Review of air pollution studies in Sri Lanka

Air pollution is a growing problem in Sri Lanka mainly due to the phenomenal increase in the number of motor vehicles and traffic congestion. Regular air pollution monitoring at automated air quality stations commenced in 1997 with two monitoring stations in Colombo. Results for the period 1997-2003 showed that the levels of sulphur dioxide, nitrogen dioxide, and ozone are steadily increasing while the carbon monoxide levels are decreasing. These pollutants are below their air quality standards except for fine particles (PM10 and PM2.5) which are always above the national standard. Air quality in Kandy is worse than that of Colombo owing to its geographical location, increased vehicle population and traffic congestion. In Kandy, sulphur dioxide, nitrogen dioxide and ozone levels exceeded the standards on 41%, 14% and 28% of the occasions during the period 2001-2005. Presence of carcinogenic polyaromatic hydrocarbons from both kitchen smoke and vehicular exhausts is a definite health hazard. Mean total concentrations of 16 prioritized PAHs (PPAHs) ranged from 57.43 to 1246.12 ng/m3 with a mean of 695.94 ng/m3 in urban heavy traffic locations in Kandy. There are increasing cases of respiratory diseases such as chronic obstructive pulmonary disease due to air pollution in Kandy. Indoor air pollution involving firewood use in congested kitchens is a major health hazard and a few limited studies show that wheezing, bronchitis and asthma incidence is found in children exposed to kitchen smoke. Air quality monitoring using bioindicators is a useful low-cost method to evaluate the pollution levels and the effects of air pollution on plants and vegetation needs more attention

Complexes of 1-Hydroxyxanthone with Cu(II), Ni(II), Co(II), Mn(II), Zn(II) & Mg(II)

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Possible links between groundwater geochemistry and chronic kidney disease of unknown etiology (CKDu): an investigation from the Ginnoruwa Region in Sri Lanka

Since at least two decades, Chronic Kidney Disease of Uncertain Etiology (CKDu) has become an increasingly discussed health issue in Sri Lanka and as well as in other tropical regions. Areas that are particularly afected with the disease are mostly located in the dry zone of Sri Lanka. The disease is more prominent among communities that consume groundwater as their main source of drinking water. Hydrogeochemical investigations were carried out in the Ginnoruwa area, a known hotspot of CKDu. It revealed possible links between drinking water chemistry and the spreading of the disease. This work compares hydrogeochemical data of drinking water sources of wells whose consumers are afected by CKDu and other nearby wells whose consumers were not afected by the disease. A total of 63 groundwater samples were collected from selected wells. About one-third of these samples (i.e., 19) were collected from wells used by CKDu patients. Signifcantly higher values of pH, total hardness, electrical conductivity, Ca2+, Mg2+, F-, Cl-, PO4 3-, and SO4 2- were found in wells that were used by CKDu patients. Mean contents of Na+, Ca2+, and Mg2+ in CKDu afected wells were 33.8 mg/L, 30.1 mg/L, and 14.9 mg/L, respectively, compared to 23.1 mg/L, 26.7 mg/L, and 9.65 mg/L in non-CKDu wells. Diferences in major ion geochemistry in groundwaters are possibly governed by variable time periods of water storage in fractured hard rock aquifers in this region. Hydrogeochemical parameters were statistically compared by a Mann–Whitney U test and indicated signifcant diferences in total dissolved solids (TDS) (p=0.016), SO4 2- (p=0.005), PO4 3- (p=0.030), F- (p=0.048), Na+ (p=0.008), and Mg2+(p=0.008) between non-CKDu and CKDu wells at p=0.050 level. Other suspected solutes such as nephrotoxic trace elements including As, Cd, and Pb were similar in both types of wells. They were also lower than the accepted guideline limits of the World Health Organization (WHO). Results of this study suggest that fuoride in drinking water in combination with water hardness may be one of the responsible factors for kidney damage and progression of the disease. This may be particularly the case when elevated amounts of Mg2+ are present in hard groundwater

