Mass exchange in a shallow channel flow with a series of groynes: LES study and comparison with laboratory and field experiments

The exchange of dissolved matter between a straight open channel and a series of shallow embayments present at one of its sides is investigated using large eddy simulation (LES). The direct link between the mechanism of mass exchange and the dynamics of coherent structures is demonstrated. It is shown that for the geometrical configuration considered in the present study, the mass exchange process is very non-uniform over the depth in the vicinity of the channel–embayment interface. Most of the contaminant is ejected from the embayments close to the free surface. The amount of contaminant re-entrained into the embayments situated downstream of the one in which contaminant was introduced is quantified. The mass exchange coefficient predicted by LES does not vary significantly with the embayment rank and is in very good agreement with the one predicted by the model proposed by Weitbrecht et al. (J Hydraul Eng 134(2):173–183, 2008) based on the value of a dimensionless morphometric groyne-field parameter. Field experiments were purposely performed in a natural stream with embayments whose length over width ratios were close to the ratio in the LES study. The concentration fields predicted by LES are compared with video-records of colored dye used to visualize the mass exchange in the field experiment. It is shown that, for both LES and the field experiment, the dominant passage frequency of the eddies inside the interfacial mixing layer is well predicted by the analytical model of Sukhodolov and Sukhodolova (in: Cowen et al (eds) Hydraulic measurements & experimental methods. Proceedings of international conference, Lake Placid, USA, pp 172–177, 2007). The model is then used to scale the time in the LES animations and field video-records showing the temporal evolution of the concentration field. The results of the comparison indicate several similarities in the mixing process, despite the differences in the bathymetry and the large difference in the Reynolds number between LES and the field experiment. This proves the usefulness of performing detailed LES and laboratory studies in well-controlled environments to understand mass-exchange processes around river groyne fields.     

Cleaner production in a small lime factory by means of process control

An approach to Cleaner Production in a small factory of hydrated lime is presented. The work aims to improving fuel and limestone utilization and reducing waste production in the plant. Efforts mainly focus on the calcination stage, where around 50% of the production costs due to fuel consumption occur. To fulfill this objective, new indicators are proposed to evaluate the performance of the lime shaft kiln, in order to develop an operational control method for the calcination process. The systematic use of the developed operational control method is a powerful tool in the daily operation of a small lime factory, since it allows a more efficient calcination process with reduced environmental impact and production cost.     

Large-scale direct shear testing of municipal solid waste

Large direct shear testing (300 mm × 300 mm box) of municipal solid waste (MSW) collected from a landfill located in the San Francisco Bay area was performed to gain insight on the shear response of MSW. The study investigated the effects of waste composition, confining stress, unit weight, and loading rate on the stress–displacement response and shear strength of MSW. The amount and orientation of the fibrous waste materials in the MSW were found to play a critical role. The fibrous material had little effect on the MSW’s strength when it was oriented parallel to the shear surface, as is typically the case when waste material is compressed vertically and then tested in a direct shear apparatus. Tests in which the fibrous material was oriented perpendicular to the horizontal shear surface produced significantly stronger MSW specimens. The test results indicate that confining stress and loading rate are also important factors. Based on 109 large-scale direct shear tests, the shear strength of MSW at low moisture contents is best characterized by cohesion = 15 kPa, friction angle = 36° at a normal stress of 1 atmosphere, and a decrease in the friction angle of 5° for every log-cycle increase in normal stress.     

Ascorbic acid, β-carotene,sugars, phenols,and heavy metals in sweet potatoes grown in soil fertilized with municipal sewage sludge

