Catalytic destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans) over V₂O₅-CeO₂/TiO₂ catalyst was investigated at a low temperature range of 140–180 °C, in the absence and presence of ozone (200 ppm). Nano-TiO₂ support was used to prepare the catalyst by step impregnation method. A stable PCDD/Fs-generating system was established to support the catalytic destruction tests. In the presence of ozone alone, destruction efficiencies of PCDD/Fs are between 32.2 and 43.1 % with temperature increasing from 140 to 180 °C. The activity of V₂O₅-CeO₂/TiO₂ catalyst alone on PCDD/Fs destruction is also studied. The increase of temperature from 140 to 180 °C enhances the activity of catalyst with destruction efficiencies increasing from 54.7 to 73.4 %. However, ozone addition greatly enhances the catalytic activity of V₂O₅-CeO₂/TiO₂ catalyst on PCDD/Fs decomposition. At 180 °C, the destruction efficiency of PCDD/Fs achieved with V₂O₅-CeO₂/TiO₂ catalyst and ozone is above 86.0 %. It indicates that the combined use of ozone and catalyst reduces the reaction temperature of PCDD/Fs oxidation and offers a new method to destroy PCDD/Fs with high destruction efficiency at a low temperature. Furthermore, the destruction efficiencies of 17 toxic PCDD/F congeners, achieved with ozone alone, catalyst alone, and catalyst/ozone are analyzed.

In this study, batch experiments have been carried out to investigate the mechanism of fluoride uptake by layered double hydroxide (LDH) and calcined layered double hydroxide (CLDH). Furthermore, practical use of these synthetic minerals was studied in continuous mini-column experiments. In these column studies, groundwater from Ethiopia was tested. LDH and CLDH were synthesized with Mg/Al mole ratio of 2. From batch experimental study, LDH and CLDH have shown maximum removal capacity of 84 and 222 mg F⁻/g from aqueous solution, respectively. It was observed that fluoride removal was pH dependent with favorable pH range of 5–7 (max. at pH 6). The mechanism of removal is suggested to be ion exchange for LDH and a memory effect followed by surface precipitation reaction for CLDH. The presence of other anions lowered defluoridation capacity of LDH in the order of PO₄ ³⁻ > SO₄ ²⁻ > NO₃ ⁻ ≈ Cl⁻. From continuous experiments at 1 mM NaHCO₃, LDH showed maximum defluoridation capacity of 1.3 mg/g and CLDH up to 20 mg/g. It was also observed that increase of bicarbonate concentration to 10 mM lowered the fluoride uptake capacity of CLDH to 4 mg/g. The presence of 1 mM H₄SiO₄ further reduced fluoride uptake capacity to 3 mg/g. CLDH column tested with groundwater from the Rift Valley with 10.5 mg F⁻/L has shown maximum removal capacity of 2.2 mg F⁻/g. Regeneration of this column indicated that CLDH has a good potential to be re-used.

Ammonia (NH₃) volatilization is one of the main pathways of N loss from farmland soil. Saline water irrigation can have direct or indirect effects on soil NH₃ volatilization, N leaching, and crop N uptake. This study was conducted to evaluate the effects of irrigation water salinity and urea-N application rate on NH₃ volatilization and N use efficiency in a drip-irrigated cotton field. The experiment consisted of three levels of irrigation water salinity: fresh water, brackish water, and saline water (electrical conductivities of 0.35, 4.61, and 8.04 dS/m, respectively). The N application rates were 0, 240, 360, and 480 kg/ha. The results showed that soil salinity and soil moisture content were significantly higher in the saline water treatment than in either the fresh or brackish water treatments. Irrigation water salinity significantly increased soil NH₄-N concentration, but NO₃-N concentration decreased as water salinity increased. The amount of N leaching varied from 5.0 to 25.5 kg/ha, accounting for 1.81 to 4.79 % of the urea-N applied under different water salinity and N application rate treatments. Both the amount of N leaching and the proportions of applied N lost through leaching significantly increased as water salinity increased. N application increased the amounts of N leaching, but the ratios of applied N were not affected by N application rate. Soil NH₃ volatilization increased rapidly after urea fertigation, and peaked at 1–2 days after N application, then decreased rapidly. The amount of NH₃ volatilization varied from 9.0 to 33.7 kg/ha, accounting for 3.2 to 3.8 % of the N applied in all treatments. Soil NH₃ volatilization was significantly higher in the saline water treatment than that in either the fresh or the brackish water treatments. Cotton N uptake increased significantly as N application rate increased, but decreased with irrigation water salinity increased. In conclusion, saline water irrigation with high N application rate induced high N leaching and NH₃ volatilization losses, thereby dramatically reducing the apparent N recovery (ANR) of cotton.

