A novel quaternary nanocomposites consisting of Ag/AgCl decorated TiO₂ introduced on graphene oxide (GO) sheets with high loading of GO (50 wt.%) were prepared for photocatalytic application. The composite powders were synthesized by a facile sol–gel method utilizing polyvinylpyrrolidone (PVP) as a reducing agent to obtain Ag particles and a modified Hummers’ method to acquire GO sheets. The influence of reducing agent concentration and type of TiO₂ was investigated. The adsorption properties of the GO/TiO₂/Ag/AgCl nanocomposites were examined, and photocatalytic activity was investigated under UV light applying methylene blue (MB) as a model pollutant. The composites displayed great adsorption capability up to 112.6 mgg⁻¹ due to GO. It is shown that the GO/TiO₂/Ag/AgCl samples prepared by Degussa P25 TiO₂ and with a reduced amount of PVP have the best photocatalytic activity, reaching up to 55% decolorization of methylene blue under UV light. The photocatalytic activity is enhanced by approximately 80% with the addition of GO to the quaternary GO/TiO₂/Ag/AgCl composites.

Vanadium has the potential to be released as a by-product of the combustion of fossil fuels such as oil and coal in the aquatic system. Presence of tailing ponds and other mining operations may pose the largest threat to downstream users and to the long-term aquatic health of the Mackenzie River Basin (MRB, Canada). The need for developing a solid baseline for the MRB aquatic ecosystem against which future changes can be measured is urgent. In this study, 36 sets of triplicate diffusive gradients in thin films (DGT) samplers were deployed in MRB during the 2012–2014 ice-free seasons to investigate temporal and spatial changes in the concentration of DGT-labile vanadium (V) as part of a Northwest Territories community-based project. Average DGT-labile V concentration (5.9 ± 0.9 nmol L⁻¹) was comparable with non-contaminated aquatic systems, suggesting no significant impact of human activities on V speciation in MRB in 2012–2014. The V concentrations reported in this study constitutes a baseline that can be used to enhance ongoing monitoring efforts. Although the DGT samplers were deployed in collaboration with northern communities, the absence of temporal changes in DGT-labile V indicated that in situ DGT passive samplers constitute a reliable and robust alternative for community-based monitoring programs. Excitation emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC) validated three humic-like (C1–C3) and one protein-like (C4) fluorescent component. However, no significant relationships were apparent between DGT-labile V and dissolved organic carbon (DOC), the PARAFAC loadings, and composition (p > 0.05). Hierarchical cluster analysis revealed that DGT-labile V concentration was negatively correlated with aromatic and humified DOM (r = − 0.70 to − 0.84, p < 0.05).

Balancing the nitrogen derived from sewage effluent and fertilizers is essential for efficiently utilizing the nitrogen and minimizing the environmental degradations when applying sewage effluent. Pot experiments of maize (Zea mays L.) under drip irrigation were performed using ¹⁵N labeled urea to quantify the nitrogen balances of sewage effluent and fertilizers. Field experiments were conducted to confirm the findings of pot experiments. Four nitrogen rates ranging from 0 to 2.64 g/pot (0–210 kg/ha equivalently) for pot experiments and from 0 to 180 kg/ha for field experiments were established applying either secondary sewage effluent (SW) or groundwater (GW). Both pot and field experiments revealed that SW irrigation boosted nitrogen uptake and yield of maize compared to GW irrigation. However, the sewage-derived effects decreased with increasing nitrogen rates. SW irrigation could facilitate the uptake of ¹⁵N labeled urea relative to GW irrigation. Nonetheless, the nitrogen containing in effluent possibly had lower uptake effectiveness than the fertilizer urea for maize, suggesting greater potential for nitrogen losses resulting from effluent nitrogen compared to urea nitrogen. The percentage utilization of effluent nitrogen declined from 43 to 34% in 2014 and 48 to 32% in 2015 as nitrogen rates increased from 0 to 2.64 g/pot. Besides, the percentages utilization of total nitrogen (including effluent and fertilizers) under SW irrigation increased from 43 to 55% in 2014 and from 48 to 55% in 2015 when the rates increased from 0 to 1.76 g/pot, and subsequently decreased to 48% in 2014 and 44% in 2015 at the rate of 2.64 g/pot. This result was strengthened by the pattern of nitrogen recovery efficiency observed in the field experiments. Overall results of pot and field experiments recommended an optimal rate of 120 kg/ha for maize under drip irrigation applying SW to maximize nitrogen use efficiency and achieve an acceptably high yield.

