Sepiolite reveals as a low-cost and efficient adsorbent for the adsorption of caffeine from aqueous solutions. The characterization of this material was carried out by N₂ adsorption–desorption at 77 K, Fourier transform infrared spectroscopy, thermogravimetric analysis, and electronic microscopy. Initially, batch adsorption experiments were developed in order to determine the equilibrium time and the adsorption isotherm of the system. Pseudo–first-order, Elovich equation, pseudo–second-order, and intra-particle diffusion models were applied to the experimental data to determine the adsorption kinetics. In continuous adsorption, the influence of several operation conditions (initial caffeine concentration, volumetric flow rate, and mass of adsorbent) on the shape of breakthrough curves and the mass transfer resistance was evaluated. Experimental data were fitted to the bed-depth service-time model bed-depth service-time (BDST). Through the calculation of the adsorption, parameters as breakthrough time or caffeine removal percentage can be concluded that the removal of this compound from aqueous solutions by adsorption in sepiolite beds is an alternative technique to the current methods, in order to eliminate this micropollutant.

Atmospheric deposition occurs in a variety of forms and is crucial for the evaluation of nutrient budgets, critical loads, and pollution inputs across space and time. Atmospheric wet deposition is typically quantified by analyzing the chemistry of precipitation that is collected in some type of container with a lid that opens in response to precipitation. However, collectors can vary in shape as well as in the sensor that signals when precipitation is occurring. Here, we compare the collectors made by Aerochem Metrics and N-CON Systems Company Inc. The former has been widely used for several decades, while the latter is relatively new and has been used in a variety of configurations depending on the solute of interest. Event-based samples were collected from August 2007 to October 2008 and analyzed for nitrate, ammonium, sulfate, chloride, and dissolved organic carbon (DOC). A variety of approaches were used to assess the comparability of the two collectors. Regressions of concentration versus concentration from the two collectors were strong, and the slope did not differ from 1 for nitrate, ammonium, or sulfate. The median concentrations of nitrate, ammonium, and sulfate were, however, significantly higher in the N-CON collector, while there were no overall differences between collectors for chloride or DOC. Although we have observed some statistically significant differences between solute concentrations of samples collected from the two collectors, our mixed results suggest that these differences are relatively small.

Finding an environmentally safe and cost-effective method which is efficient enough to meet the regulatory standards of potable and industrial wastewater presents unique challenges. In this work, Moringa stenopetala seed powder which had particle size of 300 μm was characterized; ash content 4.7 %, bulk density 0.531/cm3, particle density 0.88 g/cm3, color yellowish, and pH 4.5. Fourier transform infrared spectroscopy analysis showed the multifunctionality of the M. stenopetala seed powder. M. stenopetala seed powder was assessed for percentage chromium removal and milligrams per gram chromium uptake as a function of contact time, pH, and dose of the adsorbent and initial concentration. The maximum percent removal was 99.74 %. Sorption kinetics of chromium adsorption by M. stenopetala seed powder was predicted reliably using a pseudo-second order model. An intra-particle diffusion model revealed that the biosorption of metals proceeds through various processes. Equilibrium uptakes were evaluated using Langmuir, Freundlich, Temkin, and the Dubinin-Radushkevich adsorption isotherm models. Even though the correlation coefficient was not as high as the Langmuir and Freundlich models for Temkin adsorption isotherm model, the metal uptake which was predicted by the model is comparable with the experimental value. Generally, the seed powder of M. stenopetala was found to be effective in the removal of chromium from tannery wastewater. © 2013 Springer Science+Business Media Dordrecht.

