In this study, high surface area porous carbons were synthesized by chemical activation using petroleum coke as the precursor and KOH as the activation agent. The pore structure of the as-synthesized activated carbons was characterized by nitrogen adsorption, and their CO₂ sorption capacities were measured by a magnetic suspension balance at 1 and 10 bar, respectively. The effects of activated carbon preparation parameters (preheating temperature, preheating time, activation time, heating rate during the pyrolysis, and particle size of the precursor) on porous texture, CO₂ adsorption capacity, and CO₂/N₂ selectivity of the activated products were investigated. It has been found that at 1 bar, the CO₂ adsorption capacity is determined by the micropore contribution, i.e., the ratio between micropore surface area and Brunauer–Emmett–Teller (BET) surface area of the sorbents, while at 10 bar, CO₂ adsorption capacity is related to the BET surface area of the activated products. The maximum CO₂ adsorption uptake of 15.1 wt% together with CO₂/N₂ selectivity of 9.4 at 1 bar were obtained for a sample activated at 700 °C indicating its high potential in the capture of CO₂.

Normative regulations on benzene in fuels and urban management strategies are expected to improve air quality. The present study deals with the application of self-organizing maps (SOMs) in order to explore the spatiotemporal variations of benzene, toluene, ethylbenzene, and xylene levels in an urban atmosphere. Temperature, wind speed, and concentration values of these four volatile organic compounds were measured after passive sampling at 21 different sampling sites located in the city of Trieste (Italy) in the framework of a multi-year long-term monitoring program. SOM helps in defining pollution patterns and changes in the urban context, showing clear improvements for what concerns benzene, toluene, ethylbenzene, and xylene concentrations in air for the 2001–2008 timeframe.

In this study, the performance of a laboratory-scale soil aquifer treatment (SAT) system was investigated and treatability studies were done in order to determine organic matter removal from synthetic wastewater (SWW) and secondary treated real wastewater (RWW). The SAT system was constructed in laboratory conditions and treatability studies were conducted using soil columns, which were packed with silt loam soil samples. Each column was equipped with a series of ports at multiple depths from soil surface (10, 20, 30, 50, and 75 cm) to collect water samples. Two operational cycles were applied to represent the influence of different wetting and drying periods during wastewater application. Dissolved oxygen, chemical oxygen demand (COD), and total organic carbon (TOC) concentrations were measured in all samples. Average removal values of 61.4 % (COD) and 68.2 % (TOC) were achieved by in SWW and of 58.3 % (COD) and 51.1 % (TOC) in RWW in 55 and 25 weeks of operation, respectively. These results indicated that the performance of the columns operated with SWW was better than the performance of the columns operated with RWW. In essence, the easily biodegradable portion of organic matter was quickly consumed by microorganisms in the first 10 cm of the columns where oxygen levels peaked. Complex organic compounds that are likely to be found in RWW could thus be removed when longer residence times were achieved through the columns. When the removal performances achieved with different operating cycles were compared for each wastewater, it could be seen that longer wetting and longer drying periods yielded higher removal efficiencies in RWW and vice versa in SWW. © 2013 Springer Science+Business Media Dordrecht.

The present work explores the sorption capacity of an inexpensive and highly available agricultural waste, rice husk, to remove mercury using realistic concentrations of this metal. The efficiency of the process was evaluated for two initial Hg(II) concentrations, one representing the maximum value for Hg discharges from industrial sectors (0.05 mg L-1), and the other ten times higher. A very small amount of rice husk (0.25 and 0.50 g L-1) was able to reduce the Hg(II) levels in more than 80 % for an initial concentration of 0.05 mg L-1 and in more than 90 % for 0.50 mg L-1, corresponding to residual concentrations of Hg(II) of 0.048 and 0.009 mg L-1, respectively. The biosorvent was reused in further cleaning treatments, maintaining the efficiency and high performance. The sorption kinetics of the Hg-rice husk system is well fitted by the Elovich model and the diffusion models suggested that, depending on the initial Hg(II) concentrations, the sorption process can be controlled by intraparticle diffusion or by both film and intraparticle diffusion. The equilibrium data are well described by the linear isotherm and the distribution coefficient found was 36.1 L g-1. © 2013 Springer Science+Business Media Dordrecht.

