Hydroelastic response of a box-like floating fuel storage module modeled using non-conforming quadratic-serendipity Mindlin plate element

Presented herein are the hydroelastic responses of a floating fuel storage module under wave action. The box-like fuel storage module is modeled by an equivalent solid plate. For the analysis, a non-conforming quadratic-serendipity (NC-QS) element based on the Mindlin plate theory was developed. In this element, we make use of the reduced integration method and the superposition of non-conforming modes onto the basis function of the 8-node element in order to prevent spurious modes and shear locking phenomena. Thus the element may be applied for both thick and thin plates. The solution for the hydroelastic response involves solving the coupled plate–water equation and the water equation numerically using the hybrid finite element–boundary element (FE-BE) method. The coupled plate–water equation is derived by equating the force term in the Mindlin plate equation with the wave pressure distribution obtained from the linearized Bernoulli equation; whereas the boundary integral equation relates the displacement of the plate and water velocity potential using the free-surface Green’s function. Results of the displacement and water velocity potential are found to be more accurate when compared with existing solutions for special cases. Moreover, the stress resultants computed are significantly more accurate than previous results as spurious modes are eliminated.     

Disposal of water treatment wastes containing arsenic — A review

Solid waste management in developing countries is often unsustainable, relying on uncontrolled disposal in waste dumps. Particular problems arise from the disposal of treatment residues generated by removing arsenic (As) from drinking water because As can be highly mobile and has the potential to leach back to ground and surface waters. This paper reviews the disposal of water treatment wastes containing As, with a particular emphasis on stabilisation/solidification (S/S) technologies which are currently used to treat industrial wastes containing As. These have been assessed for their appropriateness for treating As containing water treatment wastes. Portland cement/lime mixes are expected (at least in part) to be appropriate for wastes from sorptive filters, but may not be appropriate for precipitative sludges, because ferric flocs often used to sorb As can retard cement hydration. Brine resulting from the regeneration of activated alumina filters is likely to accelerate cement hydration. Portland cement can immobilise soluble arsenites and has been successfully used to stabilise As-rich sludges and it may also be suitable for treating sludges generated from precipitative removal units. Oxidation of As(III) to As(V) and the formation of calcium-arsenic compounds are important immobilisation mechanisms for As in cements. Geopolymers are alternative binder systems that are effective for treating wastes rich in alumina and metal hydroxides and may have potential for As wastes generated using activated alumina. The long-term stability of cemented, arsenic-bearing wastes is however uncertain, as like many cements, they are susceptible to carbonation effects which may result in the subsequent re-release of As.     

Elimination kinetic model for organic chemicals in earthworms

Mechanistic understanding of bioaccumulation in different organisms and environments should take into account the influence of organism and chemical depending factors on the uptake and elimination kinetics of chemicals. Lipophilicity, metabolism, sorption (bioavailability) and biodegradation of chemicals are among the important factors that may significantly affect the bioaccumulation process in soil organisms. This study attempts to model elimination kinetics of organic chemicals in earthworms by accounting for the effects of both chemical and biological properties, including metabolism. The modeling approach that has been developed is based on the concept for simulating metabolism used in the BCF base-line model developed for predicting bioaccumulation in fish. Metabolism was explicitly accounted for by making use of the TIMES engine for simulation of metabolism and a set of principal transformations. Kinetic characteristics of transformations were estimated on the basis of observed kinetics data for the elimination of organic chemicals from earthworms.     

Transfer of mercury and methylmercury along macroinvertebrate food chains in a floodplain lake of the Beni River, Bolivian Amazonia

We have evaluated the mercury and methylmercury transfers to and within the macroinvertebrate communities of a floodplain lake of the Beni River basin, Bolivia, during three hydrological seasons and in two habitats (open water and vegetation belt). Using the stable isotopes δ¹³C and δ¹⁵N, six trophic chains were identified during a previous study. Four are based on only one source: seston, organic matter from the bottom sediment, periphyton and macrophytes. Two are based on mixed sources (seston and periphyton in one case, periphyton and macrophytes in the other). During sampling, we found only one taxon that had surface sediment organic matter as food source and very few taxa whose trophic source was constituted by macrophytes. The periphyton was the most important source during all seasons; it produced the longest chain, with three trophic positions. Whatever the season and trophic source, all collected macroinvertebrates contained methyl mercury and the latter was biomagnified in all trophic chains that we identified. The biomagnification of methylmercury through invertebrate trophic chains accurately reflected the existence and length of these chains. Biomagnification was virtually non-existent in the sediment-based chain, low and restricted to the dry season in the macrophyte-based chain. It was significant in the seston-based chain, but limited by the existence of only two trophic levels and restricted to the wet season. Finally, it was very effective in the periphyton-based chain, which offers the highest rate of contamination of the source but, above all, the largest number of trophic levels.     

