Nanocomposite of CeO₂–SnO₂ containing different CeO₂ contents was prepared by coprecipitation process. The material obtained was characterized by X-ray diffraction and N₂ adsorption–desorption isotherms. Its photocatalytic activity was tested in the degradation of azo dye of leather, Direct Black 38, in aqueous solution under sunlight. The photocatalytic activity of the coupled CeO₂–SnO₂ oxide ranged depending on the CeO₂ contents. The optimum amount of CeO₂ for the synthesis of CeO₂–SnO₂ was 7 wt.% since the nanoparticles showed high photocatalytic activity in the degradation of the dye, similar to that of the TiO₂–P25 photocatalyst. The kinetics of photocatalytic degradation and total organic carbon removal under sunlight were found to follow a first-order rate law. The results indicated that CeO₂–SnO₂ can be used for the removal of dyes from wastewater.

The characteristics (natural, socioeconomic and administrative/institutional) of Alfeios River basin, in Greece, are identified and presented, incorporating and critically reviewing all possibly found literature. The Alfeios River is a water resources system of great natural, ecological, social and economic importance for Western Greece, since it has the longest and highest flow rate watercourse in the Peloponnisos region. Moreover, the river basin was exposed in the last decades to a plethora of environmental stresses (such as hydrogeological alterations, intensively irrigated agriculture, surface and groundwater overexploitation and infrastructure developments), resulting in the degradation of its quantitative and qualitative characteristics. It is therefore necessary for the development of an integrated river basin management plan for this basin, to study and analyse the interplay between the river components and the exerted environmental stresses, taking into account the puzzle of various and conflicting water uses, including water supply, irrigation, hydropower generation, lignite thermal power production and recreation. Mitigative, preventive and control measures for the analysed environmental stresses are epigrammatically depicted. Focusing on the problematic features, the present work provides a concrete foundation for the determination and conceptualisation of management objectives and possible sustainable alternatives.

Field experiments were conducted to assess the influence of plant growth and amendment addition on phytostabilisation of copper (Cu), lead (Pb), manganese (Mn) and zinc (Zn) along highway soil in southwest British Columbia, Canada. The plant species tested were Lolium perenne L (perennial rye grass), Festuca rubra L. (creeping red fescue) and Poa pratensis L. (Kentucky blue grass) and the amendments, lime and phosphate. The treatment efficiencies were assessed during different seasons as a completely randomized factorial experiment in split plot design. The research tasks involved: (1) quantifying the seasonal extent of metal accumulation in soil and assessing the seasonal impact on metal speciation for different soil amendments and plant species; (2) determining seasonal accumulation differences between sampling periods in plant parts; and (3) assessing the influence of root–soil interactions on metal dynamics. The amendments decreased the exchangeable fraction and plant uptake of all four metals. The lowest mobile fractions (exchangeable and carbonate bound) were found in soils growing Festuca for Cu, Lolium for Mn and a Lolium/Poa/Festuca combination for Pb and Zn. Metal accumulation and metal dynamics in the rhizosphere soil are compared with those of the bulk soil. The final outcome was the development of a remediation strategy for all four metals involving suitable plants and amendments and incorporating seasonal and rhizosphere influences.

