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1.
Dynamics of transparent exopolymeric particles (TEP) and particle-associated carbohydrates in the Dona Paula bay, west coast of India 总被引:1,自引:0,他引:1
Surface seawater samples were collected over a period of 27 months at a shallow water station in Dona Paula bay from 1998–2000.
The samples were analyzed to assess the seasonal variations, inter-annual variability and the contributions of:
A distinct inter-annual variability was observed with an increase in the bacterial abundance, chlorophylla (Chl a), TEP and Sal-PCHO and their greater contribution to particulate organic carbon during May 1998–1999 than in June
1999–July 2000. Overall, there was no statistically significant correlation of TEP with phytoplankton biomass (Chl a), Sal-PCHO,
CPCHO and hydrodynamic conditions. A weak inverse correlation was observed between TEP and TBA (r = −0.397;p < 0.05) but the role of TEP as a C-source for bacteria was not evident. Both Sal-PCHO and CPCHO appeared to be two distinct
forms of carbohydrates. Unlike CPCHO, Sal-PCHO concentrations showed a positive trend with Chla and significant linear correlation with bacterial abundance (r = 0.44,p < 0.007,n = 48), indicating that Sal-PCHO as carbon source might have supported bacterioplankton abundance. The mean %TEP-C contribution
to the annual average organic carbon for 1998–2000 was 6.9% ± 5.8%, next only to phytoplankton-C (33.1 ± 22.1%) and greater
than bacterial-C (4.6% ± 4.6%) or carbohydrate-C (< 3.8%). Despite its greater contribution to the organic carbon pool, the
contribution of TEP-C to the benthic carbon demand and its fate in the study area could not be ascertained in this study. 相似文献
– | •transparent exopolymeric particles (TEP) concentration, |
– | •two forms of particle-associated carbohydrates — 1.5 M NaCl/saline extracted (Sal-PCHO) and 10 mM EDTA-extracted (CPCHO) and |
– | •total bacterial abundance (TBA) to particulate organic carbon pool. |
2.
Radiocarbon analyses were carried out in the annual bands of a 40 year old coral collected from the Gulf of Kutch (22.6°N,
70°E) in the northern Arabian Sea and in the annual rings of a teak tree from Thane (19°14′N, 73°24′E) near Bombay. These
measurements were made in order to obtain the rates of air-sea exchange of CO2 and the advective mixing of water in the Gulf of Kutch. The Δ14C peak in the Thane tree occurs in the year 1964, with a value of ∼630‰, significantly lower than that of the mean atmospheric
Δ14C of the northern hemisphere (∼ 1000‰). The radiocarbon time series of the coral was modelled considering the supply of carbon
and radiocarbon to the gulf through air-sea exchange and advective water transport from the open Arabian Sea. A reasonable
fit for the coral data was obtained with an air-sea CO2 exchange rate of 11–12 mol m−2 yr−1, and an advective velocity of 28 m yr−1 between the Arabian Sea and the Gulf of Kutch; this was based on a model generated time series for radiocarbon in the Arabian
Sea. The deduced velocity (∼ 28 m yr−1) of the advective transport of water between the gulf and the Arabian Sea is much lower than the surface tidal current velocity
in this region, but can be understood in terms of net fluxes of carbon and radiocarbon to the gulf to match the observed coral
Δ14C time series. 相似文献
3.
Vertical and temporal variations in the activities of234Th,210Po and210Pb have been measured, in both dissolved and paniculate phases, at several stations in the eastern Arabian Sea and north-central
Bay of Bengal. A comparative study allows us to make inferences about the particle associated scavenging processes in these
two seas having distinct biogeochemical properties.
