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71.
Sources of sedimentary PAHs in tropical Asian waters: Differentiation between pyrogenic and petrogenic sources by alkyl homolog abundance 总被引:2,自引:0,他引:2
Mahua Saha Kaoruko Mizukawa Hideshige Takada Mohamad P. Zakaria Bui Cach Tuyen Ruchaya Boonyatumanond Badal Bhattacharya Touch Seang Tana 《Marine pollution bulletin》2009,58(2):189-200
We collected surface sediment samples from 174 locations in India, Indonesia, Malaysia, Thailand, Vietnam, Cambodia, Laos, and the Philippines and analyzed them for polycyclic aromatic hydrocarbons (PAHs) and hopanes. PAHs were widely distributed in the sediments, with comparatively higher concentrations in urban areas (∑PAHs: ∼1000 to ∼100 000 ng/g-dry) than in rural areas (∼10 to ∼100 g-dry), indicating large sources of PAHs in urban areas. To distinguish petrogenic and pyrogenic sources of PAHs, we calculated the ratios of alkyl PAHs to parent PAHs: methylphenanthrenes to phenanthrene (MP/P), methylpyrenes + methylfluoranthenes to pyrene + fluoranthene (MPy/Py), and methylchrysenes + methylbenz[a]anthracenes to chrysene + benz[a]anthracene (MC/C). Analysis of source materials (crude oil, automobile exhaust, and coal and wood combustion products) gave thresholds of MP/P = 0.4, MPy/Py = 0.5, and MC/C = 1.0 for exclusive combustion origin. All the combustion product samples had the ratios of alkyl PAHs to parent PAHs below these threshold values. Contributions of petrogenic and pyrogenic sources to the sedimentary PAHs were uneven among the homologs: the phenanthrene series had a greater petrogenic contribution, whereas the chrysene series had a greater pyrogenic contribution. All the Indian sediments showed a strong pyrogenic signature with MP/P ≈ 0.5, MPy/Py ≈ 0.1, and MC/C ≈ 0.2, together with depletion of hopanes indicating intensive inputs of combustion products of coal and/or wood, probably due to the heavy dependence on these fuels as sources of energy. In contrast, sedimentary PAHs from all other tropical Asian cities were abundant in alkylated PAHs with MP/P ≈ 1-4, MPy/Py ≈ 0.3-1, and MC/C ≈ 0.2-1.0, suggesting a ubiquitous input of petrogenic PAHs. Petrogenic contributions to PAH homologs varied among the countries: largest in Malaysia whereas inferior in Laos. The higher abundance of alkylated PAHs together with constant hopane profiles suggests widespread inputs of automobile-derived petrogenic PAHs to Asian waters. 相似文献
72.
The granulites and granitoids around Rayagada in the north central part of the Eastern Ghats belt display structural and petrological
differences when compared to similar rocks from Chilka and Jenapore in the northern Eastern Ghats. The impress of F1 deformation is almost erased while that ofF
3 is muted. The metapelites have a restricted chemical range and are non-migmatitic. There are two varieties of leptynitic
granitoids, one of which is interlayered with yet another S-type granite containing cordierite. The maximum recorded temperature
from geothermometers is 780‡C, but the magnitude of pressure is comparatively low, the highest value being 6.3 kbar. Another
distinctive feature of the pressuretemperature record is the absence of evidence of decompression in the lower realms of pressure
and temperature. Metamorphic reactions that could be identified indicate cooling, a noteworthy reaction being the sillimanite
to andalusite transformation. Integration of data from pressure-temperature sensors suggest cooling at two pressures, 6 and
5 kbar. The generation of two types of granitoids from metapelites is interpreted to be due to intersection with solidus curves
for pelitic and graywacke-like compositions, constrained by recent experiments, at 6 and 5 kbar. The first melting occurred
on a prograde path while the second one was due to increase in temperature during exhumation at tectonic rates.
Thus inspite of a broad similarity in the geodynamic scenario across the northern part of the Eastern Ghat belt, differences
in exhumation rates and in style of melting were responsible for producing different signatures in the Rayagada granulite
terrane. 相似文献
73.
