Comparing the passive sampler and biomonitoring of organic pollutants in water: A laboratory study     

Nahla S. El-Shenawy  Richard Greenwood  Ismail M. Abdel-Nabi  Zohour I. Nabil 《Ocean Science Journal》2009,44(2):69-77

Passive sampling could provide the solution to problems associated with costly and time consuming sampling programmes and biomonitoring. Mussels (Mytilus edulis) and Chemcatcher passive sampler were simultaneously analyzed for sequestered pesticides and polychlorinated biphenyls (PCBs) by gas chromatography with mass spectrometry (GC/MSD). The Chemcatcher passive sampler based on a solid phase extraction disc with two types of diffusion-limiting membranes (polyethelene and polysulphone), were also compared. Diuron, atrazine, irgarol and lindane were accumulated in the polysulphone passive sampler in greater concentration than in the mussels or in the other passive samplers with polyethelene limiting-membrane. Mussels can accumulate in their tissue high concentration of non polar compounds such as PCB 52, dieldren and PCB 153; more than the passive sampler with polysulphone membrane. The device with polyethelene limiting membrane has high affinity capacity to concentrate high amount of phenenthrene, dieldrin, PCB 153 and PCB 52, so it acts as a sampler for non-polar compounds. The highest uptake rate of hydrophobic compounds by Chemcatcher was observed for analytes with log octanol-water partition coefficient (K_OW) between 4.5 and 7.5. Laboratory-based studies using passive samplers to assess the potential for bioaccumulation could provide robust and reliable information at relatively low cost compared to biomonitoring data. Laboratory data obtained using passive samplers could be related to accumulation under field conditions where field assessments are required.  相似文献   

Seasonal evolution of the West African heat low: a climatological perspective   总被引：1，自引：1，他引：0  

C. Lavaysse  C. Flamant  S. Janicot  D. J. Parker  J.-P. Lafore  B. Sultan  J. Pelon 《Climate Dynamics》2009,33(2-3):313-330

The West African heat low (WAHL), a region of high surface temperatures and low surface pressures, is a key element of the West African monsoon system. In this study, we propose a method to detect the WAHL in order to monitor its climatological seasonal displacement over West Africa during the period 1979–2001, using the European Centre for Medium-range Weather Forecast (ECMWF) ERA-40 reanalyses. The low-level atmospheric thickness (LLAT), a variable defined as the difference of geopotential heights at 700 and 925 hPa, is used to detect the dilatation of these levels generated by an increase of the temperature. We define grid points with 10% highest values of the LLAT as the WAHL. We show that our method reliably positions the WAHL over areas of high surface temperatures and low surface pressures, and that it is effective at detecting heat lows. In the course of the year, the climatological WAHL is shown to migrate north-westward from a position south of the Darfur mountains in the winter (November–March) to a location over the Sahara, between the Hoggar and the Atlas mountains, during the summer (June–September). The temperature tendency equation is used to investigate the processes controlling the displacement of the WAHL, and more particularly the heating at low levels. The specific period of the onset of the WAHL in its summer location over the Sahara (referred to as the Saharan heat low -SHL- onset) is also analysed during the 1984–2001 period, using complementary brightness temperature data from the European Union-funded Cloud Archive User Service (CLAUS). The climatological onset of the SHL occurs around 20 June, i.e. just before the climatological monsoon onset date. The present study suggests that the onset of the WAHL occurs approximately 5 days before the monsoon onset for the 1984–2001 period. This is confirmed independently by comparing the SHL onset date and the monsoon onset date for the 1984–2001 period. The seasonal evolution of the WAHL for the year 2006 (the year of the African Monsoon Multidisciplinary Analysis project Special Observation Period) is analysed and compared with the climatological results. The operational ECMWF analyses were used for that purpose. Except in April, the spatial distribution of the WAHL remains relatively unchanged and agrees with the climatology. The onset of the SHL in 2006 occurs on 18 June, which is close to the climatological date, in spite of the delay in the onset of the rainy season in Sahel.  相似文献   

Trace element geochemistry of groundwater from Quetta Valley,western Pakistan   总被引：1，自引：0，他引：1  

Shuhab D. Khan  Khalid Mahmood  Mohamed I. Sultan  Abdul S. Khan  Yingqian Xiong  Zhanay Sagintayev 《Environmental Earth Sciences》2010,60(3):573-582

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Sulfide-oxide minerals in eclogite from Stockdale Kimberlite,Kansas     

Henry O. A. Meyer  Nabil Z. Boctor 《Contributions to Mineralogy and Petrology》1975,52(1):57-68

