Heavy metal contamination causes significant environmental problems around the world and poses a threat to human health. Poplar hybrids present features for potential uses in phytoremediation systems in areas with heavy metal contamination. The purpose of this study was to assess the copper (Cu) accumulation level in five poplar inter-species hybrids [(Populus trichocarpa × Populus deltoides) × P. deltoides; P. deltoides × Populus nigra; P. trichocarpa × Populus maximowiczii; P. trichocarpa × P. nigra; and (P. trichocarpa × P. deltoides) × (P. trichocarpa × P. deltoides)] grown in a hydroponic system. The treatments entailed the application of low and high doses of Cu of 8.0 and 16.0 μM, respectively. Cu accumulation was observed in roots, stems, and leaves, which was determined using flame atomic absorption spectroscopy, prior acid digestion of each sample. The methodology was validated according to certified reference material (Cypress BIMEP 432). Significant differences in Cu accumulation were found among genotypes for both roots and leaves, but not for stems. In roots, the genotype P. deltoides × P. nigra had a Cu accumulation level of 169.8% higher than the average accumulation found in the other genotypes. The (P. trichocarpa × P. deltoides) × P. deltoides hybrid showed the least Cu accumulation in leaves. The results of this study can potentially be used for proper crossovers and hybrids selection within the genus Populus for phytoremediation of Cu contaminated land.

In industry areas of Poland such as Silesia or urban sites like Krakow and some other cities, the levels of pollutants frequently breach air quality standards. Particulate matter (PM) is the most important constituent of atmospheric pollution. Beginning on 1st February 2014 until 31st January 2015, the samples of fine particulate matter PM₂.₅ (aerodynamic diameter of particles less than or equal to 2.5 μm) were collected at a site in the south-eastern Krakow urban background area. During this period, 194 samples were taken. The samples showed daily variation of PM₂.₅ concentration. From these data, monthly variations were estimated and presented in this paper. Monthly integrated data are more representative for the Krakow urban background and show seasonal variation of PM₂.₅ pollution. The lowest monthly concentration value was found for August 2014—about 10 μg m⁻³, the highest for February 2014–70 μg m⁻³, whereas the average annual value was about 31 μg/m³. Utilizing X-ray fluorescence method, concentrations of 15 elements for each sample were determined and 8 inorganic ions were analyzed by ion chromatography. Additionally, the samples were analyzed for black carbon (BC). Receptor model PMF (positive matrix factorization) was used for source identification and apportionment. The modeling identified six sources and their quantitative contributions to PM₂.₅ total mass. The following sources were identified: combustion, secondary nitrate and sulfate, biomass burning, industry or/and soil and traffic. Finally, monthly variations of each source are presented.

A new dithiocarbamate-base resin was synthesized utilizing the reaction between carbon disulfide and immobilized amines on the fully cross-linked side of the styrene-maleicimide (SMI) copolymer. The sorption characteristics of the synthesized resin for copper, lead, nickel, zinc, and cadmium ions were investigated, using atomic adsorption spectroscopy (AAS). The sorption capacity of the resin for each metal ion was studied as a function of pH and time. The optimum pH range for sorption of the metal ions was between 4 and 6. The capacity of the resin for the metal ions decreases in the following order: Cu(II) ≈ Pb(II) > > Zn(II) > Ni(II) > Cd(II). The sorption rate of the metal ions in the resin decreases in the following order: Zn(II) > Ni(II) > Cd(II) > Pb(II) > Cu(II). The affinity of the resin for the ions was also studied using a mixture of the heavy metal ions. The capacities of the new resin, especially for copper and lead, are significantly higher than previously studied resins. Additionally, it was shown that desorption of the captured ions from the resin within 24 h can be done using 1 M nitric acid solution.

