The occurrence of vanadium in nature: its biogeochemical cycling and relationship with organic matter—a case study of the Early Cambrian black rocks of the Niutitang Formation,western Hunan,China     

Awan  Rizwan Sarwar  Liu  Chenglin  Yang  Shangfeng  Wu  Yuping  Zang  Qibiao  Khan  Ashar  Li  Guoxiong 《中国地球化学学报》2021,40(6):973-997

Acta Geochimica - Vanadium in the black rocks has economic and environmental impacts. In sediments, it is broadly disseminated as a multivalent metal element mainly sensitive to redox settings....  相似文献   

Provenance,tectonic setting,source weathering and palaeoenvironmental implications of Middle-Upper Jurassic rocks of Ler dome,Kachchh, western India: Inferences from petrography and geochemistry     

Asma A. Ghaznavi  Imran Khan  M.A. Quasim  A.H.M. Ahmad 《Chemie der Erde / Geochemistry》2018,78(3):356-371

The Middle-Upper Jurassic sandstones and shales of Ler dome (Chari and Katrol Formations), Kachchh, western India, have been analyzed for modal, bulk mineralogy and geochemistry to deduce their provenance, tectonic setting, source area weathering and palaeoenvironmental conditions. The detrital modes of Ler dome sandstones indicate that they were emanated from recycled orogen (uplifted shoulders of rift) and stable cratonic source in passive margin setting. Rapid deposition of sediments from a granitic source area can be predicted from feldspar abundance. A highly mature heavy mineral assemblage characterized in the form of high Zircon-Tourmaline-Rutile (ZTR) index also endorses these findings. The X-ray diffraction patterns (XRD) and scanning electron microscope (SEM) data show the presence of clay minerals depicting moderate to extensive chemical weathering in an oxidizing environment with periodic cycles of transgression and regression. The chemical index of weathering, chemical index of alteration and plagioclase index of alteration suggest moderate to high and low to moderate weathering conditions for sandstone and shales, respectively, that took place in low to moderate relief. We postulate that Ler dome sediments are derivative of the eroded and weathered parts of the Aravalli craton located on east and northeast of the basin and the Nagarparkar Massif placed to the north and northwest.  相似文献   

Chemometric evaluation of heavy metals distribution in wastewater irrigated soil of peri-urban area     

H. Ullah  N. U. Khan  F. Ali  A. Khan  I. Zeb  M. J. Khan 《International Journal of Environmental Science and Technology》2018,15(12):2519-2530

Characterization of content and source of heavy metals in soils are necessary to establish quality standards on a regional level. In relation to this, two zones, (sampling zone-1) and (sampling zone-2) depending on nature and intensity of wastewater disposal along the peri-urban area of Peshawar, Pakistan were selected. Thirty-six samples of wastewater and topsoil each were collected to determine the content of Pb, Cr, Cd, Cu, Zn, Ni, Fe and Mn, and physico-chemical parameters like pH, electrical conductivity, total solids, total dissolved solids, total suspended solids, and organic matter. Analytical determinations were performed by atomic absorption spectroscopy after microwave sample digestion in acid solution. Chemometric techniques which include hierarchical cluster analysis, principal component analysis, correlation analysis, and tukey test were applied. Concentrations of physico-chemical properties in wastewater and soil were higher in sampling zone-2. Concentrations of six heavy metals in wastewater and two in soil exceeded permissible limits of World Health Organization (Guidelines for drinking water quality, 4th edition, 2011), European Union (Heavy metals in wastes, European commission on environment. http://ec.europa.eu/environment/waste/studies/pdf/heavymetalsreport, 2002). Hierarchical cluster analysis grouped eight heavy metals into two clusters for wastewater and five clusters for soils. Principal component analysis describes four factors possessing Eigenvalues greater than 1.0 and explained the cumulative total variance of 84% with factor 1, having positive loading of anthropogenic metals (Cd, Cu, and Ni). Significant correlation was found between anthropogenic metals like Ni and Cd in water and between Cu and Cr in soil. Further research in other agricultural lands in peri-urban region would improve the basis for proposing such soil quality standards.  相似文献   

Magnetic tracing of sediment dynamics of mudbanks off southwest coast of India     

F. Badesab  V. Gaikwad  T. R. Gireeshkumar  O. Naikgaonkar  K. Deenadayalan  S. V. Samiksha  P. K. Dinesh Kumar  V. J. Loveson  S. D. Iyer  A. Khan  P. B. Udayakrishnan  A. Sardar 《Environmental Earth Sciences》2018,77(17):625

