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941.
Soil erosion by water has been a major problem since man introduced agriculture in the landscape. Soil erosion is a common hazard which is steadily increasing as a result of human activities in many parts of the world. Hunter Valley of NSW is located in subtropical eastern Australia. The region is known for its diversity in landscape that includes wide floodplains, extensive estuarine wetlands, undulating country, escarpments and rugged sandstone gorges. The region is also well known for wine production. The Hunter Valley has a long history of soil erosion following the European settlement 150 years ago. Currently there have been renewed human activities in the south central part of the region for coal mining, leading to clearance of vegetation and disturbance of soil. The present study addresses the issue of soil erosion in a part of Hunter Region by employing the Revised Universal Soil Loss Equation (RUSLE, Renard et al., 1977) model. The results indicate that the average annual soil loss from the area is 0.7 kg/m2/year, which is well beyond the tolerance limit of the soil. Statistical relationships between soil loss and each parameter of the RUSLE equation were obtained and it was found that C factor has significant influence on the average soil loss in the area. An overall picture that emerges out of the study is that the region is continuing to suffer as a result of disturbance in natural environment from the historical times till present.  相似文献   
942.
The identified mollusks from the Burullus lagoon of Egypt (Eastern Mediterranean) are represented by four bivalve species and four gastropod species. Sources of heavy metals pollution in the Burullus lagoon include phosphate fertilizers, sewage and oil spills from fishing boats.The Cerastoderma glaucum species has a wide distribution in the central part of the studied area with satisfying criteria required for good bio-monitors of pollution. High concentrations of heavy metals are found in water, at the eastern side of the lagoon, while low concentrations were detected in the central and western sides of the lagoon. Pirenella conica constitutes the total gastropods assemblages, reflecting this species tolerance to the high concentration of heavy metals. Meanwhile, the total pelecypods in bottom lagoon sediments are completely absent in the eastern parts of the lagoon, which may be due to the sensitivity of pelecypods to the accumulation of heavy metals.  相似文献   
943.
Remotely sensed thermal infrared (TIR) data have been widely used to retrieve land surface temperature (LST). LST is an important parameter in the studies of urban thermal environment and dynamics. In the study, an attempt has been made using LANDSAT 8 thermal imagery to compute LST and the associated land cover parameters viz; land surface emissivity (LSE), normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI) and normalized difference water index (NDWI). Landsat 8 TIRS band 10 & 11 (thermal bands) during 21 Oct. 2016, 22 Nov.2016, 24 Dec. 2016 and 09 Jan. 2017 were processed for LST analysis. However, band 5 & band 4 of the imagery was processed for NDVI, band 6 & band 5 for NDBI and band 2 & band 5 for NDWI analysis. LST has been derived from both the bands 10 &11 and validated by in-situ observations on the date and time of satellite overpass from the study area. Band 10 derived LST have shown much temperature difference while comparing with the in-situ observations. However, LST derived from band 11 found similar & close to the in-situ measurements. Relationship between band 11 results and in-situ observed measurements were developed, which has showing a strong correlation with (r2 = 0.991). Land surface emissivity were also evaluated which shows variation in different land cover surfaces like vegetation, settlement, forest cover and water body. The study has proven that land surface temperature derived from satellite band 11 is the actual surface temperature of the study area.  相似文献   
944.
In the present paper integrated appraisals of landform evolution and their geomorphic features, drainage networks across the upper part of Yamuna river basin have been attempted by using various geomorphic indices such as watershed, drainage density (D), drainage texture, stream-gradient index (SL), hypsometric integral (HI), drainage basin asymmetry (AF), mountain front sinuosity (Smf), sinuosity index (SI), valley floor height and width ratio (Vf) and data of historical earthquakes in characterizing the basin in view of relative index of active tectonics (RIAT) on DEM in geographic information systems (GIS) environment to assess the influence of recent tectonics on geomorphologic growth of the basin.The substantiated RIAT classes through some field observations and corroborated by recent seismicity reveal the recent activation of Yamuna tear faults in the basin with delineation of four RIAT classes such as class-1 (inactive 9.8% of the area), class-2 (low active; 16.40% of the area), class-3 (moderately active; 42.38% of the area) and class-4 (very active; 31.62%). The results suggest that the Himalayan frontal thrust (HFT) and Yamuna tear (YT) located in the basin is morphogenic in nature and got activated several times as evidenced by number of seismic activities in the basin and adjoining regions. The incision, and sharp turning of rivers, crenulations and warping of cross beddings/laminations and silt/clay beds and lenses, megascopic and mesoscopic faulting in sediment sequences suggest a very active nature of the HFT and YT till date in association with three prolific microseismogenic weak zones These active discontinuities appear to support the formation and development of different deformational features in sediment sequences which may be indirectly related to subduction and underthrusting of Indian plate under Eurasian plate below the Himalayan mountain chain.  相似文献   
945.
