Evaluation of metals that are potentially toxic to agricultural surface soils, using statistical analysis, in northwestern Saudi Arabia

© 2015, Springer-Verlag Berlin Heidelberg. Heavy metals in agricultural soils enter the food chain when taken up by plants. The main purpose of this work is to determine metal contamination in agricultural farms in northwestern Saudi Arabia. Fifty surface soil samples were collected from agricultural areas. The study focuses on the geochemical behavior of As, Cd, Co, Cr, Cu, Hg, Pb and Zn, and determines the enrichment factor and geoaccumulation index. Multivariate statistical analysis, including principle component analysis and cluster analysis, is also applied to the acquired data. The study shows considerable variation in the concentrations of the analyzed metals in the studied soil samples. This variation in concentration is attributed to the intensity of agricultural activities and, possibly, to nearby fossil fuel combustion activities, as well as to traffic flows from highways and local roads. Multivariate analysis suggests that As, Cd, Hg and Pb are associated with anthropogenic activities, whereas Co, Cr, Cu and Zn are mainly controlled by geogenic activities. Hg and Pb show the maximum concentration in the analyzed samples as compared to the background concentration

Paleozoic tectono-stratigraphic framework of the Arabian Peninsula

AbstractThick Paleozoic succession of siliciclastics and carbonates is well exposed and penetrated in the greater Arabian Basin. The succession included source, reservoir, and seal rocks. Though, oil and gas have been discovered in sandstone and limestone reservoirs in these rocks in several oilfields in the basin, the tectonic history of this succession has not been fully understood yet.The Paleozoic succession of the basin is severely affected by series of major climatic and tectonic events which have caused facies change and major stratigraphic breaks. The major tectonic movements have resulted in dividing the Paleozoic succession into mega-depositional cycles. The succession is subdivided into pre- and syn-climatic and tectonic events representing well defined depositional cycles separated by regional unconformities. These mega-depositional cycles are well preserved in basinal or less tectonically affected areas where boundaries between the respective cycles are marked by possible hiatus. In more tectonically active areas, the Paleozoic succession is less preserved and boundaries between the cycles are more complicated due to longer periods of erosion by later movements and/or non-deposition. Minor stratigraphic breaks within the mega cycles subdivide them into smaller sub-cycles.Following the deposition of the Late Caradocian Quwarah member of the Qasim Formation the area went through a gentle uplift and tilt probably related to the Taconic tectonic movements, and a drop of sea level due to glaciation. Thick succession of the Quwarah, Ra'an, Kahfah, and Hanadir members of the Qasim Formation and the Risha and Sajir members of the Saq Formation were eroded and deep paleo-valleys incised in outcrops of the two formations. Glacial and periglacial deposits of the Zarqa and/or Sarah Formations were unconformably rest on older units from Ordovician to Precambrian.The second main event occurred during Late Silurian where the pre-existing successions, mainly on paleo-highs, were affected by tectonic movements synchronous with the Acadian tectonic phase of the Caledonian tectonic movements. The Early Devonian Tawil Formation unconformably rests on eroded Silurian and Late Ordovician deposits of the Sharawra, Qusaiba, and Sarah Formations in the Qusayba Depression in central Arabia.The third main event is a regional tectonic movement contemporaneous with the Hercynian tectonic movement which have reached its maximum phase in the Late Carboniferous. Earlier successions from Carboniferous to Precambrian were affected and the Permo-Carboniferous Shajara Formation unconformably rests on all underlying Paleozoic rock units in central Arabia and other paleo-highs. The Shajara rests on the Devonian Jubah, Jauf and Tawil Formations, the Silurian Sharawra, Qusaiba, and Uqlah Formations, the Ordovician Sarah, Zarqa, and Qasim Formations, the Cambro-Ordovician Saq Formation, and finally rests on Precambrian Basement complex in central Arabia.The Paleozoic outcrops in central Arabia offer an excellent geologic window documents the influence of the three tectonic movements. The Baq'a and Buraydah quadrangles show excellent outcrops of the glacial related deposits and the merge of the sub-Zarqa/Sarah unconformity, sub-Tawil unconformity, and sub-Shajara unconformity. The three unconformities represent the Taconic, Acadian (Caledonian), and Hercynian events, respectively

Assessing groundwater quality of the shallow alluvial aquifer system in the Midyan Basin, northwestern Saudi Arabia

The Midyan Basin is characterized by arid climate with rare surface water flow. Groundwater is the main water resources in this region. In order to evaluate their suitability for drinking, domestic and irrigation purposes, chemical characteristics of groundwater in the Midyan Basin (northwestern Saudi Arabia) have been investigated and evaluated. A total of 72 water samples were collected from different wells and analyzed for hydrogen ion concentration, total dissolved solids, electrical conductivity, total hardness, Ca2+, Na+, Mg2+, K+, Cl-, HCO3-, NO3- and SO42-. To understand quality of groundwater and their suitability, chemical indices like sodium percentage, sodium adsorption ratio and salinity values have been calculated using analytical techniques. From traditional Piper diagram for water classification, the water quality is placed at Na+-Ca2+-SO42--Cl- type. According to the results of electrical conductivity and sodium adsorption ratio, 37% of the studied samples are regarded as highly saline, while 63% of them are classified as very highly saline. As per the Arab Gulf and international standards, such waters are not suitable for irrigation under normal condition and further action is required to remediate such problem by salinity control. Sodium content in 24% of the studied samples is regarded as high that can’t be used for irrigation purposes for any soils. Thus high level of salinity, sodium adsorption ratio and sodium percentage in most water samples have made them unsuitable.</jats:p