Geochemistry and mineralogy of shallow alluvial aquifers in Daudkandi upazila in the Meghna flood plain, Bangladesh 总被引:1,自引:0,他引:1
M. Aziz Hasan Mattias von Br?mssen Prosun Bhattacharya Kazi Matin Ahmed Arif Mohiuddin Sikder Gunnar Jacks Ondra Sracek 《Environmental Geology》2009,57(3):499-511
The shallow alluvial aquifers of the delta plains and flood plains of Bangladesh, comprises about 70% of total land area are
mostly affected by elevated concentrations of arsenic (As) in groundwater exposing a population of more than 35 million to
As toxicity. Geochemical studies of shallow alluvial aquifer in the Meghna flood plain show that the uppermost yellowish grey
sediment is low in As (1.03 mg/kg) compared to the lower dark grey to black sediment (5.24 mg/kg) rich in mica and organic
matter. Sequential extraction data show that solid phase As bound to poorly crystalline and amorphous metal (Fe, Mn, Al)-oxyhydroxides
is dominant in the grey to dark grey sediment and reaches its maximum level (3.05 mg/kg) in the mica rich layers. Amount of
As bound to sulphides and organic matter also peaks in the dark grey to black sediment. Vertical distributions of major elements
determined by X-ray fluorescence (XRF) show that iron (Fe2O3), aluminum (Al2O3) and manganese (MnO) follow the general trend of distribution of As in the sediments. Concentrations of As, Mn, Fe, HCO3
−, SO4
2− and NO3
− in groundwater reflect the redox status of the aquifer and are consistent with solid phase geochemistry. Mineralogical analysis
by X-ray diffraction (XRD) and scanning electron microscopy (SEM) fitted with energy dispersive X-ray spectrometer (EDS) revealed
dominance of crystalline iron oxides and hydroxides like magnetite, hematite and goethite in the oxidised yellowish grey sediment.
Amorphous Fe-oxyhydroxides identified as grain coating in the mica and organic matter rich sediment suggests weathering of
biotite is playing a critical role as the source of Fe(III)-oxyhydroxides which in turn act as sink for As. Presence of authigenic
pyrite in the dark grey sediment indicates active reduction in the aquifer. 相似文献
74.
An accurate numerical survey of the density profiles corresponding to the crusts of neutron stars for representative equation
of state models is presented. This will find application in calculations of thermal and magnetic evolution of neutron stars. 相似文献
75.
Oxygen and carbon isotopes were measured to a high depth resolution in a nannoplankton carbonate sequence spanning the Cretaceous-Tertiary boundary at Koshak Hill, Mangyshlak Peninsula, Kazakhstan. The boundary is characterized by the presence of a ∼ 1 cm thick clay layer having a sharp peak in iridium concentration with a maximum value of 3.7 ng g-1 . The δ18 O data reveal rapid (∼103 years) excursion of sea-surface temperature at the boundary where an initial cold pulse is followed by a persistent warm period. The δ13 C data, in contrast, indicate only a gradual change in productivity across the boundary. The observations suggest a biogeochemical scenario for the boundary event pertaining to shallow epicontinental seas. 相似文献
76.
Garnet-sillimanite gneisses, locally known as khondalites, occur abundantly in the Chilka Lake granulite terrane belonging
to the Eastern Ghats Proterozoic belt of India. Though their chemistry has been modified by partial melting, it is evident
that the majority of these rocks are metapelitic, with some tending to be metapsammitic. Five petrographically distinct groups
are present within the khondalites of which the most abundant group is characteristically low in Mg:Fe ratios — the main chemical
discriminant separating the five groups. The variations in Mg:Fe ratios of the garnets, biotites, cordierites, orthopyroxenes
and spinels from the metapelites are compatible with those in the bulk rocks.
A suite of granitoids containing garnet, K-feldspar, plagioclase and quartz, commonly referred to as leptynites in Indian
granulite terranes, are interlayered with khondalites on the scale of exposures; in a few spots, the intercalated layers are
thin. The peraluminous character of the leptynites and presence of sillimanite trails within garnets in some of them suggest
derivation of leptynites by partial melting of khondalites. Here we examine this connection in the light of results derived
from dehydration melting experiments of micas in pelitic and psammitic rocks.
The plots of leptynites of different chemical compositions in a (MgO + FeO)-Na2O-K2O projection match the composition of liquids derived by biotite and muscovite dehydration melting, when corrected for co-products
of melting reactions constrained by mass balance and modal considerations. The melt components of the leptynites describe
four clusters in the M-N-K diagram. One of them matches melts produced dominantly by muscovite dehydration melting, while
three clusters correspond to melting of biotite. The relative disposition of the clusters suggests two trends, which can be
correlated with different paths that pelitic and psammitic protoliths are expected to generate during dehydration melting.
