Modifications in the solubility and precipitation behavior of various metals as a result of their interaction with sedimentary humic acid     

M.A. Rashid  J.D. Leonard 《Chemical Geology》1973,11(2):89-97

The sedimentary humic acid or its acid-hydrolysate, consisting of various amino acids, was found effective in dissolving unusually large quantities of metals (up to 682 mg/g of organic matter) from their insoluble salts. The presence of humic acid in the reaction media which had favorable conditions for the precipitation of metals as carbonates, hydroxides or sulfides, prevented the formation of insoluble metal salts. Infrared analysis suggests that the metals added to various anionic systems and humic acid do not react with the anion. The most likely mechanism of reaction appears to be a complex formation between metals and organic matter which keeps the metal in solution.The enhanced solubility and consequent decrease in precipitation of metals under the influence of humic compounds, as evidenced in these studies should play a leading role in the accumulation of metals in sedimentary deposits.  相似文献   

Environmental controls of methane production in Holocene basins in eastern Canada     

M.A. Rashid  G. Vilks 《Organic Geochemistry》1977,1(1):53-59

Rapid rates of sedimentation from 54 to 134 cm/1000 yr are typical of the Holocene basins in St. Margaret's Bay and the Grand Manan Basin, Nova Scotia. The water column is well oxygenated but, because of the rapid rate of sedimentation, anoxic conditions developed and enhanced the preservation of organic matter and its fermentative degradation; also the concentrations of sulfide increased and soluble sulfates were rapidly depleted. A direct result of this has been the production of methane in amounts exceeding 22,000 ppm. In contrast, nearby cores with rates of sedimentation of less than 20 cm/1000 yr have only 30–40 ppm methane. High rates of sedimentation and the ensuing anaerobic conditions appear to be the principal factors for the genesis and preservation of methane.The δ ¹³C values and the n-alkane distribution show that there is more terrestrial organic matter in the Grand Manan Basin than in St. Margaret's Bay. This could account for the high concentrations of methane in the Grand Manan cores despite the low concentrations of organic carbon.  相似文献   

Utilization of geoinformation tools for the development of forest fire hazard mapping system: example of Pekan fire, Malaysia     

Ahmad Rodzi Mahmud  Iwan Setiawan  Shattri Mansor  Abdul Rashid Mohamed Shariff  Biswajeet Pradhan  Ahmed Nuruddin 《Central European Journal of Geosciences》2009,1(4):456-462

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High Ni Levels in Soil Can Modify Growth Performance and Mineral Status of Wheat Cultivars          下载免费PDF全文

Muhammad Sabir  Khalid Rehman Hakeem  Tariq Aziz  Muhammad Zia‐ur‐Rehman  Irfan Rashid  Munir Ozturk 《洁净——土壤、空气、水》2014,42(9):1263-1271

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Projected climate change impacts on vegetation distribution over Kashmir Himalayas   总被引：1，自引：0，他引：1  

Irfan Rashid  Shakil Ahmad Romshoo  Rajiv Kumar Chaturvedi  N. H. Ravindranath  Raman Sukumar  Mathangi Jayaraman  Thatiparthi Vijaya Lakshmi  Jagmohan Sharma 《Climatic change》2015,132(4):601-613

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An integrated approach for aquifer vulnerability mapping using GIS and rough sets: study from an alluvial aquifer in North India     

Arina Khan  Haris Hasan Khan  Rashid Umar  Muneeb Hasan Khan 《Hydrogeology Journal》2014,22(7):1561-1572

A modified DRASTIC model in a geographic information system (GIS) environment coupled with an information-analytic technique called ‘rough sets’ is used to understand the aquifer vulnerability characteristics of a segment of the lower Kali watershed in western Uttar Pradesh, India. Since the region is a flat plain, topography (T) is removed as a potential control. Other parameters are the same as in DRASTIC, hence the new model is termed as DRASIC. The rough set technique is employed to provide insight into the relative vulnerabilities of different administrative units (blocks) within the study area. Using rough sets, three important factors are computed: strength, certainty and coverage. Strength indicates how the vulnerability characteristics vary in the entire area, certainty gives the relative fractions of low, medium and high vulnerability regions within a particular block, and coverage computes the percentage of a particular vulnerability state in each block. The purpose of the work is to demonstrate the utility of this integrated approach in classifying different administrative blocks in the study area according to their aquifer vulnerability characteristics. This approach is particularly useful for block-level planning and decision making for sustainable management of groundwater resources.  相似文献   

A geospatial model for the optimization grazing management in semi-arid rangeland of Iran     

Fazel Amiri  Abdul Rashid bin Mohamed Shariff  Taybeh Tabatabaie  Biswajeet Pradhan 《Arabian Journal of Geosciences》2014,7(3):1101-1114