The aim of this work was to investigate the susceptibility of the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to biodegradation in a range of soils and to identify RDX-degrading organisms using stable isotope probing (SIP). RDX degradation was examined in ten soils, primarily from agricultural areas. RDX biodegradation was observed in six samples and only when the microcosms were not aerated. For one soil, 15N-and 13C-based DNA SIP was used to identify the microorganisms responsible for RDX degradation. Two RDX concentrations were examined (10 and 20 mg/L), however, only the higher concentration resulted in a significant SIP signal. In these ultracentrifugation fractions, one terminal restriction fragment length polymorphism (TRFLP) fragment (260 bp) showed a reliable trend of label uptake. This fragment was of higher relative abundance in the heavier fractions from labeled samples compared with the heavier fractions from the unlabeled control samples, indicating that the organism producing this fragment was responsible for label uptake (hence RDX degradation). Partial 16S rRNA gene sequencing indicated the organisms represented by fragment 260 bp belonged to either Sphingobacteria (phylum Bacteroidetes) or the phylum Acidobacteria. To date, these organisms have not previously been directly linked to RDX degradation. The 16S rRNA sequences were compared with the NCBI database and, in all cases, were most similar to uncultured bacteria. The results suggest SIP is a viable method for discovering novel, previously uncultured, RDX degraders. © Springer Science+Business Media Dordrecht 2013.

One of the major obstacles to zerovalent iron nanoparticles (nZVI) application in soil and groundwater remediation is the limited transport, especially in low-permeability soils. In this study, direct current (constant potential of 5.0 V) was used to enhance polymer-coated nZVI mobility in different porous media, including a bed of glass beads and kaolin clay. The tests were conducted using a modified electrophoretic cell and with nZVI concentrations typical of field applications (4 g L-1). Experimental results indicate that the use of direct current can enhance the transport of the polymer-modified nanoparticles when compared with natural diffusion in low permeability or surface neutral porous medium. The applied electric field appeared to enhance the oxidation-reduction potential, creating a synergistic effect of nZVI usage with electrokinetics. Aggregation of the nanoparticles, observed near the injection point, remained unresolved. © 2013 Springer Science+Business Media Dordrecht.

This work evaluated surfactant-enhanced in situ chemical oxidation (S-ISCO) in a hydrocarbon-contaminated soil. Surfactants and efficacy of oxidant activation as well as the treatability of contaminated soil were assessed. The surfactant VeruSOL-3 with a critical micelle concentration (CMC) of 5.5 g/L was selected. Based on the results, activated oxidations by sodium persulphate and hydrogen peroxide were able to effectively destroy target organic compounds in emulsion and soil. The destruction of total petroleum hydrocarbon (TPH) in emulsion was completed in 14 days and polycyclic aromatic hydrocarbons (PAHs) in excess of 96 %. Green nanoiron was much more active than other activators in emulsion. The data also indicates that oxidation using activators was much less pronounced in soil matrices. However, it is expected that given sufficient dose and treatment time, a higher destruction rate in the contaminated soil can be achieved. The study showed that the remediation of target organic contaminants (TPH, PAH) in soil by S-ISCO using activated sodium persulphate is feasible. © 2013 Springer Science+Business Media Dordrecht.

A first-to-date comprehensive climatological aspect of the regime of aerosol loading over the entire broader Greek region (19 E-30 E and 34 N-43 N) is obtained using pixel-level (50 km × 50 km) monthly aerosol optical depth (AOD) products derived from raw Level-2 (10 km × 10 km) MODIS-Terra AOD data at 550 nm. The AOD climatology (for the 8-year period from March 2000 to February 2008) indicates that the study region is significantly loaded by aerosols (mean regional AOD equal to 0.196 ± 0.030 on an annual basis, with values ranging from 0.126 up to 0.382 at pixel level). It is also found that our high-resolution AOD data can reveal spatial patterns that are not evident in studies based on lower resolution data. There is a distinct longitudinal gradient of AODs, with higher values in the eastern than western part of the Greek peninsula. There is also a strong latitudinal gradient with decreasing values from south to north attributed to the presence of the Sahara Desert in northern Africa. The annual AOD cycle presents double maximum values, in spring and summer, and minimum ones in winter. There is also a remarkable year-by-year variability of AOD levels, especially as to their maxima, influenced by varying transport of desert dust, from the south, or biomass burning aerosols, from the north, to the region under prevailing favorable synoptic conditions. In this work, the processing, consisting in averaging over space and time, is done applying/testing five different criteria varying in their flexibility/severity in both spatial and temporal data availability. The criteria selection affects the magnitude of computed regional mean AOD value modifying it by up to 19 %, although the patterns of geographical distribution of AOD and its intra-annual variability do not change drastically. © 2013 Springer Science+Business Media Dordrecht.