The fate of N-15-labeled potassium nitrate (8.5% N-15 excess) was determined in 3-year-old Valencia orange trees grown in 1-m(3) containers filled with different textured soils (sandy and loamy). The trees were fertilized either in spring (24 March) or summer (24 July). Spring fertilized trees gave higher fruit yields in sandy than in loamy soils, which exceeded summer fertilized trees in both cases. Summer fertilized trees had greater leaf biomass than spring fertilized trees. Fibrous root weight was 1.9-fold higher in sandy than in loamy soil. At the end of the cycle, tree N recovery from spring application was 45.7% for sandy and 37.7% for loamy soil; from summer fertilization, N recovery was 58.9% and 51.5% for sandy and loamy soils, respectively. The N-15 recovered in the inorganic soil fraction (0-90 cm) was higher for loamy (1.3%) than for sandy soil (0.4%). Fertilizer N immobilized in the organic matter was lower in sandy (2.5%) than in loamy soil (6.0%). Potential nitrate leaching from fertilizer ((NO)-N-15 (3) (-) -N in the 90-110-cm soil layer plus (NO)-N-15 (3) (-) -N in drainage water) was 34.8% higher in sandy than in loamy soil. The low N levels in sandy soil resulted from both higher NO (3) (-) -N leaching losses and higher N uptake of plants grown in the former. The great root mass and higher soil temperatures could account for raised plant N uptake in sandy soil and in summer, respectively.

Water monitoring results of the Danjiangkou Reservoir indicated that total nitrogen and total phosphorus concentrations are high and therefore worse than required for central drinking water supplies. Nutrients including nitrogen and phosphorus accumulated in the bank cultivated land were greater than those contained within the river estuary sediment as well as in the reservoir bay sediment. This implies that high concentrations of loosely exchangeable phosphorus (166.53 mg/kg) in cultivated land could, after the completion of the dam heightening project, easily lead to the development of algal blooms. Serious water and soil loss occurring in the reservoir area will promote the transportation of non-point source pollution mainly caused by untreated agricultural domestic wastewater, chemical fertilizer and livestock farming, which accounted for more than 50% of the total basin’s nutrient input loads. Ecological control techniques were therefore the first choice for nutrient reduction and water quality guarantee in the Danjiangkou Reservoir. In order to guide the ecological restoration process, leading international ecological methodologies were summarized and compared, taking into consideration aspects of engineering, as well as ecological, biological, environmental and economic advantages and disadvantages. Finally, novel ecological filtration and a purification dam were designed for eutrophication control.

The effect of activated sludge acclimation on the biodegradation of toluene and dimethyldisulphide (DMDS) in the presence of a non-aqueous phase liquid, polydimethylsiloxane (PDMS), in a two-phase partitioning bioreactor was characterized. The influence of the presence of PDMS, at a ratio of 25% (v/v), and acclimation of activated sludge on two hydrophobic VOC biodegradation was studied. Activated sludge were acclimated to each VOC and in the presence of the non-aqueous phase liquid, namely in the emulsion of PDMS in water. Using acclimated cells, 97.9% and 108.7% improvement of the mean biodegradation rates were recorded for toluene and DMDS, respectively, if compared to the values recorded in the absence of acclimation. While and in agreement with the lower solubility in water of DMDS if compared to toluene, a most significant effect of PDMS addition on the rate of DMDS removal was recorded, 87.0% and 153.6% for toluene and DMDS, respectively. In addition and if both biomass acclimation and PDMS addition were considered, overall improvements of the removal rates were 204% and 338% for toluene and DMDS.

Recently, specific air quality problems have been detected in the northern region of Portugal. The nitrogen oxide (NO₂) annual limit value has been surpassed at several air quality monitoring stations in the northern region, and according to European legislation, air quality plans must be designed and implemented to reduce those levels. The analysis of the air quality data from the stations concerning NO₂ exceedances indicates that traffic is responsible for an increase of more than 40 % compared with the urban background value. Specific measures to reduce NOx emissions have been selected and are related not only mainly to the traffic sector but also to the industrial and residential combustion sectors. The main objective of this study is to investigate the impact of the selected measures on the ambient levels of NO₂ in northern Portugal using a numerical modelling tool—The Air Pollution Model (TAPM). TAPM was applied over the study region using a 120 × 120-km² simulation domain and a spatial resolution of 4.8 × 4.8 km². The entire year of 2010 was simulated and was set as the base year to analyse the impact of the selected measures. Two scenarios have been defined and simulated: the base situation, which considers current NOx emissions, and the reduction scenario for which NOx emissions were re-estimated considering the implementation of the measures. The modelling results demonstrate a decrease of 4–5 μg m⁻³ in the annual NO₂ levels in the study region. Moreover, the implementation of the selected measures will allow compliance with the NO₂ annual limit values in three of the five air quality stations that measured levels surpassing those established by legislation. This situation demands additional measures that should be implemented at the local level and that particularly focus on the traffic sector.

