Organic compound tracers of fine soil and sand particles during summer in the metropolitan area of Riyadh,Saudi Arabia     

Khalid Al-Mutlaq  Ahmed I. Rushdi  Bernd R. T. Simoneit 《Environmental Geology》2007,52(3):559-571

Soil and sand fine particles, which may be resuspended as fine dust in the atmosphere, contain a variety of anthropogenic and natural organic components. Samples of fine soil and sand particles (sieved to <125 μM) were collected from the Riyadh area in the summer of 2003 and extracted with a mixture of dichloromethane and methanol (3:1, v:v). The derivatized total extracts were analyzed by gas chromatography–mass spectrometry in order to characterize the composition and sources of the organic components. Both anthropogenic and natural biogenic inputs were the major sources of the organic compounds in these extracts. Discarded plastics and vehicular emission products were the major anthropogenic sources in the fine particles from populated areas of the city. Their tracers were plasticizers, UCM, n-alkanes, hopanes and traces of steranes. Vegetation was the major natural source of organic compounds in samples from outside Riyadh and included n-alkanols, n-alkanoic acids, n-alkanes, methyl alkanoates, sterols and triterpenoids. Carbohydrates had high concentrations (42–54%) in all samples and indicate sources from decomposition of cellulose and/or the presence of viable microbiota such as bacteria and fungi. The results were also compared with the data obtained in winter 2002 and showed that anthropogenic inputs were higher in summer than in winter, whereas the opposite trend was observed for natural inputs.  相似文献   

Evaluation of the potential of friction surface analysis in modelling hurricane wind damage in an urban environment     

Robin I. Knight  Fakhar Khalid 《Natural Hazards》2015,76(2):891-911

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Evidence for and relationship between recent distributed extension and halokinesis in the Farasan Islands,southern Red Sea,Saudi Arabia     

Khalid?A.?AlmalkiEmail author  Laurent?Ailleres  Peter?G.?Betts  Rashad?A.?Bantan 《Arabian Journal of Geosciences》2015,8(10):8753-8766

This paper presents a structural evolution study of the Farasan Bank using an integration of field work, remote sensing data, and regional Bouguer gravity data interpretation. The architecture of the Farasan Islands is influenced by normal faults parallel to the Red Sea rift axis delineating a series of graben and asymmetric half-graben structures as well as salt domes. Geological data suggest that the negative gravity anomaly over the Farasan Bank reflects thick salt deposits. The gravity data shows a general NW-SE trend with the main negative anomaly coincident with the Farasan Islands. Gravity data together with seismic reflection data suggest that salt diapirs are elongated and parallel to the main rift orientation (NW-SE). This indicates that salt deposition and diapirism was controlled by rift-related basement structures. Forward modeling of gravity data constrained by marine seismic reflection interpretation reveals that the evaporites directly overlie the basement in most places. No pre-evaporite formation was detected. Integration of the modeling with field observations and interpretations suggests that the Farasan Islands are in an area of active extension. Extension and salt diapirism on the flank of the mid-ocean ridge is likely to be synchronous with renewed spreading at 5 Ma.  相似文献   

Groundwater origins and mixing pattern in the multilayer aquifer system of the Gafsa-south mining district: a chemical and isotopic approach   总被引：3，自引：2，他引：1  

Younes Hamed  Lassaad Dassi  Meriem Tarki  Riadh Ahmadi  Khalid Mehdi  Hamed Ben Dhia 《Environmental Earth Sciences》2011,63(6):1355-1368

Major ion geochemistry and environmental isotopes were used to identify the origins and the mineralisation processes of groundwater flowing within the three aquifer levels of the multilayer system of the Gafsa-south mining district (Southwestern Tunisia). It has been demonstrated that groundwaters are characterised by a Ca–Mg–SO₄ water type. Geochemical pattern is mainly controlled by the dissolution of halite, gypsum and/or anhydrite as well as by the incongruent dissolution of dolomite. δ¹⁸O and δ²H values are much lower than the isotopic signature of regional precipitation and fall close to the meteoric water lines, indicating that groundwaters have not been significantly affected by evaporation or mineral–water reactions. The distribution of stable and radiogenic isotopes (δ¹⁸O, δ²H, δ¹³C and ¹⁴C) within the aquifer levels suggests that the deep confined aquifer receives a significant modern recharge at higher altitudes, while, the shallow unconfined aquifer has been mainly recharged under cooler paleoclimatic condition, likely during Late Pleistocene and Early Holocene humid periods. However, waters from the intermediate confined/unconfined aquifer have composite isotopic signatures, highlighting that they are derived from a mixture of the two first end-members.  相似文献   