Thus the leptynites evidently represent granitoids which were produced by dehydration melting in metapelites of different
compositions.
The contents of Ti, Y, Nb, Zr and Th in several leptynites indicate departures from equilibrium melt compositions, and entrainment
of restites is considered to be the main causative factor. Disequilibrium in terms of major elements is illustrated by leucosomes
within migmatites developed in a group of metapelites. But the discrete leptynites that have been compared with experimental
melts approach equilibrium melt compositions closely. 相似文献
77.
78.
79.
S. N. Bhattacharya 《Pure and Applied Geophysics》1996,147(3):497-514
Love waves recorded by a long-period seismograph at New Delhi (NDI) from seven earthquakes of magnitude 4.3 to 5.2 in Koyna and Bhatsa on the western coast and one earthquake in Ongole on the eastern coast of the Indian Peninsula have been used to determine the seismic moment for each of the earthquakes by waveform modeling. Transverse component of the synthetic seismogram shows that the maximum amplitude of waveform decreases with an increase of source duration. Thus for an evaluation of the seismic moment by equating the amplitude level of the observed and synthetic waveforms, we must know the source duration. The synthetic seismogram also indicates that a short source duration gives rise to a small but sharp pulse and this pulse is interpreted as anLg wave. Comparison of the observed and synthetic waveforms has been used for a simultaneous evaluation of the source duration and seismic moment. The source durations are found to vary between 2.2 and 4.4 s; for earthquakes with a magnitude range between 4.3 and 5.2 these durations are slightly higher than normal. We obtain moment (M
0) of Ongole earthquake (M
L
=5.1)as 1.7×1024 dyne-cm; moments of Koyna and Bhatsa earthquakes (4.3M
L
5.2) on the western coast lie between 0.7×1023 and 3.6×1023 dyne-cm. Moment (M
0)-magnitude (M
L
) relation logM
0=1.5M
L
+16.0 for the western United States region agrees as well, in general, with the results for the earthquakes in the Indian Peninsula. 相似文献
80.
The massif-type anorthosite complex at Bolangir in the northern part of the Eastern Ghats belt occurs in a milieu of predominantly
supracrustal granulite-grade rocks. The massif is separated from the host gneisses by coarse-grained garnetiferous granitoid
gneisses which are interpreted as coeval crustallyderived melts. Melanocratic ferrodiorite rocks occur at the immediate contact
with the anorthosite massif which they intrude in cross-cutting dikes and sheets. The emplacement age of the anorthosite diapir
and the associated igneous suites is deemed to be pre-D2. Recrystallization of the igneous assemblages of the ferrodiorite suite (750–800°C, 7–8kbar,
) during a period of near-isobaric cooling from the igneous crystallization stage to the regionalP-T regime led to extensive development of coronitic garnet at the interface of plagioclase phenocrysts with the mafic matrix
assemblage (opx + fay + cpx + ilm ± amph, bio). Abundant accessory phases are zircon, apatite and thorite. The mafic phases
have extremely ferrous compositions (XFe gar: 0.93-0.87, fay: 0.90-0.87, opx: 0.80-0.60, cpx: 0.70-0.47, amph: 0.81-0.71) reflecting the low Mg-number (16-8) of the
rocks. Compared to worldwide occurrences of similar rocks, the Bolangir ferrodiorites (SiO2 36–58 wt.%, FeO*: 39-10 wt.%) are characterized by exceptionally high concentrations of HFSE and REE (TiO2: 4.8-1.0 wt.%, P2O5: 1.7-0.5 wt.%, Zr: 5900-1300 ppm, Y: 240-80 ppm, La: 540-100 ppm, Ce: 1100-200 ppm, Yb: 22-10 ppm, Th: 195-65 ppm). Well
defined linear variation trends for major and trace elements reflect progressive plagioclase accumulation towards the felsic
members of the suite. The ferrodiorites are interpreted to represent residual liquids of anorthosite crystallization which
after segregation and extraction from the ascending diapir became enriched in HFSE and REE through selective assimilation
of accessory phases (zircon, monazite, apatite) from crustal felsic melts. Ferromonzodioritic rock presumably formed through
hybridization between the ferrodiorite and overlying felsic melts. 相似文献