Actual problems of water ecosystem pollution require the ecological classification and the identification of the most influential parameters on the variability of water quality, stressing the importance of both in the realization of the sustainable water management principles according to the Water Framework Directive European Union (WFD EU), and the preservation of the quality of the environment. The aim of this paper was the assessment of the ecological status of water quality and calculating water pollution index (WPI) of the Danube River in Serbia. For all surface waters, the WFD requires “good ecological status,” i.e., low level changes of the natural state that occur as a result of human activities by 2015. The assessment was based on the data obtained from ten hydrological measuring stations on the Danube River in Serbia for 2014. It was ascertained that the ecological status of the Danube River water quality was class III, corresponding to “moderate ecological status” and deviating from the required “good ecological status.” According to the calculated WPI = 1.352, the water pollution of the Danube River in Serbia was characterized as moderately polluted and corresponded to class III of surface water. The ecosystem approach clearly indicated that the concentration of physico-chemical parameters of the watercourse deviated from the target values. Therefore, there is an urgent need to take some measures to prevent pollution and improve the water quality of the Danube River as an integral part of the environment in Serbia.

Growing rice with less water is direly needed due to declining water sources worldwide, but using methods that require less water inputs can have an impact on grain characteristics and recovery. A 2-year field study was conducted to evaluate the impact of conventionally sown flooded rice and low-water-input rice systems on the grain characteristics and recovery of fine rice. Three fine grain rice cultivars—Super Basmati, Basmati 2000, and Shaheen Basmati—were grown under conventional flooded transplanted rice (CFTR), alternate wetting and drying (AWD), and aerobic rice systems. Grain characteristics and rice recovery were significantly influenced by different water regimes (production systems). Poor milling, including the lowest percentage of brown (head) rice (65.3%) and polished (white) rice (64.2–66.9%) and the highest percentage of broken brown rice (10.2%), husk (24.5%–26.3%), polished broken rice (24.7%), and bran (11.0–12.5%), were recorded in the aerobic rice system sown with Shaheen Basmati. With a few exceptions, cultivars sown in CFTR were found to possess a higher percentage of brown (head) and polished (white) rice and they had incurred the least losses in the form of brown broken rice, husk, polished broken rice, and bran. In conclusion, better grain quality and recovery of rice can be attained by growing Super Basmati under the CFTR system. Growing Shaheen Basmati under low-water-input systems, the aerobic rice system in particular, resulted in poor grain characteristics tied with less rice recovery.

Greenhouse gas emissions from paddy soils respond differently to different combinations of crop root residues and N forms. An incubation experiment was carried out to explore the effect of four crop residues (milk vetch, ryegrass, winter wheat, and rape) and four nitrogen treatments (without fertilizer, urea, (NH₄)₂SO₄, and KNO₃) on CH₄, CO₂, and N₂O emissions in a paddy soil. Except in KNO₃ application treatments, CH₄ emissions of milk vetch residue treatments were significantly higher than those of the rest residue treatments. In the presence of milk vetch and ryegrass residues, urea application significantly increased CH₄ emissions in comparison to treatments without fertilizer. Urea significantly promoted CO₂ emissions, whereas (NH₄)₂SO₄ and KNO₃ significantly inhibited CO₂ emissions at all root residue treatments. Urea did not increase N₂O emissions, but (NH₄)₂SO₄ and KNO₃ promoted N₂O emissions at all residue treatments. In addition, KNO₃ had more effects on the increase of N₂O emissions than (NH₄)₂SO₄ in milk vetch-amended soils. Urea addition had no effect on global warming potentials, and (NH₄)₂SO₄ and KNO₃ addition significantly increased global warming potentials at all residue treatments except KNO₃ + winter wheat residue combination. Our results indicated that urea application had no additive effect on global warming when root residues were left in paddy soils, whereas (NH₄)₂SO₄ and KNO₃ application could increase the risk of global warming.