DISTRIBUTION AND COMPOSITION OF PAHs IN SURFACE WATERS, POREWATER AND SEDIMENTS FROM XIAMEN WESTERN BAY     

洪华生张祖麟  陈伟琪周俊良 《中国海洋湖沼学报》2001,19(1):73-80

Xiamen Western Bay‘s water and sedimem quality were studied by detemaining thelevels of sixteen polycyclic amrrmtic hydrocarbons PAHs in water, porewater and sediment samples from nine locations in the bay. Total PAH concentrations varied from 106 to 945 ng/1 in water, below detectionto 3548 ng/1 in porewater, and 247 to 480 ng/g dry weight in surface sediments. PAHs levels in porewaterwere higher than those in surface water, due to the preference of these hydrophobic compounds for sedimentary phase instead of water. Such a concentration gradient implies a potential flux of pollutants fromsediments to overlying water. The PAils levels in sediments were one to several orders of magnitude lowerthan those in 1993, suggesting their decreased input in recent years and possible degradation with time.  相似文献   

Amelioration of soil acidity,Olsen-P,and phosphatase activity by manure- and peat-derived biochars in different acidic soils     

Muhammad Aqeel Kamran  Jun Jiang  Jiu-yu Li  Ren-yong Shi  Khalid Mehmood  M. Abdulaha-Al Baquy  Ren-kou Xu 《Arabian Journal of Geosciences》2018,11(11):272

To increase soil productivity, ameliorate nutrient scarcity, and reduce metal toxicity in highly weathered acidic soils usually requires fertilizer and lime application. Effects of three biochars on soil acidity, Olsen-phosphorus (P), phosphatase activities, and heavy metal availability were investigated to test potential of these biochars as soil amendments in highly weathered acidic soils. Incubation experiments were conducted for 6 weeks with three acidic soils: Alfisol, Ultisol, and Oxisol. Three biochars were derived from chicken manure (CMB), pig manure (PMB), and peat moss (PB) at 400 °C and applied at 1 or 2% (wt/wt). The addition of the three biochars increased Olsen-P in the three acidic soils in the following order: CMB?>?PMB?>?PB. Application of 2% CMB increased Olsen-P contents by 2.41-, 7.4-, and 1.78-fold in the Ultisol, Oxisol, and Alfisol compared with controls, respectively. Moreover, CMB increased the soil pH, electrical conductivity (EC), cation exchange capacity (CEC), and alkaline phosphatase activity, but reduced exchangeable acidity, acid phosphatase activity, and the availability of heavy metals—more effectively than PMB and PB. Addition of CMB increased soil pH by 0.90, 0.90, and 0.92 units for the Alfisol, Ultisol, and Oxisol, respectively, correspondingly followed by 0.80, 0.84, and 0.87 units for PMB and 0.15, 0.28, and 0.25 for PM. Changes in EC, CEC, and exchangeable acidity followed the same order for the three soils: CMB?>?PMB?>?PB. The results suggested that the magnitude of changes in soil properties and Olsen-P contents depended on biochar type and application rate. Application of CMB increased nutrient availability and reduced the availability of heavy metals more than other amendments. Due to higher pH, EC, and CEC, and greater concentrations of carbon, nitrogen, and exchangeable calcium and potassium, incorporation of CMB should be a better cost-effective method to correct soil acidity and improve fertility and Olsen-P contents in Ultisols and Oxisols from tropical and subtropical regions of the world.  相似文献   

A field study investigating the potential use of phosphorus combined with organic amendments on cadmium accumulation by wheat and subsequent rice     

Muhammad Zia ur Rehman  Muhammad Rizwan  Shafaqat Ali  Asif Naeem  Balal Yousaf  Guijian Lui  Hinnan Khalid  Saifullah  Farhan Hafeez  Muhammad Azhar 《Arabian Journal of Geosciences》2018,11(19):594