Metaldehyde is a selective molluscicide used in the agricultural and residential sector to control slugs and snails for a wide variety of crops. In recent years, some water companies have started monitoring drinking water supply catchments for presence of this compound, with positive and concern results. Conventional techniques are yet to achieve complete efficient and feasible removal of metaldehyde. The aim of this study was to measure the efficiency of nano-sized zinc oxide/laponite composites (NZnC) in the effective removal of metaldehyde (influent concentration of 500 μg dm⁻³) through the interaction of photocatalysis. Reaction time, pH of sample solution and NZnC mass were tested against each other using a rotatable central composite design method of experimentation. Statistical tests showed that linear effects of time, quadratic/linear effects of NZnC mass and the interaction of pH and NZnC mass proved to be the most significant variables for degrading metaldehyde. Optimal values of each variable for the highest removal efficiency were achieved, being pH equal to 10.4 and NZnC mass added equal to 28 g. The rate of reaction was then predicted by non-linear regression of four models. The best fit was provided by the modified first-order with residual kinetic model, with the apparent degradation coefficient k equal to 0.0363 min⁻¹ and the lowest remaining metaldehyde concentration observed among all runs was 278.7 μg dm⁻³. NZnC has shown to be a prominent nanotechnology for metaldehyde removal.

This paper addresses the geochemical evolution, volumetric water content, and temperature of porewater when constructing different soil layers to improve the surface acidic conditions on a slope at a closed mine. Three cases were set under different layer systems. Case 1 was solely composed of surface-weathered rocks. A vegetation layer was constructed on the surface rocks in case 2, whereas a top vegetation and bottom low-permeable layers were constructed on the rocks in case 3. In both cases, a soil–cement layer was constructed to prevent landslides. Porewater sampling systems and soil sensors were set at different depths to collect porewater and measure the volumetric water content and temperature. The results showed that, when no layers were applied (case 1), high concentrations of heavy metals and low pH values were observed regardless of the depth and season. When a vegetation layer (case 2) was applied, a dramatic decrease in heavy metal concentrations was observed, similar to the results in case 3. In both cases, pH values were circumneutral. Moreover, the addition of the low-permeable layer reduced the infiltration of rainfall through the layers by considering the changes in volumetric water content. Also, the results of case 1 were compared with those obtained at a flat surface under similar conditions. On the slope, the pH was more acidic, and heavy metal concentrations were higher. These suggest that the dissolution of heavy metals from the weathered rocks into the porewater is enhanced on the sloping surface due to a longer solid–liquid interaction time.

In this study, we evaluated the needle anatomy of Norway spruce trees growing on a territory that was exposed to different alkaline dust pollution. The anatomy of the needles of spruce growing on a polluted site in the vicinity of the Kunda cement plant (Northeast Estonia) was compared with the anatomy and physiological state of the needles from an unpolluted site. The needles from polluted sites had a significantly larger average mesophyll area and thicker epidermis. These needles also had significantly smaller average vascular bundles and xylem areas than needles from the unpolluted site. Although in the alkalised growth conditions, the mesophyll area enlarged, the number of damaged mesophyll cells increased, and as a result, the concentration of chlorophylls decreased reducing the photosynthetic potential of trees. Our study indicates that even though cement dust pollution has practically ceased in the area, the alkalised soil is affecting physiological processes in trees for a long time.