Flexible and self-standing membrane composed of ultrafine alumina-silica nanofibers (NFs) has been successfully fabricated by the electrospinning method, and further used as an adsorbent for the adsorptive decolorization of Reactive Red-120 (RR-120) dye from an aqueous system. Effects of pH, adsorbent dosage, and contact time on adsorption have been studied. The adsorption of RR-120 on the NFs was found to be highly pH dependent and the optimum pH was found to be 3. The adsorption equilibrium data was explained well with the Langmuir isotherm model, and the maximum sorption capacity was found to be 884.95 mg/g, which was several folds higher than the adsorption capacity of a number of recently studied potential adsorbents. After adsorption, the NF mat could be separated from the liquid phase conveniently and reused. The sorption kinetics was found to follow an intraparticle diffusion model. The high adsorption performance, excellent flexibility, easy recovery, and reuse characteristic of the alumina-silica NF membrane all favor its practical application in environmental remediation.

The photo-Fenton oxidation treatment combined with a coagulation/flocculation process was investigated for removal of chemical oxygen demand (COD) from a refractory petroleum refinery wastewater. Scrap iron shavings were used as the catalyst source. A response surface methodology (RSM) with a cubic IV optimal design was employed for optimizing the treatment process. Kinetic studies showed that the proposed process could be described by a two-stage, second-order reaction model. Experiments showed that precipitation of iron ions can be utilized as a post-oxidation coagulation stage to improve the overall treatment efficiency. More than 96.9% of the COD removal was achieved under optimal conditions, with a post-oxidation coagulation stage accounting for about 30% of the removal, thus confirming the collaborative role of oxidation and coagulation in the overall treatment. A low-velocity gradient of 8.0 s⁻¹ for a short mixing time of 10 min resulted in optimum post-oxidation coagulation. Comparison of photo-Fenton oxidation to a standard Fenton reaction in the same wastewater showed more rapid COD removal for photo-Fenton, with an initial second-order rate constant of 4.0 × 10⁻⁴ L mg⁻¹ min⁻¹ compared to the Fenton reaction’s overall second-order rate constant of 7.0 × 10⁻⁵ L mg⁻¹ min⁻¹.

In this study, the adsorption kinetic of cesium, strontium, and rubidium radionuclides was investigated using ferritin magnetic molecules. Kinetic investigation of synthetic and natural wastes was carried out and the results were compared. Pseudo first-order, pseudo second-order, Elovich, double-exponential, and intraparticle diffusion models were the kinetic models used in the fitting of experimental data. The kinetic study of synthetic waste revealed that the double-exponential model demonstrated excellent fitting. Coefficient of determination resulting from fitting of cesium, strontium, and rubidium radionuclide’s adsorption results via the double-exponential model are 0.9938, 0.9905, and 0.9863, respectively. In the experiments conducted on natural wastes, too, all of the five kinetic models were investigated. Results indicated that the double-exponential model matched greatly with the experimental data, and cesium, strontium, and rubidium radionuclide’s coefficients of determination were 0.9742, 0.9613, and 0.9442, respectively. Comparison of the results of natural and synthetic wastes showed that matching with the model and recovery of target elements were more prominent in experiments with synthetic waste (unicomponent) rather than natural waste (multicomponent).

In this study, Extran (biodegradable surfactant) was used for the preparation of Fe₃O₄ nanoparticles by microemulsion process to improve removal efficiency of As(III) from aqueous solution. Fe₃O₄ nanoparticles were characterized by XRD, FTIR, FESEM, TEM, HRTEM, and VSM instrumental techniques. The effect of different parameters such as adsorbent dose, initial As(III) concentration, and solution pH were studied by response surface methodology (RSM) based on Box-Behnken design (BBD). The optimized condition for adsorption of As(III) from aqueous solution was obtained as adsorbent dose of 0.70 mg/g, solution pH of 7.7, and initial As(III) concentration of 33.32 mg/L. In this optimum condition, about 90.5% of As(III) was removed from the aqueous solution. Isotherm studies have been done at optimal condition, and it was observed that the Langmuir isotherm models were fitted well with experimental data having a high correlation coefficient of 0.993. From the Langmuir isotherm data, the maximum adsorption capacity of Fe₃O₄ nanoparticles was found to be 7.18 mg/g at pH 7.7 in room temperature. This study revealed that Fe₃O₄ nanoparticles can be used as an efficient, eco-friendly, and effective material for the adsorptive removal of As(III) from aqueous system.

