An overview of silicification in Cainozoic landscapes of arid central and southern Australia

Soil Research ◽  
1983 ◽  
Vol 21 (4) ◽  
pp. 387 ◽  
Author(s):  
AR Milnes ◽  
CR Twidale
Keyword(s):  
Chemical Compositions ◽  
Moisture Regime ◽  
Drainage Basins ◽  
Near Surface ◽  
Base Level ◽  
Silica Diagenesis ◽  
Local Fluctuations ◽  
Soluble Silica ◽  
High Concentrations ◽  
Acid Weathering

Silica diagenesis in the near-surface zones of subdued Tertiary drainage basins in the arid interior of central and southern Australia produced a mosaic of silcretes now exposed as relic duricrust on mesas that are significantly higher than the contemporary base-level of erosion. The silcretes comprise a variety of silica-cemented sediments and possibly soils that exhibit a range of textures and chemical compositions. Acid-weathering conditions in pedogenic environments near the margins of the Tertiary drainage basins are likely to have provided soluble silica for soil waters and groundwater moving slowly through the regolith into depositional zones in the lower reaches of the basins. The silica cement in silcretes ranges from ordered forms of opal to quartz overgrowths, and the existence of incomplete transformations between structural states and between textural forms suggests heterogeneous precipitation and recrystallization in response to local fluctuations in properties such as pH and moisture regime. High concentrations of titanium were precipitated from solution in bedrock fractures as well as in sediments in the piedmont of the ancient drainage basins, but as yet there is no unequivocal explanation for its occurrence. Apart from zircon, enrichment of zirconium and aluminium in areas of high titanium concentration is evident from electron probe microanalyses and X-ray scanning images, but the mineral phase or phases responsible for this distribution are unidentified.

Analytical Electron Microscopy of Ion-Implanted Metals

1985 ◽  
Vol 43 ◽  
pp. 282-285
Author(s):  
D.I. Potter ◽  
M. Ahmed ◽  
K. Ruffing
Keyword(s):  
Electron Microscopy ◽  
Ion Implantation ◽  
Friction And Wear ◽  
Analytical Electron Microscopy ◽  
Chemical Compositions ◽  
Surface Chemical ◽  
Near Surface ◽  
The Past ◽  
Analytical Electron ◽  
Property Changes

Ion implantation, used extensively for the past decade in fabricating semiconductor devices, now provides a unique means for altering the near-surface chemical compositions and microstructures of metals. These alterations often significantly improve physical properties that depend on the surface of the material; for example, catalysis, corrosion, oxidation, hardness, friction and wear. Frequently the mechanisms causing these beneficial alterations and property changes remain obscure and much of the current research in the area of ion implantation metallurgy is aimed at identifying such mechanisms. Investigators thus confront two immediate questions: To what extent is the chemical composition changed by implantation? What is the resulting microstructure? These two questions can be investigated very fruitfully with analytical electron microscopy (AEM), as described below.

scholarly journals Antioxidant and Cytotoxic Activities of Myrtaceae Essential Oils Rich in Terpenoids From Brazil

2021 ◽  
Vol 16 (2) ◽  
pp. 1934578X2199615
Author(s):  
Lucas Botelho Jerônimo ◽  
Jamile S. da Costa ◽  
Laine C. Pinto ◽  
Raquel C. Montenegro ◽  
William N. Setzer ◽  
...  
Keyword(s):  
Essential Oils ◽  
Cancer Cells ◽  
Antioxidant Activities ◽  
Human Cancer ◽  
Psidium Guajava ◽  
Cytotoxic Activities ◽  
Chemical Compositions ◽  
Main Compound ◽  
Human Cancer Cells ◽  
High Concentrations

This work analyzed the chemical compositions and evaluated the antioxidant and cytotoxic activities of essential oils (EO) of Eugenia patrisii (Epat), Eugenia stipitata (Esti), Myrcia splendens (Mspl), Myrcia sylvatica (Msyl), Psidium guajava (Pgua), and Psidium guineense (Pgui-1 and Pgui-2) from the Brazilian Amazon. Sesquiterpenoids were found in high concentrations in the oils of E. patrisii and M. splendens, which were rich in E-caryophyllene (32.0% and 45.8%); E. stipitata and M. sylvatica, which displayed germacrene D (11.8%) and germacrene B (24.5%); and P. guajava that showed epi-β-bisabolol (16.1%) as the main compound. However, P. guineense samples (Pgui-1 and Pgui-2) were rich in monoterpenoids such as limonene (Pgui-1: 30.2%; Pgui-2 30.4%) and α-pinene (Pgui-1: 22.5%; Pgui-2: 17.7%). The samples showed a weak and moderate antioxidant activities in the DPPH assay, displaying inhibition rates from 11.5% to 38.6% (at 10 mg/mL). All samples were cytotoxic against human cancer cells by the MTT method. Epat oil showed higher activity against melanoma (SKMEL-19, IC505.8 µg/mL), gastric (AGP01, IC503.2 µg/mL), and colon (HCT116, IC506.7 µg/mL). Meanwhile, the samples Pgua and Pgui were more active against breast cancer cells (MCF7, IC5012.4 µg/mL and 11.6 µg/mL, respectively).

