We investigated the potential application of pyrolysis treatment to a mixture of woody biomass and a metal-contaminated soil as an alternative eco-friendly option to stabilize metals in soils. Our specific objective was to test the optimum combination of high heating temperature (HHT) and heating time to effectively encapsulate metals in a contaminated soil into a biochar. For this purpose, we used a laboratory bench batch reactor to react a mixture of multi-element metal contaminated soil with 0% (control) 5%, 10%, and 15% (w/w) sawdust. Each mixture was reacted at 200°C and 400°C HHT for 1 and 2 h heating times. Physicochemical and morphological characterization along with standard EPA Synthetic Precipitation Leaching Procedure (SPLP) test were conducted to assess the effectiveness of the heat treatment to immobilize the metals in the contaminated soil. Compared to controls, we recorded up to 93% reduction in Cd and Zn leachability after 1 h heat treatment at 400°C, with the addition of 5–10% biomass. Pb leaching was reduced by 43% by the same treatment but without the addition of biomass. At lower pyrolysis temperature (200°C), however, there was a substantial increase in both As and Zn leaching compared to the untreated controls. Our study suggests that several factors such as the type of metal, heating temperature, heating period, and the addition of biomass influence the efficiency of pyrolysis to immobilize metals in the contaminated soil.

We performed a 2-year microcosm study to assess the effectiveness of red mud, a by-product of bauxite processing, in stabilizing contaminated mine waste and agricultural soil. Our study used red mud from a long-term disposal area in Almásfüzitő, Hungary with a pH of 9.0. A 5% (by weight) red mud addition decreased the highly mobile, water-extractable amount of Cd and Zn by 57% and 87%, respectively, in the agricultural soil and by 73% and 79%, respectively, in the mine waste. In a laboratory lysimeter study, the addition of red mud reduced the concentration of Cd and Zn in the leachate by about two third of the original. The metal content of the leachate was below the Maximum Effect Based Quality Criteria for surface water as determined by a risk assessment in the metal-contaminated area of the Toka valley near Gyöngyösoroszi, Hungary. The addition of red mud did not increase the toxicity of the treated mine waste and soil and decreased the Cd and Zn uptake of Sinapis alba test plants by 18–29%. These results indicate that red mud applied to agricultural soil has no negative effects on plants and soil microbes and decreases the amounts of mobile metals, thus indicating its value for soil remediation.

Over 5 days, Brassica juncea removed 54% of the highly toxic insecticide phorate from the medium with the formation of phorate sulfoxide in small quantity. The loss of phorate from the medium followed first-order kinetics. The half-life of phorate disappearance from water decreased by ~4.5-fold in the presence of B. juncea. Mild phorate phytotoxicity was evident from the elevated activities of the antioxidative enzymes like glutathione-disulfide reductase, glutathione S-transferase, superoxide dismutase, and catalase in the plants. Nevertheless, the ubiquitous antioxidative peroxidase was not significantly increased, nor the total glutathione content, due to phorate exposure. Phosphotriester bond hydrolysis and glutathione S-transferase-mediated conjugation seemed to be the key reactions for phorate metabolism by B. juncea. From the limited information available, for the first time, a tentative mapping of phytotransformation pathways was performed.

N-nitrosodimethylamine (NDMA) is one of the most important disinfection by-products (DBPs) due to its carcinogenicity even at low concentrations which correspond to the levels occurring in drinking water and wastewater effluents. Therefore, NDMA is a candidate DBP that is expected to be regulated in the near future. However, the measurement of NDMA in the low nanogram per liter range is challenging because of the limitations of analytical techniques including both the sample preparation and the LC-MS/MS. Moreover, the accuracy of most of the current methods is only tested for drinking water and no information is present for other matrices. In this study, a combination of solid-phase extraction (SPE) and LC-MS/MS method that does not require high-resolution MS or advanced techniques for sample pretreatment is developed. Moreover, important factors that affect the optimization of the SPE method are provided to enable readers to optimize their own SPE procedures if necessary. The proposed method was validated for surface water, groundwater, and wastewater samples and the method quantification limit was 2 ng/L. In addition, the proposed method was used to determine the concentration of NDMA precursors measured as NDMA formation potential (NDMAFP) throughout a drinking water treatment plant at two different sampling periods. NDMAFP decreased by approximately 40 % in both samples. The concentrations ranged between 4 and 11.5 ng/L and the presence of these low concentrations underlines the need for an easy to use, yet sensitive method for the determination of NDMA in environmental matrices.

An excess of phosphorus (P) is the most common cause of eutrophication of freshwater bodies. Thus, it is imperative to reduce the concentration of P to prevent harmful algal blooms. Moreover, recovery of P has been gaining importance because its natural source will be exhausted in the near future. Therefore, the present work investigated the removal and recovery of phosphate from water using a newly developed hybrid nanocomposite containing aluminium nanoparticles (HPN). The HPN-Pr removes 0.80 ± 0.01 mg P/g in a pH interval between 2.0 and 6.5. The adsorption mechanism was described by a Freundlich adsorption model. The material presented good selectivity for phosphate and can be regenerated using an HCl dilute solution. The factors that contribute most to the attractiveness of HPN-Pr as a phosphate sorbent are its moderate removal capacity, feasible production at industrial scale, reuse after regeneration and recovery of phosphate.

