Nurun Nahar

Bio: Nurun Nahar is an academic researcher from Jahangirnagar University. The author has contributed to research in topics: Metal ions in aqueous solution & Anodic stripping voltammetry. The author has an hindex of 3, co-authored 8 publications receiving 149 citations.

Organic and Black Carbon in PM2.5 at an Urban Site at Dhaka, Bangladesh

Abstract: The results from 1-year of measurements of PM2.5, organic carbon (OC) and black carbon (BC) concentrations are presented for an urban traffic-influenced site, the Farm Gate in Dhaka, Bangladesh. The measurements were based on sampling using two Air Metrics simultaneously operating samplers. The concentrations of OC and BC concentrations in PM2.5 varied from 5-96 μg/m^3 and 4-48 μg/m^3, respectively. The concentrations of PM2.5 varied from 11-328 μg/m^3. The annual particulate organic matter (POM) accounted for 46 ± 11% in PM2.5 whereas BC stayed at 33 ± 12%. The effects of meteorological conditions on the variability of OC and BC concentration were examined and the contribution of secondary organic aerosol to the total OC was calculated. The concentrations of OC and BC relative to the total PM2.5 are high and have good correlation with wind speed and temperature. The OC/BC ratio correlated with wind speed, temperature and sulfur concentration. Based on these relationships, it can be concluded that both local and regional sources of OC and BC are important. The local sources are traffic, coal and biomass burning. Distant sources include areas where there is extensive agricultural burning.

Sources of Carbonaceous Materials in the Airborne Particulate Matter of Dhaka

Abstract: To explore the sources of carbonaceous material in the airborne particulate matter (PM), comprehensive PM sampling was performed (3 to 14 January 2010) at a traffic hot spot site (HS), Farm Gate, Dhaka using several samplers: AirMetrics MiniVol (for PM10 and PM2.5) and MOUDI (for size fractionated submicron PM). Long-term PM data (April 2000 to March 2006 and April 2000 to March 2010 in two size fractions (PM2.2 and PM2.2-10) obtained from two air quality- monitoring stations, one at Farm Gate (HS) and another at a semi-residential (SR) area (Atomic Energy Centre, Dhaka Campus, (AECD)), respectively were also analyzed. The long-term PM trend shows that fine particulate matter concentrations have decreased over time as a result of government policy interventions even with increasing vehicles on the road. The ratio of PM2.5/PM10 showed that the average PM2.5 mass was about 78% of the PM10 mass. It was also found that about 63% of PM2.5 mass is PM1. The total contribution of BC to PM2.5 is about 16% and showed a decreasing trend over the years. It was observed that PM1 fractions contained the major amount of carbonaceous materials, which mainly originated from high temperature combustion process in the PM2.5. From the IMPROVE TOR protocol carbon fraction analysis, it was observed that emissions from gasoline vehicles contributed to PM1 given the high abundance of EC1 and OC2 and the contribution of diesel to PM1 is minimal as indicated by the low abundance of OC1 and EC2. Source apportionment results also show that vehicular exhaust is the largest contributors to PM in Dhaka. There is also transported PM2.2 from regional sources. With the increasing economic activities and recent GDP growth, the number of vehicles and brick kilns has significantly increased in and around Dhaka. Further action will be required to further reduce PM-related air pollution in Dhaka.

Electrochemical Studies on Speciation of Cadmium(II) in ppb Level by Complexation with Ethylenediamine in Aqueous Media

Abstract: The speciation of cadmium(II) in ppb level by complexation with ethylenediamine (EN) has been investigated by differential pulse anodic stripping voltammetry (DPASV) using thin mercury film coated glassy carbon electrode (TMFGCE). The overall work has been carried out at constant ionic strength of 0.01 mol dm -3 (NaNO 3 ) at ambient temperature. The pH was kept constant at 8.81 ± 0.10 by the addition of borate buffer. The stability constants of different species of cadmium(II) with ethylenediamine have been calculated from the variation of peak potential and diffusion current of simple and complexed metal ions under the present experimental conditions. The logarithmic values of overall stability constants: log β 1 , log β 2 and log β 3 (β i = [CdL i ]/[Cd 2+ ][L] i where i = 1, 2 and 3) have been found to be 5.01, 8.9 and 11.1 for CdL, CdL 2 and CdL 3 , respectively (charges were omitted for simplicity). The stability constants of cadmium complexes and hydrolysis constants of cadmium indicate that five different species of cadmium (Cd 2+ , CdOH + , CdL, CdL 2 and CdL 3 ) co-exist at ligand concentrations up to 5×10 4 mole dm -3 under the present experimental conditions. The results obtained by this method is applied to study the cadmium speciation in river water on the basis of competitive ligand exchange equilibrium.

Electrochemical Studies on Complexation and Speciation of Copper(II) in ppb Level with 1,10-Phenanthroline in Aqueous Media

Abstract: Complexation and speciation of copper (II) in ppb level with 1,10-phenanthroline (L) in aqueous media have been investigated by differential pulse anodic stripping voltammetry using thin mercury film glassy carbon electrode (TMFGCE). The work was carried out at constant ionic strength of 0.01 mol dm -3 using NaNO 3 at ambient temperature. The pH was kept constant at 9.12 ± 0.10 by the addition of borate buffer. Applying the concept of DeFord and Hume, the stability constants of different species of copper with 1,10-phenanthroline were calculated from the variation of peak potential and diffusion current of simple and complexed metal ions under the present experimental conditions. It was found that copper(II) form three complexes (1:1, 1:2 and 1: 3; metal : ligand) with 1,10-phenanthroline. The overall stability constant of copper complexes, MLn can be defined as β ML n = [ML n ]/[M 2 +][L] n in which M 2+ = Cu 2+ and L = 1,10-phenanthroline; n is an integer. The values of the stability constant of different copper complexes with 1,10-phenanthroline were found to be 10 9.33 , 10 15.10 and 10 20.48 for CuL, CuL 2 and CuL 3 , respectively (the overall charges were omitted for simplicity). The high values of overall stability constant indicate that the complexes are highly stable. Using the values of stability constant of copper complexes and hydrolysis constant of copper, the percentage of all possible copper species under present experimental conditions were calculated. Keywords: Electrochemical; Speciation; Complexation; Copper 1,10-phenanthroline. DOI: http://dx.doi.org/10.3329/bjsir.v46i2.8188 Bangladesh J. Sci. Ind. Res. 46(2) , 219-224, 2011

Organic/inorganic hybrid sensors: A review

Abstract: Due to the synergetic or complementary effects between organic and inorganic components, which could result in improved properties or performances, the organic/inorganic hybrid materials have recently gained extensive interest in many fields. Up to date, many reports have been published based on the organic/inorganic hybrid materials for the sensor applications. The paper provided a comprehensive review about recent progress of the organic/inorganic hybrid sensors. The organic/inorganic hybrid sensing materials could be fabricated in several configuration types such as intercalating type, core–shell type, coating type and mixed type. The sensing form of the hybrid sensors could be presented in thin-film, thick-film or pellet form, and the sensing performances could by measured in the flowing or static-state system. The hybrid sensing materials have been applied in gas sensors, humidity sensors, ultraviolet sensors, strain sensors, electrochemical immunosensors and fluorescent chemosensors. Finally, several suggestions related to future development of organic/inorganic hybrid sensing materials were also made.