This study was aimed to investigate the adsorption and fixation effects of hydroxyapatite (HAP) on lead-contaminated soil. According to the experimental results, the microstructure of hydroxyapatite was observed by a scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) showed that OH⁻ and PO₄³⁻ were the main functional groups in HAP. Optimum adsorption conditions of Pb²⁺ were obtained: 0.2 g/L, adsorbent; initial solution pH of 5.5; and contact time of 120 min. The kinetic adsorption experiments were carried out with the initial lead solution concentrations of 50 mg/L, 150 mg/L, and 250 mg/L. The kinetics fitting was consistent with the pseudo-second-kinetic model, which indicated that the main process of HAP adsorption of Pb²⁺ was mainly controlled by surface reactions and chemical reactions. The adsorption isotherms had a satisfactory fit with the Langmuir model, which indicated that the adsorption of Pb²⁺ by HAP was a monolayer adsorption. According to the experimental results, ion exchange, phosphorus supply, precipitate, and complexation are the main immobilization mechanisms for soil remediation with HAP. In remediation of Pb²⁺-contaminated soil experiments, the adsorption rate of Pb²⁺ by HAP was significantly higher than that of non-HAP soil with increasing immobilization days. With the increasing addition of HAP, the weak acid soluble (WA), reducible (RED), oxidizable (OX), and water soluble (WS) are transformed into residue (RES). The application of HAP in contaminated soil effectively reduced the leachable and exchangeable Pb²⁺, indicating that HAP is a potential material for remediating environmental pollution with Pb²⁺.

Brazil is one of the greatest producers of orange and its orange juice processing industry produces large volumes of solid and liquid waste daily. As an efficient use of the residues from citrus industry, production of bioethanol is highlighted. However, the generation of bioethanol produces a liquid effluent as a by-product, known as vinasse. The objective of this study was to evaluate the toxicity of an effluent from citrus industries, orange vinasse, when applied to soil using Allium cepa seeds. The evaluation was performed by means of germination, root growth, and genotoxic and mutagenic parameters. The EC₅₀ (effectiveness concentration) and ½ EC₅₀, defined in the germination test, were used for genotoxicity tests. Toxicity was observed in dilutions above 40%, which was responsible for reducing the germination speed index. Genotoxicity was observed only using the EC₅₀ and mutagenicity was not detected. According to the results, orange vinasse showed toxicity similar to the sugar cane vinasse, so caution is suggested in the disposal of this effluent into the environment.

The biomixture composition and the presence of a grass layer in a biobed bioremediation system can improve the performance of these systems to minimize pesticide point-source contamination. In this study, a novel biomixture composed with organic wastes from vineyards and wine industries (vermicompost of winery wastes and vine shoots) and top soil (W) was elaborated. The impact of three pesticides, commonly used in vineyards, on its microbial activity and on the development of turfgrass was determined in a short-term experiment. Moreover, the dissipation of the assayed pesticides was evaluated to stablish their distribution patterns between the turfgrass and the biomixture. For comparison, the original biomixture composed with top soil, peat, and straw (P) was also studied. After 15 days of pesticide application, the development of the turfgrass in both biomixtures was similar. However, the oxidoreductases (dehydrogenase and ortho-diphenol oxidase) and the hydrolytic (FDA and β-glucosidase) enzyme activities were greater in W-biomixture than in P-biomixture. The dissipation of metalaxyl and imidacloprid recorded in the W-biomixtures was significantly greater than in the P-biomixtures. The pesticide dissipation in W-biomixtures followed the same order of their octanol water partition coefficients. Except for tebuconazole, the lower biological activity in the P-biomixture would explain the limited pesticide dissipation. In the grassed biomixtures, most (> 83%) of the non-dissipated imidacloprid and tebuconazole remained in the biomixtures, while metalaxyl was rapidly translocated to the aerial part of the turfgrass. Our results show the potential capability of the novel biomixture as an alternative to the original one in a biobed.