A common feature of the234Th profiles, in the Arabian Sea and Bay of Bengal, is that the dissolved as well as total (dissolved + particulate) activity
of234Th is deficient in the surface 200 m with respect to its parent,238U. This gross deficiency is attributed to the preferential removal of234Th by adsorption onto settling particles which account for its net loss from the surface waters. The scavenging rates of dissolved234Th are comparable in these two basins. The temporal variations in the234Th-238U disequilibrium are significantly pronounced both in the Arabian Sea and Bay of Bengal indicating that the scavenging rates
are more influenced by the increased abundance of particles rather than their chemical make-up. In the mixed layer (0–50 m),
the scavenging residence time of234Th ranges from 30 to 100 days.
The surface and deep waters of both the seas show an enhanced deficiency of dissolved210Po relative to210Pb and that of210Pb relative to226Ra. The deficiencies of both210Po and210Pb in the dissolved phases are not balanced by their abundance in the particulate form indicating a net loss of both these
nuclides from the water column. The scavenging rates of210Po and210Pb are significantly enhanced in the Bay of Bengal compared to those in the Arabian Sea. The mean dissolved210Po/210Pb and210Pb/226Ra activity ratios in deep waters of the Bay of Bengal are ∼ 0.7 and 0.1, respectively, representing some of the most pronounced
disequilibria observed to date in the deep sea. The Bay of Bengal and the Arabian Sea appear to be the regions of most intense
particle moderated scavenging processes in the world oceans. This is evidenced by the gross disequilibria exhibited by the
three isotope pairs used in this study. 相似文献
4.
Biogeochemistry of the Russian Arctic. Kara Sea: Research results under the SIRRO project, 1995–2003
E. M. Galimov L. A. Kodina O. V. Stepanets G. S. Korobeinik 《Geochemistry International》2006,44(11):1053-1104
The Kara Sea is an area uniquely suitable for studying processes in the river-sea system. This is a shallow sea into which
two great Siberian rivers, Yenisei and Ob, flow. From 1995 to 2003, the sea was studied by six international expeditions aboard
the R/V Akademik Boris Petrov. This publication summarizes the results obtained, within the framework of this project, at the Vernadsky Institute of Geochemistry
and Analytical Chemistry, Russian Academy of Sciences. Various hydrogeochemical parameters, concentrations and isotopic composition
of organic and carbonate carbon of the sediments, plankton, particulate organic matter, hydrocarbons, and dissolved CO2 were examined throughout the whole sea area at more than 200 sites. The δ13C varies from −22 and −24‰ where Atlantic waters enter the Kara Sea and in the North-eastern part of the water area to −27‰
in the Yenisei and Ob estuaries. The value of δ13C of the plankton is only weakly correlated with the δ13C of the organic matter from the sediments and is lower by as much as 3–4‰. The paper presents the results obtained from a
number of meridional river-sea profiles. It was determined from the relations between the isotopic compositions of plankton
and particulate matter that the riverwaters carry material consisting of 70% detrital-humus matter and 30% planktonogenic
material in the river part, and the material contained in the off-shore waters consists of 30% terrigenous components, with
the contribution of bioproducers amounting to 70%. The carbon isotopic composition of the plankton ranges from −29 to −35‰
in the riverine part, from −28 to −27‰ in the estuaries, and from −27.0 to −25% in the marine part. The relative lightness
of the carbon isotopic composition of plankton in Arctic waters is explained by the temperature effect, elevated CO2 concentrations, and long-distance CO2 supply to the sea with riverwaters. The data obtained on the isotopic composition of CO2 in the surface waters of the Kara Sea were used to map the distribution of δ13CCO
2. The complex of hydrocarbon gases extracted from the waters included methane, C2–C5, and unsaturated C2=–C4= hydrocarbons, for which variations in the concentrations in the waters were studied along river-estuary-sea profiles. The
geochemistry of hydrocarbon gases in surface fresh waters is characterized by comparable concentrations of methane (0.3–5
μl/l) and heavier hydrocarbons, including unsaturated ones. Microbiological methane with δ13C from −105 to −90‰ first occurs in the sediments at depths of 40–200 cm. The sediments practically everywhere display traces
of methane oxidation in the form of a shift of the δ13C of methane toward higher values and the occurrence of autogenic carbonate material, including ikaite, enriched in the light
isotope. Ikaite (δ13C from −25 to −60‰) was found and examined in several profiles. The redox conditions in the sediments varied from normal in
the southern part of the sea to highly oxidized along the Novaya Zemlya Trough. Vertical sections through the sediments of
the latter exemplify the complete suppression of the biochemical activity of microorganisms. Our data provide insight into
the biogeochemistry of the Kara Sea and make it possible to specify the background values needed for ecological control during
the future exploration operations and extraction of hydrocarbons in the Kara Sea.
