scholarly journals Underrated primary biogenic origin and lifetime of atmospheric formic and acetic acid

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xinqing Lee ◽  
Daikuan Huang ◽  
Qi Liu ◽  
Xueyan Liu ◽  
Hui Zhou ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Atmospheric Chemistry ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Photochemical Oxidation ◽  
Long Distance ◽  
Biogenic Emission ◽  
Model Studies ◽  
Long Distance Transport ◽  
Strong Source

AbstractFormic and acetic acids are ubiquitous in the troposphere, playing an important role in the atmospheric chemistry. Recent model studies ended up with substantial low bias on their tropospheric budgets presumably due to a large missing biogenic source derived most likely from photochemical oxidation of long-lived volatile organic compound(s), i.e., a secondary biogenic emission. Here, by studying the stable carbon isotope composition of formic and acetic acid in couple in the troposphere and relevant sources, we find the gap relates to primary biogenic emission and atmospheric lifetime of the acids. We show the primary biogenic emission is only second to the secondary biogenic emission as a strong source. Marine emission is the least one yet present in all the tropospheric environments except some local air. Long-distance transport of this origin indicates the lifetime over 5 days for both acids. Our results indicate that recent simulations underrated both primary biogenic emission and the lifetime. These underestimations would inevitably bias low the modeled results, especially in the low and free troposphere where primary biogenic emission and lifetime has the most pronounced influence, respectively.

scholarly journals Molecular distributions and stable carbon isotope compositions of oxalic acid and related SOA in Beijing before, during and after the 2014 APEC

2016 ◽  
Author(s):  
Jiayuan Wang ◽  
Gehui Wang ◽  
Jian Gao ◽  
Han Wang ◽  
Yanqin Ren ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Dicarboxylic Acids ◽  
Photochemical Oxidation ◽  
Stable Carbon ◽  
Aerosol Composition ◽  
Air Masses ◽  
Emission Controls

Abstract. To ensure the good air quality for the 2014 APEC, stringent emission controls were implemented in Beijing and its surrounding regions, leading to a significant reduction in PM2.5 loadings. To investigate the impacts of the emission controls on aerosol composition and formation, high-volume PM2.5 samples were collected in Beijing from 08/10/2014 to 24/11/2014 and determined for secondary inorganic ions (SIA, i.e., SO42−, NO3− and NH4+), dicarboxylic acids, keto-carboxylic acid and α-dicarbonyls, as well as stable carbon isotope composition of oxalic acid (C2). Our results showed that SIA in PM2.5 are 52 ± 47, 18 ± 13 and 33 ± 29 μg m−3 before-, during- and after-APEC, accounting for 29 %, 18 % and 20 % of PM2.5, respectively. As the leading dicarboxylic acid, C2 in PM2.5 during the three phases are 502 ± 564, 101 ± 69 and 166 ± 157 ng  m−3, accounting for 46 %, 31 % and 34 % of total detected organic compounds (TDOC, i.e., the sum of dicarboxylic acids, keto-carboxylic acids and α-dicarbonyls). The higher values of concentrations and relative abundances of SIA and C2 before-APEC suggest that PM2.5 aerosols during this period are more enriched with secondary products, mainly due to an enhanced photochemical oxidation under the higher temperature and more humid conditions. SIA, C2 and related SOA in PM2.5 during-APEC were 2–4 times lower than those before-APEC. C2 in the regional air masses, which mostly occurred before-APEC, are abundant and enriched in 13C. On the contrary, C2 in the long-range transport air masses, which mostly occurred during-APEC, is much less abundant but still enriched in 13C. In the local air masses, which mostly occurred after-APEC, C2 concentration is lower than that before-APEC but higher than that during-APEC and enriched in lighter 12C. A comparison on chemical composition of PM2.5 and δ13C values of C2 in two events that are characterized by the highest PM2.5 levels before- and after-APEC, respectively, further showed that after-APEC SIA and TDOC are much less abundant and fine aerosols are enriched with primary organics and relatively fresh, compared with those before-APEC. Such reduction in secondary aerosols after-APEC, along with a similar reduction during-APEC, is largely due to the decreasing temperatures. Our results indicate that the significant reduction in PM2.5 during-APEC is mainly due to the efficient emission controls, but the effect of the decreasing temperatures, which suppressed secondary aerosol production, may also take an important role.

