In this study, we screened for the antifouling activity of 15 species plant extracts from Brazilian the Brazilian Caatinga Fabaceae against the initial colonization of natural marine bacterial biofilm. We also investigated the potential toxicity of extracts against planktonic and benthic non-target organisms. Aqueous extracts of plants collected in the Caatinga biome (PE, Brazil) were prepared and tested at different concentration levels (0, 0.5, 1, 2, 4, and 8 mg mL⁻¹). Natural marine bacterial consortium was inoculated in multi-well plates and incubated with the different treatments for 48 h. The biofilm and planktonic bacterial density and biomass inhibition were evaluated along with biofilm biomass eradication. The extracts that showed the highest bacterial biofilm inhibition were evaluated for toxicity against microalgae and crustaceans. The biofilm and planktonic bacterial inhibition potential were evaluated through flow cytometry and spectrophotometry. The selected treatments were evaluated for their toxicity using the microalgae Chaetoceros calcitrans, the copepod Nitokra sp., and the brine shrimp Artemia salina as bioindicators. Our work demonstrates the biotechnological potential of Fabaceae plant compounds as a safe antifouling alternative. Anadenanthera colubrina var. cebil fruits and Apuleia leiocarpa leaf extracts showed antibiofilm activity (≥ 80%), while Myroxylon peruiferum and Dioclea grandiflora leaf extracts showed antibiotic activity. These extracts were safe to planktonic and benthic non-target organisms. The results of this study point to potential substitutes to highly toxic antifouling paints and shed light on the prospect of a yet to be explored biome for more sustainable alternatives in biofouling research.

A kinetic model describing Fenton and photo-Fenton degradation of paracetamol (PCT) and consumption of hydrogen peroxide (H₂O₂) was proposed. A set of Fenton and photo-Fenton experiments (18 runs in total) was performed by fixing the initial concentration of PCT to 40 mg L⁻¹ and varying the initial concentrations of H₂O₂ and ferrous ion, Fe²⁺. The experimental set-up was a well-stirred annular photoreactor equipped with an actinic BL TL-DK 36 W/10 1SL lamp. Experimental results highlighted that PCT is no more detected by HPLC analysis within a minimum reaction time of 2.5 and a maximum reaction time of 15.0 min. Besides, a maximum conversion of total organic carbon (TOC) of 68.5% was observed after 75 min of reaction in case of using UV radiation and the highest concentrations of the Fenton reagents. The experimental data were used to fit the kinetic model. The radiation field inside the reactor was taken into account through the local volumetric rate of photon absorption, evaluated by assuming a line source model with spherical and isotropic emission. The kinetic parameters were estimated by using a non-linear least-squares regression procedure and root mean square errors (RMSE) were calculated in order to validate the feasibility of the proposed model. A good agreement between experimental and predicted data was observed and the lowest values of RMSE resulted in 5.84 and 9.59% for PCT and H₂O₂ normalized concentrations, respectively.

In order to improve the catalytic properties of Fe₃O₄ nanoparticles in wastewater treatment, the Cu-doped Fe₃O₄/graphene oxide (Fe₃₋ₓCuₓO₄/GO) nanocomposites were prepared by a modified co-precipitation method and used as heterogeneous catalyst for p-Nitrophenol (p-NP) degradation. The effect of the GO and Cu contents in the nanocomposites was investigated. Compared with the unsupported Fe₃O₄ nanoparticles, the Fe₃O₄/GO nanocomposites have obviously improved catalytic performance, especially for the nanocomposite with 6.25 wt.% of the GO content. Furthermore, the catalytic efficiency is greatly improved by doping Cu in the nanocomposite. The Fe₃₋ₓCuₓO₄/GO nanocomposite achieves the best catalytic property in our catalyst system when the x value is about 0.075. Under the optimal reaction condition (0.8 g L⁻¹ of catalyst dosage, 15 mmol L⁻¹ of initial H₂O₂ concentration, 3.0 of pH value, and 30 °C of temperature), the p-NP conversion and chemical oxygen demand removal efficiencies in 120 min for the Fe₂.₉₂₅Cu₀.₀₇₅O₄/GO nanocomposite are about 98.4% and 74.7%, respectively. And the p-NP conversion efficiency is still as high as 96.2% after four recycles under the optimum condition. The results clearly show that the Fe₂.₉₂₅Cu₀.₀₇₅O₄/GO nanocomposite has outstanding catalytic properties for the p-NP degradation.

