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Pathak B.,Dibrugarh University | Biswas J.,Birjhora Mahavidyalaya | Bharali C.,Dibrugarh University | Bhuyan P.K.,Dibrugarh University
Atmospheric Pollution Research | Year: 2015

Intensive fire ignition and cracker work activities takes place during the festival of light called Diwali in India, celebrated for a period of few days in the month of October or November every year. The firecracker releases several pollutants [such as particulate matter (PM), black carbon (BC), organics, trace gases] near the surface. The effect of firecrackers on the atmospheric constituents is evaluated over Dibrugarh by monitoring the concentrations of PM, PM10(particle radius ≤10 μm), PM2.5(particle radius ≤2.5 μm) and BC during the Diwali and post-Diwali days (5 days after the Diwali Festival) in the years 2009 and 2010. Monthly average concentrations of each species except for the Diwali and post Diwali days is considered as the background concentrations. The concentration levels of the pollutants as recorded on the Diwali days are found to be a number of times higher (5.33 and 2.50 times for PM10, 5.74 and 2.65 times for PM2.5, 1.21 and 1.66 times for BC for the year 2009 and 2010, respectively) than the background levels at the peak hours of the fire work activity. To delineate the contribution of fireworks to the high concentrations of the species we performed air mass back trajectory analysis using the NOAA-HYSPLIT model in order to examine the existence of the transported aerosols. The ten day accumulated MODIS fire maps are also analyzed to mark out the contribution of aerosols from biomass burning. These analyses reveal that the higher concentrations of near surface aerosols including BC during the festival is due to the local effect of firework activities, neither because of long-range transport nor due to biomass burning activities. However, the higher concentration of pollutants for short periods has not degraded air quality substantially to cause health risks to people exposed to the festival in this environment. © Author(s) 2015. This work is distributed under the Creative Commons Attribution 3.0 License. Source


Sah O.P.,Birjhora Mahavidyalaya
Physics of Plasmas | Year: 2011

Localized nonlinear structures associated with dispersive Alfven waves are investigated in dusty plasma in the transition limit, i.e., α ≡ (β/2 Q) ∼ 1, where β is the ratio of thermal to magnetic pressure and Q is electron to ion mass ratio. Sagdeev pseudopotential is obtained from the basic governing equations, which is then numerically solved to study the existence and the behaviors of the nonlinear structures. It is found that both compressive and rarefactive solitons can coexist above and below certain critical α- values determined by the wave direction cosine (KZ) and the Mach number (M); and the compressive (rarefactive) solitons are much wider than the rarefactive ones for the case M < KZ (M>K Z). In addition, the rarefactive solitons are found to be converted into rarefactive double layers, for the case M >KZ, if the dust grains are negatively charged and their density exceeds certain critical value. © 2011 American Institute of Physics. Source


Sah O.P.,Birjhora Mahavidyalaya
Physics of Plasmas | Year: 2010

A detailed study of nonlinear excitations (solitons and double layers) of kinetic Alfvén waves in low but finite- ß electron-positron-ion plasma is presented using pseudopotential approach, which is valid for arbitrary wave amplitude. While sub- and super-Alfvénic solitonic structures and sub-Alfvénic double layer structures are found for both r (equilibrium positron-to-ion density ratio) <1 and r>1, super-Alfvénic double layers are found to be favorable in the region r>1. In any case, however, only compressive nonlinear excitations are found to exist. This contradicts the earlier result [H. Kakati and K. S. Goswami, Phys. Plasmas 7, 808 (2000)] predicting the existence of small-amplitude rarefactive sub- and super-Alfvénic kinetic Alfvén double layers under the assumption r1. The effects of positron/ion density, ion temperature, obliqueness of the wave propagation, and plasma- ß on nonlinear excitations are also examined. © 2010 American Institute of Physics. Source


Chakravarty P.,Birjhora Mahavidyalaya | Sarma N.S.,Polymer Section | Sarma H.P.,Gauhati University
Desalination | Year: 2010

Removal of lead(II) from aqueous solution was studied using the powder of heartwood of Areca catechu as a new biosorbent under batch method at room temperature. Various sorption parameters such as contact time, initial concentration of lead(II) ion, effect of pH and amount of the biomass on the adsorption capacity of the biosorbent were studied. The adsorbent was effective for the quantitative removal of lead(II) ions in acidic conditions and equilibrium has been achieved in 25. min. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption isotherm models and the model parameters were evaluated. The kinetic study showed that the pseudo-second order rate equation better described the biosorption process. The FT-IR spectra of the adsorbent before and after treatment with lead(II) solution indicated that hydroxyl, carboxyl, amide and amine groups were major binding sites with the metal. This method is quite feasible, economic, time saving, and low cost. © 2010 Elsevier B.V. Source


Chakravarty P.,Birjhora Mahavidyalaya | Sarma N.S.,Polymer Section | Sarma H.P.,Gauhati University
Chemical Engineering Journal | Year: 2010

The ability of abundantly available heartwood of Areca catechu to adsorb cadmium(II) ions from aqueous solution has been investigated through batch experiments at room temperature. Various sorption parameters such as contact time, initial concentration of cadmium(II) ion, solution pH and amount of the biomass on the adsorption capacity, were studied. The adsorbent was found to be effective for quantitative removal of cadmium(II) ions in acidic conditions and equilibrium has been achieved in 30. min at pH 6.0. The equilibrium adsorption data were fitted to Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models and the model parameters were evaluated. The kinetic study showed that the pseudo-second-order rate equation better described the biosorption process. The FT-IR spectrum analysis revealed that hydroxyl, carboxyl, amide and amine groups were major cadmium(II) binding groups. © 2010 Elsevier B.V. Source

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