In this study, we utilized environmental magnetic in combination with sedimentological and hydrodynamic data to investigate the formative processes of mudbanks along southwest coast of India. We document the linkages between enrichment of silt-sized magnetic particles and formation processes of mudbanks along Alappuzha coast. A trend of increasing magnetite concentration and coarsening in magnetic grain size is observed at mudbank stations M2 and M3, while the mud-deficient station (M1) showed an opposite trend. A strong relationship between magnetic and physical grain size for all samples implies that the magnetic particle size and clastic grain size are largely adjunct. Analysis of rock magnetic and grain size data of surficial and suspended sediments from non-mudbank (M1) and two mudbank stations (M2, M3) reflect the differential sediment partitioning and transport regimes which controlled the formation of mudbanks along Alappuzha coast. Two plausible mechanisms responsible for the formation of mudbanks are identified: grain size-selective entrainment is the dominant process during pre-monsoon; weaker hydrodynamics (waves and bottom currents) favors accumulation of silt-sized (fine and coarse) magnetic and non-magnetic fractions resulting in the formation of magnetically low-enriched sediment bed of mixed grain sizes. At the onset of monsoon, wave-induced energetic bottom currents enhance the suspension of entire sediment bedload at stations M2, M3 to form fluid mud. Concurrently, mineral-density-based selective fractionation allows the settling of coarse silt-sized magnetic particles, while the fine magnetic silt-size particles accumulate forming thick fluid mud as a suspension load resulting in the formation of mudbanks. An observed increase in magnetic susceptibility and coarsening in magnetic grain size of surficial sediments at mudbank stations (M2, M3) during monsoon period supports the interpretation. Our findings are summarized in a conceptual model which can be very well applied to investigate sediment dynamics associated with mudbank formation in coastal and shelf sedimentary systems.  相似文献   

GIS-based landslide susceptibility evaluation using fuzzy-AHP multi-criteria decision-making techniques in the Abha Watershed,Saudi Arabia     

Javed Mallick  Ram Karan Singh  Mohammed A. AlAwadh  Saiful Islam  Roohul Abad Khan  Mohamed Noor Qureshi 《Environmental Earth Sciences》2018,77(7):276

Landslides are natural geological disasters causing massive destructions and loss of lives, as well as severe damage to natural resources, so it is essential to delineate the area that probably will be affected by landslides. Landslide susceptibility mapping (LSM) is making increasing implications for GIS-based spatial analysis in combination with multi-criteria evaluation (MCE) methods. It is considered to be an effective tool to understand natural disasters related to mass movements and carry out an appropriate risk assessment. This study is based on an integrated approach of GIS and statistical modelling including fuzzy analytical hierarchy process (FAHP), weighted linear combination and MCE models. In the modelling process, eleven causative factors include slope aspect, slope, rainfall, geology, geomorphology, distance from lineament, distance from drainage networks, distance from the road, land use/land cover, soil erodibility and vegetation proportion were identified for landslide susceptibility mapping. These factors were identified based on the (1) literature review, (2) the expert knowledge, (3) field observation, (4) geophysical investigation, and (5) multivariate techniques. Initially, analytical hierarchy process linked with the fuzzy set theory is used in pairwise comparisons of LSM criteria for ranking purposes. Thereafter, fuzzy membership functions were carried out to determine the criteria weights used in the development of a landslide susceptibility map. These selected thematic maps were integrated using a weighted linear combination method to create the final landslide susceptibility map. Finally, a validation of the results was carried out using a sensitivity analysis based on receiver operator curves and an overlay method using the landslide inventory map. The study results show that the weighted overlay analysis method using the FAHP and eigenvector method is a reliable technique to map landslide susceptibility areas. The landslide susceptibility areas were classified into five categories, viz. very low susceptibility, low susceptibility, moderate susceptibility, high susceptibility, and very high susceptibility. The very high and high susceptibility zones account for 15.11% area coverage. The results are useful to get an impression of the sustainability of the watershed in terms of landsliding and therefore may help decision makers in future planning and mitigation of landslide impacts.  相似文献   

Microfacies analysis and diagenetic fabric of the Lockhart Limestone exposed near Taxila,Margalla Hill Range,Punjab, Pakistan     

Mohibullah Khan  Mumtaz Ali Khan  Birkhez Aslam Shami  Muhammad Awais 《Arabian Journal of Geosciences》2018,11(2):29

The microfacies analysis and diagenetic fabric of the Lockhart Limestone are studied in an outcrop section exposed in the Margalla Hill ranges. The Lockhart Limestone is predominantly composed of medium to thick bedded, nodular and occasionally brecciated, highly fossiliferous limestone with thin interbeds of marl and shale. On the basis of detailed petrographic investigations, four microfacies have been identified including bioclastic packstone, wackestone (siliciclastic bioclastic rich sub-microfacies), wackestone-packstone, and mud-wackestone. Based on the microfacies analysis, the Lockhart Limestone is interpreted to have been deposited in the fore-shoal mid-ramp, mid-ramp, and outer ramp depositional environments. The Paleocene age has been assigned to the Lockhart Limestone based on age diagnostic foraminifera, i.e., Miscellanea, Lockhartia, and Ranikothalia. The diagenetic fabric of the Lockhart Limestone is characterized by several diagenetic features such as micritization, neomorphism (aragonite to calcite transformation and development of microspar), compaction, pressure dissolution (microstylolites), and cementation (calcite-filled microfractures). Such diagenetic features are developed in marine, meteoric, and burial diagenetic settings. The Paleocene Lockhart Limestone of Pakistan shows analogous features to that of the Paleocene Zongpu Formation (Member-3) of the Gamba-Tingri Basin of southern Tibet based on the outcrop features, microscopic fabric, and depositional environment.  相似文献   

