Urban heat island (UHI) influence on secondary pollutant formation in a tropical humid environment

The combined action of urbanization (change in land use) and increase in vehicular emissions intensifies the urban heat island (UHI) effect in many cities in the developed countries. The urban warming (UHI) enhances heat-stress-related diseases and ozone (O₃) levels due to a photochemical reaction. Even though UHI intensity depends on wind speed, wind direction, and solar flux, the thermodynamic properties of surface materials can accelerate the temperature profiles at the local scale. This mechanism modifies the atmospheric boundary layer (ABL) structure and mixing height in urban regions. These changes further deteriorate the local air quality. In this work, an attempt has been made to understand the interrelationship between air pollution and UHI intensity at selected urban areas located at tropical environment. The characteristics of ambient temperature profiles associated with land use changes in the different microenvironments of Chennai city were simulated using the Envi-Met model. The simulated surface 24-hr average air temperatures (11 m above the ground) for urban background and commercial and residential sites were found to be 30.81 ± 2.06, 31.51 ± 1.87, and 31.33 ± 2.1ºC, respectively. The diurnal variation of UHI intensity was determined by comparing the daytime average air temperatures to the diurnal air temperature for different wind velocity conditions. From the model simulations, we found that wind speed of 0.2 to 5 m/sec aggravates the UHI intensity. Further, the diurnal variation of mixing height was also estimated at the study locations. The estimated lowest mixing height at the residential area was found to be 60 m in the middle of night. During the same period, highest ozone (O₃) concentrations were also recorded at the continuous ambient air quality monitoring station (CAAQMS) located at the residential area.

Implications: An attempt has made to study the diurnal variation of secondary pollution levels in different study regions. This paper focuses mainly on the UHI intensity variations with respect to percentage of land use pattern change in Chennai city, India. The study simulated the area-based land use pattern with local mixing height variations. The relationship between UHI intensity and mixing height provides variations on local air quality.     

Sisal/Carbon Fibre Reinforced Hybrid Composites: Tensile, Flexural and Chemical Resistance Properties

The variation of mechanical properties such as tensile and flexural properties of randomly oriented unsaturated polyester based sisal/carbon fibre reinforced hybrid composites with different fibre weight ratios have been studied. The chemical resistance test of these hybrid composites to various solvents, acids and alkalies were studied. The effect of NaOH treatment of sisal fibres on the tensile, flexural and chemical resistance properties of these sisal/carbon hybrid composites has also been studied. The hybrid composites showed an increase in tensile and flexural properties with increase in the carbon fibre loading. The tensile properties and flexural properties of these hybrid composites have been found to be higher than that of the matrix. Significant improvement in tensile properties and flexural properties of the sisal/carbon hybrid composites has been observed by alkali treatment. The chemical resistance test results showed that these untreated and alkali treated hybrid composites are résistance to all chemicals except carbon tetra chloride. Hand lay-up technique was used for making the composites and tests are carried out by using ASTM methods.     

Photodegradation of sulfonamide antibiotics in simulated and natural sunlight: Implications for their environmental fate

The photochemical fate of seven sulfonamides was investigated in matrices representative of natural water bodies under various light sources. Fundamental photolysis parameters such as molar absorption coefficient, quantum yield (QY) and first-order rate constants were determined. The photolysis decay rate was dependent on the protonation state of the molecule, pH of the water sample and dissolved organic matter. Natural organic matter was the most significant factor in the indirect photolysis of sulfonamides. Half-lives were in the range of minutes at 254 nm to days under natural sunlight. Under natural sunlight, all sulfonamides showed higher removal rates in natural waters implying that indirect photolysis is the predominant mechanism.     

Biodegradable Water Soluble Copolymer for Antimicrobial Applications

Synthesis and characterization of novel biodegradable, water soluble and optically active DL-malic acid (DMA) and citric acid (CA) copolymers were studied for possible use as antibacterial agents. The copolymers were synthesized by direct bulk melt condensation in the absence of a catalyst above 150 °C. Characterization of obtained copolymers was carried out with the help of infrared absorption spectra, differential scanning calorimetry and thermo gravimetric analysis. The antibacterial activity of copolymers against bacteria was investigated. The results obtained shows the above copolymers possess a broad wound dressing activity against different types of bacteria and may be useful as antibacterial agents.     

In vitro brain acetylcholinesterase response among three inbred strains of mice to monocrotophos.

The strain differences in the neurotoxic potential of monocrotophos (MCP) were assessed by determining the inhibition of brain acetylcholinesterase (AChE) in BALB/cAnN, DBA/2J and C57BL/6J in vitro. MCP being a competitive inhibitor for AChE, alters the Km values widely among these inbred strains. Comparatively least alterations in Km were found in BALB/cAnN and maximum in DBA/2J. Based on the Ki values DBA/2J was found to be the most sensitive strain to MCP inhibition followed by C57BL/6J and BALB/cAnN.     

