carbon preference index
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AbstractIn the hyperarid Atacama Desert, water availability plays a crucial role in allowing plant survival. Along with scant rainfall, marine advective fog frequently occurs along the coastal escarpment fueling isolated mono-specific patches of Tillandsia vegetation. In this study, we investigate the lipid biomarker composition of the bromeliad Tillandsia landbeckii (CAM plant) to assess structural adaptations at the molecular level as a response to extremely arid conditions. We analyzed long-chain n-alkanes and fatty acids in living specimens (n = 59) collected from the main Tillandsia dune ecosystems across a 350 km coastal transect. We found that the leaf wax composition was dominated by n-alkanes with concentrations (total average 160.8 ± 91.4 µg/g) up to three times higher than fatty acids (66.7 ± 40.7 µg/g), likely as an adaptation to the hyperarid environment. Significant differences were found in leaf wax distribution (Average Chain Length [ACL] and Carbon Preference Index [CPI]) in the northern zone relative to the central and southern zones. We found strong negative correlations between fatty acid CPI and n-alkane ACL with precipitation and surface evaporation pointing at fine-scale adaptations to low moisture availability along the coastal transect. Moreover, our data indicate that the predominance of n-alkanes is reflecting the function of the wax in preventing water loss from the leaves. The hyperarid conditions and good preservation potential of both n-alkanes and fatty acids make them ideal tracers to study late Holocene climate change in the Atacama Desert.

Abstract Total petroleum hydrocarbons (TPHs)-(aliphatic and aromatic) were analysed for in atmospheric rainwater between April- June; July – August; September–October depicting early, mid, late rain of 2019. Sampling at Rumuodomaya/ Rumuodome and Ogale in Rivers State using basins fastened to a table 2 M above ground and 120 M from high features, Rainwater was analysed after treatment using Agilent GC-FID. Results show cumulative TPHs at R/R were 56.6551mg/L, 39.5201mg/L and 7.2283mg/L, Ogale: 9.1217mg/L, 59.4923mg/L and 21.9825mg/L. Aliphatic hydrocarbons: C5 – C8 were < 1, low contamination, other carbon aggregates (C9 – C16, C17– C35, and C36 – C40) indicate high contamination. Chemometric assessment showed high contamination. TPHs aggregates at Rumuodomaya/ Rumuodome were- C8 – C11 (1.034 and 1.005) early rain, C18 – C25 and C26 – C33 has Carbon preference index of 1.287 and 1.630 (mid-rain), C26 – C33 has CPI of 1.288 (late-rain), Ogale area, C26–C33 has CPI of 1.732 (early-rain), mid-rain C8 – C11 (2.768) and C12–C17 (5.368). Pristane/phytane ratio indicated biogenic and pyrogenic sources. Average carbon length of TPHs for odd n-alkanes were C9 – C11 (9.446) and C35 – C39 (38.980), C9 – C11(10.238), C35 – C39 (36.510); C9 – C11 (10.240) and C35 – C39 (36.934). Average daily intake depicted possible health issues for children and adults as hazard index > 1 for aromatics.

Polycyclic aromatic hydrocarbons (PAHs) and n-alkanes are important specific organic constituents in fine particulate matter (PM2.5). Seventy-five PM2.5 samples were collected in Spring Changzhou, to investigate the concentrations and sources of n-alkanes (C9–C40) and PAHs. The average concentrations of total PAHs (∑PAHs) and n-alkanes (∑n-alkanes) were 4.37 ± 4.95 ng/m3 and 252.37 ± 184.02 ng/m3, ranging from 0.43 to 22.22 ng/m3 and 57.37 to 972.17 ng/m3, respectively. The average concentrations of ∑n-alkanes and ∑PAHs were higher in severely polluted days (PM2.5 ≥ 150 μg/m3) in comparison to other days. Up to 85% of PAHs were four- and five-ring compounds, and the middle-chain-length n-alkanes (C25–C35) were the most abundant species (80.9%). The molecular distribution of n-alkanes was characterized by odd-number carbon predominance (carbon preference index, CPI > 1), with a maximum centered at C27, C29, and C31 revealing a significant role of biogenic sources. Principal component analysis suggested that the biogenic sources that contributed the most to n-alkanes and PAHs were from coal combustion (46.3%), followed by biomass burning (16.0%), and vehicular exhaust (10.3%). The variation in the concentration of n-alkanes and PAHs from different air mass transports was not agreement with the change in PM2.5 mass, indicating that regional transport had important impacts on the characterization of PM2.5. The results of our study can provide useful information for evaluating the influence of anthropogenic and biogenic activities on organic matters (n-alkanes and PAHs).

AbstractIsolated silica concretions in calcareous sediments have unique shapes and distinct sharp boundaries and are considered to form by diagenesis of biogenic siliceous grains. However, the details and rates of syngenetic formation of these spherical concretions are still not fully clear. Here we present a model for concretion growth by diffusion, with chemical buffering involving decomposition of organic matter leading to a pH change in the pore-water and preservation of residual bitumen cores in the concretions. The model is compatible with some pervasive silica precipitation. Based on the observed elemental distributions, C, N, S, bulk carbon isotope and carbon preference index (CPI) measurements of the silica-enriched concretions, bitumen cores and surrounding calcareous rocks, the rate of diffusive concretion growth during early diagenesis is shown using a diffusion-growth diagram. This approach reveals that ellipsoidal SiO2 concretions with a diameter of a few cm formed rapidly and the precipitated silica preserved the bitumen cores. Our work provides a generalized chemical buffering model involving organic matter that can explain the rapid syngenetic growth of other types of silica accumulation in calcareous sediments.