Two-dimensional HPLC (2D-HPLC) recently has received great attention due to providing high resolving power and higher peak capacities than that of 1D-HPLC, especially dealing with a wide spectrum of sample matrices containing several components. In this work, an on-line heart-cutting two-dimensional liquid chromatography (2D-LC) method was developed using monolithic columns coupled with reversed-phase liquid chromatography (RPLC). 2D-HPLC was successfully carried out using affinity-based monolithic columns at first dimension (20 cm × 4.6 mm I.D.) followed by a Pinnacle II PAH column (50 mm × 4.6 mm I.D.) at the second dimension. Furthermore, good linearity was observed for the correlation of the benzo[a]pyrene (BaP) molecule against the peak areas (R² = 0.994) in the concentration range of 0.01–1.0 ng/mL in 30 min. The limit of detection and the limit of quantification were found to be 4.0 pg/mL and 12.0 pg/mL, respectively. Both the intra-day and inter-day precision at 0.01 and 0.1 ng/mL spiked concentrations were below than 2.35% RSD whereas the means of the recovery data of the BaP from the water samples were found to be in the range of 93.71–98.65%. These results demonstrate that the 2D-HPLC system, developed by the combination of the P(HEMA-MAPA) column and Pinnacle II PAH column, is reliable, stable, and well qualified in the extraction of polycyclic aromatic hydrocarbons from the water samples.

To elucidate the inhibitory effects of different herbicides on soil nitrification, eight widely used herbicides, i.e., acetochlor, atrazine, dicamba, isoproturon, paraquat, puma, tribenuron-methyl, and 2,4-dichlorophenoxyacetic acid butyl ester (2,4-Dbe), which represent different chemical taxonomy were selected. Our results indicated that herbicide 2,4-Dbe displayed the best inhibitory effect on nitrification, followed by puma and tribenuron-methyl, whereas the remaining five herbicides exhibited less effect when 10 mg of active ingredient (A.I.) of every herbicide per kg of soil was applied in vegetable-planting soil. The inhibition appeared when 5–100 mg of A.I. 2,4-Dbe was employed, which was enhanced with an increment in its dose in both vegetable-planting and fluvo-aquic soils. However, the inhibitory effect of 10 mg of A. I. 2,4-Dbe exhibited obvious differences in these two types of soils, where the duration of inhibition was shorter as it only continued about a week in fluvo-aquic and calcic cambisols soils with strong nitrification activity but poorer effect as compared to 10 mg of dicyandiamide (DCD). In contrast, the duration of inhibition exceeded 2 months in dryland red and shajiang black soils with a weak nitrification activity which was equivalent to DCD. In addition, comparing with five nitrification inhibitors, 10 mg of 2,4-Dbe had better inhibition than the substituted pyrimidine (AM) and sulfocarbamide (SU), but was equivalent to DCD, nitrapirin, and 3,4-dimethylpyrazole phosphate (DMPP) at their recommended application rates in dryland red soil. These obtained data clearly indicated that 2,4-Dbe could play a stronger role as a nitrification inhibitor in soils.

Vertical variations of radionuclides, trace metals, and major elements were determined in two sediment cores, which were collected in the marine environment of Ierissos Gulf near Stratoni’s mining area. The enrichment factors (EFs) were also estimated and provided moderately severe to extremely severe enrichment for most trace elements and Mn, describing the anthropogenic influence in the gulf during the previous century. According to the applied dating models based on ²¹⁰Pb and ¹³⁷Cs, the effect in the marine sediment due to the exploitation of pyrite for the production of sulfuric acid during 1912–1920 was observed. Additionally, the decrease of mining activity during 1935–1945 due to the Second World War and the type of ore exploitation, the alteration of the exploited ores, and the construction and operation of Olympiada’s floatation plant during 1950–1970 were identified. The end of tailing discharging into the marine environment during 1980–2010 was also noted.

