Fe₃O₄ decorated multi-walled carbon nanotube (Fe₃O₄/MWCNT) nanocomposites were synthesized by co-precipitation process and used as heterogeneous Fenton catalyst for degradation of phenol and p-nitrophenol (p-NP). The Fe₃O₄ nanoparticles with size less than 20 nm were well-dispersedly coated on the surface of MWCNTs at relatively low loading. Some aggregations appear at high Fe₃O₄ content in composite. The Fe₃O₄/MWCNT with about 25 wt.% of Fe₃O₄ is the most cost-effective catalyst compared with others, whose phenol conversion and COD removal rates could, respectively, reach to 99.20 and 58.09%. And a high H₂O₂ utilization efficiency was achieved (about 132.41%) for this catalyst. For the p-NP degradation, the optimal reaction condition was that: 2.0 mg/L of catalyst dosage, 3 mmol/L of initial H₂O₂ concentration, 3 of pH value, and 40 °C of reaction temperature. At this condition, the removal rates of p-NP and COD in 120 min achieved 97.16 and 67.71%, respectively. And the Fe₃O₄/MWCNT nanocomposite also exhibits an acceptable stability and reusability.

TiO₂ nanoparticles and nanofibers have been used to carry out a comparative study of the destruction of H₂S gas. Effects of sulphur doping have also been incorporated to assess the maximum destruction potential of the nanomaterials. An analysis has been made in this paper to evaluate and compare the performance of pure and sulphur-doped TiO₂ nanoparticles and nanofibers for the destruction of H₂S gas using photocatalysis under laboratory conditions. Regression modelling has been performed to ascertain the individual degradation rates of the nanoparticles and nanofibers. In addition, oxidation rates of H₂S gas using the nanoparticles and nanofibers have been used to further elucidate our findings. It was observed that the destruction potential of nanofibers was 10 times more as compared to nanoparticles.

Rapid increase in impervious surfaces due to urbanization often intensifies the frequency of flooding which in turn increases runoff of environmental pollutants. The Brays Bayou watershed (BBW) is a heavily urbanized and densely populated watershed located mostly in Harris County, TX. The objectives of our study are (1) to analyze and interpret the spatial and temporal land use and land cover changes in BBW and (2) to determine nutrient, heavy metal, and bacterial contamination in the Brays Bayou. Water and sediment samples were collected from selected sampling locations along the Brays Bayou and analyzed for various nutrient and metal concentrations. Bacterial analysis was conducted to enumerate the fecal coliform bacteria in water samples. Landsat Thematic Mapper (TM) satellite images sampled from over three decades (1980–2010) for the BBW study area were processed and analyzed for land use and land cover changes. Our remote sensing analysis revealed that the BBW lost about 28.4% (9463 acres) vegetation during the period of 1984 to 2010. The loss in vegetative areas resulted in increased impervious surface areas. In sediment samples, increasing trends for Al, Cu, Fe, Pb, and Zn were observed towards the downstream of Brays Bayou. Lead concentrations were found at the highest concentration (70 mg/kg) in certain Brays Bayou sampling locations. Escherichia coli concentrations decreased towards the downstream of Brays Bayou and were found below 200 maximum probable numbers/100 ml. Integration of remote sensing along with the chemical and biological analysis helped to understand the impact of land cover changes on the bayou water quality.

Drought is a serious concern in many parts of the world, including in California, where paucity of available irrigation water has impaired crop production and soil health through salt accumulation. With extending water and salinity crises, there is a need for advanced salt and vegetation management. To develop more efficient management solutions, Slingram electromagnetic investigations and stochastic and statistical analyses were performed for determining optimal vegetable yields in a salt-affected farmland. The Slingram results were evaluated using multi-linear regression analyses, and the yield and salinity were characterized for central tendency, variance, distributions and symmetry. The yields of two studied vegetable crops, lettuce and tomato, increased with decreasing salinity load. The average lettuce and tomato yield potentials were 55 and 75%, respectively. The minimum yield potential for tomato was 9.5 times higher than that for lettuce. The mode value for conductivity (ECₑ) was 650 mS m⁻¹, which corresponded to 50% yield loss. The yield loss was <10% in locations with ECₑ < 250 mS m⁻¹. In zones with ECₑ > 850 mS m⁻¹, the yield reductions for lettuce and tomato reached up to 96 and 60%, respectively. About 57 and 82% of the field area could be limited to 20% yield potentials for tomato and lettuce, respectively. Lettuce had a higher cost benefit than tomato albeit with a greater yield potential of the latter crop. By delineating the spatial contours of salt-induced yield variability, vegetables can be grown in segmented soil zones based on salinity levels.

This study investigates the impact of future climate change on heavy metal (i.e., Cd and Zn) transport from soils to surface waters in a contaminated lowland catchment. The WALRUS hydrological model is employed in a semi-distributed manner to simulate current and future hydrological fluxes in the Dommel catchment in the Netherlands. The model is forced with climate change projections and the simulated fluxes are used as input to a metal transport model that simulates heavy metal concentrations and loads in quickflow and baseflow pathways. Metal transport is simulated under baseline climate (“2000–2010”) and future climate (“2090–2099”) conditions including scenarios for no climate change and climate change. The outcomes show an increase in Cd and Zn loads and the mean flux-weighted Cd and Zn concentrations in the discharged runoff, which is attributed to breakthrough of heavy metals from the soil system. Due to climate change, runoff enhances and leaching is accelerated, resulting in enhanced Cd and Zn loads. Mean flux-weighted concentrations in the discharged runoff increase during early summer and decrease during late summer and early autumn under the most extreme scenario of climate change. The results of this study provide improved understanding on the processes responsible for future changes in heavy metal contamination in lowland catchments.