This study investigated the use of napiergrass (Pennisetum purpureum Schum.) to remediate soils highly contaminated with radiocesium-137 (¹³⁷Cs) in the town of Namie, Fukushima Prefecture, which is located around 9 km northwest of the Fukushima Daiichi Nuclear Power Plant, Japan. Field experiments were performed to investigate the remediation effects using two sites (paddy or upland grassland) as replicates, three planting densities (low, medium, and high density), and two different cutting frequencies (cut once or twice a year) over 2 consecutive years. Napiergrass can be more efficient than sorghum for ¹³⁷Cs remediation. The maximum ¹³⁷Cs removal ratio (CR, %) in napiergrass achieved with high-density planting (11 plants m⁻²) was between 0.32 and 0.57%. However, cutting frequency did not affect the CR. Higher biomass leads to a dilution of ¹³⁷Cs in cutting frequency. Therefore, we suggest that the greatest CR could be achieved through a high above ground biomass (high-density planting).

The electrochemical elimination of the herbicide diquat dibromide (DQ) in an undivided electrochemical cell (Condiacell®-type cell) and an H-type cell (a divided electrochemical cell) using boron-doped diamond (BDD) electrodes is reported for the first time. The degradation of essentially 100% of the DQ present was achieved in the undivided electrochemical cell and ca. 92% in the H-type cell. Nearly 80% of the total organic carbon (TOC) and of the chemical oxygen demand (COD) were removed after 5 h of treatment at different current densities (i.e., 0.5, 1.0, and 1.5 mA/cm² for the undivided cell, and 2.5, 5.0, and 7.5 mA/cm² for the H-type cell) with a maximum specific energy consumption of approximately 150 kWh kg⁻¹ of COD degraded in the undivided cell, and 300 kWh kg⁻¹ of COD in the H-type cell. Energy consumption of about 0.30 kWh g⁻¹ of TOC occurred in the undivided electrochemical cell and 2.0 in the H-type cell. In spite of obtaining similar percentages of DQ degradation and of COD and TOC removal, a smaller energy usage was required in the undivided cell since smaller current densities were employed. Best results were obtained with the undivided cell, since it required a smaller current density to obtain virtually the same percentage of DQ degradation and removal of COD and TOC. The results obtained herein show that the use of electrochemical advanced oxidation processes may be a good alternative for DQ degradation in polluted water.

Surface modification of the silica nanoparticles was performed using trithiocyanuric acid (TCA-SNPs) so as to enhance the adsorption of Ag⁺ from aqueous solutions. The surface modification to the adsorbent was characterized by Fourier transform infrared spectroscopy, transmission electron microscope, and X-ray photoelectron spectroscopy. The Ag⁺ adsorption capacity was found to increase with increase in the solution pH, with the optimal pH being 5.0. The Ag⁺ adsorption isotherm was generated at 25 °C at the optimal solution pH and the maximum adsorption capacity was found to be 80 mg/g, significantly higher than the adsorption capacity reported for other adsorbents in literature. The increase in adsorption capacity was attributed to the presence of thiol groups on the surface of the modified adsorbents. Additionally, the adsorption kinetics was estimated at 25 °C, which indicated very high rates of adsorption initially, with rapid reduction in rate of adsorption with time. Both adsorption isotherms as well as the adsorption kinetics were modeled with popular models. The adsorption isotherm was found to match with the Langmuir model while the adsorption kinetics was found to match with the pseudo-second-order kinetic model. The adsorption-desorption cycles indicate the TCA-SNPs to be stable adsorption performance and retain high adsorption efficiency ensuring commercial adoption. A relatively low adsorption of other ions such as Mn²⁺, Cu²⁺, Ni²⁺, Co³⁺ as compared to Ag⁺ was ensured.