scholarly journals Long-term trends in aerosol and precipitation composition over the western North Atlantic Ocean at Bermuda

2014 ◽  
Vol 14 (5) ◽  
pp. 7025-7066 ◽  
Author(s):  
W. C. Keene ◽  
J. L. Moody ◽  
J. N. Galloway ◽  
J. M. Prospero ◽  
O. R. Cooper ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Flow Regimes ◽  
The United States ◽  
Open Ocean ◽  
Anthropogenic Sources ◽  
Trade Wind ◽  
Chemical Compositions ◽  
Near Surface

Abstract. Since the 1980s, emissions of SO2 and NOx (NO + NO2) from anthropogenic sources in the United States (US) and Europe have decreased significantly suggesting that the export of oxidized S and N compounds from surrounding continents to the atmosphere overlying North Atlantic Ocean (NAO) has also decreased. The chemical compositions of aerosols and precipitation sampled daily on Bermuda (32.27° N, 64.87° W) from 1989 to 1997 and from 2006 to 2009 were evaluated to quantify the magnitudes, significance, and implications of associated tends in atmospheric composition. The chemical data were stratified based on FLEXPART retroplumes into four discrete transport regimes: westerly flow from the eastern North America (NEUS/SEUS); easterly trade-wind flow from northern Africa and the subtropical NAO (Africa); long, open-ocean, anticyclonic flow around the Bermuda High (Oceanic); and transitional flow from the relatively clean open ocean to the polluted northeastern US (North). Based on all data, annual average concentrations of non-sea-salt (nss) SO42- associated with aerosols and annual VWA concentrations in precipitation decreased significantly (by 22 and 49%, respectively) whereas annual VWA concentrations of NH4+ in precipitation increased significantly (by 70%). Corresponding trends in aerosol and precipitation NO3- and of aerosol NH4+ were insignificant. Nss SO42- in precipitation under NEUS/SEUS and Oceanic flow decreased significantly (61% each) whereas corresponding trends in particulate nss SO42- under both flow regimes were insignificant. Trends for precipitation were driven in part by decreasing emissions of SO2 over upwind continents and associated decreases in anthropogenic contributions to nss SO42- concentrations. Under NEUS/SEUS and Oceanic flow, the ratio of anthropogenic to biogenic contributions to to nss SO42- in the column scavenged by precipitation were relatively greater than those in near surface aerosol, which implies that, for these flow regimes, precipitation is a better indicator of overall anthropogenic impacts on the lower troposphere. Particulate nss SO42- under African flow also decreased significantly (34%) whereas the corresponding decrease in nss SO42- associated with precipitation was marginally insignificant. We infer that these trends were driven in part by reductions in the emissions and transport of oxidized S compounds from Europe. The lack of significant trends in NO3- associated with aerosols and precipitation under NEUS/SEUS flow is notable in light of the large decrease (39%) in NOx emissions in the US over the period of record. Rapid chemical processing of oxidized N in marine air contributed to this lack of correspondence. Decreasing ratios of nss SO42- to NH4+ and the significant decreasing trend in precipitation acidity (37%) indicate that the total amount of acidity in the multiphase gas-aerosol system in the western NAO troposphere decreased over the period of record. Decreasing aerosol acidities would have shifted the phase partitioning of total NH3 (NH3 + particulate NH4+) towards the gas phase thereby decreasing the atmospheric lifetime of total NH3 against wet plus dry deposition. The trend of increasing NH4+ in precipitation at Bermuda over the period of record suggests that NH3 emissions from surrounding continents also increased. Decreasing particulate nss SO42- in near-surface air under NEUS/SEUS flow over the period of record suggests a lower limit for net warming in the range of 0.1–0.3 W m-2 resulting from the decreased shortwave scattering and absorption by nss SO42- and associated aerosol constituents.

scholarly journals Seasonal Variability in the Composition of Particulate Matter and the Microclimate in Cultural Heritage Areas