Phosphate removal from water is crucial to the prevention of eutrophication. The phosphate adsorption performance from aqueous solutions by using lanthanum-doped activated carbon fiber (ACF-La) was developed by batch and continuous column adsorption method. The batch sorption condition with respect to interfering ions was tested, and the pseudo second-order and intraparticle diffusion models were used to evaluate the adsorption kinetics of phosphate onto ACF-La in the presence of interfering ions, with the second-order model to fit the experimental data better. Moreover, three factors (phosphate concentration, flow rate, and interfering ions) were examined at column run method to evaluate the practical application of ACF-La to the continuous removal phosphate from solution. Furthermore, how the factors (eluted solution concentration, eluted time, and regeneration number) affect the regeneration efficiency of ACF-La was also investigated. These findings suggest that ACF-La has a considerable potential for the application of phosphate removal from contaminated waters.

Previous research in agricultural catchments showed that past inputs of nitrate continue to influence present observations and future characteristics of nitrate concentrations in stream water for a long period of time. This persistence manifests itself as a “memory effect” with a prolonged response of stream water nitrate levels to reductions of nitrate inputs on the catchment scale. The question we attempt to resolve is whether such a memory effect also exists in mountainous catchments with a snowmelt-dominated runoff regime. We analyzed long-term records (∼20 years) of nitrate-nitrogen concentrations measured in stream at three stations on the upper Váh River (Slovakia). Applying spectral analysis and detrended fluctuation analysis, we found a varying degree of persistence between the three analyzed sites. With increasing catchment area, the fluctuation scaling exponents generally increased from 0.77 to 0.93 (fluctuation exponents above 0.5 are usually considered as a proof of persistence while values close to 0.5 indicate “white” uncorrelated noise). The nitrate-nitrogen signals temporally scaled as a power-low function of frequency (1/f noise) with a strong annual seasonality. This increase in persistence might be attributable to the catchment areas upstream the sampling sites. These results have important implications for water quality management. In areas where reduction of nitrate in surface waters is imposed by legislation and regulatory measures, two catchments with different persistence properties may not respond to the same reduction of sources of nitrogen at the same rate.

This study was carried out to examine the phytotoxicity and oxidant stress by CuO and ZnO nanoparticles (NPs) in Cumumis sativus and the characterization of CuO and ZnO NP suspensions. We estimated the bioaccumulation of CuO and ZnO NP in plant, reactive oxygen species enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activities in plant tissue of root, and observed CuO and ZnO NPs with transmission electron microscopy. We found that the seedling biomass significantly decreased to 75% and 35% of that of control at 1,000 mg/L of CuO and ZnO NPs, respectively. The bioavailability and oxidant stress potential of plants exposed to metal oxide particles were dependent in the size, concentration, and species of the NPs. The median inhibition concentrations of CuO and ZnO NPs were 376 and 215 mg/L, respectively. In transmission electron microscopy, CuO and ZnO NPs greatly adhered to the root cell wall, and NPs were observed in the root cells. Another finding indicated that both CuO and ZnO NPs caused statistically significant increase in SOD, CAT, and POD activities and significant increase at 100 mg/L concentration levels. These results indicated that NPs alter both phytotoxicity and oxidative stress in plant assays. We further suggest that the oxidative stress markers appear to be a good predator of potential future toxicity of nanoparticles.

The behavior of estrone (E1) and 17β-estradiol (E2) in relatively closed water environment was studied by continuous flow experiment using sediments from a freshwater reservoir. For this, four sediment columns (two oxic ones and two anoxic ones) were employed, which were structured by packing 30 cm of undisturbed sediment and 60 cm of overlying water collected from two sites within a reservoir. A mass balance model that considered the influent flux, the effluent flux, mass transfer, sorption, and biodegradation was proposed to describe the behavior of E2 and E1 in the columns. The results indicated that the water–sediment partition coefficient of E1 [Formula: see text] was higher than E2 [Formula: see text]. The degradation rate of E1 (k E1) was smaller than E2 (k E2). Under both oxic and anoxic conditions, E1 was formed from E2. Furthermore, to clarify the impact of the model parameters such as the hydraulic retention time (HRT), K d, and k on the behavior of E2 and E1, variance analysis was performed based on the results of model simulations. The results showed that the concentrations of E2 and E1 in the column effluent were controlled most significantly by the sorption capacity of the natural estrogens onto sediment particles, with the determined contributory ratios changing in the order of sorption > HRT > degradation.

Vicinities of manufactured gas plants were often contaminated with solid iron–cyanide complexes as a result of the coal gasification process. During the remediation of affected soils, knowledge about contaminant concentrations is crucial, but laboratory methods are often expensive and time consuming. Rapid and non-destructive field methods for contaminant determination permit an analysis of large sample numbers and hence, facilitate identification of ‘hot spots’ of contamination. Diffuse near infrared reflectance spectroscopy has proven to be a reliable analytical tool in soil investigation. In order to determine the feasibility of a Polychromix Handheld Field Portable Near-Infrared Analyzer (FP NIR), various sample preparation methods were examined, including homogenizing, sieving, drying, and grinding. Partial least squares calibration models were developed to determine near infrared (NIR) spectral responses to the cyanide concentration in the soil samples. As a control, the contaminant concentration was determined using conventional flow injection analysis. The experiments revealed that portable near-infrared spectrometers could be a reliable device for detecting cyanide concentrations >2,400 mg kg⁻¹ in the field and >1,750 mg kg⁻¹ after sample preparation in the laboratory. We found that portable NIR spectrometry cannot replace traditional laboratory analyses due to high limits of detection, but that it could be used for identification of contamination ‘hot spots’.