Washing of contaminated soils or sediments using humic substances (HS) extracted either from source-rich materials or compost has been tested effective to remove various heavy metals. Nevertheless, the remaining chemical fractionation of metals and post-washing biological responses were not discussed in previous research. In this study, we used a HS extracted from green waste compost to wash off Cd, As, and Ni from a contaminated sediment, and evaluated the washing effect on sediment microbes by measuring a series of indexes with regard to microbial biomass and enzyme activities. Results showed that HS washing was more effective in removing the cationic metals Cd and Ni than the anionic metal As. The highest HS dose of 2000 mg L⁻¹ resulted in 24.5-, 33.1-, and 12-fold increases of removal for Cd, Ni, and As, respectively. The remaining Cd and As were found to migrate to less stable fractions, whereas the remaining Ni was dominantly found in the residual fraction. Increases of metal removal efficiency, microbial biomass, and dehydrogenase activity were found to correlate with the increase of HS concentrations. Increasing doses of HS slightly altered sediment pH to the lower range but did not cause any significant effect on microbial activities. The study proves that HS washing is indeed a more environmental-friendly strategy than many existing washing agents which have exerted various side effects on soil properties.

Experiments were conducted under lead (Pb), cadmium (Cd), and copper (Cu) exposure to observe germination and seedling growth of wheat (Triticum aestivum L), pea (Pisum sativum), and tomato (Solanum lycopersicum L.). Metals were applied in five concentrations (20, 65, 110, 175, and 220 ppm) and Hoagland solution was used to feed the seedlings. Irrespective of the tested crop seeds, copper revealed maximum effect (51.2%) on germination followed by lead (47.5%) and cadmium (35.3%). Tomato seeds were most sensitive in germination stage followed by pea and wheat. In seedling stage, tomato also showed highest sensitivity to both Cd and Cu. However, pea seedlings showed higher tolerance to Pb and wheat seedlings had the highest tolerance to both Cu and Cd. Toxicity and tolerance of metals was found to vary with crops and growth stages. Higher transfer of metals (Pb, Cd, and Cu) in wheat seedling indicates higher risk of food chain contamination when grown in polluted soil. Higher mobility and uptake of Cd in tomato and wheat seedlings even under lower concentration of exposure needs further study.

The exploration and production of shale gas technology provides a way for utilization of clean fuels. However, during the exploration process of shale gas, enormous amount of drilling cutting was generated and had to be solidified and landfilled. So the accumulation of shale gas drilling cutting solidified body (SGDS)causes severe land resource misuse and environmental complications. This study focuses on the utilization of SGDS as a raw material for the production of cement clinker, and the phase composition, microstructure, and environmental performance of the cement clinker was investigated by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), energy-dispersive X-ray spectrum analysis (EDX), and soaking test, respectively. The results show that the cement clinker obtained mainly constitutes of typical Portland cement mineral (C₃S, C₂S, C₃A, and C₄AF). The leaching test indicated that the concentration of heavy metal ions in leachate is within the limits allowed by the state “Technical specification for co-processing of solid wastes in cement kiln” (GB 30760-2014). This study therefore provides a benchmark on environmental effects resulting from drilling cuttings and utilization of resources.

The present study reports the use of Citrus limetta (CL) residue for cultivating Chlorella sp. mixotrophically to augment production of biodiesel. The cultivation of Chlorella sp. using CL as media was carried out by employing a fed-batch technique in open tray (open tray+CL) and in software (BioXpert V2)–attached automated photobioreactor (PBR+CL) systems. Data showed the limit of nitrogen substituent and satisfactory organic source of carbon (OSC) in CL, causing > 2-fold higher lipid content in cells, cultivated in both the systems than in control. For the cells grown in both the systems, ≥ 3-fold enhancement in lipid productivity was observed than in control. The total fatty acid methyl ester (FAME) concentrations from lipids extracted from cells grew in PBR+CL and in open tray+CL techniques were calculated as 50.59% and 38.31%, respectively. The PBR+CL system showed improved outcomes for lipid content, lipid and biomass productivity, FAME characteristics and physical property parameters of biodiesel than those obtained from the open tray+CL system. The physical property parameters of biodiesel produced from algal cells grown in PBR+CL were comparable to existing fuel standards. The results have shown lower cold filter plugging point (− 6.57 °C), higher cetane number (58.04) and average oxidative stability (3.60 h). Collectively, this investigation unveils the novel deployment of CL as a cost-effective feedstock for commercialisation of biodiesel production.