Microbial processes have shown promise for the remediation of uranium and nitrate in groundwater impacted by uranium mine tailings. This study investigated the inhibitory impact of uranium(VI) towards different microbial populations in anaerobic biofilms, including methanogenic, denitrifying, and uranium-reducing microorganisms, which are commonly found at uranium bioremediation sites. Results of batch activity bioassays indicated a very distinct level of toxicity depending on the targeted microbial community. U(VI) caused severe inhibition of acetoclastic methanogenesis as indicated by a 50 % inhibiting concentration (IC₅₀) of only 0.16 mM. Denitrifying populations were also impacted by uranium, but their sensitivity depended on the electron donor utilized. Sulfur-oxidizing denitrifiers were the least affected (IC₅₀ for denitrification activity = 0.32 mM), followed by H₂- and acetate-utilizing denitrifiers (IC₅₀ of 0.20 and 0.15 mM, respectively). In contrast, exposure to U(VI) concentrations up to 1.0 mM did not inhibit the rate of U(VI) bioreduction with H₂ as electron donor in the presence or absence of nitrate. On the contrary, a considerable increase in the uranium-reducing activity of the denitrifying and methanogenic mixed cultures was observed with increasing uranium concentrations. The results suggest that microorganisms responsible for U(V) reduction could tolerate much higher uranium concentrations compared to the other microbial populations assayed.

A simulation-based interval-fuzzy nonlinear programming (SIFNP) approach was developed for seasonal planning of stream water quality management. The techniques of inexact modeling, nonlinear programming, and interval-fuzzy optimization were incorporated within a general framework. Based on a multi-segment stream water quality simulation model, dynamic waste assimilative capacity of a river system within a multi-season context was considered in the optimization process. The method could not only address complexities of various system uncertainties but also tackle nonlinear environmental–economic interrelationships in water quality management problems. In addition, interval-fuzzy numbers were introduced to reflect the dual uncertainties, i.e., imprecision associated with fixing the lower and upper bounds of membership functions. The proposed method was applied to a case of water quality management in the Guoyang section of the Guo River in China. Interval solutions reflecting the inherent uncertainties were generated, and a spectrum of cost-effective schemes for seasonal water quality management could thus be obtained by adjusting different combinations of the decision variables within their solution intervals. The results indicated that SIFNP could effectively communicate dual uncertainties into the optimization process and help decision makers to identify desired options under various complexities of system components.

Rare earth mineral based adsorbent viz. lanthanum oxide was investigated for potential application in defluoridation of drinking water for isolated and rural communities. Results of batch experiments indicated about 90% removal in 30 min from a 4 mg L−1 synthetic fluoride solution. The effects of various parameters like contact time, pH, initial concentration, and sorbent dose on sorption efficiency were investigated. Adsorption efficiency was dependent on initial fluoride concentration and the sorption process followed BET model. Variation of pH up to 9.5 has insignificant effect on sorption and beyond a pH of 9.5, the effect was drastic. Among anions investigated, carbonates exhibited high detrimental effect on fluoride adsorption while anions like bicarbonates, chlorides, and sulfates did not seriously affect the process. Adsorbent showed negligible desorption of fluoride in distilled water. Alum was more effective regenerant than HCl and NaOH. Results of cyclic regeneration with alum indicated that the sorbent could be regenerated for ten cycles without significant loss of sorption capacity. Studies with upflow fixed-bed continuous flow columns indicated the usefulness of sorbent for fluoride removal in continuous flow process.