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51.
Farhat Abbas Ashfaq Ahmad Mohammad Safeeq Shafaqat Ali Farhan Saleem Hafiz Mohkum Hammad Wajid Farhad 《Theoretical and Applied Climatology》2014,116(3-4):671-680
Asymmetrical monsoons during the recent past have resulted into spatially variable and devastating floods in South Asia. Analysis of historic precipitation extremes record may help in formulating mitigation strategies at local level. Eleven indices of precipitation extremes were evaluated using RClimDex and daily time series data for analysis period of 1981–2010 from five representative cities across Punjab province of Pakistan. The indices include consecutive dry days, consecutive wet days, number of days above daily average precipitation, number of days with precipitation ≥10 mm, number of days with precipitation ≥20 mm, very wet days, extremely wet days, simple daily intensity index, maximum 1-day precipitation quantity, maximum 5 consecutive day precipitation quantity, and annual total wet-day precipitation. Mann-Kendall test and Sen’s slope extremes were used to detect trends in indices. Droughts and excessive precipitation were dictated by elevation from mean sea level with prolonged dry spells in southern Punjab and vice versa confirming spatial trends for precipitation extremes. However, no temporal trend was observed for any of the indices. Summer in the region is the wettest season depicting contribution of monsoons during June through August toward devastating floods in the region. 相似文献
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Ali Akbar Shahsavari Kamal Khodaei Farhad Asadian Farhad Ahmadi Seyed Mohammad Zamanzadeh 《Environmental Earth Sciences》2012,65(1):231-239
Study area with an area of about 415 km2 is located from 31°40′ to 32°05′ northern latitudes and 48°45′ to 49°00′ eastern longitudes 85 km to the north-east of Ahwaz
city, in the north of Khuzestan province, and south west of Iran. The purpose of this study is: (1) the determination of the
pesticides concentration in the groundwater of the Shushtar plain (Mian-Ab) and (2) the assessment of geology, hydrogeology
and anthropogenic activities impacts the groundwater quality. Thirty-seven groundwater samples were taken from product wells
based on the standard methods. A simple and efficient automated method for extraction and preconcentration was used. In this
method, a pyrrole-based polymer was synthesized and applied as an efficient sorbent for micro-solid-phase extraction. After
extraction, analytes were desorbed in ethyl acetate and analyzed using gas chromatography–flame. The study area is surrounded
by Aghajari Formation dominated by silt and clay sediments and the Bakhtiari Formation dominated by sand and gravel. Existence
of these formations affects the aquifer sediments and the hydrogeological properties. In the study area, the sediments grade
from gravel and sand in the north and east into silt and clay to the south and west, respectively. The topsoil in the south
of the study area contains more clay sediments. In this study, the concentration of two common herbicides, i.e., 2,4-D and
clodinafop propargyl and two pesticides, i.e., permethrin and diazinon, in the groundwater of Mian-Ab aquifer was assessed.