Surfactants always play a special role in wastewater processes due to their amphiphilic properties. The performance of ultrafiltration was investigated for the treatment of wastewater containing low-level anionic surfactant and trace-level nuclides. Results showed that sodium dodecyl benzene sulfonate (SDBS) below the critical micelle concentration (CMC) caused significant effects on membrane fouling and rejection of nuclides. The membrane flux decreased at SDBS concentrations below the CMC but increased at the concentrations near the CMC. The phenomenon was caused by two distinct effects of SDBS, pore blocking by the monomers and enhancement of nuclide scaling caused a decrease in flux, while hydrophilic modification of the membrane surface by micelles caused an increase in flux. The nuclides alone had no significant effect on membrane fouling, but the flux decreased upon an increase in nuclide concentration when coexisting with SDBS. After the addition of low-level SDBS, the rejections of nuclides increased sharply from 20–30 to 60–98 %. The rejections of Sr(II) and Co(II) were higher than those of Ag(I) and Cs(I) due to stronger complexation of SDBS with divalent cations compared with monovalent cations. Deposition of nuclides increased with the addition of SDBS and with increasing of nuclide concentration, resulting in more radioactive solid waste production and more frequent replacement of membrane module.

Di-n-butyl phthalate (DBP) widely used as plastic films’ plasticizer, can cause agricultural pollution which is of increasing concern because of the food safety issues. Cucumber (Cucumis sativus Linn.), commonly cultured in greenhouse, was exposed to DBP stress to gain more information about the ecological risk of DBP in this study. Changes of DBP residues and fruit quality of cucumber at different DBP concentrations (0, 5, 10, 20, 40 mg/kg of dry soil) were investigated in pot experiments using an agricultural soil under greenhouse condition, respectively. DBP residue in cucumber fruits ranged from 0.5326 to 1.8938 mg/kg, and the quality of cucumber fruits (organic acids, vitamin C, soluble protein, and soluble sugar) were influenced by DBP stress. Moreover, the health risk assessment was evaluated by estimate daily intakes (EDI) and the target hazard quotient (THQ) was analyzed. Under 40 mg/kg DBP condition, the highest value of EDI was 2.49 μg/kg bw/day and the THQ ranged from 0.000700 to 0.0249. Although the risk of DBP in cucumber fruits was lower than the threshold limit value of risk, the potential health risk was not a negligible issue.

Preparation and characterization of a novel activated carbon obtained from vine shoots by ZnCl₂ activation and its rifampicine removal capacity were investigated in this study. The effects of activation temperature and impregnation ratio (precursor/ZnCl₂) on the activated carbon properties were investigated. The prepared activated carbon was characterized by BET surface area, surface functional group analysis by Boehm’s titration and FT-IR analysis, pHₚzc, iodine number, SEM-EDX, and particle size distribution. The results showed that the surface area, pore size, and pore volume of the activated carbon increased with the increasing temperature and impregnation ratio and reached maxima at the impregnation ratio of 40/30 at 700 °C. Under the optimal conditions, it was determined that the BET surface area, total pore volume, iodine number, and pHₚzc of the activated carbon were 1689 m²/g, 0.842 cm³/g, 1276 mg/g, and 4.8, respectively, and it has mainly acidic functional groups (total 0.2516 meq/g) on its surface. The activated carbon obtained was evaluated for rifampicine removal efficiency depending on contact time, adsorbent dosage, and initial concentration of rifampicine. Maximum adsorption capacity of rifampicine by the activated carbon (Q°) was determined according to Langmuir adsorption isotherm. The adsorption data was best fitted to the Langmuir isotherm with R ² of 0.983 and Q° was found to be 476.2 mg/g.