The objective of this study is to investigate the potential impact of future climate change on ozone air quality in Europe. To provide a full assessment, simulations with the global chemical transport model GEOS-CHEM driven by the NASA Goddard Institute for Space Studies general circulation model (NASA/GISS GCM) are conducted. To isolate the effects from changes in climate and anthropogenic emissions four types of simulations are performed: (1) present-day climate and emissions (2) future climate following the IPCC Special Report on Emission Scenarios (SRES) A1B scenario and present-day anthropogenic emissions of ozone precursors (3) present-day climate and future emissions and (4) future climate and future emissions. Results indicate that climate change impact on its own leads to an increase of less than 3 ppb in western and central Europe whereas decreases are evident for the rest of the areas with the highest (about 2.5 ppb) in southeastern Europe (Italy, Greece). Increases are attributed to the increases of isoprene biogenic emissions due to increasing temperatures whereas decreases are associated with the increase of water vapor over sea which tends to decrease the lifetime of ozone as well as the increased wind speeds in the 2050 climate. When future emissions are implemented in the future climate simulations, the greatest increases are seen in the southwest and southeast Mediterranean (about 16 ppb) due to the increased isoprene biogenic emissions under higher levels of NO ₓ in the model. Decreases up to 2 ppb of ozone are shown for France, Switzerland, Northern Italy and northern Europe.

Centrifugal mother liquid (CML) is one of the main sources of wastewater produced during the production of polyvinyl chloride in chlor-alkali industry. CML is a typical poorly biodegradable organic wastewater, containing many kinds of refractory pollutants. Specifically, it contains dissolved refractory polymers, especially polyvinyl alcohol (PVA), which can pass though the biotreatment processes and clog the membranes used for further treatment. In this study, to ensure the CML applicable to biotreatment and membrane treatment, a novel efficient and mild technique, air-Fenton treatment, was employed as a pretreatment technique to improve biodegradability of the CML and to break down the polymers in the CML. Firstly, the technique was optimized for the CML treatment by optimizing the main parameters, including the dosage of ferrous sulfate, initial pH of the wastewater, [H2O2]/[Fe(2+)], aeration rate, reaction time, and temperature, based on removal efficiency of COD and PVA from the CML. Then, the optimized technique was tested and evaluated. The results indicated that under the optimized conditions, the air-Fenton treatment could remove 66, 98, and 55 % of the COD, PVA, and TOC, respectively, from the CML. After the treatment, biodegradability of the wastewater increased significantly (BOD/COD increased from 0.31 to 0.68), and almost all of the PVA polymers were removed or broken down. Meanwhile, concentration of the remaining iron ions, which were added during the treatment, was also quite low (only 2.9 mg/L). Furthermore, most of the suspended materials and ammonia nitrogen, and some of the phosphorus in the wastewater were removed simultaneously.

Adsorption together with size exclusion and charge attraction/repulsion has to be taken into account when considering removal of pharmaceuticals as emerging contaminants from water by reverse osmosis and nanofiltration membranes. Glucocorticosteroids (hydrocortisone (HYDRO), dexamethasone (DEXA)), anesthetics (procaine, lidocaine) with relatively weak hydrophobicities (1 < log K O/W < 3), and membranes (XLE, LFC–1, CPA3, SWC1, NF90, and NF270) have been investigated in this study. Adsorption was studied by measuring the concentration of compounds in feed and permeate and by monitoring changes in membrane flux in the batch mode operation during 24 h. A decrease in the feed concentrations for HYDRO and DEXA (log K O/W < 2) was observed. The loss of these compounds in feed was associated with irreversible adsorption onto an NF270 and a CPA3 membrane. Therefore, when considering removal of pharmaceuticals with lower hydrophobicity, adsorption has to be particularly taken into account for membranes with bigger pores in the selective layer. Also, a high dipole moment and low water solubility affected adsorption on the membranes. For smaller and slightly more hydrophobic pharmaceuticals (log K O/W > 2), an increase in the feed concentration was obtained. Firstly, these compounds instantly adsorbed to the membrane. Secondly, the compounds diffused through the polymer matrix and desorbed to the permeate side after equilibrium had been reached.