The model of contaminant transport between the abiotic components of the lake water-sediment system is presented. The implementation of the model, which uses radioactive material as a contaminant, and the evaluation of parameter values are discussed in the work. A semi-analytical solution of the simulation of the dynamics of contaminant transport in the lake water and one-dimensional sediment solute transport including non-equilibrium processes is presented. The model includes a concept of dynamics of the contaminant sorption in lake water and sediment compartments, considering the specific porous structure of sediments, the contaminant material exchange between the liquid and solid phases of sediments. The key processes included in the model are sedimentation, resuspension, diffusive exchange of solute at the lake water-sediment interface and advection-diffusion in sediment solute. Modelling of the contaminant transport in both spheres (lake water and bottom sediments) is influenced by non-equilibrium and transformation reactions. Special attention was paid to the contamination balance between the two spheres in the interface area. The ranges of boundary and initial conditions were extended, and final results were obtained using an accurate and robust numerical inversion calculation based on the De Hoog algorithm. Therefore, the model can be used in experimental measurements interpreting the contaminant profile in lake sediments as well as a part associated with the comprehensive determination of the volumetric activity, in the estimation of irradiation doses due to radionuclides released into the lake water.

Conversion of native forest to pastures is a common practice worldwide; it has complex effects on river biota that are related to activity type and intensity. This work was conducted in order to evaluate the effects of cattle grazing on environmental features and to select the most appropriate measures based on the macroinvertebrate community as indicators of ecological changes. Physicochemical features, riparian ecosystem quality, habitat condition, and benthic macroinvertebrates were investigated in streams draining pastures and were compared to reference streams located in nonimpacted native forested catchments. Strong evidence of sediment deposition was observed at pasture streams, which had higher percentage of sand in the streambed but also increased levels of suspended solids. Pasture sites had significantly higher water temperature and conductivity as well as lower dissolved oxygen concentrations than did forested sites. Both riparian quality and in-stream habitat condition were degraded at pasture sites. Among metrics, total richness, Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, Plecoptera richness, Shannon diversity, percentage of dominant taxon, percentage of Chironomidae species, shredder richness, and percentage of predator resulted to be the most consistent measures by displaying stronger responses to impairment. Our results suggest that forest conversion to pasture for livestock practices is diminishing macroinvertebrate biodiversity and potentially changing functioning and dynamics of Patagonian mountain streams as well. Damage prevention on riverine landscapes by restoring riparian ecosystems, replanting missing vegetation in buffer areas, and limiting livestock access to the riverbanks could contribute to enhance the ecological integrity at converted areas. A more extended and comprehensive use of macroinvertebrate metrics could contribute to better understand and evaluate impact effects of these extended land use activities and to promote conservation strategies.

The performance of a laboratory-scale biofilter packed with a mixture of compost and woodchip on formaldehyde removal from polluted air streams was investigated. The reactor was inoculated with aerobic sludge as a source of bacteria, obtained from a municipal wastewater treatment plant. A nutrient solution was daily added to the reactor media. An airflow containing different concentrations of formaldehyde (from 20 ± 2 to 276 ± 5 mg m⁻³) was introduced into the reactor. In inlet formaldehyde concentration, an average removal efficiency and elimination capacity of 91 % and 0.36 g m⁻³ h⁻¹were attained, respectively, at180 s empty bed residence time (EBRT). After acclimatization of the system for increased formaldehyde concentrations of up to 276 ± 5 mg m⁻³and for EBRT of 180 s, those values were stabilized at around 72 % and 3.98g⁻³ h⁻¹, respectively. The experimental results showed that the system was effective for a high loading rate of formaldehyde with an acceptable EBRT. Compared to the application of compost alone as a media, a mixture of compost and woodchip (50/50 v/v%) enhanced the performance of the biofilter. The most predominant microorganism involved in the biodegradation of formaldehyde was a species of citrobacter called Citrobacter freundii, an aerobic gram-negative bacillus. Pressure drop of the reactor over the entire operations was about 1 mmH₂O m⁻¹.

Zero-valent iron has received considerable attention for its potential application in the removal of heavy metals from water. This paper considers the possibility of removal of zinc ions from water by causing precipitates to form on the surface of iron. The chemical states and the atomic concentrations of solids which have formed on the surface of zero-valent iron as well as the type of the deposited polycrystalline substances have been analyzed with the use of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The BET surface area, the pH at point of zero charge (pHPZC), the ORP of the solutions, and the pH and chemical concentrations in the solutions have also been measured. Furthermore, the paper also considers the possibility of release of zinc from the precipitates to demineralised water in changing physicochemical and chemical conditions. In a wide range of pH values, Zn ₓ Fe₃ ₋ ₓ O₄ (where x ≤ 1) was the main compound resulting from the removal of zinc in ionic form from water. In neutral and alkaline conditions, the adsorption occurred as an additional process.

