Heterogeneous photocatalytic oxidation systems using titanium dioxide (TiO₂) have been extensively studied for the removal of several volatile organic compounds (VOCs). The addition of noble metals such as palladium on TiO₂ may improve photocatalytic activity by increasing charge separation efficiency. In this work, palladium was impregnated on TiO₂ and the efficiency of the new catalyst was tested and compared with that of pure TiO₂. Pd was impregnated on TiO₂ by the reduction method, using NaBH₄, and was characterized by XRD, XPS, UV–Vis, and H₂ chemisorption. The photocatalytic tests were performed in an annular coated-wall reactor using octane, isooctane, n-hexane, and cyclohexane at inlet concentrations varying from 100 to 120 ppmv. Compared with pure TiO₂ film, the photocatalytic activity of TiO₂ impregnated with 1 wt% of palladium was improved. All the aforementioned analytical techniques confirmed the presence of Pd incorporated into the structure of TiO₂, and the conversion rates were studied in a broad range of residence times, yielding up to 90 % or higher rates in 40 s of residence time, thus underscoring the relevant contribution of the technology.

Chromium (Cr) is among the most toxic pollutants in the environment that adversely affect the living organisms and physiological processes in different plants. The present study investigated the effect of 15 mg L⁻¹ of 5-aminolevulinic acid (ALA) on morpho-physiological attributes of cauliflower (Brassica oleracea botrytis L.) under different Cr concentrations (0, 10, 100, and 200 μM) in the growth medium. The results showed that Cr stress decreased the growth, biomass, photosynthetic, and gas exchange parameters. Chromium stress enhanced the activities of enzymatic antioxidants, catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) in response to oxidative stress caused by the elevated levels of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and electrolyte leakage (EL) in both roots and leaves of cauliflower. Chromium concentrations and total Cr uptake were increased in leaves, stems, and roots with increasing Cr levels in the culture medium. Foliar application of ALA increased the plant growth parameters, biomass, gas exchange parameters, and photosynthetic pigments under Cr stress compared to the treatments without ALA. Foliar application ALA decreased the levels of MDA, EL, and H₂O₂ while further improved the performance of antioxidant in both leaves and roots compared to only Cr-stressed plant. Chromium concentrations and total Cr uptake were decreased by the ALA application compared to treatments without ALA application. The results of the present study indicated that foliar application of ALA might be beneficial in minimizing Cr uptake and its toxic effects in cauliflower.

The cytotoxicity of nanoparticles (NPs) and their properties are important issues in nanotechnology research. Particularly, NPs affect the metabolism of microorganisms due to NP interactions with some biomolecules. In order to assess the mechanisms underlying NPs toxicity, we studied the damage caused by copper oxide nanoparticles (CuO-NPs) on Staphylococcus aureus ATCC 24213 and Pseudomonas aeruginosa ATCC 27833. Spherical CuO-NPs characterized by their diameter (13 ± 3 nm) were synthesized with a maximum of 254 nm. These NPs reduced cell viability, with a minimum inhibitory concentration (MIC) of 500 and 700 ppm for Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Surfactant was added to reduce the NP agglomeration, but it did not present any effect. The mechanism of CuO-NPs as antimicrobial agent was assessed by analyzing solubilized Cu²⁺, quantifying DNA release in the culture media, and measuring intracellular reactive oxygen species (ROS). CuO-NPs induced severe damage on cells as revealed by confocal optical microscopy and scanning electron microscopy (SEM). Our results indicated that CuO-NPs interacted with bacteria, triggering an intracellular signaling network which produced oxidative stress, leading to ROS generation. Finally, we concluded that CuO-NPs exhibited higher antibacterial activity on Gram-negative bacteria than on Gram-positive ones.