The present study presented an inclusive analysis of engine exhaust emission characteristics of direct injection diesel engine fuelled with diesel and biofuel. Biofuel used in this investigation was obtained by steam distillation from pine oil. A single-cylinder, four-stroke diesel engine was used for this purpose. In this work, performance characteristics like brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC) were analysed. The engine pollutants, namely nitrogen oxide (NO), carbon monoxide (CO), hydrocarbon (HC), and smoke, were examined. In addition, combustion characteristics like in-cylinder pressure and heat release rate were presented. Two engine modification techniques, namely thermal barrier coating and the addition of antioxidant to biofuel, were attempted. The advantage of thermal barrier coating is to reduce heat loss from the engine and convert the accumulated heat into useful piston work. In this work, partially stabilised zirconia was used as the coating material. The usage of antioxidant-treated biofuel in a diesel engine was said to be the prominent approach for NOx emission reduction. Three different antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary-butyl hydroquinone (TBHQ), were exclusively dissolved at a concentration of 1% by volume with PO fuel. The obtained performance and emission characteristics of the uncoated engine were compared with the thermally coated engine. From the results, it was observed that the PO biofuel may be a promising alternative in the near prospect with the thermal barrier coating technique to enhance the performance, combustion and emission characteristics of diesel engine. The PO+TBHQ blend was considered as more beneficial than PO+BHT and PO+BHA on account of its performance, combustion and emission characteristics. The effectiveness of the antioxidant was shown in the order of TBHQ>BHA>BHT.

In this study, the removal of diclofenac (DCF) from aqueous phase by birnessite, a layered manganese oxide, was investigated by batch experiments. The results indicated that 90% of DCF was removed by birnessite within 4 h in different initial concentrations of DCF, and the kinetic experiment data were well fitted with pseudo-first-order kinetic model (R² > 0.98). The removal of DCF by birnessite was pH-dependent, and low pH was beneficial to the reaction. The presence of Fe²⁺ and Mn²⁺ strongly inhibited the removal of DCF. However, Ca²⁺, Mg²⁺, Zn²⁺, Cu²⁺, and humic acid (HA) promoted the reaction and following the order: Cu²⁺ > Zn²⁺ > HA > Mg²⁺ ≈ Ca²⁺. In addition, some typical anions, such as NO₃⁻, PO₄³⁻, and SO₄²⁻, had slight effects on the reaction. Electrochemical results demonstrated that the adsorption of DCF on birnessite was reaction rate-limiting step. Graphical Abstract ᅟ

Climate change may result in increased variability in rainfall intensity in the future, leading to more frequent flooding and a substantial loss of lives and properties. To mitigate the impact from flooding events, flood control facilities need to be designed and operated more efficiently, which requires a better understanding of the relationship between climate change and flood events. This study proposed a framework combining the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and the Coupled Model Intercomparison Project Phase 5 (CMIP5) general circulation models to assess the impact of climate change on flood events. HEC-HMS is one of the most commonly used hydrologic models in the USA, and CMIP5 provides the latest climate data for potential future climate scenarios. The proposed approach is applied to the Nippersink Creek watershed, which shows that 10-, 25-, 50-, and 100-year precipitations for the low, medium, and high emission scenarios are all greater than the historic observations. The corresponding 10-, 25-, 50-, and 100-year floods are remarkably higher than in the historic observations for the three climate scenarios. The high emission scenario results in dramatically increased flood risks in the future. The case study demonstrates that the framework combining HEC-HMS and CMIP5 is easy to use and efficient for assessing climate change impacts on flood events. It is a valuable tool when complicated and distributed hydrologic modeling is not an option because of time or monetary constraints.

The effects of elevated ozone (O₃) levels (80 ppb and 120 ppb) on photosynthetic efficiency and growth of canola plants were studied in open-top chambers. The chlorophyll a polyphasic fluorescence rise kinetics OJIP, stomatal conductance and Chlorophyll Content Index (CCI) were measured after 15 and 30 days of O₃ fumigation, as well as in control plants; biomass measurements were done only after 30 days with and without fumigation. Analysis of the OJIP kinetics by the JIP-test led to the calculation of several photosynthetic parameters and the total Performance Index (PIₜₒₜₐₗ). The decline of PIₜₒₜₐₗ under the 80 ppb O₃ treatment was due to a lower density of reaction centres (RC/ABS), while the notable decline under the 120 ppb treatment was found to be due both to a further decline of RC/ABS and to a pronounced lowering of the efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end acceptors (δRₒ). Stomatal conductance was affected by both treatments. Biomass was found to be affected by O₃ fumigation (for 30 days), decreasing by 40% at 80 ppb and by more than 70% under 120 ppb. Our findings indicate that biomass decline is due both to the lowering of CCI and the lowering of photosynthetic efficiency parameters. They thus suggest that two simple, non-invasive and rapid methods, namely, the analysis of OJIP fluorescence transients and the measurement of CCI, can be used to screen the effect of elevated O₃ on biomass of canola plants.

