Road traffic impact on urban atmospheric aerosol loading at Oporto,Portugal

At urban areas in south Europe atmospheric aerosol levels are frequently above legislation limits as a result of road traffic and favourable climatic conditions for photochemical formation and dust suspension. Strategies for urban particulate pollution control have to take into account specific regional characteristics and need correct information concerning the sources of the aerosol.With these objectives, the ionic and elemental composition of the fine (PM_2.5) and coarse (PM_2.5–10) aerosol was measured at two contrasting sites in the centre of the city of Oporto, roadside (R) and urban background (UB), during two campaigns, in winter and summer.Application of Spatial Variability Factors, in association with Principal Component/Multilinear Regression/Inter-site Mass Balance Analysis, to aerosol data permitted to identify and quantify 5 main groups of sources, namely direct car emissions, industry, photochemical production, dust suspension and sea salt transport. Traffic strongly influenced PM mass and composition. Direct car emissions and road dust resuspension contributed with 44–66% to the fine aerosol and with 12 to 55% to the coarse particles mass at both sites, showing typically highest loads at roadside. In fine particles secondary origin was also quite important in aerosol loading, principally during summer, with 28–48% mass contribution, at R and UB sites respectively. Sea spray has an important contribution of 18–28% to coarse aerosol mass in the studied area, with a highest relative contribution at UB site.Application of Spatial Variability/Mass Balance Analysis permitted the estimation of traffic contribution to soil dust in both size ranges, across sites and seasons, demonstrating that as much as 80% of present dust can result from road traffic resuspension.     

Computational fluid dynamics analysis of liquefied natural gas dispersion for risk assessment strategies

Computational fluid dynamics (CFD) simulations have been conducted for dense gas dispersion of liquefied natural gas (LNG). The simulations have taken into account the effects of gravity, time-dependent downwind and crosswind dispersion, and terrain. Experimental data from the Burro series field tests, and results from integral model (DEGADIS) have been used to assess the validity of simulation results, which were found to compare better with experimental data than the commonly used integral model DEGADIS. The average relative error in maximum downwind gas concentration between CFD predictions and experimental data was 19.62%.The validated CFD model was then used to perform risk assessment for most-likely-spill scenario at LNG stations as described in the standard of NFPA 59A (2009) “Standard for the Production, Storage and Handling of Liquefied Natural Gas”. Simulations were conducted to calculate the gas dispersion behaviour in the presence of obstacles (dikes walls). Interestingly for spill at a higher elevation, e.g., tank top, the effect of impounding dikes on the affected area was minimal. However, the impoundment zone did affect the wind velocity field in general, and generated a swirl inside it, which then played an important function in confining the dispersion cloud inside the dike. For most cases, almost 75% of the dispersed vapour was retained inside the impoundment zone. The finding and analysis presented here will provide an important tool for designing LNG plant layout and site selection.     

Release of zooxanthellae with intact photosynthetic activity by the coral<Emphasis Type="Italic"> Galaxea fascicularis</Emphasis> in response to high temperature stress

Damage to zooxanthellae photosynthetic apparatus has been proposed to be the underlying mechanism of coral bleaching, but how the expulsion of zooxanthellae is triggered is still not understood. The present study compared the photosystem II (PSII) functioning and overall photosynthesis of retained and released zooxanthellae from the reef-building coral Galaxea fascicularis exposed to high temperature stress. The use of pulse-amplitude-modulated (PAM) fluorometry for isolated zooxanthellae was validated and used to measure photosynthesis. There was no significant difference in PSII functioning and the overall photosynthesis between retained zooxanthellae, which were isolated immediately after stress treatment, and those released from the coral exposed to either 30 or 32°C, while the zooxanthellae population released at 28°C showed significantly lower PSII functioning than those retained in the polyps. The release of healthy-looking zooxanthellae by polyps exposed to elevated temperatures was significantly higher than those in the control (28°C). Higher release of undischarged cnidae, indicative of host cell necrosis or detachment, was observed in 32°C treatments. These findings indicate that the zooxanthellae released in 30 or 32°C treatments exhibited normal morphology and intact photosynthetic activity. The present results strongly suggest that the release of zooxanthellae from G. fascicularis at 30 or 32°C is a non-selective process with respect to the zooxanthellar PSII functioning and thus the host seems to be the first partner to be physiologically affected in temperature-induced bleaching.Communicated by T. Ikeda, Hakodate     

In situ net primary productivity and photosynthesis of Antarctic sea ice algal, phytoplankton and benthic algal communities

Primary production at Antarctic coastal sites is contributed from sea ice algae, phytoplankton and benthic algae. Oxygen microelectrodes were used to estimate sea ice and benthic primary production at several sites around Casey, a coastal area in eastern Antarctica. Maximum oxygen export from sea ice was 0.95 mmol O₂ m⁻² h⁻¹ (~11.7 mg C m⁻² h⁻¹) while from the sediment it was 6.08 mmol O₂ m⁻² h⁻¹ (~70.8 mg C m⁻² h⁻¹). When the ice was present O₂ export from the benthos was either low or negative. Sea ice algae assimilation rates were up to 3.77 mg C (mg Chl-a)⁻¹ h⁻¹ while those from the benthos were up to 1.53 mg C (mg Chl-a)⁻¹ h⁻¹. The contribution of the major components of primary productivity was assessed using fluorometric techniques. When the ice was present approximately 55–65% of total daily primary production occurred in the sea ice with the remainder unequally partitioned between the sediment and the water column. When the ice was absent, the benthos contributed nearly 90% of the primary production.     

Contamination of microplastics,surface morphology and risk assessment in beaches along the Thoothukudi coast,Gulf of Mannar region

Environmental Science and Pollution Research - Microplastics accumulation on beaches raises a serious concern worldwide. Hence, the present study was conducted with the focus of investigating the...