Passive treatment of acid mine drainage with high metal concentrations using dispersed alkaline substrate

Passive treatment systems based on the dissolution of coarse calcite grains are widely used to remediate acid mine drainage (AMD). Unfortunately, they tolerate only low metal concentrations or acidity loads, because they are prone to passivation (loss of reactivity due to coating) and/or clogging (loss of permeability) by precipitates. To overcome these problems, a dispersed alkaline substrate (DAS) composed of a fine-grained alkaline reagent (calcite sand) mixed with a coarse inert matrix (wood chips) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate, whereas the dispersion of nuclei for precipitation on the inert surfaces retards clogging. Chemical and hydraulic performance of DAS was investigated in two laboratory columns fed at different flow rates with natural AMD of pH 2.3 to 3.5 and inflow net acidity 1350 to 2300 mg/L as CaCO(3). The DAS columns removed 900 to 1600 mg/L net acidity, 3 to 4.5 times more than conventional passive treatment systems. Regardless of the flow rate employed, Al, Fe(III), Cu, and Pb were virtually eliminated. Minor Zn, Ni, and Cd were removed at low flow rates. High acidity removal is possible because these metals accumulate intentionally in DAS, and their precipitation promotes further calcite dissolution. During 15 mo, DAS operated without clogging at 120 g acidity/m(2).d, four times the loading rate recommended for conventional passive systems; DAS may therefore be capable of treating AMD at sites where influent chemistry precludes the use of other passive systems.     

Distribution and biological impact of dioxin-like compounds in risk zones along the Ebro River basin (Spain)

The aim of this investigation was to evaluate the environmental impact associated to PCDDs/Fs and dioxin-like PCBs in the Ebro River basin. Sediments and fish from several species were sampled at three sites with different historical pollution records, including the Barbastro area with different industrial activities, and the Flix and Monzón sites, associated to heavy organochlorine compound pollution. Seventeen toxic PCDDs/Fs and 12 dioxin-like PCBs were analyzed by GC-MS. The results obtained indicated significant accumulation of dioxin-like PCBs, but not PCDDs/Fs, in sediments and fish at the Flix site compared to the other sites. Concomitantly, cytochrome p450 1A (CYP1A) expression, a known indicator for pollution by dioxins and dioxin-like PCBs, was significantly elevated in barbel (Barbus graellsii) from the Flix site, compared to the population from the Barbastro site. CYP1A expression correlated with the concentration of dioxin-like PCBs in the fish fat, whereas no significant correlation was found with PCDDs/Fs concentrations. Our data suggest a significant biological impact at the Flix site, closely related to the presence of dioxin-like PCBs, whereas the PCDDs/Fs contribution to this impact appears to be non-significant, at least in the studied sites.     

Hydrodynamics of a periodically wind-forced small and narrow stratified basin: a large-eddy simulation experiment

Environmental Fluid Mechanics - We report novel results of a numerical experiment designed for examining the basin-scale hydrodynamics that control the mass, momentum, and energy distribution in a...     

Climate change can reduce shrimp catches in equatorial Brazil

Regional Environmental Change - Shrimps are an important and valuable fishing resource, being increasingly exploited worldwide, demanding appropriate management. However, factors such as how...     

Recovery after trampling disturbance in a canopy-forming seaweed population

The recovery of Ascophyllum nodosum, and the associated benthic community, was followed after repeated trampling disturbance at different intensities, from 2005 to 2010, at its southern limit (41°41′27″N; 8°50′57″W). The cover of A. nodosum and associated organisms and the demography of A. nodosum individuals in the most disturbed areas were followed over a recovery period of 54 months. Recovery of A. nodosum assemblages was negatively affected by increasing trampling intensity. After 54 months, the highest intensity plots were still significantly different from control plots. Growth and mortality rates of A. nodosum increased shortly after disturbance but progressively recovered to levels close to control plots. The results of this study demonstrate the sensitivity of this habitat-building species to human trampling and also show its plasticity to cope with disturbance events.     

Extensive review of shale gas environmental impacts from scientific literature (2010–2015)

Extensive reviews and meta-analyses are essential to summarize emerging developments in a specific field and offering information on the current trends in the scientific literature. Shale gas exploration and exploitation has been extensively debated in literature, but a comprehensive review of recent studies on the environmental impacts has yet to be carried out. Therefore, the goal of this article is to systematically examine scientific articles published between 2010 and 2015 and identify recent advances and existing data gaps. The examined articles were classified into six main categories (water resources, atmospheric emissions, land use, induced seismicity, occupational and public health and safety, and other impacts). These categories are analyzed separately to identify specific challenges, possibly existing consensus and data gaps yet remained in the literature.     

Assessment of Ball Milling as a Compounding Technique to Develop Nanocomposites of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) and Bacterial Cellulose Nanowhiskers

The aim of this study was the assessment of high energy ball milling technique to develop poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites containing bacterial cellulose nanowhiskers (BCNW). Crystallization behaviour of PHBV/BCNW nanocomposites was studied under non-isothermal and isothermal conditions using differential scanning calorimetry. The changes in PHBV crystalline structure were also studied using X-ray diffraction. The results confirmed that BCNW acted as nucleating agents and, hence, favored the crystallization of the PHBV. The oxygen permeability of the nanocomposites was reduced by ~22 % when compared to that of the neat PHBV. This work provides a new insight into the development of polyhydroxyalkanoate composites by means of the high energy ball milling technique.