Original Russian Text ? E.M. Galimov, L.A. Kodina, O.V. Stepanets, G.S. Korobeinik, 2006, published in Geokhimiya, 2006, No.
11, pp. 1139–1191. 相似文献
5.
V. V. S. S. Sarma 《Journal of Earth System Science》2006,115(4):433-450
Data on ocean color chlorophylla (Chl a) obtained using Sea-viewing Wide Field of view Sensor (SeaWiFS), sea surface temperature (SST) by Advanced Very High
Resolution Radiometer (AVHRR), and sea surface height (SSH) by TOPEX/POSEIDON were analyzed to examine the influence of Indian
Ocean Dipole (IOD) on the physical and biogeochemical processes with special reference to phytoplankton primary production
and air-sea fluxes of carbon dioxide in the Arabian Sea. Positive SST anomalies (SSTA) were found in the Arabian Sea (0.4
to 1.8°C) with higher values in the southwestern Arabian Sea that decreased towards north. The SSH anomalies (SSHA) and turbulent
kinetic energy anomalies (TKEA) suggest decreased mixing during the IOD compared to the normal period. Chlorophylla displayed significant negative correlations with SSTA and SSHA in the Arabian Sea. Consistently, Chla showed negative anomalies (low Chl a) during the IOD period which could be due to reduced inputs of nutrients. The photic
zone integrated primary production decreased by 30% during the IOD period compared to the normal whereas pCO2 levels were higher (by 10–20μatm). However, sea to air fluxes were lower by 10% during the IOD period due to prevailing weaker
winds. Primary production seems to be the key process controlling the surface pCO2 levels in the Arabian Sea. In future, the influence of IOD on ecosystem structure, export production and bacterial respiration
rates are to be probed throughin situ time-series observations. 相似文献
6.
S. S. C. Shenoi D. Shankar G. S. Michael J. Kurian K. K. Varma M. R. Ramesh Kumar A. M. Almeida A. S. Unnikrishnan W. Fernandes N. Barreto C. Gnanaseelan R. Mathew K. V. Praju V. Mahale 《Journal of Earth System Science》2005,114(5):475-491
This paper describes the hydrographic observations in the southeastern Arabian Sea (SEAS) during two cruises carried out in
March–June 2003 as part of the Arabian Sea Monsoon Experiment. The surface hydrography during March–April was dominated by
the intrusion of low-salinity waters from the south; during May–June, the low-salinity waters were beginning to be replaced
by the highsalinity waters from the north. There was considerable mixing at the bottom of the surface mixed layer, leading
to interleaving of low-salinity and high-salinity layers. The flow paths constructed following the spatial patterns of salinity
along the sections mimic those inferred from numerical models. Time-series measurements showed the presence of Persian Gulf
and Red Sea Waters in the SEAS to be intermittent during both cruises: they appeared and disappeared during both the fortnight-long
time series. 相似文献
7.