A novel magnetic pyridinium-functionalized mesoporous silica adsorbent (Fe₃O₄@SiO₂@Py-Cl) was synthesized for nitrate removal from aqueous solutions. The adsorption performances were investigated by varying experimental conditions such as pH, contact time, and initial concentration. The adsorbent was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and magnetic hysteresis loops. The results showed that the adsorption equilibrium could be reached within 30 min and the kinetic data were fitted well by pseudo-second-order and intra-particle diffusion model. The adsorbent exhibited a favorable performance, and its maximum adsorption capacity calculated by the Langmuir isotherm model was 1.755 mmol/g. The nitrate adsorption mechanism was mainly controlled by the material through ion exchange of nitrate with chloridion, as determined by XPS. This study indicated that this novel pyridinium-functionalized mesoporous material had excellent adsorption capacity. Meanwhile, compared with other adsorbents, it could remove nitrate fast and easy to be collected by magnetic separation, showing great potential application for nitrate removal from aqueous solution.

A series of column experiments was conducted to evaluate the effect of organic carbon fraction on long-term atrazine elution tailing for calcareous soil (foc = 0.97 %) and calcareous soil with 10 % by weight terra rossa amendment (foc = 1.20 %). Effluent atrazine concentrations were monitored for approximately 400 pore volume to understand the influence of controlling sorption–desorption kinetics on long-term tailing behavior. Laboratory studies showed that the sorption of atrazine was described by rate-limited, nonlinear reversible processes for both soils. Atrazine transport exhibited extensive elution tailing for all experiments due to the presence of hard carbon components such as black carbon and kerogen in both soils. This nonlinear sorption and extensive atrazine tailing behavior were more pronounced and extensive for soil with terra rossa amendment due to the addition of approximately 20 % organic carbon including 10 % hard carbon components from terra rossa soil. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous distribution function was used to successfully simulate atrazine transport early-time breakthrough and long-term concentration tailing for both porous media.

The study analyzes the presence and the origin of heavy metals in environmental compartments affected by anthropogenic activities. The paper presents the results of a field study performed on the sediments of two of the main small urban creeks of the city of Prague (Czech Republic). The aim of the survey was to verify the presence and bioavailability of heavy metals (Cu, Cr, Ni, Pb, Zn) in the aquatic environment (water as well as bottom sediments), and to assess the source of these pollutants. The results were processed to evaluate the enrichment factor and the partition coefficient, and were statistically analyzed through the analysis of variance and the principal component analysis. Comparison with relevant environmental quality standards showed that measured heavy metal concentrations were always lower than the probable effect concentration (PEC). On the contrary, the threshold effect concentration (TEC) was frequently exceeded. Sequential extraction analysis showed that the bioavailability of studied metals is quite high, suggesting that they could be easily released from the sediment to the aquatic environment. Overall, several sources of pollution, different for the different metals, were identified, all related with anthropogenic factors.

A significant amount of artificial radionuclides has been introduced into the environment in the last century during atmospheric nuclear weapons tests and the Chernobyl accident. In this study, we investigated the temporal changes of concentrations and amounts of these radionuclides (⁹⁰Sr and ¹³⁷Cs) in surface water and river bed sediments. In order to evaluate the artificial radionuclide contamination diminution, we used and compared two different approaches: using a kinetic equation of the first order and, if needed, dividing the monitored period into two intervals, and in addition expressing the whole process in one equation with a series of exponential functions. Effective ecological half-lives were estimated as rates of decrease. In most cases, the ecological processes were proven to affect the radionuclide removal from the hydrosphere besides their radioactive decay. Furthermore, based on the assessment made, the ⁹⁰Sr and ¹³⁷Cs data were extrapolated and the radionuclide concentrations, which occurred in the hydrosphere after the fallout deposition in 1986, were estimated.

Because of its long half-life, endosulfan can persist for a long time in the environment, especially in soil. However, little is known about its effect on fungi, which is an important part of microorganisms in soil. In this study, agricultural soil treated with endosulfan (0.1 and 1.0 mg kg⁻¹) in a laboratory experiment was analyzed over 42 days. The effect of endosulfan on bacterial and fungal quantity and community structure were determined by quantitative polymerase chain reaction (qPCR) and denaturing gradient gel electrophoresis (DGGE). The results revealed that endosulfan was removed more than 50 % after 42 days, and its removal fitted single first-order kinetics. The exposure to endosulfan caused a short-lived inhibition on fungal and bacterial quantity, but no effect was observed in both treatments after 42 days. Furthermore, this inhibition was greater in higher endosulfan-treated soil. A significant change in bacterial community structure was found in both treatments after endosulfan application, while the change of fungal community structure was observed only in 1 mg kg⁻¹endosulfan treatment.

In this study, we developed a new method for the preconcentration and spectrophotometric determination of vanadium (V) using dispersive liquid-liquid microextraction (DLLME) and optical sensors using 4-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) as a complexing reagent. The preconcentration is based on the extraction of vanadium ions (V) in trichloroethylene in the form of a complex with Br-PADAP, using ethanol as a dispersion solvent. After injecting the solvent into a solution containing vanadium, a homogeneous mixture is obtained. The mixture is centrifuged to deposit the desired phase onto a triacetylcellulose membrane. Then, the supernatant is discarded, and the membrane is exposed to the radiation beam of a spectrophotometer without the use of a microcuvette. Under optimal conditions, the detection limit was determined to be 0.57 μg L⁻¹, and the quantification limit was 1.91 μg L⁻¹. The accuracy of the method was verified by analyzing a certified reference material, BCR®414, plankton. The procedure was applied to the determination of vanadium levels in shellfish samples, specifically shrimp and oyster.