This study evaluates the treatment efficacy and biogas yield of an integrated system composed of a plug-flow biodigester (with sludge recirculation) followed by polishing in a stabilization pond. The system was operated in real scale for 12 months at ambient temperature and under continuous flow. The volumetric yields of biogas varied according to the organic loads applied, between 114 and 294 Kg COD day⁻¹, reaching levels of 0.026 to 0.173 m³ m⁻³ day⁻¹, with concentrations of CH₄ between 56 and 70%. The monthly biogas productions were between 378.5 and 2186.1 m³ month⁻¹ equal to an energy potential of approximately 2070 to 19,168 KWh month⁻¹.The average yearly removals of BOD₅,₂₀ and COD by the integrated treatment system were 70 and 86%, respectively. The average annual removals of NH₄ and TKN were 88.5 and 85.5%, respectively. The pH values were always near neutral, and the alkalinity was in ranges propitious for anaerobic digestion. The results of this study indicate good efficacy in terms of removal of organic matter and nitrogen compounds, with the added benefits of generation of energy and use of the treated effluent as biofertilizer, enabling significant cost reductions to cattle farmers.

The aim of this study was to evaluate the genotoxic and mutagenic potential of contaminated soil diluted in acidic solutions and not acidic, in the offspring of rats exposed during pregnancy and neonatal periods. To this end, a comet assay and micronucleus test were performed. Soil samples were solubilized in the following three solvents: distilled water (control group), acid solvent at pH 5.2, and acid solvent at pH 3.6. Soil and solvent were mixed in a rate of 1:2 in g/mL, and hydrofluoric acid was used in the acid solvents. In the comet assay, the tail length, percentage of DNA within the tail and tail moment was analyzed in the whole blood of the pups that were studied. The number of micronuclei found in the bone marrow cells was counted in the micronucleus test. In all parameters evaluated in the comet assay, the group exposed to the lowest pH value when associated with contaminated soil (p < 0.05) had the most damage. However, the micronucleus test showed differences between all exposed groups and the control group (p < 0.05). These results reaffirm the health risks related to the exposure to soil contaminants.

Sediment losses as concentrations and yields were measured for a year from 12 segments of a newly constructed (buried) natural gas pipeline on the US Forest Service’s Fernow Experimental Forest in West Virginia. Pipeline segments were separated by waterbars which served as drainage features. Six segments were northwest-facing, and six were southeast-facing. Three segments on each aspect were seeded with warm season native herbaceous species at rates used by the Forest Service (1×). All remaining segments received seeding at three times that rate (3×). Forest Service-established rates of fertilizer, lime, and straw mulch were applied to all segments. Sediment concentrations and yields generally were highest at the start of the study, respectively, averaging approximately 1660 mg L⁻¹ and 340 kg ha⁻¹ during the first 3 months following completion of corridor reclamation, but they were less than from nearby less-steep forest road corridors. Concentrations and yields fell significantly after the first 3 months; declines were attributed to revegetation on the ROW. At the end of the first growing season, vegetative cover on all segments ranged from 55 to 79%, with no differences between seeding rates. Mean runoff was significantly higher on the northwest-facing segments than on the southeast-facing segments, but runoff volumes did not decrease on either aspect in concert with loadings or concentrations. Higher runoff on the northwest-facing segments may have been due to clay-skinned peds in subsurface soil that limited vertical drainage. Even with a heavy straw mulch cover on the right-of-way, the timing of the highest sediment losses immediately following pipeline construction suggests that implementation of additional surface-protection best management practices could be beneficial until vegetation is reestablished.