946.
In the present investigation, an attempt has been made to explore the possibility of hydrocarbon prospects in the carbonaceous shale deposits of Spiti and Chikkim formations exposed in the Spiti valley of the Tethys Himalaya. Twenty samples, collected from successive levels of these litho-units, have been subjected to maceral analysis, Rock-Eval Pyrolysis and six samples to Fourier Transform Infra-red Spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses. The study reveals the presence of mainly kerogen-III type of organic matter but some of the shale samples have shown a good amount of total organic carbon (TOC) to the tune of 3.19% which is sufficient to produce hydrocarbon. The results indicate the presence of methane occurring as free and fixed hydrocarbon in the shale samples. Few levels are especially rich in hydrocarbon. They have shown encouraging results with potential for generating liquid as well as lighter hydrocarbon. The data is also supported by the FTIR and NMR studies.  相似文献   
947.
Flood is among the deadliest disasters in India, and the frequency of floods and extreme precipitation events is projected to increase under the warming climate. The frequency of floods in India varies geographically as some regions are more prone to floods than the others. The Kerala flood of 2018 caused enormous economic damage, affected millions of people, and resulted in the death of more than 400 people. Here we provide a hydroclimatological perspective on the Kerala flood of 2018. Using the observations and model simulations from the Variable Infiltration Capacity (VIC) model, we show that the 2018 extreme precipitation and runoff conditions that caused flooding were unprecedented in the record of the past 66 years (1951–2017). Our results show that mean monsoon precipitation has significantly declined while air temperature has significantly increased during 1951–2017 in Kerala. The drying and warming trends during the monsoon season resulted in a declined total runoff in large part of the state in the last 66 years. Apart from the mean hydroclimatic conditions, extreme precipitation, and extreme total runoff have also declined from 1951 to 2017. However, 1 and 2-day extreme precipitation and extreme runoff conditions in August 2018 exceeded substantially from the long-term 95th percentiles recorded during 1951–2017. Since there is no increase in mean and extreme precipitation in Kerala over the last six decades, the extreme event during August 2018 is likely to be driven by anomalous atmospheric conditions due to climate variability rather anthropogenic climate warming. The severity of the Kerala flood of 2018 and the damage caused might be affected by several factors including land use/land cover change, antecedent hydrologic conditions, reservoir storage and operations, encroachment of flood plains, and other natural factors. The impacts of key drivers (anthropogenic and natural) on flood severity need to be established to improve our understanding of floods and associated damage.  相似文献   
948.
949.
950.
Granitic plutons occurring within and to the west of the Delhi Fold Belt in the Aravalli craton, northwestern India are the result of widespread felsic magmatism during Neoproterozoic, some of which are associated with greisen and skarn tungsten deposits. In this paper, we present the result of our study on fluid inclusions, geochemistry and geochronology of two such tungsten mineralized granite plutons at Degana and Balda, and interpret the nature of ore fluid, and petrogenesis and age of these mineralized granites. Fluid inclusion study reveals coexistence of moderate and hyper-saline aqueous fluid inclusions along with aqueous-carbonic inclusions, suggesting their origin due to liquid immiscibility during fluid–rock interaction. Geochemically, the granites are peraluminous, Rb enriched, Sr and Ba depleted and highly differentiated. The Rb–Sr isotopic systematics yielded \(795\pm 11\) Ma for Balda granite and \(827\pm 8\) Ma for Degana granite. We show that major phase of widespread granitoid magmatism and mineralization during the Neoproterozoic (840–790 Ma) in NW India is coeval with breakup of the Rodinia supercontinent and infer a causal relationship between them.  相似文献   
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