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Research paper thumbnail of Strength of Concrete Filled Steel Tubular Columns

Tsinghua Science & Technology, 2006

Composite columns of steel and concrete have been used and studied world wide, but filled tubular... more Composite columns of steel and concrete have been used and studied world wide, but filled tubular columns need more attention. This paper presents an experimental study on the behavior of short concrete filled steel tubular columns (CFT) axially loaded in compression to failure. A total of 28 specimens (16 were filled with concrete and 12 were kept hollow) with different cross-sections were tested to investigate the load capacity. The length-to-diameter ratios of these columns were between 4 and 9. Parameters for the tests were tube shape and diameter-to-thickness ratio. Some of the concrete filled columns had internal bracing of #3 deformed bars. The test results are compared with the theoretical results and previous studies.

Research paper thumbnail of Distribution of highly arsenic and fluoride contaminated groundwater from east Punjab, Pakistan, and the controlling role of anthropogenic pollutants in the natural hydrological cycle

This paper reports the extended study from a previously-described study on As and F contaminated ... more This paper reports the extended study from a previously-described study on As and F contaminated groundwater from a small village, Kalalanwala, in east Punjab, Pakistan (Farooqi et al., 2007). Of the 147 groundwater samples investigated, 91% exceeded the WHO standard (10 µg/L) for As and 75% exceeded the WHO standard (1.5 mg/L) for F -. The highly contaminated As (max. 2400 µg/L) and F -(max. 22.8 mg/L) groundwaters were found from shallow depths down to 30 m from the surface. The contaminated groundwaters are characterized by high pH (max. 8.8), alkalinity (HCO 3 up to 1281 mg/L), SO 4 2-(max. 960 mg/L), Na + (max. 1058 mg/L) and maximum electric conductivity >4.6 mS/cm. Fluoride concentrations showed positive correlations with those of Na + and HCO 3 and negative ones with Ca 2+ and Mg 2+ . The alkaline waters were saturated with calcite in spite of the low Ca 2+ concentrations. Fluoride concentration is governed by fluorite solubility. Speciation analysis showed As is mostly in the form of As V . There was a positive correlation between As and pH, while there is no relationship between As vs. Fe and F -. Thus, the fluoride and As contamination occurred in the oxidizing and alkaline conditions of the groundwater. However, Fand As are derived from two or more sources. Suspected contaminant sources in the study area contained considerable amounts of Fand As; fertilizers (DAP, n = 5) contained leachable Franging from 53-255 mg/kg, and As 5-10 mg/kg, and coals (n = 8) contained Franging from 5-20 mg/kg. Sulfur isotopic ratios indicated that the high SO 4 2in groundwater (3.2-7.0‰, CDT) is mainly derived from coal combusted atmospheric pollutants, fertilizers and household wastes. Nitrogen isotope data (8-30‰, Air) showed that NO 3 --N is attributed to animal waste distributed in the study area. The major chemical characteristics of the groundwaters are related with anthropogenic activities on the ground surface. The resultant major chemistry, especially highly alkaline and low Ca 2+ and Mg 2+ concentrations, must promote the high concentrations of Fand As in the studied groundwaters.

Research paper thumbnail of Sources of Arsenic and Fluoride in Highly Contaminated Soils Causing Groundwater Contamination in Punjab, Pakistan

Archives of Environmental Contamination and Toxicology, 2009

Highly contaminated groundwater, with arsenic (As) and fluoride (F−) concentrations of up to 2.4 ... more Highly contaminated groundwater, with arsenic (As) and fluoride (F−) concentrations of up to 2.4 and 22.8 mg/L, respectively, has been traced to anthropogenic inputs to the soil. In the present study, samples collected from the soil surface and sediments from the most heavily polluted area of Punjab were analyzed to determine the F− and As distribution in the soil. The surface soils mainly comprise permeable aeolian sediment on a Pleistocene terrace and layers of sand and silt on an alluvial flood plain. Although the alluvial sediments contain low levels of F, the terrace soils contain high concentrations of soluble F− (maximum, 16 mg/kg; mean, 4 mg/kg; pH > 8.0). Three anthropogenic sources were identified as fertilizers, combusted coal, and industrial waste, with phosphate fertilizer being the most significance source of F− accumulated in the soil. The mean concentration of As in the surface soil samples was 10.2 mg/kg, with the highest concentration being 35 mg/kg. The presence of high levels of As in the surface soil implies the contribution of air pollutants derived from coal combustion and the use of fertilizers. Intensive mineral weathering under oxidizing conditions produces highly alkaline water that dissolves the F− and As adsorbed on the soil, thus releasing it into the local groundwater.