Lina P. Mergulhao Rahul Mohan V. S. N. Murty M. V. S. Guptha D. K. Sinha 《Journal of Earth System Science》2006,115(4):415-428
Sediment trap samples collected from a depth of 1018 m in the Central Arabian Sea Trap (CAST) at 14°28.2′N, 64°35.8′E were
analyzed for temporal variation of coccolithophore fluxes from October 1993 to August 1994. Out of the twenty species of coccolithophores
encountered,Gephyrocapsa oceanica, Emiliania huxleyi, Umbilicosphaera sibogae andUmbellosphaera irregularis were the most abundant. The total coccolithophore fluxes ranged from 28.5 × 106m-2d-1 to 50.3 × 106m-2d-1 showing seasonality with higher fluxes during the northeast (NE) monsoon and lower fluxes during the spring intermonsoon.
The higher fluxes were attributed to the enhancement of primary production in the central Arabian Sea due to southward extent
of nutrients from the northeast Arabian Sea by the prevailing surface currents. Similarly, the occurrences of relatively lower
coccolithophore fluxes during the spring intermonsoon and southwest (SW) monsoon were attributed to the low nutrients in the
warm, shallow surface mixed layer and downwelling to the south of Findlater Jet respectively in the central Arabian Sea. Some
of the coccolithophore species such asE. huxleyi, G. oceanica, Calcidiscus leptoporus andUmbellosphaera tenuis showed signs of dissolution. 相似文献
8.
V. V. S. S. Sarma M. Dileep Kumar M. Gauns M. Madhupratap 《Journal of Earth System Science》2000,109(4):471-479
The variability in partial pressure of carbon dioxide (pCO2) and its control by biological and physical processes in the mixed layer (ML) of the central and eastern Arabian Sea during
inter-monsoon, northeast monsoon, and southwest monsoon seasons were studied. The ML varied from 80–120 m during NE monsoon,
60–80 m and 20–30 m during SW- and inter-monsoon seasons, respectively, and the variability resulted from different physical
processes. Significant seasonal variability was found in pCO2 levels. During SW monsoon, coastal waters contain two contrasting regimes; (a) pCO2 levels of 520–685 μatm were observed in the SW coast of India, the highest found so far from this region, driven by intense
upwelling and (b) low levels of pCO2 (266 μatm) were found associated with monsoonal fresh water influx. It varied in ranges of 416–527 μatm and 375–446 μatm
during inter- and NE monsoon, respectively, in coastal waters with higher values occurring in the north. The central Arabian
Sea pCO2 levels were 351–433, 379–475 and 385–432 μatm during NE-inter and SW monsoon seasons, respectively. The mixed layer pCO2 relations with temperature, oxygen, chlorophylla and primary production revealed that the former is largely regulated by physical processes during SW- and NE monsoon whereas
both physical and biological processes are important in inter-monsoon. Application of Louanchiet al (1996) model revealed that the mixing effect is the dominant during monsoons, however, the biological effect is equally significant
during SW monsoon whereas thermodynamics and fluxes influence during inter-monsoons. 相似文献
9.
S. W. A. Naqvi 《Journal of Earth System Science》1994,103(2):279-300
Recent information on some consequences of the acute mid-water oxygen deficiency in the Arabian Sea, especially on carbon-nitrogen
cycling, is reviewed. An evaluation of published estimates of water column denitrification rate suggests an overall rate in
the vicinity of 30Tg Ny-1, but the extent of benthic contribution remains unknown. A decoupling of denitrification from primary production, unique
to the Arabian Sea, is revealed by nitrite, electron transport system (ETS) activity and bacterial production data. Results
of both enzymatic and microbiological investigations strongly point to a major role of organic carbon other than that sinking
from surface layers in supporting denitrification. Although denitrification is associated with an intermediate nepheloid layer,
it seems unlikely that the excess carbon comes with particles re-suspended along the continental margins and transported quasi-horizontally
into the ocean interior; instead, the particle maximum may directly reflect a higher bacterial abundance. It is proposed that
denitrification may be predominantly fuelled by the dissolved organic matter. 相似文献
10.
