Fine mode aerosol chemistry over a tropical urban atmosphere: characterization of ionic and carbonaceous species

An extensive aerosol sampling program was conducted during January-December 2006 over Kolkata (22o33?? N and 88o20?? E), a mega-city in eastern India in order to understand the sources, distributions and properties of atmospheric fine mode aerosol (PM_2.5). The primary focus of this study is to determine the relative contribution of natural and anthropogenic as well as local and transported components to the total fine mode aerosol loading and their seasonal distributions over the metropolis. The average concentrations of fine mode aerosol was found to be 71.2?±?25.2???gm^-3 varying between 34.5???gm^-3 in monsoon and 112.6???gm^-3 in winter. The formation pathways of major secondary aerosol components like nitrate and sulphate in different seasons are discussed. A long range transport of dust aerosol from arid and semi-arid regions of western India and beyond was observed during pre-monsoon which significantly enriched the total aerosol concentration. Vehicular emissions, biomass burning and transported dust particles were the major sources of PM_2.5 from local and continental regions whereas sea-salt aerosol was the major source of PM_2.5 from marine source regions.     

Two types of ultrapotassic plutonic rocks in the Bohemian Massif — Coeval intrusions at different crustal levels

We present U–Pb zircon age determinations of two Variscan ultrapotassic plutonic rocks from the Moldanubian Zone (Bohemian Massif). Equant, multifaceted zircons without inherited cores from a two-pyroxene–biotite quartz monzonite of the Jihlava Pluton yielded a precise age of 335.12 ± 0.57 Ma, interpreted as dating magma crystallization. The majority of both tabular and prismatic grains from the amphibole–biotite melagranite (“durbachite”) from the T?ebí? Pluton plot along a discordia intersecting the concordia at 334.8 ± 3.2 Ma; prismatic zircon grains commonly contain inherited cores and yield an upper intercept age of 2.2 Ga, indicating early Proterozoic inheritance. We therefore suggest that both types of the ultrapotassic plutonic rocks from the Bohemian Massif crystallized at ca 335 Ma, and the previously published ages higher than ca 340 Ma for “durbachites” were biased by a small amount of unresolved inheritance. The ultrapotassic magma emplacement in the middle crust was related to rapid exhumation of a deep crustal segment, considered as isothermal decompression between high-pressure (～ 340 Ma) and medium-pressure (～ 333 Ma) stages recorded in granulites. Mineral assemblages as well as external and internal zircon morphology suggest that the Jihlava intrusion was deep and dry, whereas the T?ebí? intrusion was shallow and wet. Low ε_Hf values of zircons (? 4.4 to ? 7.5) in both rock types suggest a similar source with a predominant crustal component. However, inherited grains in the T?ebí? melagranite indicate its contamination with crustal material during emplacement, and thus possibly a slower rate of exhumation and/or of magma ascent through the crust.     

Summer evapotranspiration in western Siberia: a comparison between eddy covariance and Penman method formulations

Evapotranspiration is difficult to quantify because of the many factors and complex processes that influence it. Several empirical methods have been developed over the years to estimate potential evapotranspiration based on easily available parameters. Directly measured data of actual evapotranspiration have been rather sparse in the past and still need to be improved in particular regions like western Siberia. The transition zone between the warm temperate and cold temperate continental climates is very sensitive to climate change, and water stress is an increasingly important issue in these regions with a highly dynamic agricultural activity. So there is a growing need to estimate actual evapotranspiration. Widely usable approximations are needed. In this study, the values of potential evapotranspiration computed with the original version, and eight modifications of the Penman formulation were compared and related to the actual evapotranspiration measured by eddy covariance over a grassland area in western Siberia. The original 1948 and 1963 Penman formulations are best for estimating potential evapotranspiration in the transition zone between the forest steppes and the pre‐taiga. A nearly linear relationship between the potential and actual evapotranspiration was found. A simple modification of the Penman equation (i.e. the multiplication of the result by a factor of 0.47) is suggested for approximating the actual evapotranspiration based on standard meteorological data for the region. The original Penman formulation is most robust and will provide the widest applicability in the future under changing climate and environmental conditions. In this context, it is further recommended not to neglect the ventilation term of the Penman equation, which is often assumed to be negligibly small. A detailed correlation analysis showed that under dry soil conditions, the vegetation largely contributed to the actual evapotranspiration and, in contrast to widely held expectations, that the Penman equation is best adapted to vegetated surfaces. Copyright © 2015 John Wiley & Sons, Ltd.     