Water pollution caused by anthropogenic activities and driven by changes in rural livelihood strategies in an agricultural system has received increasing attention in recent decades. To simulate the effects of rural household livelihood transition on non-point source (NPS) pollution, a model combining an agent-based model (ABM) and an improved export coefficient model (IECM) was developed. The ABM was adopted to simulate the dynamic process of household livelihood transition, and the IECM was employed to estimate the effects of household livelihood transition on NPS pollution. The coupled model was tested in a small catchment in the Dongting Lake region, China. The simulated results reveal that the transition of household livelihood strategies occurred with the changes in the prices of rice, pig, and labor. Thus, the cropping system, land-use intensity, resident population, and number of pigs changed in the small catchment from 2000 to 2014. As a result of these changes, the total nitrogen load discharged into the river initially increased from 6841.0 kg in 2000 to 8446.3 kg in 2004 and then decreased to 6063.9 kg in 2014. Results also suggest that rural living, livestock, paddy field, and precipitation alternately became the main causes of NPS pollution in the small catchment, and the midstream region of the small catchment was the primary area for NPS pollution from 2000 to 2014. Despite some limitations, the coupled model provides an innovative way to simulate the effects of rural household livelihood transition on NPS pollution with the change of socioeconomic factors, and thereby identify the key factors influencing water pollution to provide valuable suggestions on how agricultural environmental risks can be reduced through the regulation of the behaviors of farming households in the future.

Recycled paper mill effluent (RPME) contains high levels of organic and solid compounds, causing operational problems for anaerobic biological treatment. In this study, a unique modified anaerobic inclining-baffled reactor (MAI-BR) has been developed to treat RPME at various initial chemical oxygen demand (COD) concentrations (1000–4000 mg/L) and hydraulic retention times (HRTs) (3 and 1 day). The COD removal efficiency was decreased from 96 to 83% when the organic loading rate (OLR) was increased from 0.33 to 4 g/L day. Throughout the study, a maximum methane yield of 0.25 L CH₄/g COD was obtained, while the pH fluctuated in the range of 5.8 to 7.8. The reactor performance was influenced by the development and distribution of the microbial communities. Based on the next-generation sequencing (NGS) analysis, the microbial community represented a variety of bacterial phyla with significant homology to Euryarchaeota (43.06%), Planctomycetes (24.68%), Proteobacteria (21.58%), Acidobacteria (4.12%), Chloroflexi (3.14%), Firmicutes (1.12%), Bacteroidetes (1.02%), and others (1.28%). The NGS analysis showed that the microbial community was dominated by Methanosaeta concilii and Candidatus Kuenenia stuttgartiensis. This can be supported by the presence of filamentous and spherical microbes of different sizes. Additionally, methanogenic and anaerobic ammonium oxidation (ANAMMOX) microorganisms coexisted in all compartments, and these contributed to the overall degradation of substances in the RPME. Graphical abstract ᅟ

Feedback between hydrologic variations and chemical weathering is thought to play a crucial role in modulating global carbon cycling. The mechanisms associated with the impacts of hydrologic variations on solute sources and chemical weathering were evaluated by examining the relationships between river discharge and hydrochemistry based on high-frequency sampling of the Min River, which originates in the Himalayan–Tibetan region. Fluid transit times and flow pathways vary with changes in discharge, thereby affecting various biogeochemical processes. Although shorter transit times occur during the high-flow season than during the low-flow season, concentrations of chemical weathering products exhibit chemostatic behaviour (less variation than changes in discharge) in response to increasing discharge due to hydrologic flushing of minerals, which increases the amount of reactive mineral surface area. The contributions of various sources to dissolved loads in the Min River were estimated using a forward model. The calculated annual carbonate and silicate weathering fluxes are 24.1 and 9.6 t/km² year, respectively. Atmospheric contributions increase with increasing discharge, whereas the contributions of silicate weathering decrease with increasing discharge. Both the carbonate weathering flux (FCₐᵣb) and silicate weathering flux (FSᵢₗ) are positively correlated with the discharge, indicating that temporal variations in chemical weathering fluxes in the Min River are highly affected by hydrologic variations. The slope of the relationship between FCₐᵣb and discharge is much greater than that between FSᵢₗ and discharge due to the rapid dissolution of carbonate minerals, suggesting that carbonate weathering is more sensitive than silicate weathering to hydrologic variations. This study demonstrates that high-frequency sampling is necessary when investigating solute sources and chemical weathering processes in river basins influenced by a monsoon climate.

