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Abstract The Khulais plain lies within a typical arid area in western Saudi Arabia. Groundwater occurs within two aquifers in the area: the alluvium of the wadi system, and the sandy layers of the Cretaceous-Tertiary sedimentary succession. Detailed field investigations and laboratory analysis helped in determining the aquifer properties for each of the water-bearing units. Groundwater movement has been thoroughly studied, and distribution maps prepared to explain the variations in transmissivity, permeability, porosity and specific yield. An attempt has been made to estimate volumes of groundwater flow towards the plain. This study presents a first attempt towards determining groundwater availability in the Cretaceous-Tertiary succession of this part of the world. 相似文献
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TAREQ HUSSEIN JYRKI MARTIKAINEN HEIKKI JUNNINEN LARISA SOGACHEVA ROBERT WAGNER MIIKKA DAL MASO ILONA RIIPINEN PASI P. AALTO MARKKU KULMALA 《Tellus. Series B, Chemical and physical meteorology》2008,60(4):509-521
Long-term measurements of fine particle number-size distributions were carried out over 9.5 yr (May 1997–December 2006), in the urban background atmosphere of Helsinki. The total number of days was 3528 with about 91.9% valid data. A new particle formation event (NPF) is defined if a distinct nucleation mode of aerosol particles is observed below 25 nm for several hours, and it shows a growth pattern. We observed 185 NPF events, 111 d were clear non-events and most of the days (around 83.5%) were undefined. The observed events were regional because they were observed at Hyytiälä (250 km north of Helsinki). The events occurred most frequently during spring and autumn. The observed formation rate was maximum during the spring and summer (monthly median 2.87 cm−3 s−1 ) and the modal growth rate was maximum during late summer and Autumn (monthly median 6.55 nm h−1 ). The events were observed around noon, and the growth pattern often continued on the following day. The observation of weak NPF events was hindered due to pre-existing particles from both local sources. It is clear that regional NPF events have a clear influence on the dynamic behaviour of aerosol particles in the urban atmosphere. 相似文献
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Abstract Runoff and soil erosion are known to cause a degradation in soil and water quality. Six natural runoff plots (three 10 m long and three 30 m long) were established on 6% uniform slope area for the study of P and N losses associated with runoff and soil erosion in northern Iraq. The soil at the site belongs to the Calciorthid suborder which dominates in the low rainfall zone of northern Iraq. Runoff, erosion, and associated P and N losses, were recorded from these plots for three rainfall seasons. Results illustrated that eroded sediment is always rich in available P and inorganic N compared to the original soil. Concentrations of soluble P and soluble N in runoff illustrated significant variability both between storms and between seasons. Both sediment-bound P and soluble P were significantly correlated with the ratio of runoff to rainfall. 相似文献
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分别选取2011-11-01精河Ms6.0地震和2012-06-30新源-和静Ms6.6地震自2009-01以来100 km范围内ML3.0以上地震, 使用CAP和P波初动方法计算震源机制解,并对主震前震源机制解进行聚类分析。结果表明,震中附近震前半年左右,震区周围地震断层性质逐渐由紊乱变为统一;最大主压应力P轴方位由随机逐步呈现相对突出方向,且逐步与主震方向一致。 相似文献
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