T. M. Balakrishnan Nair 《Journal of Earth System Science》2006,115(4):461-472
Particulate fluxes of aluminium, iron, magnesium and titanium were measured using six time-series sediment traps deployed
in the eastern, central and western Arabian Sea. Annual Al fluxes at shallow and deep trap depths were 0.47 and 0.46 g m-2 in the western Arabian Sea, and 0.33 and 0.47 g m-2 in the eastern Arabian Sea. There is a difference of about 0.9–1.8 g m-2y-1 in the lithogenic fluxes determined analytically (residue remaining after leaching out all biogenic particles) and estimated
from the Al fluxes in the western Arabian Sea. This arises due to higher fluxes of Mg (as dolomite) in the western Arabian
Sea (6–11 times higher than the eastern Arabian Sea). The estimated dolomite fluxes at the western Arabian Sea site range
from 0.9 to 1.35gm-2y-1. Fe fluxes in the Arabian Sea were less than that of the reported atmospheric fluxes without any evidence for the presence
of labile fraction/excess of Fe in the settling particles. More than 75% of Al, Fe, Ti and Mg fluxes occurred during the southwest
(SW) monsoon in the western Arabian Sea. In the eastern Arabian Sea, peak Al, Fe, Mg and Ti fluxes were recorded during both
the northeast (NE) and SW monsoons. During the SW monsoon, there exists a time lag of around one month between the increases
in lithogenic and dolomite fluxes. Total lithogenic fluxes increase when the southern branch of dust bearing northwesterlies
is dragged by the SW monsoon winds to the trap locations. However, the dolomite fluxes increase only when the northern branch
of the northwesterlies (which carries a huge amount of dolomite accounting 60% of the total dust load) is dragged, from further
north, by SW monsoon winds. The potential for the use of Mg/Fe ratio as a paleo-monsoonal proxy is examined. 相似文献
11.
S. K. Sasamal 《Journal of Earth System Science》1990,99(3):367-381
Bay of Bengal is well known for less saline waters in the surface layer of northern Indian Ocean. High saline waters of the
Bay are considered as an influx from the Arabian Sea within a depth range of 200 to 900 m. Some of the recent observations
in the western Bay of Bengal have shown salinity values higher than those reported earlier (35-2 × 10−3). Such values are explained on the basis of regional climatology suggesting their local formation on the shallow continental
shelf during pre-monsoon months and their subsequent distribution along the coast. 相似文献
12.
Bruce A. Warren 《Journal of Earth System Science》1994,103(2):301-314
The setting of the Arabian Sea is reviewed in order to examine which of the circumstances causing large oxygen depletion in
the ocean are responsible for the suboxic layer (concentrations < 0.1 ml 1−1) in the northern thermocline there. The wind field forces circulations that restrict but do not exclude exchange with the
south, and a recent box-model interpretation of trichlorofluoromethane measurements indicates a modest throughflow for the
layer of about 5 × 106m3s
−1.The associated oxygen-flux divergence is roughly consistent with biochemical determinations of local oxygen-consumption rates,
both approaches giving values (3–6 pl 1−1 sτ-1) that are modest in comparison with estimates elsewhere in the world ocean. Despite the high mean-annual surface productivity
in the region (nearly 1gCm−2 day−1), it seems plausible that too little of this particulate matter is consumed at thermocline depths to cause an inflated oxygen
demand there. Since the layer is neither an isolated pool, nor a sluggish backwater, nor a conspicuous oxygen sink, the suboxic
concentrations must be due (as earlier proposed) to the low concentration in the water entering the layer from the south.
That depletion in turn seems due to moderate consumption as the water travels the very long trajectories from its zone of
sea-surface renewal (Lats. 40–50°S). Although large seasonal variations are expected in both throughflow volume transport
and surface productivity (suggesting comparable changes in consumption rate), the volume of the suboxic layer seems big enough
to buffer the oxygen levels there against any very noticeable overall variability. 相似文献
13.