Phthalic acid esters (PAEs) is a class of refractory organic compounds, widely used as additives or plasticizers in plastic industry. PAEs are ubiquitous endocrine-disrupting pollutants and can be degraded by microorganisms. The present study described the assimilation of four PAE mixture (dimethyl, diethyl, dipropyl, and dibutyl phthalate) by two bacillus species: Bacillus thuringiensis and Bacillus cereus, isolated from different agricultural soil and their consortium. Among which, the optimal degradation of 82–96% was achieved by B. thuringiensis. This is the first report on the metabolic breakdown of four basic PAE mixture. The optimum conditions for biodegradation were found to be pH 7, temperature 30 °C, inoculum size 10 mL, and concentration 400 mg/L. Moreover, the respective biodegradation followed the first-order kinetic model. Our results proffered supplementary confirmation of the wide spectrum of PAE utilization by B. thuringiensis and suggest the possibility of applying it for the remediation of PAE contamination waste.

In order to determine the possible impact on the marine environment, we present a study on the dispersal and bioavailability of sediment-associated heavy metals related to underwater blasting and dredging of bedrock operations during a quay construction. The environmental impact was primarily assessed by deploying a buoy setup including sediment traps, blue mussels, and passive samplers (diffusive gradient in thin films, DGTs) in a gradient from the construction site during the operations. Samplings were made during five separate periods covering a total span of about 2.5 months. Analyses included sedimentation rates, organic content, and metal concentrations of the material collected in the sediment traps and metal concentrations of the mussels and passive samplers. The construction work was associated with a considerable dispersion of sediments, organic material, and associated heavy metals. The major fraction of the sediment settled in the vicinity of the construction site. While the mussels were found to accumulate some metals in a distance-related manner to the construction site and no such accumulation in the DGTs occurred, we conclude that most of the dispersed metals were particle associated. It was found that while a large part of the material settled in the vicinity of the construction site, most of the fine-grained and/or organic sediment that was brought into suspension was transported further away from the construction site (beyond the 350 m) most likely carrying contaminants including heavy metals. For future studies of risks and monitoring of underwater blasting and dredging, we recommend to include a larger monitoring area and more importantly water samples of the suspended plumes. Graphical Abstract The dispersal of sediments and bioavailability of heavy metals were assessed using a buoy setup during underwater blasting and dredging. ᅟ

In two soils from Central Greece, a pot experiment was conducted with the addition of mixture at various ratios of zeolite and compost (based on Posidonia oceanica (L.) leaves) applied at a rate of 5% w/w (calculated on a soil dry weight basis). Three varieties of tobacco (Burley, Virginia, and Oriental) were cultivated, and Cu, Zn, and Cd concentrations in tobacco leaves were measured at first, second, and third primings. We found that the addition of zeolite in the soil1 led to a significant reduction of metal concentration in all three tobacco varieties compared to the control. Also, zeolite addition reduced significantly the water-soluble, as well as, DTPA-extractable metal concentrations, compared to the other treatments. Our results suggest that the most effective amendment in soil 1 was the mixture consisting of 20% compost and 80% zeolite; this mixture led to higher reduction of metal concentration in all tobacco varieties. As for soil 2, which had almost twice as high Cd concentrations as than in soil 1, Posidonia compost was more effective in reducing Cd concentrations from all three tobacco varieties. In all cases studied, both in soils 1 and 2, Cd concentration was higher in Burley tobacco leaves. The results indicate that a mixture of zeolite and compost consisting of Posidonia oceanica (L.) is a low-cost soil conditioner that is effective in reducing tobacco Cu, Zn, and Cd uptake.