A Computational Program for Estimating Atmospheric Corrosion of Monuments

This study developed a novel computer program for predicting the deterioration of various types of materials from historic monuments caused by exposure to atmospheric pollution. The program was designed based on a set of materials’ dose-response functions, which take air pollutants together with climatic parameters into account. It is a web-based application that requires three input datasets: monuments’ material characteristics, local meteorological data and air pollution levels over a defined exposure time. It is also capable of estimating restoration costs. Quantification of future monument deterioration is possible by extrapolation of linear temporal relationships for air pollution and meteorological parameters. This user-friendly-interface program cooperates with Google Maps™ to find the nearest air pollution and meteorological stations to the monument site. The program may be used as a tool providing quantitative information for effective policy-making in conservation of cultural heritage monuments. To illustrate its use, the program was employed to assess the accumulated deterioration of 75 Buddhist monuments comprised of various materials located in a historical area of Bangkok, Thailand. It was estimated that the total accumulated material loss from all monuments over seven years exposure in this environment to be approximately 410 cm3 with an overall restoration cost of about 210,000 USD

Community noise exposure and annoyance, activity interference, and academic achievement among university students

Background: Noise annoyance and effects on academic performance have been investigated for primary and secondary school students but comparatively little work has been conducted with university students who generally spend more time in dormitories or accommodation for their self-study. Objective: To determine, using a socio-acoustic approach involving face-to-face interviews and actual noise measurements, the effect of various community noise sources on student activities in accommodation both inside and outside a university precinct and also relationships with cumulative grade point average (GPA). Materials and Methods: The study sample comprised a student group resident off-campus (n = 450) and a control group resident in dormitories on-campus (n = 336). Noise levels [LA (dB)] were measured at both locations according to International Organization for Standardization standards. The extent of community noise interference with the student activities was examined with bivariate and stratified analyses and results presented as Mantel–Haenszel weighted odds ratios (ORMH) with 95% confidence intervals. Binary logistic regression was employed to assess the association between noise-disturbed student activities and dichotomized GPA values and derive odds ratios (ORs) for these associations. Results: Measured noise levels were all significantly (P < 0.05) higher for off-campus students. This was not reflected in the interviewed students’ subjective perceptions of how “noisy” their respective environments were. The off-campus student cohort was, however, more annoyed by all community noise categories (P < 0.001) except road traffic noise. For impact on specific student activities, the largest differences between on- and off-campus students were found for telephone and personal communication regardless of the type of community noise. There was no significant difference in the relationships between perceived annoyance due to community noise categories and cumulative GPA in the off-campus group compared to those for on-campus residents with ORMH values ranging from 1.049 to 1.164. The most important noise-impacted factors affecting off-campus students’ cumulative GPA were reading and mental tasks (OR = 2.801). Rest disturbance had a positive influence on cumulative GPA for on-campus students. Conclusion: These results provide support that various contemporary community noise sources affect university students’ activities and possibly influence their educational achievement as well

Some reactions of tris(trimethylstannyl)- and tetrakis(trimethylstannyl)-methane

With a variety of electrophilic reagents reaction occurs exclusively at the CHSn bonds of [(CH)Sn]C and [(CH)Sn]CH. While the inner SnC bonds remain intact, methyl groups may be progressively cleaved off, one from each of the trimethylstannyl groups; in the case of bromine a second Me group may be cleaved from each of the SnMeBr groups. The various products were identified by H, C and Sn NMR spectroscopy

Polycyclic aromatic hydrocarbons in the atmospheric environment of Brisbane, Australia

Atmospheric concentrations of PAHs were determined in air samples collected at various sites in Brisbane, Australia. Results for a given air sample are presented as the sum of the vapour and particle associated fraction of the compounds. PAH concentrations were highest at sites located in the vicinity of major roads. At a site located adjacent to a major road with a high frequency of heavy vehicle traffic, levels of B(a)P exceeded 1 ng m(-3) air. Overall, traffic was found to be the dominant source for PAHs in Brisbane air. The results further indicated the existence of seasonal variations with highest levels in winter. The use of PAH profiles and ratios for identifying sources and processes is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved

Calculation of bioconcentration factors of persistent hydrophobic compounds in the air/vegetation system

