Secular Variation of Geomagnetic Field at Karachi Observatory     

Hussain  Sumrah  Khan  Muhammad Nehal 《Geomagnetism and Aeronomy》2021,61(8):1234-1239

Geomagnetism and Aeronomy - In this work, the secular variation of noon/midnight geomagnetic observed field has been investigated at Karachi observatory using the data of total geomagnetic field...  相似文献   

Experimental and Numerical Studies of Velocity and Turbulence Intensities for Mid-Channel Bar     

Khan  Md. Amir  Sharma  Nayan  Odgaard  Jacob 《Water Resources》2021,48(5):746-762

Water Resources - Turbulent phenomenon in braided rivers is much more complex compared to the straight and meandering rivers. The turbulent flow structure at locations upstream and downstream of...  相似文献   

Modelling sediment (dis)connectivity across a river network to understand locational-transmission-filter sensitivity for identifying hotspots of potential geomorphic adjustment     

Sana Khan  Kirstie Fryirs  Simone Bizzi 《地球表面变化过程与地形》2021,46(14):2856-2869

Rivers act as ‘jerky conveyor belts’ that transmit fluxes of flow and sediment downstream. This transmission of fluxes can be highly variable within a drainage basin resulting in either abrupt or gradational sediment (dis)connectivity patterns and processes. This study assesses sediment (dis)connectivity across a basin as a means to understand the locational, transmission and filter sensitivity properties of a fluvial system. Drawing upon the case study of Richmond River Catchment, New South Wales, Australia we use the concepts of effective catchment area and buffers, along with graph theory and an empirical sediment transport model CASCADE (Catchment Sediment Connectivity and Delivery), to assess (1) the degree to which modelled sediment cascades along the river network are connected or disconnected (2) how the position, pattern and configuration of (dis)connection facilitates or restricts geomorphic adjustment in different parts of a catchment, and (3) use the findings as a basis to explain the locational-transmission-filter sensitivity of the catchment. We use this analysis to segregate supply limited and transport limited reaches and identify various controls on sediment dynamics: in-stream sediment storage units, junctions between different geomorphic river types, tributary confluences and sediment storage units within partly confined floodplain units. Such analysis lays the foundation for network scale identification of potential hotspots of geomorphic adjustment.  相似文献   

Scientists' warning on extreme wildfire risks to water supply     

François-Nicolas Robinne  Dennis W. Hallema  Kevin D. Bladon  Mike D. Flannigan  Gabrielle Boisramé  Christian M. Bréthaut  Stefan H. Doerr  Giuliano Di Baldassarre  Louise A. Gallagher  Amanda K. Hohner  Stuart J. Khan  Alicia M. Kinoshita  Rua Mordecai  João Pedro Nunes  Petter Nyman  Cristina Santín  Gary Sheridan  Cathelijne R. Stoof  Matthew P. Thompson  James M. Waddington  Yu Wei 《水文研究》2021,35(5):e14086

2020 is the year of wildfire records. California experienced its three largest fires early in its fire season. The Pantanal, the largest wetland on the planet, burned over 20% of its surface. More than 18 million hectares of forest and bushland burned during the 2019–2020 fire season in Australia, killing 33 people, destroying nearly 2500 homes, and endangering many endemic species. The direct cost of damages is being counted in dozens of billion dollars, but the indirect costs on water-related ecosystem services and benefits could be equally expensive, with impacts lasting for decades. In Australia, the extreme precipitation (“200 mm day −1 in several location”) that interrupted the catastrophic wildfire season triggered a series of watershed effects from headwaters to areas downstream. The increased runoff and erosion from burned areas disrupted water supplies in several locations. These post-fire watershed hazards via source water contamination, flash floods, and mudslides can represent substantial, systemic long-term risks to drinking water production, aquatic life, and socio-economic activity. Scenarios similar to the recent event in Australia are now predicted to unfold in the Western USA. This is a new reality that societies will have to live with as uncharted fire activity, water crises, and widespread human footprint collide all-around of the world. Therefore, we advocate for a more proactive approach to wildfire-watershed risk governance in an effort to advance and protect water security. We also argue that there is no easy solution to reducing this risk and that investments in both green (i.e., natural) and grey (i.e., built) infrastructure will be necessary. Further, we propose strategies to combine modern data analytics with existing tools for use by water and land managers worldwide to leverage several decades worth of data and knowledge on post-fire hydrology.  相似文献   