Research paper thumbnail of Strength of Concrete Filled Steel Tubular Columns

Tsinghua Science & Technology, 2006

Composite columns of steel and concrete have been used and studied world wide, but filled tubular... more Composite columns of steel and concrete have been used and studied world wide, but filled tubular columns need more attention. This paper presents an experimental study on the behavior of short concrete filled steel tubular columns (CFT) axially loaded in compression to failure. A total of 28 specimens (16 were filled with concrete and 12 were kept hollow) with different cross-sections were tested to investigate the load capacity. The length-to-diameter ratios of these columns were between 4 and 9. Parameters for the tests were tube shape and diameter-to-thickness ratio. Some of the concrete filled columns had internal bracing of #3 deformed bars. The test results are compared with the theoretical results and previous studies.

Research paper thumbnail of Distribution of highly arsenic and fluoride contaminated groundwater from east Punjab, Pakistan, and the controlling role of anthropogenic pollutants in the natural hydrological cycle

This paper reports the extended study from a previously-described study on As and F contaminated ... more This paper reports the extended study from a previously-described study on As and F contaminated groundwater from a small village, Kalalanwala, in east Punjab, Pakistan (Farooqi et al., 2007). Of the 147 groundwater samples investigated, 91% exceeded the WHO standard (10 µg/L) for As and 75% exceeded the WHO standard (1.5 mg/L) for F -. The highly contaminated As (max. 2400 µg/L) and F -(max. 22.8 mg/L) groundwaters were found from shallow depths down to 30 m from the surface. The contaminated groundwaters are characterized by high pH (max. 8.8), alkalinity (HCO 3 up to 1281 mg/L), SO 4 2-(max. 960 mg/L), Na + (max. 1058 mg/L) and maximum electric conductivity >4.6 mS/cm. Fluoride concentrations showed positive correlations with those of Na + and HCO 3 and negative ones with Ca 2+ and Mg 2+ . The alkaline waters were saturated with calcite in spite of the low Ca 2+ concentrations. Fluoride concentration is governed by fluorite solubility. Speciation analysis showed As is mostly in the form of As V . There was a positive correlation between As and pH, while there is no relationship between As vs. Fe and F -. Thus, the fluoride and As contamination occurred in the oxidizing and alkaline conditions of the groundwater. However, Fand As are derived from two or more sources. Suspected contaminant sources in the study area contained considerable amounts of Fand As; fertilizers (DAP, n = 5) contained leachable Franging from 53-255 mg/kg, and As 5-10 mg/kg, and coals (n = 8) contained Franging from 5-20 mg/kg. Sulfur isotopic ratios indicated that the high SO 4 2in groundwater (3.2-7.0‰, CDT) is mainly derived from coal combusted atmospheric pollutants, fertilizers and household wastes. Nitrogen isotope data (8-30‰, Air) showed that NO 3 --N is attributed to animal waste distributed in the study area. The major chemical characteristics of the groundwaters are related with anthropogenic activities on the ground surface. The resultant major chemistry, especially highly alkaline and low Ca 2+ and Mg 2+ concentrations, must promote the high concentrations of Fand As in the studied groundwaters.

Research paper thumbnail of Sources of Arsenic and Fluoride in Highly Contaminated Soils Causing Groundwater Contamination in Punjab, Pakistan

Archives of Environmental Contamination and Toxicology, 2009

Highly contaminated groundwater, with arsenic (As) and fluoride (F−) concentrations of up to 2.4 ... more Highly contaminated groundwater, with arsenic (As) and fluoride (F−) concentrations of up to 2.4 and 22.8 mg/L, respectively, has been traced to anthropogenic inputs to the soil. In the present study, samples collected from the soil surface and sediments from the most heavily polluted area of Punjab were analyzed to determine the F− and As distribution in the soil. The surface soils mainly comprise permeable aeolian sediment on a Pleistocene terrace and layers of sand and silt on an alluvial flood plain. Although the alluvial sediments contain low levels of F, the terrace soils contain high concentrations of soluble F− (maximum, 16 mg/kg; mean, 4 mg/kg; pH > 8.0). Three anthropogenic sources were identified as fertilizers, combusted coal, and industrial waste, with phosphate fertilizer being the most significance source of F− accumulated in the soil. The mean concentration of As in the surface soil samples was 10.2 mg/kg, with the highest concentration being 35 mg/kg. The presence of high levels of As in the surface soil implies the contribution of air pollutants derived from coal combustion and the use of fertilizers. Intensive mineral weathering under oxidizing conditions produces highly alkaline water that dissolves the F− and As adsorbed on the soil, thus releasing it into the local groundwater.