Stable Carbon Isotope Biogeochemistry and Anthropogenic Impacts on Karst Ground Water, Zunyi, Southwest China 总被引:2,自引:0,他引:2
Si-Liang Li Cong-Qiang Liu Yun-Chao Lang Faxiang Tao Zhiqi Zhao Zhihua Zhou 《Aquatic Geochemistry》2008,14(3):211-221
Natural and anthropogenic impacts on karst ground water, Zunyi, Southwest China, are discussed using the stable isotope composition
of dissolved inorganic carbon and particulate organic carbon, together with carbon species contents and water chemistry. The
waters can be mainly characterized as HCO3–Ca type, HCO3 · SO4–Ca type, or HCO3 · SO4–Ca · Mg type, according to mass balance considerations. It is found that the average δ13CDIC values of ground waters are higher in winter (low-flow season) than in summer (high-flow season). Lower contents of dissolved
inorganic carbon (DIC) and lower values of δ13CDIC in summer than in winter, indicate that local rain events in summer and a longer residence time of water in winter play an
important role in the evolution of ground water carbon in karst flow systems; therefore, soil CO2 makes a larger contribution to the DIC in summer than in winter. The range of δ13CDIC values indicate that dissolved inorganic carbon is mainly controlled by the rate of carbonate dissolution. The concentrations
of dissolved organic carbon and particulate organic carbon in most ground water samples are lower than 2.0 mg C L−1 and 0.5 mg C L−1, respectively, but some waters have slightly higher contents of organic carbon. The waters with high organic carbon contents
are generally located in the urban area where lower δ13CDIC values suggest that urbanization has had an effect on the ground water biogeochemistry and might threaten the water quality. 相似文献
14.
Recent sedimentary records from the Arabian Sea 总被引:1,自引:0,他引:1
An attempt is made to understand the redox conditions that prevailed in the north eastern continental margins of the Arabian
Sea and in the nearby deep water regions during the past few centuries using short undisturbed sediment cores. The geochronology
is accomplished using210Pb excess method and the proxy indicators chosen for productivity and associated redox changes are CaCO3, organic matter (OM), Mn and U along with major elements Fe and Al. Such changes in principle are related to high productivity
in the overlying waters which in turn depend on monsoonal intensity that causes upwelling responsible for increase in productivity.
Alongwith the published data on gravity cores from the same region, our measurements suggest the following:
At ∼ 300 m water depth, south of 21°N, the sediment-water interface at depths of ∼ 300 m had been anoxic during the time span
represented by the presently studied cores for approximately ∼ 700y as evidenced by low Mn/Al (< 0.7 × 10−2) and high U/Al (> 10−4) weight ratios. In some adjacent deeper regions, however, the environment turned oxic around ∼ 200 y BP. Whereas both Mn
and Ra were lost to the overlying waters in the anoxic regions (depth ∼340m), the Mn that diffused from deeper sections appears
to have mineralized at the sediment-water-interface. Studies of this type on long undisturbed cores from the margins of the
Arabian Sea and the Bay of Bengal, involving several proxies and geochronology by more than one method are needed to understand
short term environmental (and monsoonal intensity) changes of the recent past with high resolution. 相似文献
15.
The concentrations of N, P and Fe in surface sediments and interstitial and overlying (bottom and surface) waters of the
Ashtamudi estuary located in the southwest coast of India are reported along with the various chemical species of N (NO2–N, NO3–N, NH3–N and total N) and P (organic P, inorganic P and total P) in interstitial and overlying waters and discussed in terms of
the physico-chemical environment of the system. The interstitial water exhibits higher salinity values compared to bottom
and surface waters, indicating the coupled effects of salt-wedge phenomena and gravitational convection of more saline-denser
marine water downward through surface sediments. N, P and Fe as well as their chemical forms are enriched in the interstitial
water compared to bottom and surface waters. However, the dissolved oxygen (DO) shows an opposite trend. The marked enrichment
of NH3–N in the interstitial water and its marginal presence in bottom and surface waters, together with the substantial decrease
in the DO concentrations of bottom water and consequent increase in the concentrations of NO2–N and NO3–N in interstitial and bottom waters, points to the nitrification process operating in the sediment-water interface of the
Ashtamudi estuary. The enrichment of total N, P and Fe in the interstitial water compared to the overlying counterparts and
the positive correlation of sediment N, P and Fe with mud contents as well as organic carbon indicate that these elements
are liberated during the early diagenetic decomposition of organic matter trapped in estuarine muds.