The opaque minerals in eclogite xenoliths from Stockdale Kimberlite are rutile, ilmenite, and a complex polysulfide assemblage. Rutile shows exsolutions of ilmenite and spinel. Discrete ilmenite contains up to 10 wt % MgO in solid solution and is a primary mineral, but not of kimberlitic origin. Pyrrhotite containing exsolved pentlandite is the major sulfide mineral, and is usually rimmed by chalcopyrite which may display exsolution of cubanite. A veneer of monosulfide solid solution (12 wt % Ni and 5 wt % Cu) forms a rim on the chalcopyrite-pyrrhotite masses. The simple model of sulfide liquid immiscibility within a silicate melt may account for the origin of the pyrrhotite-pentlandite-chalcopyrite assemblage, but it fails to explain the occurrence within one and the same sulfide globule of a monosulfide_ss rim, separated from an exsolved pyrrhotite core by chalcopyrite. The monosulfide_ss is probably a metastable phase produced by the partial melting of a preexisting sulfide assemblage of similar bulk chemical composition to that existing at present. The melting possibly took place instantaneously when the eclogite was incorporated into the rising hot kimberlitic magma. Fast cooling during the explosive ascent of the kimberlite could have led to the quenching of the monosulfide solid solution. Rutile in the eclogite xenolith was unaffected by the heating, but secondary amphibole and biotite may have possibly formed during this event.  相似文献   

Wetter or colder during the Last Glacial Maximum? Revisiting the pluvial lake question in southwestern North America     

Kirsten M. Menking  Roger Y. Anderson  Nabil G. Shafike  Kamran H. Syed  Bruce D. Allen 《Quaternary Research》2004,62(3):174-288

Well-preserved shorelines in Estancia basin and a relatively simple hydrologic setting have prompted several inquiries into the basin's hydrologic balance for the purpose of estimating regional precipitation during the late Pleistocene. Estimates have ranged from 86% to 150% of modern, the disparity largely the result of assumptions about past temperatures. In this study, we use an array of models for surface-water runoff, groundwater flow, and lake energy balance to examine previously proposed scenarios for late Pleistocene climate. Constraints imposed by geologic evidence of past lake levels indicate that precipitation for the Last Glacial Maximum (LGM) may have doubled relative to modern values during brief episodes of colder and wetter climate and that annual runoff was as much as 15% of annual precipitation during these episodes.  相似文献   

Hydraulic evaluation of aquifer storage and recovery (ASR) with urban stormwater in a brackish limestone aquifer     

Paul Pavelic  Peter J. Dillon  Karen E. Barry  Nabil Z. Gerges 《Hydrogeology Journal》2006,14(8):1544-1555

A 5-year aquifer storage and recovery trial at Andrews Farm in South Australia involving the injection of more than 250 ML (250,000 m³) of fresh but turbid stormwater into a brackish limestone aquifer over 4 years and recovery of 150 ML in the fifth provided the opportunity to evaluate rates of clogging and unclogging and the potential to recover water suitable for irrigation supplies. Results reveal there is some clogging by injected sediment, but only to a relatively small degree considering the high suspended solid concentrations and moderate aquifer transmissivity. This clogging was offset by increased matrix porosity through calcite dissolution and by routine well redevelopments after each 40 ML of injection. No significant microbial clogging occurred. Breakthrough responses at three observation wells and the proportion of injectant in the recovered water were determined from chloride data. Temperature and caliper profiles clearly indicate the heterogeneous nature of the aquifer that is attributed, in part, to sand removal during the initial well development. The recovery efficiency was greater than 60%. The trial demonstrates that urban stormwater containing high and variable particulate levels, which receives only passive pre-treatment and is not disinfected, can be used to freshen a heterogeneous brackish aquifer to create a useful water resource.  相似文献   

A model investigation of the impact of increases in anthropogenic NO x emissions between 1967 and 1980 on tropospheric ozone     

Jane Dignon  Sultan Hameed 《Journal of Atmospheric Chemistry》1985,3(4):491-506

Recent observations suggest that the abundance of ozone between 2 and 8 km in the Northern Hemisphere mid-latitudes has increased by about 12% during the period from 1970 to 1981. Earlier estimates were somewhat more conservative suggesting increases at the rate of 7% per decade since the start of regular observations in 1967. Previous photochemical model studies have indicated that tropospheric ozone concentrations would increase with increases in emissions of CO, CH₄ and NO _x . This paper presents an analysis of tropospheric ozone which suggests that a significant portion of its increase may be attributed to the increase in global anthropogenic NO _x emissions during this period while the contribution of CH₄ to the increase is quite small. Two statistical models are presented for estimating annual global anthropogenic emissions of NO _x and are used to derive the trend in the emissions for the years 1966–1980. These show steady increase in the emissions during this interval except for brief periods of leveling off after 1973 and 1978. The impact of this increase in emissions on ozone is estimated by calculations with a onedimensional (latitudinal) model which includes coupled tropospheric photochemistry and diffusive meridional transport. Steady-state photochemical calculations with prescribed NO _x emissions appropriate for 1966 and 1980 indicate an ozone increase of 8–11% in the Northern Hemisphere, a result which is compatible with the rise in ozone suggested by the observations.  相似文献   