Ultraviolet (UV) disinfection of wastewater is adversely affected by the presence of particle-associated bacteria. Earlier studies have shown that disrupting these particles by ultrasonic cavitation can enhance the UV disinfection of wastewater. However, the use of ultrasound as a pretreatment technology for UV disinfection is hindered by its high energy demand. In this work, the addition of several organic solutes, including 1-propanol, 1-hexanol, and pentyl acetate, to promote the cavitation process and to improve the breakage of wastewater particles was examined. It was found that the enhancement in the cavitation and the breakage efficiency of particles was positively related to the hydrophobicity of surfactant. In addition, particle breakage was a function of the concentration of surfactant as well as the delivered ultrasound energy density. Sonication of wastewater samples containing small amounts of 1-hexanol (16 mM) or pentyl acetate (12 mM) increased the UV disinfection efficiency and decreased the required UV dose to achieve the disinfection target by a factor of more than 2.5.

In this study, a comparison of the photocatalytic activity efficiency of the catalysts WO₃/TiO₂, Fe₂O₃/TiO₂, and TiO₂ in the degradation of the herbicide 2,4-D and its main by-product (2,4-dichlorophenol, 2,4-DCP), under natural sunlight, visible, and UV light, was carried out. The catalysts were synthesized by the sol-gel method. All the catalysts showed anatase crystalline phase, and they exhibited similar values of band gap, specific surface area, and crystallite size; however, different photocatalytic activity was observed under the different light sources. Complete degradation of 2,4-D and near to 89% of mineralization using WO₃/TiO₂ and Fe₂O₃/TiO₂ was achieved after 150 min under solar light, while using TiO₂ sol-gel, lower degradation rate was obtained. By using artificial light (UV and visible lamp), the degradation and mineralization rates were lower than those obtained under natural sunlight. The produced 2,4-DCP intermediate was completely degraded after 240 min under sunlight only with the modified catalysts.

In the present study, the ability of Hibiscus rosa-sinensis leaf extract (HLE) to act as a natural coagulant for the water treatment was tested. Synthetic turbid solutions were prepared using kaolinite, and the efficiency of HLE was examined for low and high turbid solutions. HLE was very effective in high turbid solutions than in low turbid water and follows enmeshment mechanism of destabilization. An insignificant effect of alkalinity on the performance of HLE was observed. The addition of NaCl increased the dissolution of coagulation active species and enhanced the efficiency of HLE, significantly. Hydroxyl and carboxyl groups present in HLE were the major functional groups responsible for the bonding between coagulant and kaolinite. The efficiency of alum was very high compared to that of HLE in both turbid solutions. But the optimal dosages of HLE were lesser than that of alum. Thus, HLE can be used as a coagulant aid for the effective treatment of water.

Acute (24 h) and sublethal (35 days) effects of cadmium chloride (CdCl₂) were examined in Cirrhinus mrigala using various endpoints (accumulation pattern, thyroid hormones (THs), and antioxidants). The mean concentrations of CdCl₂ for 24 and 96 h were found to be 35.974 and 22.387 mg L⁻ˡ, respectively. LC50 concentration of CdCl₂ for 24 h (35.97 mg L⁻ˡ) was used for the acute study. For the sublethal studies, fish were exposed to 3.59 mg L⁻¹ (Treatment I) and 7.19 mg L⁻¹ (Treatment II) corresponding to 1/10th and 1/5th of 24 h LC50 of the CdCl₂. During acute exposure, higher accumulation of CdCl₂ was noticed in the gill, liver, and kidney of C. mrigala, which is found in the order gill > liver > kidney tissues. Similarly, in sublethal treatments (Treatment I and II), a concentration and time-dependent increase of CdCl₂ accumulation was noticed in the order of gill > liver > kidney. GSH, GST, and GPx activities were found to be relatively lower from the treated groups in both acute and sublethal treatments. However, LPO activity was significantly increased in CdCl₂-treated fish C. mrigala. Further, plasma T₃ reduction was more pronounced than T₄ in acute study. During sublethal treatments, both T₄ and T₃ levels showed a continuous decrease as the exposure period extended. All the values in this study were statically significant (P < 0.01 and P < 0.05).

Herein, we report the synthesis of carbon spheres (CS) using a relatively low-temperature hydrothermal technique using lactose as precursor pre-treated with HCl. The successful synthesis, spherical morphology, porous morphology, and monodispersed nature of CS were confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Isoelectric point (IEP) was determined as 3.8, and at neutral conditions the prepared carbon particles are negatively charged at − 43 ± 2.50 mV. Owing to their spherical morphology, almost uniform distribution and negatively charged surface at neutral conditions, the prepared CS were used as adsorbent for the removal of methylene blue (MB) and Geimsa stain (GS) from aqueous environments at pH 7. It was shown that CS has 97% adsorption capability for GS, whereas for methylene MB, the maximum adsorption capacity was 67% for 0.1-g CS from 50-ppm dye solutions in DI water. The adsorption studies revealed that the Langmuir and modified Fruendlich (MFE) adsorption models resulted in considerably high linear correlation coefficient (r ²) values and the efficient adsorption of positively charged species on CS can be represented better with the MFE model. Graphical Abstract Carbon spheres from D-lactose for environmental application