Chemical analysis results showed that the 2,4-D residue in the groundwater has the highest concentration (15 ppm). About 50%
of the samples have concentration values more than the maximum contamination level based on EPA drinking standard. The pesticides
concentrations decrease from the north to the south of the study area. Pesticides influx to the groundwater in the south of
the area is prevented or diminished due to the specific geological situation and soil type. Distribution pattern of population
centers, which increase to the north of the study area, and the role of groundwater as the main source of drinking water are
two important issues that must be considered in management of pesticides use in the area. 相似文献
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Farhad Ehya 《Mineralogy and Petrology》2012,104(1-2):81-93
The Bijgan barite deposit, which is located northeast of Delijan in Markazi Province of Iran, occurs as a small lenticular body at the uppermost part of an Eocene volcano-sedimentary rock unit. The presence of fossiliferous and carbonaceous strata suggests that the host rocks were deposited in a quiet marine sedimentary environment. Barite, calcite, iron oxides and carbonaceous clay materials are found as massive patches as well as thin layers in the deposit. Barite is marked by very low concentrations of Sr (1–2%) and total amounts of rare earth elements (REEs) (6.25–17.39?ppm). Chondrite-normalized REE patterns of barite indicate a fractionation of light REEs (LREEs) from La to Sm, similar to those for barite of different origins from elsewhere. The LaCN/LuCN ratios and chondrite-normalized REE patterns reveal that barite in the Bijgan deposit is enriched in LREE relative to heavy rare earth elements (HREEs). The similarity between the Ce/La ratios in the barite samples and those found in deep-sea barite supports a marine origin for barite. Lanthanum and Gd exhibit positive anomalies, which are common features of marine chemical sediments. Cerium shows a negative anomaly in most samples that was inherited from the negative Ce anomaly of hydrothermal fluid that mixed with seawater at the time of barite precipitation. The δ18O values of barites show a narrow range of 9.1–11.4‰, which is close to or slightly lower than that of contemporaneous seawater at the end of the Eocene. This suggests a contribution of oxygen from seawater in the barite-forming solution. The δ34S values of barites (9.5–15.3‰) are lower than that of contemporaneous seawater, which suggests a contribution of magmatic sulfur to the ore-forming solution. The oxygen and sulfur isotope ratios indicate that submarine hydrothermal vent fluids are a good analog for solutions that precipitated barite, due to similarities in the isotopic composition of the sulfates. The available data including tectonic setting, host rock characteristics, REE geochemistry, and oxygen and sulfur isotopic compositions support a submarine hydrothermal origin for the Bijgan barite deposit. At the seafloor, barite deposition occurred where ascending Ba-bearing hydrothermal fluids encountered seawater. Sulfate was derived from the sulfate-bearing marine waters, and, to a lesser extent, by oxidized H2S, which was derived from magmatic hydrothermal fluids. 相似文献
54.
Farhad Tabaddor 《国际地质力学数值与分析法杂志》1978,2(2):177-187
The problem of plates on consolidating soil is considered. Biot's three-dimensional consolidation theory, the generalization of Terzaghi's model, is employed to account for the consolidation process. A mathematical model is developed and the differential equations governing the system together with the proper boundary conditions are derived. A variational formulation of the problem and a convenient approximate method of solution are also presented. For numerical analysis, the problem of a rectangular plate on consolidating soil under various loading conditions is numerically solved and the effects of various physical factors on the settlements and the pore pressures are studied. 相似文献
55.
Farhad Nadim Shili Liu Ph.D. George E. Hoag Ph.D. 《Ground Water Monitoring & Remediation》2001,21(1):89-96
The presence of headspace and air bubbles in volatile organic analysis sampling vials lowers the actual aqueous concentration of these compounds due to the partitioning of solutes into the gaseous phase. This could make the sample invalid for analysis.
In this work, the effects of air bubbles and headspace on the aqueous concentration of 60 volatile organic compounds listed in U.S.Environmental Protection Agency (U.S. EPA) Method 8260 were evaluated experimentally and theoretically. The results showed that for air to water ratios of 1 to 20 and less, there was no significant effect on the aqueous concentrations of target organic solutes in the sampling vials. When the air to water ratio was increased to 1 to 10, the recovery rates of four organic compounds were lower than the control. Laboratory experiments on sampling vials showed that the presence of air bubbles or headspace with the volumetric air to water ratios of 1 to 20 and less do not produce any significant effect on the original concentrations for most targeted volatile organic compounds.