Organic geochemical characterization of Wondama coal samples from the Lengguru Folding Belt has been carried out through the study of its aliphatic hydrocarbon biomarkers. This study is to determine the origin, depositional environment and maturity of coal which is useful for determining the use of coal as an energy source. Aliphatic hydrocarbon biomarkers were identified by using gas chromatography-mass spectroscopy methods which showed the presence of n-alkane homologs (n-C15 - n-C33), which was dominated by n-C31. This indicates that the organic material originates from Angiosperms of terrestrial higher plants. The ratio of pristane to phytane (Pr/Ph) with value of 3.74 indicates that the Wondama coal is buried in an oxic depositional environment. The Carbon Preference Index (CPI) value of 7.82 and the C31αβS/(S + R) ratio of 0.27 indicate low maturity of Wondama coal and is classified into a sub-bituminous coal ranks.

In leaf cuticular wax of Pinus pinaster, content of nonacosan-10-ol is high (77.1% on average). n-Alkanes ranged from C18 to C35 with the most dominant C29 (24.8%). The carbon preference index (CPItotal) ranged from 3.1 to 5.6 (4.0 on average), while the average chain length (ACLtotal) ranged from 14.0 to 17.0 (14.8 on average). Long-chain n-alkanes ( n-C25-35) strongly dominated (80.1%) over middle-chain ( n-C21-24 = 18.9%) and short-chain ( n -C18-20 = 0.9%) n-alkanes.

In needle cuticular wax of Pinus halepensis, nonacosan-10-ol is high (77.08% on average). n-Alkanes ranged from C18 to C35 with the most dominant C27 and C29 (32.4% and 25.8%, respectively). The carbon preference index ranged from 3.2 to 5.4 (3.4 on average), while the average chain length ranged from 14.0 to 18.0 (17.2 on average). Long-chain n-alkanes strongly dominated (95.1%).

&lt;p&gt;Samples of detrital lignite have been collected for organic geochemical and carbon isotope analyses from the First Lusatian lignite seam at the Adam&amp;#243;w, J&amp;#243;&amp;#197;&amp;#186;win IIB and Tomis&amp;#197;&amp;#130;awice opencast mines, deposited after the last peak of the Mid-Miocene Climatic Optimum. The aim of the study is to improve the chemotaxonomic value of biomarkers by relating the results to existing paleobotanical data, and to gain information about the influencing factors on &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C of lignite and lipids. Furthermore, biomarker and isotopic proxies are tested for their applicability in paleoclimate studies.&lt;/p&gt;&lt;p&gt;The relative abundances of mid-chain (C&lt;sub&gt;23&lt;/sub&gt;, C&lt;sub&gt;25&lt;/sub&gt;) &lt;em&gt;n&lt;/em&gt;-alkanes and their 1&amp;#8211;2&amp;#8240; higher &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values compared to long-chain &lt;em&gt;n&lt;/em&gt;-alkanes (C&lt;sub&gt;29&lt;/sub&gt;, C&lt;sub&gt;31&lt;/sub&gt;) argue for a minor contribution of macrophytes (graminoids, etc.) to peat formation, enhanced during periods of raised water level. The presence of ferruginol and dehydroferruginol testifies the contribution of taxodioid Cupressaceae. The abundances of pimarane-type diterpenoids and the presence of non-aromatic abietane-derivatives argue for the contribution of Pinaceae. Based on the presence of lupeol and lupane-type triterpenoids, an input of Betulaceae can be concluded. The contribution of further angiosperms cannot be specified based on the composition of pentacyclic triterpenoids. However, the results indicate mixed vegetation, and are in agreement with paleobotanical data highlighting abundant conifers of the Cupressaceae and Pinaceae families, as well as angiosperms of various families (e.g., &lt;em&gt;Nyssa, Quercus, Fagus&lt;/em&gt;), including Betulaceae (e.g., &lt;em&gt;Alnus, Betula, Corylus&lt;/em&gt;). Based on the relationship between the carbon preference index of &lt;em&gt;n&lt;/em&gt;-alkanes and mean annual air temperatures, obtained from a global database of peatlands, an average temperature of 24.5 &amp;#176;C is obtained. This value is significantly higher as estimated from paleobotanical data (15.7&amp;#8211;19.7 &amp;#176;C), probably due to the influence of changes in vegetation on carbon preference index.&lt;/p&gt;&lt;p&gt;The relative abundances of diterpenoids versus di- plus angiosperm-derived triterpenoids in detrital lignite samples revealed variable contributions of gymnosperms and angiosperms during the middle Miocene. Consistent with these results, a positive relationship exists between the di-/(di- + tri-) terpenoid biomarker ratios and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C of lignite samples, indicating the dominating role of varying gymnosperm/angiosperm contributions on the carbon isotopic composition of lignite. The C-isotope data of long-chain n-alkanes, diterpenoids, and angiosperm-derived triterpenoids co-vary within the profiles, arguing for an overall control of changes in &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; on &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C of plant lipids. Fluctuations in &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C of individual compounds may also be related to changes in carbon cycling within the peat, humidity and air temperature.&lt;/p&gt;