthropogenic sulfur. Only in the case of sulfur components did the coverage allow the presentation of very coarse seasonal distributions which reflect the spring blooms in the appropriate parts of the oceans. As an example of the potential value in comparing the marine aerosol data base to chemical transport models, global seasonal meridional MSA distributions were compared to modelled MSA distributions. The general good agreement in mass concentrations is encouraging while some latitudinal discrepancies warrant further investigations covering other aerosol components such as black carbon and metals

Premiedifferentiatie, bonus-malus en solidariteit.

In deze tekst worden enkele bedenkingen gemaakt bij het verband tussen de begrippen solidariteit en verzekeringen. We zullen ons in hoofdzaak beperken tot het domein van motorrijtuigenverzekering, alhoewel een aantal van de bevindingen eveneens van toepassing zijn op private verzekeringen in het algemeen. We zullen onze aandacht toespitsen op de risicopremies, dat wil zeggen dat we het probleem van kosten, winst,… buiten beschouwing laten. Vooreerst zullen we de begrippen solidariteit en segmentatie in een verzekeringscontext nader omschrijven. Vervolgens zullen we deze begrippen illustreren aan de hand van (theoretische) voorbeelden.

Marginal Damage of Methane Emissions: Ozone Impacts on Agriculture

Methane directly contributes to air pollution, as an ozone precursor, and to climate change, generating physical and economic damages to different systems, namely agriculture, vegetation, energy, human health, or biodiversity. The methane-related damages to climate, measured as the Social Cost of Methane, and to human health have been analyzed by different studies and considered by government rulemaking in the last decades, but the ozone-related damages to crop revenues associated to methane emissions have not been incorporated to policy agenda. Using a combination of the Global Change Analysis Model and the TM5-FASST Scenario Screening Tool, we estimate that global marginal agricultural damages range from ~ 423 to 556 $2010/t-CH4, of which 98$2010/t-CH4 occur in the USA, which is the most affected region due to its role as a major crop producer, followed by China, EU-15, and India. These damages would represent 39–59% of the climate damages and 28–64% of the human health damages associated with methane emissions by previous studies. The marginal damages to crop revenues calculated in this study complement the damages from methane to climate and human health, and provides valuable information to be considered in future cost-benefits analyses. © 2023, The Author(s).JS and SW were supported by the U.S. Environmental Protection Agency, under Interagency Agreement DW-089-92459801. The views expressed in this article are purely those of the authors and do not, under any circumstances, represent the views or policies of the U.S. Environmental Protection Agency or the European Commission. JS and SW were supported by the U.S. Environmental Protection Agency, under Interagency Agreement DW-089-92459801. The views expressed in this article are purely those of the authors and do not, under any circumstances, represent the views or policies of the U.S. Environmental Protection Agency or the European Commission

Chloroplasts are central players in sugar-induced leaf growth

Leaves are the plant's powerhouses, providing energy for all organs through sugar production during photosynthesis. However, sugars serve not only as a metabolic energy source for sink tissues but also as signaling molecules, affecting gene expression through conserved signaling pathways to regulate plant growth and development. Here, we describe an in vitro experimental assay, allowing one to alter the sucrose (Suc) availability during early Arabidopsis (Arabidopsis thaliana) leaf development, with the aim to identify the affected cellular and molecular processes. The transfer of seedlings to Suc-containing medium showed a profound effect on leaf growth by stimulating cell proliferation and postponing the transition to cell expansion. Furthermore, rapidly after transfer to Suc, mesophyll cells contained fewer and smaller plastids, which are irregular in shape and contain fewer starch granules compared with control mesophyll cells. Short-term transcriptional responses after transfer to Suc revealed the repression of well-known sugar-responsive genes and multiple genes encoded by the plastid, on the one hand, and up-regulation of a GLUCOSE-6-PHOSPHATE TRANSPORTER (GPT2), on the other hand. Mutant gpt2 seedlings showed no stimulation of cell proliferation and no repression of chloroplast-encoded transcripts when transferred to Suc, suggesting that GPT2 plays a critical role in the Suc-mediated effects on early leaf growth. Our findings, therefore, suggest that induction of GPT2 expression by Suc increases the import of glucose-6-phosphate into the plastids that would repress chloroplast-encoded transcripts, restricting chloroplast differentiation. Retrograde signaling from the plastids would then delay the transition to cell expansion and stimulate cell proliferation

Physical aerosol properties and their relation to air mass origin at Monte Cimone (Italy) during the first MINATROC campaign