The experimental results also indicated that in 40 mL sampling vials with headspace range of 2 to 8 mL, the recovery rates of most volatile organic compounds with high values of Henry's law constant (> 0.01 Atm m3 /mol. at 25°C) were larger than the calculated rates. 相似文献
In this work, the effects of air bubbles and headspace on the aqueous concentration of 60 volatile organic compounds listed in U.S.Environmental Protection Agency (U.S. EPA) Method 8260 were evaluated experimentally and theoretically. The results showed that for air to water ratios of 1 to 20 and less, there was no significant effect on the aqueous concentrations of target organic solutes in the sampling vials. When the air to water ratio was increased to 1 to 10, the recovery rates of four organic compounds were lower than the control. Laboratory experiments on sampling vials showed that the presence of air bubbles or headspace with the volumetric air to water ratios of 1 to 20 and less do not produce any significant effect on the original concentrations for most targeted volatile organic compounds.
The experimental results also indicated that in 40 mL sampling vials with headspace range of 2 to 8 mL, the recovery rates of most volatile organic compounds with high values of Henry's law constant (> 0.01 Atm m
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Geochemical, mineralogical, and micromorphological characteristics of soils and their relevant parent rocks including loess, ignimbrite, sandstone and limestone were investigated to identify the soil-parent material uniformity and the weathering degree of soils in Golestan Province, northern Iran. Highly developed Calcixerolls and moderately developed Haploxerepts were formed on loess and limestone, respectively. In contrast, the soils formed on ignimbrite and sandstone were non-developed Entisols. Illite was the dominant clay mineral found in ignimbrite and sandstone in both the A horizon and parent material. In loess derived soils however, smectite was dominant especially in the Bt horizon compared to its parent material indicating partly to its pedogenic formation. In limestone, illite and vermiculite were dominant both in the A and C horizons. Ti/Zr ratio proved that the studied soils were closely related to their underlying parent materials geochemically. Chemical index of alteration (CIA), micromorphological index of soil development (MISECA), smectite/illite+chlorite ratio and magnetic susceptibility were applied to investigate the degree of soil development. Results showed that the most and the least developed soils were those formed on loess deposits and limestone, respectively. Application of the different geochemical and pedogenetic approaches was proved to be useful in identifying the relevance of soils to their underlying parent materials and also their degree of development. 相似文献
58.
Prediction of River Stage-Discharge Process Based on a Conceptual Model Using EEMD-WT-LSSVM Approach
Farhad Alizadeh Gharamaleki Alireza Faregh Jalilzadeh Mojtaba Akhoundzadeh Ali 《Water Resources》2020,47(1):41-53
Water Resources - This study proposed a hybrid pre-processing approach along with a conceptual model to enhance the accuracy of river discharge prediction. In order to achieve this goal, Ensemble... 相似文献
59.
Determination of homogenous precipitation-based regions is a very important task in effective management of water resources. The present study tried to propose an effective precipitation-based regionalization methodology by conjugating both temporal pre-processing and spatial clustering approaches in a way to take advantage of multiscale properties of precipitation time series. Annual precipitation data of 51 years (1960-2010) for 31 rain gauges (RGs) were collected and used in proposed clustering approaches. Discreet wavelet transform (DWT) was used to capture the time-frequency attributes of the time series and multiscale regionalization was performed by using k-means and Self Organizing Maps (SOM) clustering techniques. Daubechies function (db) was selected as mother wavelet to decompose the precipitation time series. Also, proper boundary extensions and decomposition level were applied. Different combinations of the approximation (A) and detail (D) coefficients were used to determine the input dataset as a basis of spatial clustering. The proposed model’s efficiency in spatial clustering stage was verified using three different indexes namely, Silhouette Coefficient (SC), Dunn index and Davis Bouldin index (DB). Results approved superior performance of k-means technique in comparison to SOM. It was also deduced that DWT-based regionalization methodology showed improvements in comparison to historical-based models. Cross mutual information was used to investigate the RGs of cluster 3’s homogeneousness in DWT-k-means approach. Results of non-linear correlation approach verified homogeneity of cluster 3. Verifications based on mean annual precipitation values of rain gauges in each cluster also approved the capability of multiscale approach in precipitation regionalization. 相似文献
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