Studies On the Effect of Hexachlorocyclohexane On the Growth and Silk Qualities of Silkworm, Bombyx Mori L

Toxicity of an organochloride insecticide, hexachlorocyclohexane (HCH) on the alterations in the growth and silk qualities of silkworm, Bombyx mori L were investigated. HCH yielded higher growth constants (K), indicating impairment of growth of silkworms and silk gland. the decrement in fibroin content is significant. HCH treatment also resulted in considerable reduction in the cocoon, pupal and shell weights, survival and emergence of pupae and number of eggs laid and deterioration in quality and quantity of silk thread.     

Tree recruitment in an empty forest

To assess how the decimation of large vertebrates by hunting alters recruitment processes in a tropical forest, we compared the sapling cohorts of two structurally and compositionally similar forests in the Rio Manu floodplain in southeastern Peru. Large vertebrates were severely depleted at one site, Boca Manu (BM), whereas the other, Cocha Cashu Biological Station (CC), supported an intact fauna. At both sites we sampled small (> or =1 m tall, <1 cm dbh) and large (> or =1 cm and <10 cm dbh) saplings in the central portion of 4-ha plots within which all trees > or =10 cm dbh were mapped and identified. This design ensured that all conspecific adults within at least 50 m (BM) or 55 m (CC) of any sapling would have known locations. We used the Janzen-Connell model to make five predictions about the sapling cohorts at BM with respect to CC: (1) reduced overall sapling recruitment, (2) increased recruitment of species dispersed by abiotic means, (3) altered relative abundances of species, (4) prominence of large-seeded species among those showing depressed recruitment, and (5) little or no tendency for saplings to cluster closer to adults at BM. Our results affirmed each of these predictions. Interpreted at face value, the evidence suggests that few species are demographically stable at BM and that up to 28% are increasing and 72% decreasing. Loss of dispersal function allows species dispersed abiotically and by small birds and mammals to substitute for those dispersed by large birds and mammals. Although we regard these conclusions as preliminary, over the long run, the observed type of directional change in tree composition is likely to result in biodiversity loss and negative feedbacks on both the animal and plant communities. Our results suggest that the best, and perhaps only, way to prevent compositional change and probable loss of diversity in tropical tree communities is to prohibit hunting.     

Water quality assessment of Lake Pandu Bodhan, Andhra Pradesh State, India

A systematic investigation of variations in some nutrient levels at Pandu Lake from August 2002 to July 2004 was carried out. The untreated domestic wastes from various parts of Bodhan town are directly discharged into Pandu Lake leading to gross pollution. Therefore present investigation was under taken to assess the magnitude of sewage pollution by monitoring key water quality parameters dissolved oxygen, biological oxygen demand, alkalinity, calcium, nitrates and phosphates etc. Monthly water samples were collected from three different sampling stations. Low Dissolved oxygen and high biological oxygen demand, elevated Nitrates and Phosphates levels were found, which gives the information about conversion of this water body from oligotrophic to eutrophic nature. Phosphates were found to be in the range of 0.9 to 4.0 mg/L. Nitrates were found to be higher in Pandu Lake and their number is more in summer, and suitable explanation was given. Nitrates were found to be in range between 24.8mg/L to 71.2mg/L. Data on various chemical characteristics vary at different sites in different months in Pandu Lake. Some of the characteristics like Dissolved Oxygen, Biological Oxygen Demand, Nitrates, Phosphates and nutrient loading are contributing to eutrophication process in this lake and the lake seems to be eutrophic through out the year.     

Tensile,Flexural and Chemical Resistance Properties of Sisal Fibre Reinforced Polymer Composites: Effect of Fibre Surface Treatment

In this study, effect of fibre surface treatment on tensile, flexural and chemical resistance properties were studied for sisal fibre reinforced composites. Natural ligno cellulosic sisal fibre reinforced composites were prepared by different surface treatments by hand lay-up method. Fibre surface treatments were carried out to produce good interface between the fibre and the matrix to improve the mechanical properties. Fibre surface treatments were done by boiled the sisal fibres in different % of NaOH and treated the fibres in different % of NaOH, treated in acetic acid and methanol. Unsaturated polyester resin was used as the matrix for preparing the composites. For comparison, these properties for untreated sisal fibre reinforced composites were also studied. From the results it was observed that 18% aqueous NaOH boiled sisal fibre reinforced composites have higher tensile, flexural properties than other composites. Untreated sisal fibre composites show lower properties than treated composites. Chemical resistance properties indicate that all sisal fibre reinforced composites are resistance to all chemicals except carbon tetra chloride. The tests are carried out as per the ASTM standards.     

Microbial degradation of pyridine using Pseudomonas sp. and isolation of plasmid responsible for degradation

Pseudomonas (PI2) capable of degrading pyridine was isolated from the mixed population of the activated sludge unit which was being used for treating complex effluents, the strain was characterized. Aerobic degradation of pyridine was studied with the isolated strain and the growth parameters were evaluated. Pyridine degradation was further conformed by chromatography (HPLC) analysis. The process parameters like biomass growth and dissolved oxygen consumption were monitored during pyridine degradation. In order to conform with the plasmid capability to degrade pyridine, the requisite plasmid was isolated and transferred to DH 5alpha Escherichia coli. The subsequent biodegradation studies revealed the ability of the transformed plasmid capability to degrade the pyridine.