Hydrogeology,water quality,and microbial assessment of a coastal alluvial aquifer in western Saudi Arabia: potential use of coastal wadi aquifers for desalination water supplies     

Thomas M. Missimer  Christiane Hoppe-Jones  Khan Z. Jadoon  Dong Li  Samir K. Al-Mashharawi 《Hydrogeology Journal》2014,22(8):1921-1934

Wadi alluvial aquifers located along coastal areas of the Middle East have been assumed to be suitable sources of feed water for seawater reverse osmosis facilities based on high productivity, connectedness to the sea for recharge, and the occurrence of seawater with chemistry similar to that in the adjacent Red Sea. An investigation of the intersection of Wadi Wasimi with the Red Sea in western Saudi Arabia has revealed that the associated predominantly unconfined alluvial aquifer divides into two sand-and-gravel aquifers at the coast, each with high productivity (transmissivity?=?42,000 m²/day). This aquifer system becomes confined near the coast and contains hypersaline water. The hydrogeology of Wadi Wasimi shows that two of the assumptions are incorrect in that the aquifer is not well connected to the sea because of confinement by very low hydraulic conductivity terrigenous and marine muds and the aquifer contains hypersaline water as a result of a hydraulic connection to a coastal sabkha. A supplemental study shows that the aquifer system contains a diverse microbial community composed of predominantly of Proteobacteria with accompanying high percentages of Gammaproteobacteria, Alphaproteobacteria and Deltaproteobacteria.  相似文献   

Measurements of indoor radon, thoron, and their progeny using twin cup dosimeters in rural areas of Northern India     

M. Shakir Khan  Ameer Azam 《Environmental Earth Sciences》2014,71(3):1319-1325

Radon, thoron, and their progeny are largest contributors to the radiation dose received by human beings present in the natural environment. The indoor radon depends upon many factors such as building materials, meteorology, ventilation, and occupant’s behavior. This paper presents the measurements of indoor radon, thoron, and their progeny in four villages in rural area of district Kanshiram Nagar (Kasganj) in the state of Uttar Pradesh in Northern India. The concentration of indoor radon and thoron varies from 10.32 to 72.24 and 11.61 to 84.49 Bq m^?3 with a geometric mean (GM) of 29.49 and 31.20 Bq m^?3, respectively. The concentration of radon and thoron daughters was found to vary from 1.11 to 7.80 and 0.31 to 2.28 mWL, respectively. The annual exposure due to radon and thoron mainly vary from 0.05 to 0.30 WLM. The preliminary results (i.e., bare mode exposure of the LR-115 detectors fixed on cards) of this study have been separately published and compared this recent data with those results.  相似文献   

Petrography and geochemistry of Jumara Dome sediments,Kachchh Basin: Implications for provenance,tectonic setting and weathering intensity   总被引：1，自引：1，他引：0  

A. H. M. Ahmad  K. N. Noufal  Alam M. Masroor  Tavheed Khan 《中国地球化学学报》2014,33(1):9-23

In the Kachchh Mainland, the Jumara Dome mixed carbonate-siliciclastic succession is represented by the Jhurio and Patcham formations and siliciclastic-dominating Chari Formation （Bathonian to Oxfordian）. The Ju- mara Dome sediments were deposited during sea-level fluctuating, and were interrupted by storms in the shallow marine environment. The sandstones are generally medium-grained, moderately sorted, subangular to subrounded and of low sphericity. The sandstones are mineralogically mature and mainly composed of quartzarenite and subar- kose. The plots of petrofacies in the Qt-F-L, Qm-F-Lt, Qp-Lv-Ls and Qm-P-K ternary diagrams suggest mainly the basement uplift source （craton interior） in rifted continental margin basin setting. The sandstones were cemented by carbonate, iron oxide and silica overgrowth. The Chemical Index of Alteration values （73% sandstone and 81% shale） indicate high weathering conditions in the source area. Overall study suggests that such strong chemical weathering conditions are of unconformity with worldwide humid and warm climates during the Jurassic period. Positive correlations between A1203 and Fe203, TiO2, Na20, MgO, K20 are evident. A high correlation coefficient between A1203 and K20 in shale samples suggests that clay minerals control the major oxides, The analogous con- tents of Si, A1, Ti, LREE and TTE in the shale to PAAS with slightly depleted values of other elements ascribe a PAAS like source （granitic gneiss and minor mafics） to the present study. The petrographic and geochemical data strongly suggest that the studied sandstones/shales were deposited on a passive margin of the stable intracratonic basin.  相似文献   