Seaweeds have been used as a source of traditional medicine worldwide for the treatment of various ailments, mainly due to their ability to quench the free radicals. The present study aims at evaluating the protective effect of methanolic extract of Gelidiella acerosa, an edible red seaweed against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced toxicity in peripheral blood mononuclear cells (PBMC). For evaluating the protective effect of G. acerosa, PBMC were divided into four groups: vehicle control, TCDD (10 nM), TCDD + G. acerosa (300 μg/ml), and G. acerosa alone treated. Scavenging of intracellular reactive oxygen species (ROS) induced by TCDD was assessed by the dichloro-dihydro-fluorescein diacetate (DCFH-DA) method. Alterations at macromolecular level were quantified through lipid peroxidation (LPO) level, protein carbonyl content (PCC) level, and comet assay. The cellular morphology upon TCDD toxicity and G. acerosa treatment was obtained by light microscopy and histopathological studies. The chemical composition present in the methanolic extract of G. acerosa was determined by gas chromatography-mass spectrometry (GC-MS) analysis. The results reveal that 10 nM TCDD caused significant (P < 0.05) reduction in cell viability (94.10 ± 0.99), and treatment with 300 μg/ml extract increased the cell viability (99.24 ± 0.69). TCDD treatment resulted in a significant increase in the production of ROS, LPO (114 ± 0.09), and PCC (15.13 ± 1.53) compared to the control, whereas co-treatment with G. acerosa significantly (P < 0.05) mitigated the effects. Further, G. acerosa significantly (P < 0.05) prevented TCDD-induced genotoxicity and cell damage. GC-MS analysis showed the presence of n-hexadecanoic acid (retention time (RT) 13.15), cholesterol (RT 28.80), α-D-glucopyranose, 4-O-α-D-galactopyranosyl (RT 20.01), and azulene (RT 4.20). The findings suggest that G. acerosa has a strong protective ability against TCDD-induced cytotoxicity, oxidative stress, and DNA damage.

Dissolved organic matter (DOM) in wastewater can be characterized using fluorescence excitation-emission matrix and parallel factor (EEM-PARAFAC) analysis. Wastewater from animal farms or pharmaceutical plants usually contains high concentration of antibiotics. In this study, the quenching effect of antibiotics on the typical components of DOM was explored using fluorescence EEM-PARAFAC analysis. Four antibiotics (roxarsone, sulfaquinoxaline sodium, oxytetracycline, and erythromycin) at the concentration of 0.5∼4.0 mg/L and three typical components of DOM (tyrosine, tryptophan, and humic acid) were selected. Fluorescence quenching effects were observed with the addition of antibiotics. Among these four antibiotics, roxarsone (2.9∼20.2 %), sulfaquinoxaline sodium (0∼32.0 %), and oxytetracycline (0∼41.8 %) led to a stronger quenching effect than erythromycin (0∼8.0 %). From the side of DOM, tyrosine and tryptophan (0.5∼41.8 %) exhibited a similar quenching effect, but they were higher than humic acids (0∼20.2 %) at the same concentration of antibiotics. For humic acid, a significant quenching effect was observed only with the addition of roxarsone. This might be the first report about the fluorescence quenching effect caused by antibiotics. The results from this study confirmed the interference of antibiotics on the fluorescence intensity of the main components of DOM and highlighted the importance of correcting fluorescence data in the wastewater containing antibiotics.