U–Pb,Lu–Hf and Sm–Nd isotopic constraints on provenance and depositional timing of metasedimentary rocks in the western Gawler Craton: Implications for Proterozoic reconstruction models

The Gawler Craton forms the bulk of the South Australian Craton and occupies a pivotal location that links rock systems in Antarctica to those in northern Australia. The western Gawler Craton is a virtually unexposed region where the timing of basin development and metamorphism is largely unknown, making the region ambiguous in the context of models seeking to reconstruct the Australian Proterozoic.Detrital zircon data from metasedimentary rocks in the central Fowler Domain in the western Gawler Craton provide maximum depositional ages between 1760 and 1700 Ma, with rare older detrital components ranging in age up to 3130 Ma. In the bulk of samples, ?_Nd(1700 Ma) values range between ?4.3 and ?3.8. The combination of these data suggest on average, comparatively evolved but age-restricted source regions. Lu–Hf isotopic data from the ca 1700 Ma aged zircons provide a wide range of values (?_Hf(1700 Ma) +6 to ?6). Monazite U–Pb data from granulite-grade metasedimentary rocks yield metamorphic ages of 1690–1670 Ma. This range overlaps with and extends the timing of the widespread Kimban Orogeny in the Gawler Craton, and provides minimum depositional age constraints, indicating that basin development immediately preceded medium to high grade metamorphism.The timing of Paleoproterozoic basin development and metamorphism in the western Gawler Craton coincides with that in the northern and eastern Gawler Craton, and also in the adjacent Curnamona Province, suggesting protoliths to the rocks within the Fowler Domain may have originally formed part of a large ca 1760–1700 Ma basin system in the southern Australian Proterozoic. Provenance characteristics between these basins are remarkably similar and point to the Arunta Region in the North Australian Craton as a potential source. In this context there is little support for tectonic reconstruction models that: (1) suggest components of the Gawler Craton accreted together at different stages in the interval ca 1760–1680 Ma; and (2) that the North Australian Craton and the southern Australian Proterozoic were separate continental fragments between 1760 and 1700 Ma.     

Electrical conductivity at mid-mantle depths estimated from the data of Sq and long period geomagnetic variations

We present results of a classical global induction analysis of the geomagnetic variation data in the range of daily Sq variations, as well as for long period variations within the period range of about 8 to 400 days. The Sq data from 88 to 94 world observatories are processed in two ways, first by constructing and analyzing average monthly daily variations for the whole months of the International Quiet Sun Year (IQSY) 1995, and second by analyzing the individual, especially quiet Q* daily records from the same year. The electrical images of the Sq response functions obtained via the Schmucker’s ρ* — z* procedure show a good fit with results of other induction studies, though especially our global impedance phases show a larger scatter than two other published data sets used for comparison.     

Effect of some climatic parameters on tropospheric and total ozone column over Alipore (22.52 ∘ N, 88.33 ∘ E), India

The paper presents the nature of variations of tropospheric and total ozone column retrieved from the Convective Cloud Differential (CCD) technique, Ozone Monitoring Instrument (OMI), and Total Ozone Mapping Spectrometer (TOMS) data, National Aeronautics and Space Administrations (NASA), USA, respectively; surface temperature, relative humidity, total rainfall, ozone precursors (non-methane hydrocarbon, carbon monoxide, nitrogen dioxide, and sulphur dioxide) that are collected from India Meteorological Department (IMD), Alipore, Kolkata; solar insolation obtained from Solar Geophysical Data Book and El-Niño index collected from National Climatic Data Center, US Department of Commerce, National Oceanic and Atmospheric Administration, USA. The effect of these climatic parameters and ozone precursors on ozone variations is critically analyzed and explained on the basis of linear regression and correlation. It has been observed that the maximum, minimum and mean temperature, relative humidity, solar insolation, tropospheric, and total ozone column (TOC) showed slight increasing tendencies from October 2004 to December 2011, while total rainfall and El-Niño index showed little decreasing tendencies for the same period. Amongst selected climatic parameters and ozone precursors, the solar insolation and the average temperature had a significant influence on both, the tropospheric ozone and total ozone column formation. The solar insolation had contributed more in tropospheric ozone than in total ozone column; while El-Niño index had played a more significant role in total ozone column build up than in tropospheric ozone. Negative correlation was observed between almost all ozone precursors with the tropospheric and total ozone. The tropospheric ozone and total ozone column were also significantly correlated. The level of significance and contribution of different climatic parameters are determined from correlation technique and Multiple Linear Regression (MLR) method. The related chemical kinetics for ozone production processes has been critically described.     