Pipe section reactor (PSR) is a well-controlled laboratory reactor, which is used to simulate the water quality variations in drinking water distribution systems. However, the hydraulics condition within PSR, which is an essential prerequisite of the water quality studies, still remains unclear. Consequently, the objective of this study is to analyze the hydraulic conditions within PSR by means of a computational fluid dynamics (CFD) approach. The influences of configuration parameters on the hydraulic conditions were tested including propeller diameter, inclined angle of the propeller, distance between the top and inner cylinder, distance between the bottom and inner cylinder, outer cylinder length, baffle length, number of the baffles, rotational speed of the propeller, and inner and outer cylinder diameters. According to the CFD analysis, an optimal structure of PSR was suggested. The data presented here could facilitate the PSR application and improve the simulation of water quality in distribution systems.

Hydrophilic carbonaceous nanoparticles (HNPs) of uniform sizes with a good degree of dispersion in water were produced from a commercial carbon black by nitric acid treatment. The surface treatment, performed at different reaction times, generates a variable number of oxygen functional groups, mainly carboxylic, which enhance the nanoparticles hydrophilicity and heavy metal adsorption capability. The HNPs were characterized by a number of analytical techniques, including FTIR spectroscopy, thermal and elemental analysis, N₂ adsorption, dynamic light scattering, and zeta-potential measurements. The acid–base properties of the functional groups on the HNPs surface were also investigated by coulometric–potentiometric titrations. Cadmium adsorption tests were carried out in stirred reactors containing colloidal aqueous suspensions of HNPs and HNPs supported over silica. The effects of several parameters, such as the cadmium concentration, the temperature, and the solution pH, were studied. Sorbents showed an appreciable cadmium adsorption capability at different temperatures and in a wide range of pH values comparable or superior to several carbon-based sorbents, indicating a feasible use in commercial units.

Contaminant elution and tracer (CET) tests are one method for characterizing the impact of mass transfer, transformation, and other attenuation processes on contaminant transport and mass removal for subsurface systems. The purpose of the work reported herein is to explore specific well-field configurations for improving CET tests by reducing the influence of preferential flow and surrounding plume effects. Three injection-extraction well configurations were tested for different domain conditions using a three-dimensional numerical model. The three configurations were the traditional configuration with a single pair of injection-extraction wells, modified configuration I with one extraction well located between two injection wells, and modified configuration II with two pairs of injection-extraction couplets (one nested within the other). Elution curves for resident contaminant and breakthrough curves from simulated tracer tests were examined for specific landmarks such as the presence and extent of steady state (relatively high concentrations) and asymptotic (asymptotic decrease to low concentrations) phases, as well as distinct changes in slope. Temporal moment analysis of the breakthrough curves was conducted to evaluate mass recovery. Effective diffusion coefficients were obtained by fitting selected functions to the elution curves. Based on simulation results for a homogeneous domain, full isolation of the inner extraction well from the surrounding plume was obtained for the modified configuration II, whereas the extraction wells are impacted by the surrounding plume for the other two configurations. Therefore, configuration II was used for additional simulations conducted with layered and heterogeneous domains. Tracer test simulations for homogeneous and layered domains indicate 100% mass recovery for the inner extraction well. For the heterogeneous domain, decreasing the distance between the inner injection-extraction well couplet and adjusting the pumping rate distribution between the two extraction wells increased the mass recovery from 69 to 99%.

In this study, a process has been proposed whereby the sulfide required for autotrophic denitrification is supplied by reducing the sulfate of influent water without the need to add an external sulfide source. The molar ratio of nitrate-to-sulfide was maintained at 1.6. The proposed system was operated continuously for 6 months, including two anoxic and anaerobic reactors with upward flow. The results indicate that the average amount of nitrate declined by 74%. The pH of 7–8 was more effective than a pH of 6 in removing the nitrate. As the hydraulic retention time was prolonged from 1.5 to 3 and was further prolonged to 5 h, the system efficiency was enhanced by removing the nitrate. An alkalinity consumption rate of 1.15 mg (as CaCO₃) per mg of removed NO₃ ⁻-N was achieved. In the effluent water, the increased sulfate was 6.7 mg per mg of removed NO⁻ ₃-N, while the hardness was diminished by 2.85 mg (as CaCO₃).