Aerosol physical properties were measured at the Monte Cimone Observatory (Italy) from 1 June till 6 July 2000. The measurement site is located in the transition zone between the continental boundary layer and the free troposphere (FT), at the border between the Mediterranean area and Central Europe, and is exposed to a variety of air masses. Sub-&mu;m number size distributions, aerosol hygroscopicity near 90% RH, refractory size distribution at 270&deg;C and equivalent black carbon mass were continuously measured. Number size distributions and hygroscopic properties indicate that the site is exposed to aged continental air masses, however during daytime it is also affected by upslope winds. The mixing of this transported polluted boundary layer air masses with relatively clean FT air leads to frequent nucleation events around local noon. <P style='line-height: 20px;'> Night-time size distributions, including fine and coarse fractions for each air mass episode, have been parameterized by a 3-modal lognormal distribution. Number and volume concentrations in the sub-&mu;m modes are strongly affected by the air mass origin, with highest levels in NW-European air masses, versus very clean, free tropospheric air coming from the N-European sector. During a brief but distinct dust episode, the coarse mode is clearly enhanced. <P style='line-height: 20px;'> The observed hygroscopic behavior of the aerosol is consistent with the chemical composition described by Putaud et al.&nbsp;(2004), but no closure between known chemical composition and measured hygroscopicity could be made because the hygroscopic properties of the water-soluble organic matter (WSOM) are not known. The data suggest that WSOM is slightly-to-moderately hygroscopic (hygroscopic growth factor GF at 90% relative humidity between 1.05 and 1.51), and that this property may well depend on the air mass origin and history. <P style='line-height: 20px;'> External mixing of aerosol particles is observed in all air masses through the occurrence of two hygroscopicity modes (average GF of 1.22 and 1.37, respectively). However, the presence of 'less' hygroscopic particles has mostly such a low occurrence rate that the average growth factor distribution for each air mass sector actually appears as a single mode. This is not the case for the dust episode, where the external mixing between less hygroscopic and more hygroscopic particles is very prominent, and indicating clearly the occurrence of a dust accumulation mode, extending down to 50 nm particles, along with an anthropogenic pollution mode. <P style='line-height: 20px;'> The presented physical measurements finally allow us to provide a partitioning of the sub-&mu;m aerosol in four non-overlapping fractions (soluble/volatile, non-soluble/volatile, refractory/non-black carbon, black carbon) which can be associated with separate groups of chemical compounds determined with chemical-analytical techniques (ions, non-water soluble organic matter, dust, elemental carbon). All air masses except the free-tropospheric N-European and Dust episodes show a similar composition within the uncertainty of the data (53%, 37%, 5% and 5% respectively for the four defined fractions). Compared to these sectors, the dust episode shows a clearly enhanced refractory-non-BC fraction (17%), attributed to dust in the accumulation mode, whereas for the very clean N-EUR sector, the total refractory fraction is 25%, of which 13% non-BC and 12% BC

Preliminary exploratory impact assessment of short-lived pollutants over the Danube Basin

This report is presented as deliverable D2.3 of work package 2 of the Danube Air Nexus. It presents the results of an exploratory impact assessment of short-lived air pollutant emissions on human health, crop production and near-term climate with a focus on the Danube basin. We use a global reduced-form source receptor air quality model TM5-FASST and a recent global pollutant emission inventory (HTAP V2, 2014) to make an attribution by sector of the various impacts and to explore the challenges and opportunities for possible. Preliminary results show that trans-boundary pollution is significantly contributing to population exposure to PM2.5 in the Danube area. Dominating polluting sectors are residential sector and agriculture. We estimate that annually 170000 premature mortalities can be attributed to PM2.5 pollution in the Danube area, and annual crop losses add up to an economic value of nearly 1 billion US$. This analysis is a first step in a more detailed, country-wise analysis that will be carried out as a follow-up of this report, with an improved version of the model and specifically designed scenarios for the Danube Basin.JRC.H.2-Air and Climat

LC-MS analysis of aerosol particles from the oxidation of ?-pinene by ozone and OH-radicals

International audienceThe time resolved chemical composition of aerosol particles, formed by the oxidation of alpha-pinene has been investigated by liquid chromatography/mass spectrometry (LC-MS) using negative and positive ionisation methods (ESI(-) and APCI(+)). The experiments were performed at the EUPHORE facility in Valencia (Spain) under various experimental conditions, including dark ozone reactions, photosmog experiments with low NOx mixing ratios and reaction with OH radicals in the absence of NOx (H2O2-photolysis). Particles were sampled on PTFE f ilters at different stages of the reaction and extracted with methanol. The predominant products from alpha-pinene in the particulate phase are cis-pinic acid, cis-pinonic acid and hydroxy-pinonic acid isomers. Another major compound with molecular weight 172 was detected, possibly a hydroxy-carboxylic acid. These major compounds account for 50% to 80% of the identified aerosol products, depending on the time of sampling and type of experiment. In addition, more than 20 different products have been detected and structures have been tentatively assigned based on their molecular weight and responses to the different ionisation modes. The different experiments performed showed that the aerosol formation is mainly caused by the ozonolysis reaction. The highest aerosol yields were observed in the dark ozone experiments, for which also the highest ratios of mass of identified products to the formed aerosol mass were found (30% to 50%, assuming a density of 1 g cm-3)