Magnetic activated carbon (MAC) was fabricated to improve biohydrogen (bio-H₂) production. The MAC exhibited higher biocatalytic capability and better microbial immobilization than activated carbon (AC) during the bio-H₂ process. Glucose supplemented with 200 mg/L MAC obtained the highest H₂ yield of 214 mL/g glucose, much higher than that (130 mL/g glucose) of the control group without MAC. Suitable dosage such as 300 mg/L AC or 200 mg/L MAC promoted volatile fatty acid (VFA) formation and H₂ generation. Besides, the metabolites showed that AC or MAC did not change the bio-H₂ evolution pathway. Some possible biochemical mechanisms were as follows: MAC served as a microbial carrier to promote cell colonization and electron transfer rate, and it released Fe³⁺ to enhance glucose acidogenesis and Fe²⁺ to increase microbial concentration and activity in the bio-H₂ evolution. Graphical Abstract Magnetic activated carbon (MAC) was fabricated and subsequently used in bio-H₂ process through glucose-fed anaerobic mixed bacteria at 37 °C. The MAC acted as a carrier of anaerobes to promote cell growth and electron transfer rate, and released Fe³⁺ to increase glucose acidogenesis and Fe²⁺ to improve microbial concentration and activity in the bio-H₂ evolution process.

Pollution of environmental endocrine disruptors has caused increasing concern globally. In the current study, a simple colorimetric method with high sensitivity and good selectivity for 17β-estradiol (E2) detection was developed, which employed gold nanoparticles (AuNPs) as colorimetric probe for specific recognition of shortening DNA aptamer. Visible color change from bright red to violet was observed for aggregation of AuNPs without the protection of DNA aptamer. After optimization, the method exhibited great performance for E2 detection with good linearity between E2 concentrations from 0.2 to 5 nM and the absorbance ratio at 620 and 523 nm, with the limit of detection of 0.1 nM. The method was also successfully applied to E2 determination in different spiked water samples including fishpond water, lake water, and tap water, in which good recoveries from 93.1 to 108.9% and acceptable relative standard deviations from 3.4 to 8.9% were obtained. This technique showed great potential for on-site fast determination of E2 in environmental water samples.

Successive applications of pig manure increase Cu and Zn contents in soils and may cause toxicity to plants. However, plants may have defense strategies that reduce Cu and Zn availability in rhizosphere soil. The study aimed to evaluate growth of white oats (Avena sativa) and Cu and Zn availability in rhizosphere soil subjected to long-term applications of pig slurry (PS) and pig deep litter (PL). The study was carried out with samples of a Typic Hapludalf soil from an 11-year experiment with annual fertilization of 180 kg N ha⁻¹ as pig slurry (PS180) and pig deep litter (PL180) and a control (C) treatment. White oats were grown in pots with soil collected at 0.0–0.10 m depth. Thirty-five and 70 days after emergence (DAE), rhizosphere (RS) and bulk soil (BS) were analyzed to determine Cu and Zn availability. Plant growth, tissue Cu and Zn concentration, and content (concentration X dry weight) were measured. The application of pig manure for 11 years increased available soil Cu and Zn, as well as tissue concentration and content. Dry matter yield and plant height in PL180 were similar to those found in plants grown in the control treatment, while plants grown in PS180 had higher dry matter than in C. We found few differences in soil chemical characteristics and Cu and Zn contents between RS and BS. The high Cu concentrations in roots, especially in soil treated with PL180, show that Cu retention in the roots prevents excess Cu transport to white oat shoots.