Control tuning of a simplified VAV system: Methodology and impact on energy consumption and IAQ

Nowadays, with the improvement of living standards, air-conditioning systems have been widely used causing more health problems linked to air-conditioning systems and indoor air quality. When an air handling unit is designed for a conference room, its variable use demands an outdoor air rate control in particular to optimize energy consumption of the new air heating/cooling. Based on an experimental site, the present work shows how to combine air quality and the improvement of energy consumption thanks to a way to define a control strategy. The control problem considered here is the management of air quality associated to a control of the outdoor air rates. A review of classical tuning methods is led in order to select suitable ones. Thus, a linearization of the phenomena must be done to border the system expression in tuning methods. Several classical methods are studied and the family model is chosen: monovariable and multivariable applications are brought to fruition. Simulations and applications permit to enhance energy consumption through the choice of a strict way to tune such control equipments.     

Seismic demand evaluation of steel MRF buildings with simple and detailed connection models

A detailed connection model can take into account effects such as strength and stiffness degradation, pinching and brittle behavior while a simple one cannot. This study investigates the effects of using the detailed and simple connection models on the seismic behavior of steel moment resisting frame (MRF) buildings. The frame models designed by 1994 UBC and 2000 IBC provisions involved the use of clear length dimensions of elements, panel zone models, and connection models subjected to suites of 20 accelerograms with 50/50, 10/50 and 2/50 hazard levels. The interstory drifts, column axial forces, and probability of building failure were investigated. The results show that the discrepancy of the building behaviors between using the detailed and simple connections became larger when the more severe seismic hazard levels and higher percentile values were considered. Therefore, the detailed connection models would be recommended to evaluate and predict seismic performance of steel MRF buildings.     

Migration of As, and H/He ages, in groundwater from West Bengal: Implications for monitoring

From 2002 to 2010 inclusive we monitored concentrations of arsenic (As) and major ions (Ca, Mg, Sr, Na, K, Fe, Mn, Cl, and SO₄) in groundwater from 14 domestic wells and three piezometer nests in a shallow aquifer (<60 m depth), and 3 wells in a deep aquifer (>70 m depth), in southern West Bengal, India. In the deep aquifer, concentrations of As did not change over time despite increases in the concentration of Fe in two wells. The shallow aquifer occurs in two sedimentological settings: palaeo-channel and palaeo-interfluve. At the top of the shallow aquifer of the palaeo-channel, decreases in all constituent concentrations with time, and an ³H/³He age of 1.4 years, proves that the aquifer is beginning to be flushed of pollutants. In As-polluted groundwater (>50 μg/L As) tapped from deeper grey sands of the shallow, palaeo-channel, aquifer, concentrations of As were mostly stable over time, but both increases and decreases occurred with time in response to downward migration of the chemically-stratified water column. In groundwater tapped from Pleistocene brown sands, the concentration of As remained either low and stable (<2 μg/L As), or increased at rates up to 34 μg/L per year. The increases were caused by the flow of As-rich groundwater either downward into brown sand at the base of palaeo-channels, or laterally into a confined, unpolluted, palaeo-interfluvial, aquifer of brown sand that lies regionally beneath a palaeosol.Under the present pumping regime, the prognosis for As-pollution in the shallow aquifer is complex. Wells in brown sand may become polluted over timescales of as little as 2 years, whilst some wells tapping As-polluted groundwater from grey sand will become fit for potable use (<50 μg/L) within a few decades. The evidence of flushing, and of declining As in some of the groundwater from palaeo-channels, which are conduits for recharge of the confined, As-free, palaeo-interfluve aquifer, and probably also the deeper aquifer, offers hopes that the spread of As-pollution will be limited.     