Received: 5 Oktober 1998 · Accepted: 9 February 1999 相似文献
16.
Badia Chulli Aysen Davraz Jalila Makni Mourad Bedir Hamed Ben Dhia 《Environmental Earth Sciences》2012,66(1):1-16
The Sfax Basin in eastern Tunisia is bounded to the east by the Mediterranean Sea. Thermal waters of the Sfax area have measured
temperatures of 23–36°C, and electrical conductivities of 3,200 and 14,980 μS/cm. Most of the thermal waters are characterized
as Na–Cl type although there are a few Na–SO4–Cl waters. They issue from Miocene units which are made up sands and sandstones interbedded with clay. The Quaternary sediments
cap the system. The heat source is high geothermal gradient which are determined downhole temperature measurements caused
by graben tectonics of the area. The results of mineral equilibrium modeling indicate that the thermal waters of the Sfax
Basin are undersaturated with respect to gypsum, anhydrite and fluorite, oversaturated with respect to kaolinite, dolomite,
calcite, microcline, quartz, chalcedony, and muscovite. Assessments from various chemical geothermometers, Na–K–Mg ternary
and mineral equilibrium diagrams suggest that the reservoir temperature of the Sfax area can reach up to 120°C. According
to δ18O and δ2H values, all thermal and cold groundwater is of meteoric origin. 相似文献
17.
H. A. Al Darwish E. A. Abd El-Gawad F. H. Mohammed M. M. Lotfy 《Environmental Geology》2005,48(4-5):531-542
Fifteen stations (st) were selected along Dubai coastal region to delineate the distribution and the source of total petroleum
hydrocarbon (TPH), total organic carbon (TOC), total Kjeldhal nitrogen (TKN), polycyclic aromatic hydrocarbon (PAHs) and polychlorinated
biphenyls. The concentrations of TPH fluctuated between 2 μg g −1 and 48018 μg g −1 and the values of TOC were in the range of 0.16–5.9 wt%, while TPAHs ranged from 0.09 μg g −1 to 161.72 μg g −1. On the other hand, TPCBs showed values between 0.8 μg kg−1 and 93.3 μg kg−1 and TKN values varied from 218 μg g−1 to 2457 μg g −1. Distribution of oil and organic compounds in Dubai sediments are safe compared with previous studies except for limited
areas at the northeastern offshore. These readings are probably due to: (1) presence of commercial or industrial ports, dry
docks and fishing harbours and (2) population centers mainly concentrated at the northern part of the study area. Results
indicate that TOC can be used as indicator of oil pollution only in heavily oiled sediments. The highest values of TOC, TPH,
TPAHs and TPCBs corresponded to the stations covered with fine sand, due to adsorption properties and larger surface area.
The evaporation of low boiling point compounds from surface layers led to enrichment of sediments with the thick residual.
Al-Hamriya St 3 exhibited the highest values of TPH, TOC, TPAHs and TPCBs and the second highest value of TKN. 相似文献
18.