The remediation of dioxin-contaminated soil of a specific coastal area previously employed for the manufacture of pentachlorophenol (PCP) in southern Taiwan’s Tainan City has attracted much attention of researchers there. This work addresses the possibility of providing an effective and environmentally friendly option for removing PCDD/Fs from soil in that field. Soil screening/sieving was first conducted to assess particle distribution. Fine sand was observed to be the major component of the soil, accounting for more than 60% of the total mass. A combination of ultrasonification and mechanical double-blade agitation was used to facilitate the washing of the soil using the biosurfactant anaerobic compost tea. More than 85 and 95% of total removal efficiencies were achieved for moderately and highly contaminated soils after 6 and 10 washing cycles, respectively, under ambient temperature, a soil/liquid ratio 1:2.5, 700 rpm, and over a relatively short duration. These results were achieved through the collision and penetration effects of this combined treatment as well as PCDD/F partitioning between the particles and anaerobic compost tea. This study represents the first to report the use of anaerobic compost tea solvent to wash soil highly contaminated by dioxin. It was concluded that anaerobic compost tea, rich in non-toxic bio-surfactants (e.g., alcohols, humic acids), can be used to improve bioavailability and bioactivity of the soil making bio-attenuation and full remediation more efficient.

The concentrations of six heavy metals (HMs) and 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) in sediment samples of the confluence of rivers Niger and Benue were investigated. The ecological risk assessment of the contaminants was carried out. The results showed that the sediment samples were heavily polluted with iron and moderately polluted with Cd while other metals posed no pollution problem when compared with USEPA sediment quality guidelines. Only six out of the 16 priority PAHs were detected in the samples, and source apportionment of the PAHs indicated that they are of pyrogenic origin. The ∑PAHs in the samples were lower than many of similar studies and were of no pollution risk. The ecological risk assessment result of the heavy metals showed that the sediments were of considerable risk due majorly to Cd levels. The HM concentration results statistically showed significant difference between seasons at probability value (P < .05). Data analysis by PCA classified the metals into three different components according to sources. The levels of HMS and PAHs detected in the sediments were correlated for source identification, and the correlation showed that the majority of the pollutants were mainly from anthropogenic sources. There is increasing level of anthropogenic activities at the vicinity of the confluence due to urbanization which may call for periodic monitoring of the sediment quality.

The epiphytic lichen Pseudevernia furfuracea is widely used as biomonitor of airborne trace elements and other contaminants and consists of two taxonomic varieties (var. furfuracea and var. ceratea). Here, we assessed the occurrence of inter-varietal differences in the elemental composition of paired samples of var. furfuracea and var. ceratea collected in 20 remote sites of Italian mountains. The concentration of 40 elements was measured by inductively coupled plasma mass spectroscopy, after digestion with HNO₃ and aqua regia. The magnitude of inter-varietal differences compared to the effect of large-scale site-dependent environmental factors (i.e., lithological substrate, host tree species, and altitude) on overall element content was explored by multivariate analysis techniques and tested by generalized linear mixed modeling (GLMM). Further GLMMs were separately fitted for each element testing taxonomic-related variability against uncertainty associated to the analytical procedure. Inter-varietal differences were statistically significant only for Hg and P, with higher content in var. ceratea at most sites, and for Mg and Zn, showing the opposite pattern. Since the elemental composition of P. furfuracea in remote sites was mostly affected by local lithology and climatic conditions, our results confirm that lichen material for active biomonitoring should be collected in a single ecologically homogeneous remote area. We also indicate sites in the Eastern Alps where P. furfuracea showed the minimum content of most elements, which are suggested as locations to collect lichen material for transplants. Besides the context-dependency at large spatial scale, variations of elemental composition apparently related to taxonomy, could possibly be due to unequal incidence of morphological traits of the collected material. Further research is needed to clarify this issue, and how it affects bioaccumulation phenomena.

One of the main sources of reactive nitrogen pollution is animal manure. The disposal of digestate (material remaining after the anaerobic digestion of a biodegradable feedstock) in agricultural soils could solve both the problems of soil fertilization and waste removal, but the fate of digestate in the environment must be assessed carefully before its massive utilization. To investigate whether digestate could be safely employed as a soil fertilizer, an agricultural field located in Monastier di Treviso (Northern Italy) and characterized by the presence of low hydraulic conductivity clay soils, was selected to be amended with bovine digestate. The experimental site was intensively monitored by a three-dimensional array of probes recording soil water content, temperature, and electrical conductivity, to solve the water and bulk mass fluxes in the unsaturated zone. High-resolution soil coring allowed the characterization of soil water composition over two hydrological years. Chloride, found in high concentrations in the digestate, was used as environmental tracer to track the fate of the percolating water. The study concluded that digestate could be confidently employed in short rotation buffer areas at an average rate of 195 ± 26 kg-N/ha/year in low hydraulic conductivity soils not affected by diffuse fracturing during dry periods.