Analysis of landslide causes and associated damages in the Kashmir Himalayas of Pakistan   总被引：1，自引：1，他引：0  

Atta-ur Rahman  Amir Nawaz Khan  Andrew E. Collins 《Natural Hazards》2014,71(1):803-821

This article deals with the analysis of landslide causes and associated damages in the Kashmir Himalayas of Pakistan. The present study is based on Muzaffarabad, which lies in the lesser Himalayas. Geologically, the Kashmir Himalaya is the young and most dynamic system in the world. In Muzaffarabad, mostly, people live on the fragile mountain slopes, and therefore, they are highly vulnerable to the risk of landslides. To achieve the objectives of the study, data were collected both from primary and secondary sources. Primary data were obtained through intensive field work and human perception survey, while secondary data were obtained from the related line agencies. The analysis reveals that in the study area, immature geology, active seismic zone, wide range of temperature and seasonal rain are the major physical factors, whereas human interventions on the fragile slopes are intensifying factors which in effect contribute to the landslide incidence. As a result, the adverse impacts on housing, sources of livelihood earnings and human casualties are escalating day-by-day. There are several implementing agencies which are responsible for reducing the risk of landsliding. So far, these agencies have not reduced the landslide damages rather their intensity and frequency have been increased especially after 2005 Kashmir earthquake.  相似文献   

Impact of haze and fog on filter characteristics in the process of monitoring radioactive aerosol     

B. I. Ogorodnikov  V. E. Khan 《Russian Meteorology and Hydrology》2013,38(11):787-791

Presented are the results of observations of the impact of fog and haze on the operation of filtering units for the sampling of radioactive aerosols in the process of monitoring radiation conditions in the Chernobyl exclusion zone. It is revealed that the performance of installations decreases in the case of the formation of fog and mist (as a rule, at the relative air humidity of more than 90%). This is associated with the settling of finest water droplets on the fibers and with the clogging of the filter. As the fog disappears, the droplets evaporate from the filtering fibers and the performance of the unit increases. In the case of fog and haze at night in November 2012, the performance of AURA-02.11 installation decreased almost by three times as compared with the initial one. To reduce the negative impact of fog and haze on the operation of units, it is reasonable to use the filters made of hydrophobic fibers.  相似文献   

Arsenite removal from water by electro-coagulation on zinc–zinc and copper–copper electrodes     

I. Ali  Mohd. Asim  T. A. Khan 《International Journal of Environmental Science and Technology》2013,10(2):377-384

Removal of arsenite from aqueous solution was carried out using electro-coagulation method. The experiments were conducted using copper–copper and zinc–zinc electrodes. The optimized experimental parameters were 2.0 mg/L initial concentration, 16.0-min processing time, 6.0 pH, 3.0-V applied voltage and 30 °C temperature for zinc–zinc electrodes while these values for copper–copper electrodes were 2.0 mg/L initial concentration, 20.0-min processing time, 7.0 pH, 5.0-V applied voltage and 30 °C temperature. The results demonstrated that zinc–zinc and copper–copper electrodes removed arsenite up to 99.89 and 99.56 %, respectively. The treated water was clear, colorless and odorless without any secondary contamination. There was no change in water quality after the removal of arsenite. The reported method is capable to remove arsenite from water at 6–7 pH range, which is a pH range of natural water. Therefore, this method may be the choice of arsenite removal from natural ground water.  相似文献