Unique reactivity characteristics of Mo-coordinated S2-2 and S2-4 ligands

The synthesis of the new dithiolene complexes, [{(MeOOC)2C2S2}2Mo([mu]2-S)]-2 and [OMo(S2C2(COOMe)2)2]-, is reported. These complexes are obtained by the reaction of dicarbomethoxyacetylene (DMA) with either [(S4)Mo(S)([mu]2-S)2Mo(S)(S4)]2- or [(CS4)Mo(S)([mu]2-S)2Mo(S)(CS4)]2- and [OMo(S4)2]2-, respectively. The reaction of [(S4)Mo(O)([mu]2-S)2Mo(O)(S2)]2- with DMA results in the new dithiolene complex [{(MeOOC)2C2S2}Mo(O)([mu]2-S)]-2, which is the isomeric form of the vinyl disulfide complex obtained in the reaction of the [(S2)Mo(O)([mu]2-S)2Mo(O)(S2)]2- complex with DMA. The difference in reactivity between the two complexes that contain the same [Mo2O2S2]2+ core is attributed to the intrinsically different reactivity characteristics of the S2-4 and S2-2 ligands. As a result of Mo-S d[pi]-p[pi] bonding an alternation in the S---S bond lengths is observed in virtually all of the structurally characterized Mo-S4 units. The consequent weakening of the S---S bonds adjacent to the Mo---S bonds allows for the ready dissociation of S02 from the Mo-coordinated S2-4 ligands. This weakening also accounts for the facile formation of dithiolenes in cycloaddition reactions of alkynes with the Mo-S4 units. By comparison, the S---S bond in side-on Mo-coordinated S2-2 ligands is strengthened as a result of depopulation of the ligand [pi]*-orbitals. Reactions of the latter with alkynes do not proceed by cycloaddition. Instead, insertion into the Mo---O bond has been reported for at least one such reaction. The importance of activated polysulfide ligands in the hydrodesulfurization reaction is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26402/1/0000489.pd

A Nitronitrosyliron Complex as a Potential Oxygen Transfer Reagent

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Correlation of atmospheric purity index to the diversity of lichens in the Horton Plains National Park, Sri Lanka

Horton Plains National Park (HPNP) has been declared as a world heritage site, because of its unique biodiversity. Die-back of certain areas of this park is widely believed to be due to acidic precursor depositions carried over from other parts of the country and also from neighboring countries. Air pollution data for the two pollutants, NO2 and SO2 were obtained from the passive air sampling method. The data revealed that the concentrations of ambient NO2 and SO2 were very low in the HPNP. The variations of ambient NO2 and SO2 concentrations during the study period showed insignificant positive correlation (p≥ 0.05) with the rainfall data. Considering the variations of these two pollutants with Relative Humidity and the number of vehicles visiting HPNP, both pollutants had insignificant positive correlation. The Index of Atmospheric Purity (IAP) value obtained for the whole area of the HPNP was 54.22. This value belongs to the quality level 5 which represents the ‘very low’ pollution level. The results including lichen distribution and air quality data could confirm that the ambient air quality at HPNP is very high. The high diversity of lichens and the minimum levels of air pollutants suggested that the forest health of HPNP is at a favorable level. Therefore, it is essential to maintain at least the current air pollution level of HPNP in order to conserve the forest and its biodiversity

Comparison of CdS thin films prepared by different techniques for applications in solar cells as window materials

CdS thin films as window materials for solar cells have been prepared by three procedures; chemical bath deposition, electrodeposition in an aqueous medium at 80 degrees C and electrodeposition in a non-aqueous medium at 170 degrees C. As deposited films along with those obtained after annealing in air at 400 degrees C for 15 min were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM), optical absorption spectra and photoelectrochemical spectroscopy (PEC) techniques under identical experimental conditions. X-ray diffraction data indicate the formation of hexagonal CdS as the predominent phase, but the SEM studies show that their textures are widely dependent on the conditions employed. GDOES profiling indicates the incorporation of Na and Si into CdS films prepared by all three techniques. Annealing of chemical bath deposited films causes a red shift of the absorbance edge and also a shift in the maxima of the photocurrent action spectra towards the low energy side. However, this effect was comparatively negligible for the samples prepared by the other two techniques. PEC studies indicate that CdS materials grown by all three techniques are all n-type. All studies indicate that the films grown at 170 degrees C using non-aqueous solutions are of better crystallinity and of improved electrical properties. (C) 1998 Kluwer Academic Publishers

Polyethyleneoxide (PEO)-based, anion conducting solid polymer electrolyte for PEC solar cells

Solid polymer electrolyte membranes were prepared by complexing tetrapropylammoniumiodide (Pr4N+I-) salt with polyethylene oxide (PEO) plasticized with ethylene carbonate (EC), and these were used in photoelectrochemical (PEC) solar cells fabricated with the configuration glass/FTO/TiO2/dye/electrolyte/Pt/FTO/glass. The PEO/Pr4N+I-+I-2=9:1 ratio gave the best room temperature conductivity for the electrolyte. For this composition, the plasticizer EC was added to increase the conductivity, and a further conductivity enhancement of four orders of magnitude was observed. An abrupt increase in conductivity occurs around 60-70 wt% EC; the room temperature conductivity was 5.4 x 10(-7) S cm(-1) for 60 wt% EC and 4.9 x 10(-5) S cm(-1) for the 70 wt% EC. For solar cells with electrolytes containing PEO/Pr4N+I-+I-2=9:1 and EC, IV curves and photocurrent action spectra were obtained. The photocurrent also increased with increasing amounts of EC, up to three orders of magnitude. However, the energy conversion efficiency of this cell was rather low