CeO₂/Ag₂CrO₄ composite photocatalyst was successfully fabricated using electrospinning and calcination and chemical precipitation method based on CeO₂ ribbon-like fibers and characterized by field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS) and Fourier-transform infrared spectroscopy (FT-IR). The as-obtained CeO₂/Ag₂CrO₄ composite used photocatalytic performance in the sonophotodegradation of rhodamine B in aqueous solution under visible-light (LED) irradiation. DRS analysis illustrates that CeO₂/Ag₂CrO₄ composite exhibited enhanced absorption in the visible region-attributed CeO₂ nanofibers. The effect of four effective parameters including initial concentration of rhodamine B (RhB), photocatalyst dosage, pH, and irradiation time was studied and optimized using central composite design. The kinetic studies confirmed ability of pseudo first-order reaction based on the Langmuir–Hinshelwood model for fitting empirical data, while its rate constant (kₒbₛ), L–H rate constants (kᵣ), and L–H adsorption constants (KA) were 0.0449 min⁻¹, 11.66 mg L⁻¹ min⁻¹ and 1.09E−3 mg L⁻¹, respectively. The enhanced photocatalytic activity could be ascribed to the ultrasound field and formation of a heterojunction system among CeO₂ and Ag₂CrO₄, which lead to a better mass transfer and higher efficiency of charge electron–hole separation, respectively.

Industrial transfer has swept through in China. However, there is still a knowledge gap about its environmental effects. In this study, industrial transfer status was assessed and evaluated by industrial ratios (%; the gross product contributions of the secondary industry to the whole industry) and the impact of such transfer on atmospheric environment (SO₂, NO₂, PM₁₀ (particles with aerodynamic diameter less than 10 μm), precipitations of SO₄²⁻, NO₃⁻, and NH₄⁺) in the 38 districts and counties in Chongqing was analyzed and discussed for the period of 2006–2015. Results showed that industries were transferred obviously from the main urban region (MUR) into the 1-h economic region (OHER). Atmospheric sulfur and PM₁₀ were efficiently put in control, but atmospheric nitrogen (NO₂; precipitations of NO₃⁻ and NH₄⁺) was increasing and posted a potential threat to air quality especially during 2011–2015. Correlations showed that industrial ratios had significantly positive relationships with concentrations of ambient SO₂ and PM₁₀ in the MUR and ambient NO₂ in the OHER (p < 0.05) while a remarkably negative one with concentrations of ambient SO₂ in the OHER (p < 0.05) during 2006–2015, implying that industrial transfer could be effective in transferring sulfur pollution but not as efficient in transferring atmospheric nitrogen and PM₁₀ pollutions as SO₂ between in the MUR and OHER. More measures should be taken to reduce nitrogen and PM₁₀ emission and a regional monitoring network of ambient NH₃ is in urgent need.

Acid gases such as carbon dioxide and hydrogen sulfide are common contaminants in oil and gas operations, landfill gases, and exhaust stacks from power plants. While there are processes currently used to treat these effluents (e.g., amine absorption and adsorption using zeolite), many of these processes require high energy, space, and hazardous chemicals. Removal using biochar derived from the fast pyrolysis of forestry residues represents a more sustainable option. In this study, adsorption using CO₂ as a surrogate for acid gases was investigated using various biochars produced from fast pyrolysis of sawmill residues. Response surface methodology was used to determine operating conditions for maximum adsorption and assess interaction of the adsorption parameters, i.e., temperature, inlet feed flow rate, and CO₂ concentration, on biochar adsorption capacity. The Freundlich isotherm best represented the equilibrium adsorption, and the kinetic model was pseudo first-order. Thermodynamic analysis indicated the adsorption process was spontaneous and exothermic. The biochar had better adsorption capacity relative to commercial zeolite. Our results suggested that biochar could be used as a sustainable and cost-effective option for contaminant removal from acid gases produced in landfill gas treatment, fossil fuel extraction, and/or combustion.