The Fine Structure of Phloem Cells

1985 ◽  
Vol 43 ◽  
pp. 632-635
Author(s):  
James Cronshaw
Keyword(s):  
Structural Studies ◽  
High Concentration ◽  
Long Distance ◽  
Phloem Tissue ◽  
Sieve Elements ◽  
Long Distance Transport ◽  
P Protein ◽  
Companion Cells ◽  
Electron Microscopical ◽  
Distance Transport

Long distance transport in plants takes place in phloem tissue which has characteristic cells, the sieve elements. At maturity these cells have sieve areas in their end walls with specialized perforations. They are associated with companion cells, parenchyma cells, and in some species, with transfer cells. The protoplast of the functioning sieve element contains a high concentration of sugar, and consequently a high hydrostatic pressure, which makes it extremely difficult to fix mature sieve elements for electron microscopical observation without the formation of surge artifacts. Despite many structural studies which have attempted to prevent surge artifacts, several features of mature sieve elements, such as the distribution of P-protein and the nature of the contents of the sieve area pores, remain controversial.

When animals are not quite what they eat: diet digestibility influences 13C-incorporation rates and apparent discrimination in a mixed-feeding herbivore

2011 ◽  
Vol 89 (6) ◽  
pp. 453-465 ◽  
Author(s):  
Daryl Codron ◽  
Jacqui Codron ◽  
Matt Sponheimer ◽  
Stefano M. Bernasconi ◽  
Marcus Clauss
Keyword(s):  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Food Sources ◽  
Capra Hircus ◽  
Stable Carbon ◽  
Animal Tissues ◽  
Themeda Triandra ◽  
Low Protein ◽  
Medicago Sativa L ◽  
Discrimination Factors

The stable carbon isotope composition of animal tissues represents the weighted sum of the variety of food sources eaten. If sources differ in digestibility, tissues may overrepresent intake of more digestible items and faeces may overrepresent less digestible items. We tested this idea using whole blood and faeces of goats ( Capra hircus L., 1758) fed different food mixtures of C3 lucerne ( Medicago sativa L.) and C4 grass ( Themeda triandra Forssk.). Although blood and faecal δ13C values were broadly consistent with diet, results indicate mismatch between consumer and diet isotope compositions: both materials overrepresented the C3 (lucerne) component of diets. Lucerne had lower fibre digestibility than T. triandra, which explains the results for faeces, whereas underrepresentation of dietary C4 in blood is consistent with low protein content of the grass hay. A diet switch experiment revealed an important difference in 13C-incorporation rates across diets, which were slower for grass than lucerne diets, and in fact equilibrium states were not reached for all diets. Although more research is needed to link digestive kinetics with isotope incorporation, these results provide evidence for nonlinear relationships between consumers and their diets, invoking concerns about the conceptual value of “discrimination factors” as the prime currency for contemporary isotope ecology.

scholarly journals From tree to architecture: how functional morphology of arborescence connects plant biology, evolution and physics

2021 ◽  
Author(s):  
Anita Roth-Nebelsick ◽  
Tatiana Miranda ◽  
Martin Ebner ◽  
Wilfried Konrad ◽  
Christopher Traiser
Keyword(s):  
Land Plant ◽  
Plant Evolution ◽  
Ecological Niches ◽  
Long Distance ◽  
Ongoing Research ◽  
Long Distance Transport ◽  
Theoretical Approaches ◽  
Trade Offs ◽  
Interfacial Physics ◽  
Plant Water Transport

AbstractTrees are the fundamental element of forest ecosystems, made possible by their mechanical qualities and their highly sophisticated conductive tissues. The evolution of trees, and thereby the evolution of forests, were ecologically transformative and affected climate and biogeochemical cycles fundamentally. Trees also offer a substantial amount of ecological niches for other organisms, such as epiphytes, creating a vast amount of habitats. During land plant evolution, a variety of different tree constructions evolved and their constructional principles are a subject of ongoing research. Understanding the “natural construction” of trees benefits strongly from methods and approaches from physics and engineering. Plant water transport is a good example for the ongoing demand for interdisciplinary efforts to unravel form-function relationships on vastly differing scales. Identification of the unique mechanism of water long-distance transport requires a solid basis of interfacial physics and thermodynamics. Studying tree functions by using theoretical approaches is, however, not a one-sided affair: The complex interrelationships between traits, functionality, trade-offs and phylogeny inspire engineers, physicists and architects until today.

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