Temporal and spatial variations in water flow and sediment load in Narmada River Basin, India: natural and man-made factors 总被引:1,自引:0,他引:1
The Narmada River flows through the Deccan volcanics and transports water and sediments to the adjacent Arabian Sea. In a
first-ever attempt, spatial and temporal (annual, seasonal, monthly and daily) variations in water discharge and sediment
loads of Narmada River and its tributaries and the probable causes for these variations are discussed. The study has been
carried out with data from twenty-two years of daily water discharge at nineteen locations and sediment concentrations data
at fourteen locations in the entire Narmada River Basin. Water flow in the river is a major factor influencing sediment loads
in the river. The monsoon season, which accounts for 85 to 95% of total annual rainfall in the basin, is the main source of
water flow in the river. Almost 85 to 98% of annual sediment loads in the river are transported during the monsoon season
(June to November). The average annual sediment flux to the Arabian Sea at Garudeshwar (farthest downstream location) is 34.29×106 t year−1 with a water discharge of 23.57 km3 year−1. These numbers are the latest and revised estimates for Narmada River. Water flow in the river is influenced by rainfall,
catchment area and groundwater inputs, whereas rainfall intensity, geology/soil characteristics of the catchment area and
presence of reservoirs/dams play a major role in sediment discharge. The largest dam in the basin, namely Sardar Sarovar Dam,
traps almost 60–80% of sediments carried by the river before it reaches the Arabian Sea. 相似文献
19.
T. K. Manual Ateef Khan Y. Nazeer Ahammed R. S. Tanwar R. S. Parmar K. S. Zalpuri Prabhat K. Gupta S. L. Jain Risal Singh A. P. Mitra S. C. Garg A. Suryanarayana V. S. N. Murty M. Dileep Kumar Andrew J. Shepherd 《Journal of Earth System Science》2006,115(4):473-484
Characteristics of trace gases (O3, CO, CO2, CH4 and N2O) and aerosols (particle size of 2.5 micron) were studied over the Arabian Sea, equatorial Indian Ocean and southwest part
of the Bay of Bengal during the monsoon transition period (October–November, 2004). Flow of pollutants is expected from south
and southeast Asia during the monsoonal transition period due to the patterns of wind flow which are different from the monsoon
period. This is the first detailed report on aerosols and trace gases during the sampled period as the earlier Bay of Bengal
Experiment (BOBMEX), Arabian Sea Monsoon Experiment (ARMEX) and Indian Ocean Experiments (INDOEX) were during monsoon seasons.
The significant observations during the transition period include: (i) low ozone concentration of the order of 5 ppbv around
the equator, (ii) high concentrations of CO2, CH4 and N2O and (iii) variations in PM2.5 of 5–20μg/m3. 相似文献
20.
In order to investigate how monsoons influence biogeochemical fluxes in the ocean, twelve time-series sediment traps were
deployed at six locations in the northern Indian Ocean. In this paper we present particle flux data collected during May 1986
to November 1991 and November 1987 to November 1992 in the Arabian Sea and Bay of Bengal respectively. Particle fluxes were
high during both the SW and NE monsoons in the Arabian Sea as well as in the Bay of Bengal. The mechanisms of particle production
and transport, however, differ in both the regions.
In the Arabian Sea, average annual fluxes are over 50gm-2y-1 in the western Arabian Sea and less than 27gm-2 y-1 in the central part. Biogenic matter is dominant at sites located near upwelling centers, and is less degraded during peak
flux periods. High particle fluxes in the offshore areas of the Arabian Sea are caused by injection of nutrients into the
euphotic zone due to wind-induced mixed layer deepening. In the Bay of Bengal, average annual fluxes are highest in the central
Bay of Bengal (over
50gm-2y-1) and are least in the southern part of the Bay (37gm-2y-1). Particle flux patterns coincide with freshwater discharge patterns of the Ganges-Brahmaputra river system. Opal/carbonate
and organic carbon/carbonate carbon ratios increase during the SW monsoon due to variations in salinity and productivity patterns
in the surface waters as a result of increased freshwater and nutrient input from rivers.
Comparison of S years data show that fluxes of biogenic and lithogenic particulate matter are higher in the Bay of Bengal
even though the Arabian Sea is considered to be more productive. Our results indicate that in the northern Indian Ocean interannual
variability in organic carbon flux is directly related to the strength and intensity of the SW monsoon while its transfer
from the upper layers to the deep sea is partly controlled by input of lithogenic matter from adjacent continents. 相似文献