Nowadays, Varroa destructor is considered as a serious pest of honeybees (Apis mellifera) and its resistance to acaricides has been reported in Europe since the early 1990s. That is why new methods of treatment for Varroa mites are still in focus of many scientists. In our study, we determined the lethal concentration LC₅₀ (72 h) of 2.425% oxalic acid solution following single spray exposure of honeybee larvae under laboratory conditions (Guideline OECD 237 2013). Potential sublethal effects of oxalic acid were monitored through the determination of the activity of antioxidant enzymes. Activation of primary antioxidant enzymes was observed at 1.75% of oxalic acid; 3.5% of oxalic acid brought on a statistically significant increase of glutathione S-transferase activity. This change was accompanied by an increase in thiobarbituric acid reactive substances, products of lipid peroxidation. Our results indicate that oxalic acid may be harmful to bee brood when present during application.

A simple and economical method was proposed to synthesize the shaddock peels-based activated carbon (SPAC) for their application as efficient sorbents to eliminate Cr (VI) and methyl orange (MO) from one-component and two-component systems. The synthesis was conducted via activation of phosphoric acid and high-temperature carbonization. The as-prepared SPAC was characterized by Brunauer–Emmett–Teller, scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy, among other techniques. The adsorption experiment, which used five types of fruit peel (shaddock peels, orange peels, apple peels, banana peels, and tangerine peels), indicated that shaddock peels were the optimal precursors, with the high removal efficiencies for Cr (VI) (21.2%) and MO (54.25%). The effects of various factors (e.g., initial concentration, sorbent dosage, pH values, and contact time) were systematically evaluated. For the one-component system, the maximum adsorption capacities of Cr (VI) (9.95 mg/g) and MO (94.59 mg/g) reached pH levels 2 and 3, respectively. Kinetic modeling demonstrated that the pseudo-second-order kinetic model was adopted for the one-component and two-component systems. Isotherm studies suggested that Cr (VI) and MO sorption processes in the one-component explained well the Langmuir and Freundlich models, respectively. The extended Freundlich multicomponent isotherm model was more compatible for explaining competitive adsorption in the binary component system. The adsorbed amount of Cr (VI) was markedly suppressed by MO, whereas MO adsorption was not significantly influenced owing to the existence of Cr (VI). The higher adsorption capacity of MO could be mainly attributed to the strong force acting between MO and SPAC. The findings of this study confirmed that SPAC provided a sustainable choice for cycling solid waste shaddock peels to remove hazardous contaminants.

Intensive anthropogenic activities may add to pollution risks to lakes and rivers, which can be revealed by the magnetic characteristics of sediments. The present study aims to assess the pollution status of the sediment of a typical reservoir in northwestern China by application of magnetic susceptibility. The values of magnetic susceptibility exhibited significant positive correlations with trace metals (Co, Cu, Mn, Ni, and V) and natural radionuclides (²³²Th and ⁴⁰K). Multivariate statistical analysis indicated common sources and similar deposition characteristics of magnetic particles and trace metals. It was conformed that magnetic susceptibility could be used as an indicator to identify industrial sources of trace metals, but was not suitable to indicate the traffic or natural sources. Linear regression equations between the low-frequency magnetic susceptibility and the integrated pollution index as well as annual effective dose rate indicated a potential for using magnetic susceptibility in semi-quantitative assessment of trace metal pollution and radiological hazard in sediments. A three-step procedure is proposed for the use of magnetic susceptibility in pollution monitoring, which provides a fast and effective method for estimating the pollution extent and tracing the major sources of trace metals in the sediment of lakes and rivers.

A total of 26 samples of surface sediments collected in the Neva River (including the St. Petersburg city area) and in the Russian part of the Gulf of Finland were analyzed for 17 polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/Fs), 12 dioxin-like polychlorinated biphenyls (dl-PCBs), and 10 polybrominated diphenyl ethers (PBDEs). The concentrations of total PCDD/Fs and dl-PCBs in sediments ranged from < 0.05 to 219 pg g⁻¹ d.w. and from 44 to 246,600 pg g⁻¹ d.w. respectively. The total World Health Organization toxic equivalent (WHO-TEQPCDD/F ₊ PCB) values varied between 0.01 and 59.0 pg g⁻¹. In the majority of cases, the PCDD/F and dl-PCB concentrations do not exceed the threshold effect level (TEL) recommended by Helsinki Commission (HELCOM) as quantitative target for the sum of PCDD/Fs and dl-PCBs. The congener profile indicates that combustion is the primary source of PCDD/Fs in most of the studied samples. For the PCBs, the historical use of technical PCB products was identified as the major source. ΣPBDE₁₀ concentrations ranged from 0.004 to 1.8 ng g⁻¹ d.w. The congener profile results show that BDE-47 (tetra-BDE) is the dominant congener in sediment samples. According to the sediment and water quality guidelines established in the EU (PNEC) and in Canada (FEQG), all the samples studied can be classified as lowly contaminated by PBDEs. The sediment concentrations of PCDD/Fs, dl-PCBs, and PBDEs measured in this study were comparable to or lower than those reported for other areas of the Baltic Sea.