Bisphenol-A (BPA) is an environmental contaminant used in the manufacturing of polycarbonate plastics and epoxy resins, which has been discovered in freshwater systemsworldwide as a result of effluent from manufacturing. This bioactive molecule is an estrogen mimic and has become a concern for exposure, especially during development, resulting in its removal from baby bottles and other consumer products. BPA is an endocrine disruptor in a variety of species and has been classified as a toxic substance in multiple countries. In this study, we examined the effect of BPA exposure on leukocyte counts in wild yellow perch, Perca flavescens. Yellow perch were exposed to either 2, 4, and 8 ppb BPA; Saprolegnia; or a blank control for a period of 7 days. Leukocyte blood counts were significantly higher in Saprolegnia, 4 ppb BPA, and 8 ppb BPA treatments compared to control. To test compound effects of BPA and Saprolegnia on leukocyte counts over a 7-day period, perch were exposed to either 4 ppb BPA, 4 ppb BPA+Saprolegnia, or control. Leukocyte counts were significantly higher in the 4 ppb BPA treatment relative to control. The 4 ppb BPA+Saprolegnia treatment was numerically elevated from the control, exhibiting a 153 % increase relative to control. BPA represents a contaminant with immunomodulatory properties that remain to be determined. © Springer Science+Business Media Dordrecht 2013.

Pathogens are the leading cause of water quality impairments as defined by the US Environmental Protection Agency and their transport within water bodies is poorly understood. Because of this, watershed-scale, water quality models often have poor bacterial prediction capabilities. To improve the understanding of in-stream bacterial transport, a cow pie was deposited in a recirculating flume with flows ranging from 0.0102 to 0.0176 m³ s⁻¹. Water samples were collected and analyzed for Escherichia coli concentration, E. coli attached fraction, and turbidity. E. coli concentrations ranged from 4.72 × 10³ to 1.70 × 10⁵ CFU 100 mL⁻¹ and turbidity ranged from 1.93 to 369 NTU over both locations and all times. The percentage of E. coli attached to particles ranged from an average of 2.9 to 31 % downstream of the fecal deposition point. Spearman correlation analysis demonstrated that bacteria concentrations were significantly related with water depth (ρ = 0.128, p = 0.018), and the concentration of attached bacteria was significantly correlated with both the total concentration of E. coli (ρ = 0.4081, p = 0.009) and turbidity (ρ = 0.3627, p = 0.0214). This analysis is useful to indicate parameters that should be considered when monitoring or predicting bacteria transport in streams.

A chitosan-graft-poly(N-allyl maleamic acid) hydrogel membrane was prepared by radical polymerization in the absence of a cross-linker. The product was characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) to confirm the formation of hydrogels. Transparent hydrogels have been observed to exhibit as much as 223.4 % swelling capacity, following pseudo-second-order kinetic models. The synthesized hydrogel membrane was subsequently utilized for removal of copper ions from an aqueous solution in the presence of several different functional groups. The effects on adsorption efficiency of various parameters such as time, temperature, pH, initial concentration of copper (II) solution, and amount of hydrogel were also investigated. The maximum adsorption capacity and efficiency were found to be 50.75 mg g-1 and 99.91 %, respectively, by the 0.004 mg adsorbent after 12 h of immersion in copper solution. Finally, the result showed that hydrogel membrane is pH sensitive to copper (II) adsorption and has maximum adsorption efficiency near to the pH of ground water. © 2013 Springer Science+Business Media Dordrecht.