Municipal sewage sludge (MSS) used for land farming typically contains heavy metals that might impact crop quality and human health. A completely randomized experimental design with three treatments (six replicates each) was used to monitor the impact of mixing native soil with MSS or yard waste (YW) mixed with MSS (YW +MSS) on: i) sweet potato yield and quality; ii) concentration of seven heavy metals (Cd, Cr, Mo, Cu, Zn, Pb, and Ni) in sweet potato plant parts (edible roots, leaves, stem, and feeder roots); and iii) concentrations of ascorbic acid, total phenols, free sugars, and β-carotene in sweet potato edible roots at harvest. Soil samples were collected and analyzed for total and extractable metals using two extraction procedures, concentrated nitric acid (to extract total metals from soil) as well as CaCl₂ solution (to extract soluble metals in soil that are available to plants), respectively. Elemental analyses were performed using inductively coupled plasma mass spectrometry (ICP-MS). Overall, plant available metals were greater in soils amended with MSS compared to control plots. Concentration of Pb was greater in YW than MSS amendments. Total concentrations of Pb, Ni, and Cr were greater in plants grown in MSS+YW treatments compared to control plants. MSS+YW treatments increased sweet potato yield, ascorbic acid, soluble sugars, and phenols in edible roots by 53, 28, 27, and 48%, respectively compared to plants grown in native soil. B-carotene concentration (157.5 μg g^?1 fresh weight) was greater in the roots of plants grown in MSS compared to roots of plants grown in MSS+YW treatments (99.9 μg g^?1 fresh weight). Concentration of heavy metals in MSS-amended soil and in sweet potato roots were below their respective permissible limits.     

Sediment Parameters of Northwest Black Sea Shelf and Slope: Implications for Transport of Heavy Metals and Radionuclides

In June 1990, sediment cores were obtained from several locations in the Northwest Black Sea shelf and slope by a joint US/USSR scientific team aboard the survey vessel R/V VODYANITSKY. the goal of this investigation was to determine the distribution and levels of radioactivity resulting from the Chernobyl 1986 nuclear accident. the sediment was characterized for texture, mineral composition, redox state, heavy metals, and radionuclides. Correlations emerging from these data reveal paths of dispersal and transport of materials from river sources to deposition sites on the shelf and slope. Kaolinite in the clay mineral suite clearly reflects a dispersal pattern originating in the Danube River and progressing in an easterly direction across the shelf. Sand-size gypsum and the elemental heavy metals Zn, Cu, Cr, and Pb (probable industrial source) as well as the elements Al and Mg (probable terrigenous source) also show a dispersal pattern from the Danube station location in an easterly direction across the shelf. the dispersal direction indicated by these materials is not in conflict with recent existing notions concerning the hydrology of the Northwest Black Sea. Barium anomalies at a midshelf location may be related to operations in the Lebada oil fields situated updrift. Heavy mineral dispersal reflect the Danube and -Crimean Provinces established for the shelf and relate to terrestrial source areas. in addition, the heavy mineral monazite correlates with the radioactive Th 232 found most abundantly in the Crimean Province. Local anomalies of Mn, Fe and U in the sediment at station locations are related to redox (Eh) conditions and other factors. Cs^134/137 data, reported by Curtis and Broadway (1991), correspond to transport and dispersal patterns implicit in the mineralogic, anthropogenic indicators, and sediment characteristics of the study area.     

Synthesis of activated carbon from food waste

Environmental Chemistry Letters - Activated carbon is a material for many adsorption applications, combining low-cost and high-quality properties. Many sources of activated carbon have...     

Coastal inundation in the north-eastern mediterranean coastal zone due to storm surge events

Low-elevation coastal areas and their populations are at risk during and after the appearance of a storm surge event. Coastal flooding as a result of storm surge events is investigated in this paper for a number of areas around the north-eastern (NE) Mediterranean coastal zone (Adriatic, Aegean and north Levantine seas). The sea level rise (SLR) due to storm surge events is examined for the period 2000?C2004. Wind data, atmospheric pressure and wave data for this period as well as in situ sea elevation measurements (from stations around the Mediterranean coasts) were used. Potential inundation zones were then identified using a 90-m horizontal resolution digital elevation model (DEM). At these zones, the sea surface elevations were calculated for the study period, using the collected data and a 2D storm surge simulation model (1/10^o??1/10^o) output, examining the sea level alteration in specific coastal areas, where in situ measurements are absent and are characterised as ??risky?? in inundation areas, due to their topography. In order to determine the level of storm track implication on major SLR incidents, the trajectories of the respective storm events were computed. The aim of this paper is to investigate the major storm surge events that appeared during the study period, identify the major ??risky?? costal regions along the north-eastern Mediterranean coast and determine their hazard level due to inundation caused by storm surge phenomena. The combination of the risk level determination of an area and the calculation of sea level alteration is an important tool in terms of predicting and protecting the coastal area from extreme meteorological incidents.