Bauxite and iron ore mining is the major contributor to metal pollution in Tasik Chini, Malaysia. Deforestation of the protected zone of reserve forest exacerbates the problem. The current study is to understand the speciation of metals spatially in sediment to analyse the risk associated in terms of its mobility and bioavailability. The samples of sediment are collected from Sungai Jemberau, Laut Jemberau, and Laut Gumum of Tasik Chini. Four samplings were conducted for a year, by collecting the surface sediment. Sequential extraction method was followed for speciation of sediment and classified it into exchangeable, reducible, Fe–Mn oxides, organic and residual fractions. The results were also analyzed using principal component analysis (PCA) and cluster analysis (CA). The result reveals that Fe, Al, Mn, Zn, and Pb are the primary constituents of sediment contributing to about 98% of residual fraction. Co, Cd, Cr, As, and Ni are found in trace metal concentration and are identified to be mainly released from anthropogenic sources nearby. Although the individual proportion is less than major metals in exchangeable and carbonate fraction, they possess geochemically significant concentration above the permissible limit. More than 70–80% of all its total concentration proportion is hence found in mobile and bioavailable state. These possess toxic and have chronic effects to aquatic life and public health even in trace elemental concentration. Hence, these metals are the most toxic and bioavailable metals pausing risk for aquatic and public health. PCA analysis highlights that the enrichment of heavy metals in bioavailable fraction is mostly contributed from anthropogenic sources. The same results are emphasized by cluster analysis.

To estimate the impact of mercury discharged from artisanal and small-scale gold mining (ASGM) activity, variations in the concentrations of elemental mercury (Hg0), mercury ion (Hg2+), particulate mercury (P-Hg), and total mercury in filtered river water (FT-Hg) were investigated from sampling locations extending from 10 km upstream to 30 km downstream of ASGM operations in West Java, Indonesia. The average of the annual concentrations at the ASGM site from 2013 to 2017 were 0.14–0.85 μg L⁻¹, 0.27–12.9 μg L⁻¹, 4.3–49.5 μg L⁻¹, and 1.2–12.5 μg L⁻¹ for Hg0, Hg²⁺, P-Hg, and FT-Hg, respectively. The concentration of mercury species decreased as the distance from the ASGM site increased, while the ratio of P-Hg increased towards the lower reaches of the river system, with the percentage of P-Hg estimated at 90% of Hg at the sample location furthest downstream. A high mercury concentration of 600 mg kg⁻¹ was observed for suspended particulate matter (SPM) at the ASGM site. The SPM maintained a high concentration of mercury, even in the downstream area. In the annual variations of the mercury species from 2013 to 2017, FT-Hg and P-Hg concentrations tended to decrease from 2016, which suggested a decline of ASGM activity in this area. However, SPM and river sediment showed no apparent changes in their mercury concentrations over this period, indicating that the contamination in the river system is persistent and does not recover quickly.

Soils and different vegetable species in Costa de Caparica (Portugal) are subject to the intensive use of inorganic fertilizers and pesticides. Thus, the concentrations of As, Cu, Fe, Mn, Pb, and Zn were evaluated. Lettuce, spinach, and potatoes collected in station 9 cause reason for concern due to their high Pb concentrations close to 20 μg g⁻¹ which is probably related to an intensive use of copper and iron sulphate fertilizers. Additionally, the consumption of Portulaca oleracea collected in stations 3 and 4 must be avoided due to the high concentrations of Zn, and even Cu. The derived estimated daily intake (EDI) dose of Zn will be a risk to human consumption if P. oleracea was the single basis of a soup, although the addition of other ingredients might lower the tolerable upper intake (TUI) value of 39 mg/day of P. oleracea, to admissible levels, i.e., not exceeding 25 mg/day. Pumpkin collected in station 1 contained 44.1 μg g⁻¹ Cu and a TUI value of 9.8 mg/day, when the recommendation must not exceed 5.0 mg/day. In this context, it is strongly advised to not include this vegetable in household menus.