Aridity indices to assess desertification susceptibility: a methodological approach using gridded climate data and cartographic modeling

Natural Hazards - Desertification is a land degradation phenomenon with dire and irreversible consequences, affecting different regions of the world. Assessment of spatial climate susceptibility to...     

Solid solutions in the system acanthite (Ag<Subscript>2</Subscript>S)–naumannite (Ag<Subscript>2</Subscript>Se) and the relationships between Ag-sulfoselenides and Se-bearing polybasite from the Kongsberg silver district,Norway, with implications for sulfur–selenium fractionation

Sulfoselenides [Ag₂(S,Se)] and Se-bearing polybasite have been discovered at the Kongsberg silver district. The selenium-bearing minerals occur in two samples from the northern part of the district, forming either single or polyphase inclusions together with chalcopyrite within native silver. The Ag-sulfoselenides show large chemical variations, covering nearly the complete compositional range between acanthite (Ag₂S) and naumannite (Ag₂Se). For the data presented here, there is no local maximum at the composition Ag₄SSe attributed to the distinct phase called aguilarite, suggesting that this composition can be considered as one of many possible along the monoclinic Ag₂S–Ag₂S_0.4Se_0.6 solid solution series rather than a specific mineral phase. We present a model explaining the variations in the Se-content of Ag₂(S,Se) as a result of gradual de-sulfidization of the rock under oxidizing conditions. During this process, sulfur from the Ag₂S-component of Ag₂(S,Se) oxidized and dissolved in the fluid phase as SO₄^2?, resulting in the formation of native silver. The activity ratio \({a_{{{\text{S}}^{2 - }}}}/{a_{{\text{S}}{{\text{e}}^{2 - }}}}\) of the system gradually decreased due to the removal of SO₄^2?, which resulted in the stabilization of a sulfoselenide with higher selenium content. As a result of reaction progress, grains of Ag₂(S,Se) became gradually enclosed in newly formed native silver, and therefore isolated from further reactions with the grain-boundary fluid. Grains isolated early during the process show low content of Se reflecting high \({a_{{{\text{S}}^{2 - }}}}/{a_{{\text{S}}{{\text{e}}^{2 - }}}}\) of the equilibrium fluid, while grains showing high Se reflect the composition of late low \({a_{{{\text{S}}^{2 - }}}}/{a_{{\text{S}}{{\text{e}}^{2 - }}}}\) fluids. Analyses of Se-bearing polybasite show that selenium is preferentially partitioned into Ag₂(S,Se) compared to polybasite. The model presented here demonstrates how oxidation of sulfoselenides leads to fractionation of sulfur and selenium.     

A laboratory study of the pollution of formaldehyde in cemeteries (South Africa)

Cemeteries are known to be associated with soil and groundwater pollution from contaminants in coffin materials. However, possible contamination from embalming fluids such as formaldehyde has not been investigated. Formaldehyde is a recognised carcinogen, which is primarily toxic after inhalation, skin contact or ingestion. Although it is maintained that formaldehyde breaks down into innocuous compounds, this has not been established at sites such as cemeteries where there is a continuous addition of formaldehyde-preserved bodies, sometimes on a daily basis. It is also not confirmed whether different soil types and environmental conditions affect the leaching of formaldehyde into groundwater resources. This study comprises a laboratory study of the leaching potential of formaldehyde through different soils and environmental conditions. Twenty-seven containers with taps were filled with either sandy, silty or clayey soils. Samples of burial materials and a cloth saturated with formalin were buried within each column. These were exposed to conditions simulating that of the environment, i.e. (1) different temperatures, (2) heavy or prolonged rainfall and (3) using either acidic or slightly acid water. Leachate samples were collected every 2 weeks for a period of 24 weeks and analysed for formaldehyde using acid titration. The results showed that most formaldehyde percolated through the soil between week 6 and week 14 of interment, with a greater amount being leached from sand. Neither temperature nor pH affected the amount of formaldehyde leached; however, conditions simulating heavy rainfall facilitated leaching. Although a total of only 3% of the initial amount of formaldehyde mobilised, concentrations of up to 15 mg/L formaldehyde were recorded on two occasions, exceeding the tolerable concentration recommended by the World Health Organisation.