Examining the rainfall–topography relationship using non-stationary modelling technique in semi-arid Aseer region,Saudi Arabia     

Javed Mallick  Ram Karan Singh  Roohul Abad Khan  Chander Kumar Singh  Nabil Ben Kahla  Essam Ibrahim Warrag  Saiful Islam  Atiqur Rahman 《Arabian Journal of Geosciences》2018,11(9):215

The mountainous region of Aseer, corresponding to the Afromontane phytogeographic region, is an eco-sensitive zone and has complex relationship between topography and rainfall. The region is located inland of the red sea escarpment edge in the west. Therefore, rainfall can occur during any month of the year in the mountain of the high Aseer region when moist air forces up the escarpment from the red sea. Monitoring the rainfall data and its topographical elevation variable in Aseer region is an essential requirement for feasible and accurate rainfall-based data for different applications, such as hydrological and ecological resource management in rugged terrain and remote areas. The relationship of elevation and rainfall are spatially non-stationary, non-linear, scale dependent, and often modelled by conventional regression models. Therefore, a local modelling technique, geographically weighted regression (GWR), was applied to deal with non-stationary, non-linear, scale-dependent problems. The GWR using topoclimatic data (elevation and rainfall) to analyse the cumulative rainfall data for rainy months (March to June) of the 4 years estimated from CHIRPS (Climate Hazards Group InfraRed Precipitation with Stations) product for Aseer region. The bandwidth (scale-size) of the Aseer region rainfall–elevation relationship has stabilised at round off 12 km. By selecting the suitable bandwidth, the spatial pattern of the rainfall–elevation relationship was significantly enhanced by using the GWR than the traditional ordinary least squares (OLS) regression model. GWR local modelling techniques estimated well in terms of accuracy, predictive power and decreased residual autocorrelation. Additionally, GWR assesses the significance of local statistic at each location and identified the location of spatial clusters with local regression coefficients significantly improved as compared with global OLS model, thereby highlighting local variations. Therefore, the GWR, local modelling approach managed to produce more accurate estimates by taking into account local characteristics.  相似文献   

Large scale mass movements triggered by the Kashmir earthquake 2005, Pakistan   总被引：2，自引：1，他引：1  

Muhammad BASHARAT  Joachim ROHN  Mirza Shahid BAIG  Muhammad Rustam KHAN  Markus SCHLEIER 《山地科学学报》2014,11(1):19-30

The SPOT image analysis in Muzaffarabad Azad Kashmir,northwest Himalayas,Pakistan reveals that the Kashmir earthquake 2005 triggered a number of coseismic mass movements along the hanging wall block of the Muzaffarabad Fault.The Neelidandi and Langarpura rock falls have been identified as two major reactivated mass movements with an estimated volume of 3.1 × 106m3and 5.76 × 106m3,respectively.The Neelidandi and Langarpura mass movements were initiated during earthquake in the direction of northwest-southeast extension and northeastsouthwest directed thrusting,respectively.The Neelidandi rock fall occurred in sheared cherty dolomites and limestones of the Cambrian Muzaffarabad Formation,whereas the Langarpura rock fall occurred in alternating clays,shales,claystones,siltstones and sandstones of the Miocene Murree Formation.These rock units along the fault are highly fractured and jointed.The geotechnical maps and geological longitudinal profiles show the relationship between the geometrical characteristics and mechanism of these mass movements.Their characteristics were analyzed according to the role of topographic,seismic,geological and tectonic factors.The steep topography,sheared rocks,lithology,coseismic uplift and strong ground shaking of the hanging wall block along Muzaffarabad Fault facilitated the gravity collapse of these mass movements.  相似文献   

A new fuzzy linear regression approach for dissolved oxygen prediction     

Usman T. Khan 《水文科学杂志》2013,58(6):1096-1119

Abstract

A new method for fuzzy linear regression is proposed to predict dissolved oxygen using abiotic factors in a riverine environment, in Calgary, Canada. The proposed method is designed to accommodate fuzzy regressors, regressand and coefficients, i.e. representing full system uncertainty. The regression equation is built to minimize the distance between fuzzy numbers, and generalizes to crisp regression when crisp parameters are used. The method is compared to two existing fuzzy linear regression techniques: the Tanaka method and the Diamond method. The proposed new method outperforms the existing methods with higher Nash-Sutcliffe efficiency, and lower RMSE, AIC and total fuzzy distance. The new method demonstrates that nonlinear membership functions are more suitable for representing uncertain environmental data than the typical triangular representations. A result of this research is that low DO prediction is improved and consequently the approach can be used for risk analysis by water resource managers.