Dissolved silver in European estuarine and coastal waters

Silver is one of the most toxic elements for the marine microbial and invertebrate community. However, little is known about the distribution and behaviour of dissolved silver in marine systems. This paper reports data on dissolved and sediment-associated silver in European estuaries and coastal waters which have been impacted to different extents by past and present anthropogenic inputs. This is the first extended dataset for dissolved silver in European marine waters. Lowest dissolved silver concentrations were observed in the Gullmar Fjord, Sweden (8.9 ± 2.9 pM; x ± 1σ), the Tamar Estuary, UK (9.7 ± 6.2 pM), the Fal Estuary, UK (20.6 ± 8.3 pM), and the Adriatic Sea (21.2 ± 6.8 pM). Enhanced silver concentrations were observed in Atlantic coastal waters receiving untreated sewage effluent from the city of A Cor?na, Spain (243 ± 195 pM), and in the mine-impacted Restronguet Creek, UK (91 ± 71 pM). Anthropogenic wastewater inputs were a source of dissolved silver in the regions studied, with the exception of the Gullmar Fjord. Remobilisation of dissolved silver from historically contaminated sediments, resulting from acid mine drainage or sewage inputs, provided an additional source of dissolved silver to the estuaries. The ranges in the log particle-water partition coefficient (K_d) values of 5-6 were similar for the Tamar and Mero estuaries and agreed with reported values for other estuaries. These high K_d values indicate the particle reactive nature of silver with oxic sediments. In contrast, low K_d values (1.4-2.7) were observed in the Fal system, which may have been due to enhanced benthic inputs of dissolved silver coupled to limited scavenging of silver on to sediments rich in Fe oxide.     

Ambient wood smoke exposure and respiratory symptoms in Tasmania, Australia

Wood smoke exposure has been associated with adverse respiratory health outcomes, with much of the current research focused on wood smoke from domestic heating and cooking. This study examined the association between respiratory symptoms and outdoor wood smoke in Launceston, Tasmania, where ~ 30% of homes use wood burners for domestic heating. This ecological study examined data from participants of the 2004 Tasmanian Longitudinal Health Study postal survey and compared the prevalence of respiratory symptoms in Launceston (n = 601) with that in Hobart (n = 1071), a larger Tasmanian city with much less wood smoke. Multivariate logistic regression models were used to investigate the associations of interest while adjusting for gender, atopy, history of allergic disease and current smoking status. There were no significant differences in symptom prevalence between Launceston and Hobart. Two subgroup analyses, which examined participants with pre-existing chronic respiratory disease, and those who reported actively using a wood burner in their home, also did not find significant differences. Any impact of wood smoke on non-specific respiratory symptoms might have been overshadowed by other important determinants of respiratory health, such as vehicle exhaust and tobacco smoking, or were too small to have been detected. However, the lack of detectable differences in symptom prevalence might also reflect the success of regulatory action by local governments to reduce wood smoke emissions in Launceston. The results of other epidemiological studies support an association between ambient wood smoke exposure and adverse respiratory health. Further investigations of wood smoke exposure in Australian settings are needed to investigate the lack of significant associations found in this study, especially studies of indoor air quality and health impacts in children and elderly populations.     

Short-term exposure to the environmentally relevant estrogenic mycotoxin zearalenone impairs reproduction in fish

Zearalenone (ZON) is one of the worldwide most common mycotoxins and exhibits estrogenic activity in the range of natural steroid estrogens such as 17β-estradiol (E2). The occurrence of ZON has been reported in drainage water, soil, wastewater effluents and rivers, but its ecotoxicological effects on fish have hardly been investigated.In this study the estrogenic potency of the ZON was compared to E2 in a recombinant yeast estrogen screen (rYES) and the effects of waterborne ZON exposure on reproduction, physiology and morphology of zebrafish (Danio rerio) were investigated in a 42-day reproduction experiment. E2 as well as ZON evoked a sigmoid concentration-response curve in the rYES with a mean EC₅₀ of 2 and 500 μg/L, respectively, resulting in an E2:ZON EC₅₀ ratio of 1:250. Exposure to ZON for 21 days reduced relative spawning frequency at 1000 and 3200 ng/L to 38.9 and 37.6%, respectively, and relative fecundity at 100, 320, 1000 and 3200 ng/L to 74.2, 41.7, 43.8 and 16.7%, respectively, in relation to the 21-day pre-exposure period. A 4.4 and 8.1 fold induction of plasma vitellogenin (VTG) was observed in male zebrafish at 1000 and 3200 ng/L ZON, respectively. Exposure to ZON did not affect fertility, hatch, embryo survival and gonad morphology of zebrafish.The results of this study demonstrate that although ZON possesses a moderate estrogenic potency in vitro, it exhibits a comparably strong effect on induction of VTG and reproduction in vivo. This indicates that ZON might contribute to the overall estrogenic activity in the environment and could therefore pose a risk for wild fish in their natural habitat.