A field study was performed to determine the efficiency of diammonium phosphate (DAP) applied alone or combined with biochar, lignite, and farmyard manure (FYM) on growth and cadmium (Cd) accumulation in wheat and rice. Before crop sowing, different treatments were applied in the field such as a control (T₁), DAP alone (0.1%, T₂), DAP + lignite (0.05% each, T₃), DAP + FYM (0.05% each, T₄), and DAP + biochar (0.05% each, T₅). Afterwards, the wheat seeds were sown in the soil. At wheat postharvest, rice was sown without any further treatment. Raw effluent was applied as an irrigation source during the whole growth period of both crops since it is the common practice of the farmers of study area. It was revealed that the use of amendments enhanced the yield and photosynthesis but lowered the Cd contents in straw as well as grains of both crops. In both crops, the highest yield of straw and grain was found in DAP + FYM whereas the lowest Cd concentration was found in DAP alone. The ammonium bicarbonate-DTPA extractable Cd of post wheat and post rice soils were decreased while the soil pH and immobilization index were increased in all treatments as compared with the control. The present field study highlighted that the DAP + FYM can be effective in increasing yield with decreased Cd concentrations in crop grains.  相似文献   

Gradient-based Pareto optimal history matching for noisy data of multiple types     

Oleg Volkov  Vladislav Bukshtynov  Louis J. Durlofsky  Khalid Aziz 《Computational Geosciences》2018,22(6):1465-1485

The advantages of the simultaneous integration of production and time-lapse seismic data for history matching have been demonstrated in a number of previous studies. Production data provide accurate observations at particular spatial locations (wells), while seismic data enable global, though filtered/noisy, estimates of state variables. In this work, we present an efficient computational tool for bi-objective history matching, in which data misfits for both production and seismic measurements are minimized using an adjoint-gradient approach. This enables us to obtain a set of Pareto optimal solutions defining the optimal trade-off between production and seismic data misfits (which are, to some extent, conflicting). The impact of noise structure and noise level on Pareto optimal solutions is investigated in detail. We discuss the existence of the “best” trade-off solution, or least-conflicting posterior model, which corresponds to the history-matched model that is expected to provide the least-conflicting forecast of future reservoir performance. The overall framework is successfully applied in 2D and 3D compositional simulation problems to provide a single least-conflicting posterior model and, for the 2D case, multiple samples from the posterior distribution using the randomized maximum likelihood method.  相似文献   

Spectral wave characteristics along the central coast of eastern Red Sea     

P. R. Shanas  V. M. Aboobacker  Khalid M. Zubier  Alaa M. A. Albarakati 《Arabian Journal of Geosciences》2018,11(5):90

The Jeddah coast lies in the central eastern Red Sea, which is characterized by the predominant northwest winds and the associated wind waves throughout the year. A detailed investigation on the spectral wave characteristics in the nearshore regions of the Jeddah coast has not been carried out yet, primarily due to the lack of data. In the present study, we have analyzed the available wave spectra measured at two nearshore locations along the Jeddah coast using wave gauges. The wave spectra were separated into wind sea and swell components using a frequency-based algorithm, and the integral wave parameters corresponding to each component were derived. Although the measurements were limited to the summer season, notable features such as the diurnal variability and the superimposition of wind seas and swells have been identified from the spectra. The superimposition is mainly due to the interaction of the young swells propagated from the northern Red Sea and the local breezes prevailing along the coast at certain periods in a diurnal cycle. Based on the wave speed calculations and the estimated time shifts between the wind and waves, the potential swell regions have been backtracked.  相似文献   

Geological structure of the coastal aquifer in the southern part of the Gaza Strip,Palestine     

Usama Zaineldeen  Khalid Qahman  Jehad Al-Dasht 《Arabian Journal of Geosciences》2014,7(10):4343-4354

The current study introduces the geological subsurface cross-sections in the southern part of the Gaza Strip to show the structure of the aquifer in the area. The cross-sections give evidence of four subaquifers of the coastal aquifer in the southern part of the Gaza Strip. These cross-sections give the natural reasons for the deterioration of the groundwater in the study area. The results show presence of clay lenses that prevent the replenishment processes of the aquifer of fresh water from the rainfall and returns flow from agricultural activities. Lithological formation was evident as one of the natural causes which accelerate destroying process of the coastal aquifer. The results also show that the structure of the aquifer causes the increase of the groundwater salinity in the Gaza Strip. The cross-sections had shown the shortage of storage capacity of high quantities of fresh water in the coastal aquifer in these areas. The role of lithological formation was evident as one of the natural causes to accelerate the process of destroying the coastal aquifer.  相似文献