Atmosphere ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 595 ◽  
Author(s):  
Radulescu ◽  
Stihi ◽  
Ion ◽  
Dulama ◽  
Stanescu ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Inductively Coupled Plasma ◽  
Chemical Compositions ◽  
Potential Health ◽  
Museum Exhibits ◽  
Inductively Coupled ◽  
Chemical Measurements ◽  
Low Concentrations ◽  
High Concentrations ◽  
Indoor And Outdoor

This study is the first attempt to decipher the effect of particulate matter (PM) composition on people’s health and on historic sites, in correlation with the daily and seasonal microclimate monitoring of the indoor and outdoor areas of the Roman Mosaic Edifice museum (the maritime port of Constanta, Romania). More specifically, the increase of metal concentrations in particulate matter during the summer of 2018 and spring of 2019 in the museum under investigation could possibly be associated with the microclimates of both seasons, with coastal factors, as well as with the anthropic activities specific to the port of Constanta. FTIR and inductively coupled plasma mass spectroscopy (ICP-MS) techniques, used for the investigation of PM2.5–10 samples, revealed high concentrations of Fe, Al-rich, and soluble particles inside the investigated museum area. In this respect, the chemical measurements of the PM2.5–10 masses highlighted high concentrations of heavy metals (i.e., Al, Fe, Zn, Mn, and Pb) and low concentrations of trace metals (i.e., Cr, Ni, Cu, and Cd). Statistical analysis showed that the chemical compositions of the particulate matter in the indoor and outdoor areas of the Roman Mosaic Edifice were influenced by microclimatic conditions, mainly temperature and relative humidity (RH). A potential health risk for tourists is the thermal and humid conditions, alongside the toxic components of the particulate matter. This research seeks to provide solutions for improving the environmental conditions inside the Roman Mosaic Edifice and to offer useful suggestions concerning health promotion and the protection of museum exhibits against possible future deterioration.

scholarly journals Chemotype of Litsea cubeba Essential Oil and Its Bioactivity

2015 ◽  
Vol 10 (7) ◽  
pp. 1934578X1501000 ◽  
Author(s):  
Syaliza Abdul Hammid ◽  
Fasihuddin Ahmad
Keyword(s):  
Essential Oil ◽  
Brine Shrimp ◽  
Wide Spectrum ◽  
Supplementary Information ◽  
Chemical Compositions ◽  
Litsea Cubeba ◽  
Geographical Variations ◽  
Chemical Profiles ◽  
Leaf Oil ◽  
High Concentrations

The essential oils from different parts of Litsea cubeba, collected from the highlands of Sarawak, were isolated and their chemical compositions analyzed. This study demonstrated significant variations in the chemical compositions and the chemical profiles of the volatiles and could provide valuable supplementary information on the geographical variations of the species. The fruit essential oil was dominated by citronellal, d-limonene and citronellol, while the leaf oil was high in eucalyptol and α-terpineol. High concentrations of citronellal and citronellol in both the root and bark oils were identified. In the stem, the oil was dominated by eucalyptol, d-limonene and α-terpineol. The activity of the oils against brine shrimp larvae, bacteria, yeast and fungi was determined. The oils were toxic against brine shrimp larvae with LC50 values ranging from 25.1 – 30.9 μL/mL. The oils also demonstrated a wide spectrum of inhibition against microorganisms with inhibition zones between 19.5 – 46.7 mm against Gram-positive bacteria and 10.5 – 90.0 mm against yeast and fungi. However, the oils were not active against Gram-negative bacteria.

scholarly journals On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East

2016 ◽  
Vol 16 (21) ◽  
pp. 14025-14039 ◽  
Author(s):  
Dimitris Akritidis ◽  
Andrea Pozzer ◽  
Prodromos Zanis ◽  
Evangelos Tyrlis ◽  
Bojan Škerlak ◽  
...  
Keyword(s):  
Middle East ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Free Troposphere ◽  
Near Surface ◽  
Grid Points ◽  
High Concentrations

Abstract. We study the contribution of tropopause folds in the summertime pool of tropospheric ozone over the eastern Mediterranean and the Middle East (EMME) with the aid of the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model. Tropopause fold events in EMAC simulations were identified with a 3-D labeling algorithm that detects folds at grid points where multiple crossings of the dynamical tropopause are computed. Subsequently the events featuring the largest horizontal and vertical extent were selected for further study. For the selection of these events we identified a significant contribution of the stratospheric ozone reservoir to the high concentrations of ozone in the middle and lower free troposphere over the EMME. A distinct increase of ozone is found over the EMME in the middle troposphere during summer as a result of the fold activity, shifting towards the southeast and decreasing altitude. We find that the interannual variability of near-surface ozone over the eastern Mediterranean (EM) during summer is related to that of both tropopause folds and ozone in the free troposphere.