Extensive livestock grazing even in unsuitable land has increasingly grown in most parts of semi-arid rangeland. Therefore, it is of paramount importance to identify suitable land for livestock grazing for optimum utilization while causing minimum impact to the environment. This paper adapted the schematic model based on the concepts presented by the Food and Agriculture Organization of suitability analysis for optimal grazing management in semi-arid rangeland in Iran. Factors affecting extensive grazing were determined and incorporated into the model. Semi-arid rangeland with variable such as climate and other agents were examined for common types of animal grazing and the advantages and limitations were elicited. Many ecosystem components affect land suitability for livestock grazing but due to time and funding restrictions, the most important and feasible elements were investigated. Within the model parameters, three submodels including water accessibility source, forage production, and erosion sensitivity were considered. Suitable areas at four levels of suitability were determined using geographic information systems. This suitability modeling approach was adopted due to its simplicity and the minimal time required for transforming and analyzing datasets. The most important reducing factors in model suitability were found to be: (a) land use and vegetation cover (in relation to soil erosion sensitivity), (b) the amount of the available forage in comparison with the total production, and (c) the existence of less palatability plants among the pasture plant species (forage production suitability). The results of the study would be beneficial to rangeland managers in devising measures more wisely to cope with the limitations and enhance the health and productivity of the rangelands.  相似文献   

Assessing the impacts of changing land cover and climate on Hokersar wetland in Indian Himalayas     

Shakil Ahmad Romshoo  Irfan Rashid 《Arabian Journal of Geosciences》2014,7(1):143-160

Monitoring the spatiotemporal changes in wetlands and assessing their causal factors is critical for developing robust strategies for the conservation and restoration of these ecologically important ecosystems. In this study, the spatiotemporal changes in the land cover system within a Himalayan wetland and its catchment were assessed and correlated using a time series of satellite, historical, and field data. Significant changes in the spatial extent, water depth, and the land system of the Hokersar wetland were observed from the spatiotemporal analysis of the data from 1969 to 2008. The wetland area has shrunk from 18.75 km² in 1969 to 13 km² in 2008 with drastic reduction in the water depth of the wetland. The marshy lands, habitat of the migratory birds, have shrunk from 16.3 km² in 1969 to 5.62 km² in 2008 and have been colonized by various other land cover types. The land system and water extent changes within the wetland were related to the spatiotemporal changes in the land cover and hydrometeorological variables at the catchment scale. Significant changes in the forest cover (88.33–55.78 km²), settlement (4.63–15.35 km²), and water bodies (1.75–0.51 km²) were observed in the catchment. It is concluded that the urbanization, deforestation, changes in the hydrologic and climatic conditions, and other land system changes observed in the catchment are the main causes responsible for the depleting wetland extent, water depth, and biodiversity by adversely influencing the hydrologic erosion and other land surface processes in the catchment. All these causes and effects are manifest in the form of deterioration of the water quality, water quantity, the biodiversity changes, and the decreasing migratory bird population in the wetland.  相似文献   

Monitoring rangeland ground cover vegetation using multitemporal MODIS data     

Hassan Yeganeh  Seyed jamale Khajedein  Fazel Amiri  Abdul Rashid B. Mohamed Shariff 《Arabian Journal of Geosciences》2014,7(1):287-298

The aim of the present research is to monitor changes in herbage production during the grazing season in the Semirom and Brojen regions, Iran, using multitemporal Moderate Resolution Imaging Spectroradiometer (MODIS) data. At first, various preprocessing steps were applied to a topography map. The atmospheric and topographic corrections were applied using subtraction of the dark object method and the Lambert method. Image processing, including false-color composite, principal component analysis, and vegetation indices were employed to produce land use and pasture production maps. Vegetation sampling was carried out over a period of 4 months during June–September 2008, using a stratified random sampling method. Twenty random sampling points were selected, and herbage production was estimated and verified with the double-checking method. Four MODIS data sets were used in this study. The models for image processing and integrating ground data with satellite images were processed, and the resulting images were categorized into seven classes. Finally, the land covers were verified for accuracy. A postclassification analysis was carried out to verify the seven class change detections. The results confirmed that Normalized Difference Vegetation Index (NDVI) and Soil-Adjusted Vegetation Index (SAVI) maps had a close relationship with the field data. The indices produced with shortwave infrared bands had a close relationship with field data where the ground cover and yields were high. The R ² value observed was 0.85. The changes in the pasture vegetation were high during the growing season in more than 90 % of the pastures. During the growing season, most changes in the pastures belonged to class 5 and 2 in the NDVI and SAVI index maps, respectively.  相似文献