Tropical forests play an important role in carbon cycle. However, the temporal and spatial variation in soil carbon dioxide (CO₂) emission of tropical forest remains uncertain, especially near the Tropic of Cancer. In this research, we studied the annual soil CO₂ fluxes from three tropical montane rainforests on the Hainan Island of China (pristine montane rainforest, PF; secondary montane rainforest, SF; and Podocarpus imbricatus plantation, PP). The results showed a lower annual average soil CO₂ flux as 6.85 ± 0.52 Mg C-CO₂ ha⁻¹ (9.17 Mg C-CO₂ ha⁻¹ in the wet season and 4.50 Mg C-CO₂ ha⁻¹ in the dry season). The CO₂ fluxes exhibited obviously seasonal variation during the study period. Among the three forest types, PF had the highest average CO₂ flux rate of 317.77 ± 147.71 mg CO₂ m⁻² h⁻¹ (433.08 mg CO₂ m⁻² h⁻¹ in the wet season and 202.47 mg CO₂ m⁻² h⁻¹ in the dry season), followed by PP of 286.84 ± 137.48 mg CO₂ m⁻² h⁻¹ (367.12 mg CO₂ m⁻² h⁻¹ in the wet season and 206.56 mg CO₂ m⁻² h⁻¹ in the dry season) and SF of 255.09 ± 155.26 mg CO₂ m⁻² h⁻¹ (351.48 mg CO₂ m⁻² h⁻¹ in the wet season and 155.71 mg CO₂ m⁻² h⁻¹ in the dry season). We found between CO₂ fluxes and soil temperature a highly significant linear relation (P < 0.01) at 5 cm depth and a highly significant exponential correlation (P < 0.01) at 10 cm depth for all three forest types; a significant linear relation (P < 0.05) between CO₂ fluxes and soil moisture content was found for SF and PF, but not for PP (P > 0.05). The CO₂ flux was significantly correlated (P < 0.05) with water-filled pore space only for PF. In conclusion, our results suggested soil CO₂ fluxes in the three forest types that exhibit obviously spatial and temporal variation, and the temperature is the major factor affecting soil CO₂ fluxes from this region.

The Sharm El-Sheikh area is one of the most attractive touristic resorts in Egypt and in the world in general. The Sharm El-Shiekh area is located at the arid region of the South Sinai Peninsula, Egypt. Water desalination is considered the main freshwater supply for hotels and resorts. Scarcity of rainfall during the last decades, high pumping rates, disposal of reject brine water back into the aquifer, and seawater intrusion have resulted in the degradation of groundwater quality in the main aquifer. Water chemistry, stable isotopes, Seawater Mixing Index (SWMI), and factorial analyses were utilized to determine the main recharge and salinization sources as well as to estimate the mixing ratios between different end members affecting groundwater salinity in the aquifer. The groundwater of the Miocene aquifer is classified into two groups: group I represents 10 % of the total samples, has a moderately high saline groundwater, and is mostly affected by seawater intrusion. Group II represents 90 % of the total samples and has a high groundwater salinity due to the anthropological impact of the reject brine saline water deeper into the Miocene aquifer. The main groundwater recharge comes from the western watershed mountain and the elevated plateau while the seawater and reject brine are considering the main sources for groundwater salinization. The mixing ratios between groundwater recharge, seawater, and reject brine water were calculated using water chemistry and isotopes. The calculated mixing ratios of group I range between 25 and 84 % recharge groundwater to 75 and 16 % seawater, respectively, in groundwater located close to the western watershed mountain indicating further extension of seawater intrusion. However, the mixing percentages of group II range between 21 and 88 % reject brine water to 79 and 12 % seawater, respectively, in groundwater located close to the desalination plants. The outcomes and conclusion of this study highlight the importance of groundwater management to limit further groundwater deterioration of the Miocene groundwater aquifer and limit seawater intrusion along the coast.