Concentrations and speciation of lead, zinc and cadmium in seawater-like smelter effluent and adjacent marine environments, Port Pirie, South Australia

1983 ◽  
Vol 34 (3) ◽  
pp. 375 ◽  
Author(s):  
J Ferguson
Keyword(s):  
South Australia ◽  
Tidal Channel ◽  
Significant Extent ◽  
Dissolved Metals ◽  
Metal Concentrations ◽  
Near Surface ◽  
Unicellular Algae ◽  
Particulate Metal ◽  
Lead Zinc ◽  
High Concentrations

High concentrations of particulate and dissolved lead, zinc and cadmium (total dissolved Pb, 750�g l-1; Zn, 4300�g 1-1; Cd, 64 �g l-1; particulate Pb, 236 �g l-1; Zn, 64 �g l-1; Cd, < 1 �g l-1) occur in seawater- like effluent from a lead-zinc smelting complex at Port Pirie. This effluent is discharged through a silled tidal channel into the offshore marine environment, where dilution by seawater eventually reduces the metal concentrations to values similar to those in near-surface seawater in Spencer Gulf, remote from centres of industrial activity (average total dissolved Pb, 0 4 �g 1-1; Zn, < 10 μg l-1; Cd, 0 3 �g l-1; average particulate Pb, <0.05 �g l-1; Zn, 0 21 �g I-1). Precipitation of dissolved metals or conversion of originally weakly complexed dissolved metals to more strongly complexed species does not occur to a significant extent. Particulate metal concentrations are influenced by resuspension of metal-rich sediments and by uptake of dissolved cadmium by unicellular algae that grow in the tidal channel.

scholarly journals Air quality and climate change, Topic 3 of the Model Inter-Comparison Study for Asia Phase III (MICS-Asia III) – Part 1: Overview and model evaluation

2018 ◽  
Vol 18 (7) ◽  
pp. 4859-4884 ◽  
Author(s):  
Meng Gao ◽  
Zhiwei Han ◽  
Zirui Liu ◽  
Meng Li ◽  
Jinyuan Xin ◽  
...  
Keyword(s):  
Air Quality ◽  
Model Evaluation ◽  
The United States ◽  
Chemical Mechanism ◽  
Research Network ◽  
Phase Iii ◽  
Chemical Compositions ◽  
Comparison Study ◽  
Near Surface ◽  
Ensemble Mean

Abstract. Topic 3 of the Model Inter-Comparison Study for Asia (MICS-Asia) Phase III examines how online coupled air quality models perform in simulating high aerosol pollution in the North China Plain region during wintertime haze events and evaluates the importance of aerosol radiative and microphysical feedbacks. A comprehensive overview of the MICS-Asia III Topic 3 study design, including descriptions of participating models and model inputs, the experimental designs, and results of model evaluation, are presented. Six modeling groups from China, Korea and the United States submitted results from seven applications of online coupled chemistry–meteorology models. Results are compared to meteorology and air quality measurements, including data from the Campaign on Atmospheric Aerosol Research Network of China (CARE-China) and the Acid Deposition Monitoring Network in East Asia (EANET). The correlation coefficients between the multi-model ensemble mean and the CARE-China observed near-surface air pollutants range from 0.51 to 0.94 (0.51 for ozone and 0.94 for PM2.5) for January 2010. However, large discrepancies exist between simulated aerosol chemical compositions from different models. The coefficient of variation (SD divided by the mean) can reach above 1.3 for sulfate in Beijing and above 1.6 for nitrate and organic aerosols in coastal regions, indicating that these compositions are less consistent from different models. During clean periods, simulated aerosol optical depths (AODs) from different models are similar, but peak values differ during severe haze events, which can be explained by the differences in simulated inorganic aerosol concentrations and the hygroscopic growth efficiency (affected by varied relative humidity). These differences in composition and AOD suggest that future models can be improved by including new heterogeneous or aqueous pathways for sulfate and nitrate formation under hazy conditions, a secondary organic aerosol (SOA) formation chemical mechanism with new volatile organic compound (VOCs) precursors, yield data and approaches, and a more detailed evaluation of the dependence of aerosol optical properties on size distribution and mixing state. It was also found that using the ensemble mean of the models produced the best prediction skill. While this has been shown for other conditions (for example, the prediction of high-ozone events in the US (McKeen et al., 2005)), this is to our knowledge the first time it has been shown for heavy haze events.