U-Pb (zircon) ages for the gneissic terrane west of the Nile,southern Egypt     

M. Sultan  R. D. Tucker  Z. El Alfy  R. Attia  Abdel Ghany Ragab 《International Journal of Earth Sciences》1994,83(3):514-522

The first U-Pb zircon ages are reported for the gneissic bedrock inliers previously interpreted as part of the Nile Craton. The inliers crop out in the Egyptian Western Desert, east of the Uweinat area and west of the Eastern Desert. Multi- and single-grain zircon analyses of granitoid gneiss and migmatite from Gebel Um Shagir, Aswan, and another locality approximately 160 km south-west of Aswan, yield simple discordia with near modern day Pb loss trajectories, and the following Neoproterozoic crystallization ages: 626+4/–3, 634 ± 4 and 741 ± 3 Ma. In contrast, multi- and single-grain U-Pb analyses (zircon and sphene) from an anorthositic gabbro at Gebel Kamil (22°46N 26°21E) and an anorthosite at Gebel El Asr (22°46N 31°10E) yield Archean and Paleoproterozoic emplacement ages. The former yield a crystallization age of > 2.67 Ga and a metamorphic age of 2.0 Ga; the latter a metamorphic age of 0.69 Ga and an inheritance age of 1.9–2.1 Ga. Because high grade gneiss and migmatite of Neoproterozoic, Paleoproterozoic and Archean age crop out west of the Nile, pre-Neoproterozoic crust should no longer be identified by its metamorphic grade. By contrast, mapping the anorthosite and related rocks might provide first-order estimates for the extension of pre-Neoproterozoic crust in north-east Africa. It is suggested that Archean and Paleoproterozoic crust of the Uweinat and Congo Craton are contiguous because these U-Pb (zircon) data show no evidence for a Neoproterozoic thermal overprint in the Gebel Kamil area and there is no pronounced Neoproterozoic magmatic activity south of the Uweinat inlier and north of the Congo Craton.  相似文献   

Efficiency of carrier-phase integer ambiguity resolution for precise GPS positioning in noisy environments   总被引：1，自引：0，他引：1  

Liqiang Zhu  Ying-Cheng Lai  Mayur Shah  Sultan Mahmood 《Journal of Geodesy》2007,81(2):149-156

Precise GPS positioning relies on tracking the carrier-phase. The fractional part of carrier-phase can be measured directly using a standard phase-locked loop, but the integer part is ambiguous and the ambiguity must be resolved based on sequential carrier-phase measurements to ensure the required positioning precision. In the presence of large phase-measurement noise, as can be expected in a jamming environment for example, the amount of data required to resolve the integer ambiguity can be large, which requires a long time for any generic integer parameter estimation algorithm to converge. A key question of interest in significant applications of GPS where fast and accurate positioning is desired is then how the convergence time depends on the noise amplitude. Here we address this question by investigating integer least-sqaures estimation algorithms. Our theoretical derivation and numerical experiments indicate that the convergence time increases linearly with the noise variance, suggesting a less stringent requirement for the convergence time than intuitively expected, even in a jamming environment where the phase noise amplitude is large. This finding can be useful for practical design of GPS-based systems in a jamming environment, for which the ambiguity resolution time for precise positioning may be critical.  相似文献   

New Larvicidal Acetogenin from the Red Alga Laurencia papillosa     

Zeinab S. Abou‐Elnaga  Walied M. Alarif  Sultan S. Al‐lihaibi 《洁净——土壤、空气、水》2011,39(8):787-794

A new C₁₅ acetogenin, cyclic enyne (12E)‐cis‐maneonene‐E ( 1 ) and (12Z)‐trans‐maneonene‐B ( 2 ), together with different secondary metabolites including sesquiterpenoid 2,10‐dibromo‐3‐chloro‐α‐chamigrene ( 3 ) and fatty acid aldehydes ( 4–8 ) were isolated from the petroleum ether extract of a red alga, identified as Laurencia papillosa, collected from the Saudi Red Sea coast. The L. papillosa crude extract and its active ingredient acetogenin ( 1 ) have been evaluated for the ability to control two main economically important pests, the confused flour beetle larvae Tribolium confusum and Culex pipiens mosquito larvae. Compound 1 showed high potential as a natural insecticide against these two pests. In the case of T. confusum larvae, the LD₅₀ values were 0.21 and 0.16% after 6 and 12 days of treatment with crude extract and acetogenin, respectively. On the other hand, the resulting LC₅₀ values of mosquito larvae bioassay were 30.7, 36.9, and 41.8 ppm after 24 h treatment against 2nd, 3rd, and 4th larval instars, respectively. Also, an increase of the insecticidal effects against mosquito larvae was recorded after extending treatment time to 48 h.  相似文献