A multi-compartment model based on equilibrium partitioning has been developed for predicting leaf/atmosphere partition coefficients (theoretical K-BA) of persistent hydrophobic organic compounds. The leaf was considered to consist of five major phases i.e. cuticular lipids, cellular lipids, protein, structural carbohydrate and water, with chemicals partitioned between these compartments and the vapour phase in the ambient atmosphere. The input data required for the model were the 1-octanol/water partition coefficient (K-OW) and Henry's Law constant (H) of the compound, together with the volume fractions of the individual phases in the leaf. The model was evaluated using laboratory-based experimentally determined partition coefficients (experimental K-BA) for a group of organic chemicals, mostly chlorohydrocarbons. The model was in relatively good agreement with the experimental values, and can take into account differences in leaf composition. Values for different plants can be successfully calculated since the results indicate that plant composition is the major influence on the partition coefficient of a compound

Spatio-temporal variations in hexachlorobenzene partitioning in a near shore Antarctic marine environment from a one-dimensional coupled ecosystem-chemical distribution model

Hexachlorobenzene (HCB) is an example of a persistent organic pollutant (POP) that is relatively abundant and widespread in near shore Antarctic marine environments. By definition, POPs may distribute with an ecosystem, bioaccumulating and potentially reaching hazardous levels in some organisms. Modelling approaches may provide insight into this behaviour and complement physical sampling that is difficult in such environments. Here, a dynamic, trophically complex ecosystem (biological) model comprising biological groups from plankton to apex predators is coupled to a mass conserving, fugacity based chemical distribution model with vertical resolution of the seawater compartment. The model accommodates seasonal variations in solar irradiance, sea ice coverage, and boundary layer air temperature. The greatest proportion of the HCB is predicted to be in sediment with comparatively little intra-annual variation. For biota, highest lipid based concentrations are in aerial seabirds, baleen whales and seals but considerable seasonal variation is apparent. The POPcline, the water depth where vertical HCB concentration gradient is greatest, is coupled with the base of the mixed layer throughout the Antarctic year. Seasonal partitioning of POPs in Antarctic environments is shown to be subject to oscillating or “flip-flop” dynamics with significantly different controlling factors in summer and winter. In summer, HCB in the surface waters, where most of the biological activity is occurring, is isolated from the sediments that contain most of the POP mass. During winter however, fractional sea ice cover increases turbulent diffusion and the mixed layer and POPcline deepen increasing homogenisation in water column. Surface waters are more likely to come into direct contact with sediments, and biota such as krill migrate to the ocean floor and feed on detritus produced from summer plankton blooms that has since sunk to the ocean floor

Sludge-derived Cu and Zn in a humic-gley soil: effect of dissolved metal-organic matter complexes on sorption and partitioning

A sequential extraction scheme was combined with sorption isotherm analysis in order to investigate sorption of sewage sludge-derived Cu and Zn to the A-horizon of a humic-gley soil as a whole, and to the operationally defined exchangeable (1 M MgCl2), carbonate (1 M NaOAc), Fe/Mn oxide (0.04 M NH2OH.HCl), and organic (0.02 M HNO3+30% H2O2) soil fractions. Sorption parameters were compared for a sample of sludge leachate (with 97.4% of Cu and 63.2% of Zn present as dissolved metal-organic matter complexes, as calculated by geochemical modelling involving MINTEQA2 and verified using an ion exchange resin method) with that of a reference solution exhibiting the same chemical characteristics as the leachate, except for the presence of dissolved organic material. Dissolved metal-organic matter complexes were found to significantly (P\u3c0.05) depress sorption to the bulk soil and each fraction. The greatest depression of Cu and Zn sorption was observed for the exchangeable, carbonate, and Fe/Mn oxide fractions, while the organic fraction of the soil was the least affected. This reflects a greater affinity for the exchangeable, carbonate, and Fe/Mn oxide fractions by the free divalent metal (Cu2+, Zn2+), with sorption by these fractions attributed to cation exchange, chemisorption, and co-precipitation processes. The sorption characteristics of the organic fraction indicated that Cu and Zn sorption by soil organic matter mostly involved dissolved metal-organic matter complexes. This may be attributed to hydrophobic interactions between nonpolar regions of the dissolved metal-organic matter complexes and solid-phase soil organic matter