Effect of fire intensity on solution chemistry of surface soil under a Eucalyptus pauciflora forest

Soil Research ◽  
1986 ◽  
Vol 24 (3) ◽  
pp. 423 ◽  
Author(s):  
PK Khanna ◽  
RJ Raison
Keyword(s):  
Organic Matter ◽  
Soil Layer ◽  
Solution Chemistry ◽  
Water Soluble ◽  
Fire Intensity ◽  
Soil Solutions ◽  
Soluble Silica ◽  
High Concentrations ◽  
One Year ◽  
Heated Soil

The chemical composition of soil solutions (field percolates collected in situ and laboratory saturation extracts) was measured at three sites subjected to widely varying fire intensity in subalpine Eucalyptus paucfiora forest near Canberra. The sites were unburnt forest, areas prescribed burnt resulting in almost complete canopy scorch, and ashbeds (intensely heated soil). Saturation extracts were obtained 1, 58, 375, 745 and 1095 days after the fire, and soil percolates were collected on 17 occasions during the initial year after burning. Large quantities of cations (Ca2+, Mg2+, K+ , NH+4) and anions (Cl-, SO24-) and soluble silica were mobilized by burning, especially under ashbeds. Mobilization resulted from deposition of water-soluble elements in ash, immediate effects of soil heating, and enhanced rates of mineralisation of soil organic matter indicated by high concentrations of NH+4 which persisted for more than one year in surface soils under the ashbeds. After burning Ca2+ became the dominant cation in saturation extracts of surface (0-5 cm) soils for the entire 3-year study period. In the 5-15 cm soil layer, firstly NH+4 and later K+ replaced some of the Na+ in the solution phase. Most of the Cl- deposited in ash was leached below 15 cm depth within one year and was probably accompanied by transport of K+, Mg2+, Na+ and NH+4, but very little transfer of Ca2+ occurred. Concentrations of NO-3 and phosphate were always low in saturation extracts and soil percolates, and levels were unaffected by burning, despite the presence of large amounts of exchangeable NH+4 in the soil and the deposition of significant amounts of phosphate in ash. Burning increased the concentrations of soluble silica and SO24- in saturation extracts for at least 3 years after the fire. Most of the changes in soil solution chemistry measured would increase nutrient availability to the vegetation during the initial year after burning, but these changes must be balanced against losses of organic matter and nutrients during and after fires.

scholarly journals Summertime ozone formation in Xi'an and surrounding areas, China

2015 ◽  
Vol 15 (21) ◽  
pp. 30563-30608 ◽  
Author(s):  
T. Feng ◽  
N. Bei ◽  
R. Huang ◽  
J. Cao ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Control Strategies ◽  
Surface Wind ◽  
Temporal Variations ◽  
Anthropogenic Sources ◽  
Anthropogenic Emissions ◽  
Near Surface ◽  
Production Regime ◽  
High Concentrations ◽  
Surrounding Areas ◽  
Surface O3

Abstract. In the study, the ozone (O3) formation is investigated in Xi'an and surrounding areas, China using the WRF-CHEM model during the period from 22 to 24 August 2013 corresponding to a heavy air pollution episode with high concentrations of O3 and PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm). The WRF-CHEM model generally performs well in simulating the surface temperature and relative humidity compared to the observations and also reasonably reproduces the observed temporal variations of the surface wind speed and direction. The convergence formed in Xi'an and surrounding areas is favorable for the accumulation of pollutants, causing high concentrations of O3 and PM2.5. In general, the calculated spatial patterns and temporal variations of near-surface O3 and PM2.5 are consistent well with the measurement at the ambient monitoring stations. The simulated daily mass concentrations of aerosol constituents, including sulfate, nitrate, ammonium, elemental and organic carbon, are also in good agreement with the filter measurements. High aerosol concentrations in Xi'an and surrounding areas significantly decrease the photolysis frequencies and can reduce near-surface O3 concentrations by more than 50 μg m−3 (around 25 ppb) on average. Sensitivity studies show that the O3 production regime in Xi'an and surrounding areas is complicated, varying from NOx to VOC-sensitive chemistry. The industry emissions contribute the most to the O3 concentrations compared to the natural and other anthropogenic sources, but still do not play a determined role in the O3 formation. The complicated O3 production regime and high aerosol levels constitute a dilemma for O3 control strategies in Xi'an and surrounding areas. In the condition with high O3 and PM2.5 concentrations, decreasing various anthropogenic emissions cannot efficiently mitigate the O3 pollution, and a 50 % reduction of all the anthropogenic emissions only decreases near-surface O3 concentrations by less than 14 % during daytime. Further studies need to be performed for O3 control strategies considering manifest changes of the emission inventory and uncertainties of meteorological field simulations.

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