A comprehensive ecotoxicity assessment of three different nanosized TiO₂ (with 16, 36 and 89 nm particle diameter) and one microscale TiO₂ suspension (with 3264 nm particle diameter) was carried out with a special emphasis on the relation between product characteristics and toxic effect. The applied test battery included the combination of modified standardized tests (Aliivibrio fischeri bioluminescence inhibition test, Lemna minor growth inhibition test), and nonstandardized bioassays with unconventional physiological endpoints (Tetrahymena pyriformis phagocytic activity, the Daphnia magna heartbeat rate). Based on the lowest significant effect values, the tested aquatic organisms were the most sensitive to the microscale TiO₂ suspension (with 3264 nm particle size). Although the three nanoscale TiO₂ particles were aggregated in the A. fischeri and the L. minor growth media, significant inhibition rates were experienced at 0.1 and at 1 μg L─¹ concentration of nTiO₂ suspensions with 16 and 36 nm primary particle size, respectively. Larger aggregates may have also high impact on biological organisms. In case of the D. magna heartbeat rate test rapid agglomeration was avoided, but lower responses were found compared to other investigated systems. The short term T. pyriformis phagocytic activity test demonstrated outstanding sensitivity; three TiO₂ suspensions were significantly toxic even at 0.1 μg L─¹. The consequences of our study clearly indicated that nanoscale TiO₂ may have an impact on the aquatic ecosystem which is strongly influenced by aggregation. The effect of exposure duration and concentration as contributing factors in nano-titanium dioxide mediated toxicity was also demonstrated.

Mesoporous silica with wormhole framework structure (HMS-OH) and its amine-functionalized material (HMS-NH₂) were prepared through an electrically neutral assembly pathways, post-grafting process of 3-aminopropyltriethoxysilane (APTES), respectively. Their adsorption behaviors toward cationic dyes as well as heavy metal ions in aqueous system and the capture capacities for CO₂ molecules all have been investigated. As-synthesized HMS-OH showed a high removal efficiency and rapid sorption rate to cationic dyes because of large surface area and versatile pore structure. HMS-NH₂ exhibited better heavy metal ions and more CO₂ gas sorption capacities due to the intrinsic property of amine groups grafted on the surface. The adsorption isotherms of methylene blue (MB) onto HMS-OH, Cu(II) onto HMS-NH₂ were fitted with Langmuir model and kinetic processes followed well the pseudo-second order pattern. There results revealed that both HMS-OH and HMS-NH₂ had a potential application in the treatment of cationic dyes, heavy metal ions, and greenhouse gas CO₂.

Adsorption of hexavalent chromium (Cr(VI)) using pomelo peel activated biochar (PPAB) as a adsorbent was investigated. The characterization of the adsorbent was studied by Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and zeta potentials analysis. The results showed that the PPAB had a high microporous structure and the existence of organic compounds such as hemicellulose, cellulose, and lignin. Various parameters including initial Cr(VI) concentration, pH, and adsorbent dosage were studied. The results indicated that the adsorption process was pH dependent and maximum adsorption capacity of Cr(VI) was 57.637 mg/g at pH 2.0 and 35 °C with PPAB dosage of 0.05 g. The adsorption kinetics fitted well to the pseudo-second-order model and the correlation coefficients were greater than 0.999. The adsorption isotherm data could be better described with the Langmuir model, suggesting the homogeneous and monolayer adsorption. Moreover, the scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and Fourier transform infrared spectrum (FTIR) results showed that the surface of PPAB had plenty of developed pores after activation and the modification process was deemed to proceed between the O–H groups from pomelo peel and H₃PO₄ molecules. The main adsorption mechanism was attributed electrostatic interaction and ion exchange between the surface of PPAB and Cr(VI).

With the organic carbon of acetate (SBR-A) and propionate (SBR-P), the effect of organic carbon sources on nitrogen removal and nitrous oxide (N₂O) emission in the multiple anoxic and aerobic process was investigated. The nitrogen removal percentages in SBR-A and SBR-P reactor were both 72%, and the phosphate removal percentages were 97 and 85.4%, respectively. During nitrification, both the NH₄⁺-N oxidation rate in the SBR-A and SBR-P had a small change without the influence of the addition of nitrite nitrogen (NO₂⁻-N). With the addition of 10 mg/L NO₂⁻-N, the nitrate nitrogen (NO₃⁻-N) production rate, N₂O accumulation rate and emission factor had increased. At the same time, the N₂O emission factor of SBR-A and SBR-P reactors increased from 2.13 and 0.87% to 4.66 and 2.08%, respectively. During exogenous denitrification, when nitrite was used as electron acceptor, the N₂O emission factors were 34.1 and 8.6 times more than those of NO₃⁻-N as electron acceptor in SBR-A and SBR-P. During endogenous denitrification with NO₂⁻-N as electron acceptor, the accumulation rate and emission factor of N₂O were higher than those of NO₃⁻-N as electron acceptor. High-throughput sequencing test showed that the dominant bacteria were Proteobacteria and Bacteroidetes in both reactors at the phylum level, while the main denitrification functional bacteria were Thauera sp., Zoogloea sp. and Dechloromonas sp. at the genus level.