Nesamalar Kantasamy

Rainwater characterization at Global Atmospheric Watch in Danum Valley, Sabah

Air quality and pollution may be partly assessed by examination of rainwater compositions. Long term monitoring is essential in detecting signs of changing trend and hence any plausible air pollution and atmospheric acidification. Weekly samples of rainwater were collected by using a wet-only sampler at Global Atmospheric Watch (GAW) station in Danum Valley, Sabah in East Malaysia for a period between January 2005 and December 2006. Composition of wet deposition was determined for major cations (H⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, and NH<inf>4</inf>⁺) and major anions (Cl⁻, NO<inf>3</inf>⁻ SO<inf>4</inf>²⁻, CH<inf>3</inf>COO⁻ and HCOO⁻). In addition, the pH, electroconductivity and volume of rainwater were also determined. The results reveal that there was a steady decrease in pH of rainwater from annual average of 5.37 in 2005 to 5.14 in 2006. These pH values were below 5.6, the limiting value for clean rainwater. The lowest value recorded was 4.79 in October 2006 while the highest was 5.80 in January 2005. This is a worrying indication that atmospheric acidification may has made its presence felt in this remote area which was destined to be pristine environment. The volume-weighted mean concentrations of major ions followed the order: H⁺ > SO<inf>4</inf>²⁻ > Cl⁻ > Na⁺ > Ca²⁺ > NO<inf>3</inf>⁻ > NH<inf>4</inf>⁺ > K⁺ > Mg²⁺ > acetate > oxalate > formate. Both acidic and basic species concentrations were much lower compared to typical values in urban areas. The acid rain precursors; SO<inf>4</inf>²⁻ and NO<inf>3</inf>⁻ were well correlated and so were the sea-salt species, Mg²⁺, Na⁺ and Cl⁻. The buffering systems to potential acidity are mainly due to crustal origins (Ca²⁺) and anthropogenic activities (NH<inf>4</inf>⁺) with contribution from sea salts (Na⁺, Mg²⁺ and K⁺). Biogenic emissions producing weak organic acids was negligible.

Cogon Grass for Oil Sorption: Characterization and Sorption Studies

Cogon grass (Imperata cylindrica), an invasive, unwanted grass was used and evaluated for its applicability for the sorption of engine oil. Other than dried and ground for smaller size, no notable treatment was performed on the cogon grass. The physical and chemical properties of cogon grass were characterized by ash content, bulk density, pH slurry, and Field Emission Scanning Electron Microscopy (FESEM). The oil sorption was performed in a batch adsorption system. The effects of contact time, dosage of adsorbent and oil retention were investigated. The bulk density and ash content of the prepared carbon was 0.34 g/ml and 7.80 %, respectively. The pH slurry value was near neutrality (6.48). FESEM micrograph of cogon grass showed jagged and rough surface. FTIR spectra revealed the presence of aromatic rings of lignin and some aromatic compounds associated with CH. Carbon, hydrogen and nitrogen (CHN) analysis revealed that 41% of cogon grass consists of carbon. The cogon grass was observed to wet oil almost instantly with sorption equilibrium time of 5 min. The dose of cogon grass was found to slightly affect the sorption capacity. Oil retention experiments reveal the good ability of cogon grass to hold oil with about 96% retention after 24 h dripping. This study may provide an insight on the usefulness of cogon grass for removal of engine oils.

Adsorption of arsenic (V) and phosphate onto MgAlNO 3 -LDHs

LDH with nitrate in the interlayer and Mg-Al (3:1) in the layer have been synthesized by co-precipitation method. The adsorption of arsenic and phosphate onto MgAlNO3 hydrotalcite was evaluated with respect to pH, contact time, initial concentration and adsorbent dosage. The kinetic data were fitted into the pseudo-first-order equation, and the pseudo-second-order equations, and the intra-particle diffusion model. The results indicate that the pseudo-second-order model generates the best agreement with the experimental data for both arsenic and phosphate suggesting that the adsorption process might involve chemical sorption.

Removal of reactive dyes from single and binary mixture by Mg/Al-NO 3 -layered double hydroxide

The adsorption of two reactive dyes, Orange 16 (RO16) and a Reactive Red 120 (RR120) by Mg/Al-NO3 layered double hydroxide in single and binary mixture (1:1 ratio) was conducted in a batch mode. Spectrophotometric method using first order derivative and zero crossing was applied to analyse colour removal of RO16 and RR120 dyes from solutions. The effects of contact time in single and binary systems were compared. The results obtained at pH of 5 indicated that the percentage removal of dyes initially increased rapidly as contact time increased, then gradually until saturation was reached in both single and binary mixture. Increasing initial dye concentration lowered efficiency. The presence of RO16 in binary mixture RO16-RR120 did not alter the efficiency removal of RR120 and vice versa to a significant level at 50 mg/L.

A 5-Year study of inland aquatic acidification at Semenyih Dam

A 5-year inland aquatic acidification study was conducted on surface water of Semenyih Dam from 2005 to 2009. This study is part of a continous acidification monitoring programme for Malaysia as a participatory country of EANET (East Asia Acid Monitoring Network). Water samples were taken every three months at selected points of the dam. Besides pH, temperature and electrical conductivity, these samples were also analysed for soluble ions using ion chromatography. The ions analysed include SO₄^2-, NO₃^-, Cl^-, NH₄⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺. Basic pH, together with high acid neutralizing capacity (ANC) and alkalinity especially in 2005 and 2006 indicate Semenyih Dam was capable of neutralization any acidification due to anthropogenic activities. However, in 2008 and 2009, decreases in pH, alkalinity and ANC indicate surface water at Semenyih Dam was experiencing some acidification due to increases in acidifying species with respect to basic neutralizing cations.