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.

The chiral herbicide imazethapyr (IM) is frequently used to control weeds in soybean fields in northeast China. However, the impact of IM enantiomers on microbial communities in soil is still unknown. Genetic markers (16S rRNA V3-V4 regions) were used to characterize and evaluate the variation of the bacterial communities potentially effected by IM enantiomers. Globally, the bacterial community structure based on the OTU profiles in (−)-R-IM-treated soils was significantly different from those in (+)-S-IM-treated soils, and the differences were enlarged with the treatment dose increasing. Interestingly, the Rhizobiaceae family and several other beneficial bacteria, including Bradyrhizobium, Methylobacterium, and Paenibacillus, were strongly enriched in (−)-R-IM treatment compared to (+)-S-IM treatment. In contrast, the pathogenic bacteria, including Erwinia, Pseudomonas, Burkholderia, Streptomyces, and Agrobacterium, were suppressed in the presence of (−)-R-IM compared to (+)-S-IM. Furthermore, we also observed that the bacterial community structure in (−)-R-IM-treated soils was more quickly restored to its original state compared with those in (+)-S-IM-treated soils. These findings unveil a new role of chiral herbicide in the development of soil microbial ecology and provide theoretical support for the application of low-persistence, high-efficiency, and eco-friendly optical rotatory (−)-R-IM.

Swine production chain generates residues with potential application in environmental processes. This study aimed at the use of swine hair as a potential biofilter for hexavalent chromium (Cr(VI)) removal from wastewater of tannery industry. The hair was pretreated using H₂O₂ in alkaline medium, and statistical analysis was carried out to evaluate the hair degradation, as well the Cr(VI) removal by the potential pretreated biofilter. The results showed 99% of Cr(VI) removal in 105 min of treatment in large pH range (1–10). Treated and untreated effluents were submitted to cytotoxicity study using vegetable and animal cells, demonstrating a significant reduction on toxicity to both cells. Therefore, swine hair demonstrated to be a promising residue for heavy metal removal on the perspective of an environmentally friendly technique.

The anaerobic digestion of wastewater from the cleaning of tank cars transporting food and fodder was investigated in both bench and pilot scales with a single-stage, mesophilic (39 °C), completely mixed process. The promising results lead to the planning and building of a 1200-m³ full-scale biogas plant at TS-Clean cleaning station in Fahrbinde, Germany. Due to softened water used in the cleaning of the car tanks, the alkalinity in the digester decreased as predicted by the physicochemical model developed for this treatment process. The model showed that 2.4 kg NaHCO₃/m³ of wastewater has to be added in order to control digester pH at 7.2 and to maintain the digester alkalinity at 3.1 g CaCO₃/L. In a laboratory study, the decrease of alkalinity caused a volatile organic acids accumulation and pH drop below the optimal range. In this case, if chemical buffering was not added into the digester, the digester deteriorated. In a 3-year investigation, we confirmed that the strongly polluted WW from the cleaning of tank cars transporting food and fodder is suitable for an anaerobic treatment if the organic loading rate is controlled below 4 kg COD/m³/day, digester alkalinity is adjusted by NaHCO₃, and micronutrients are added despite constant considerable variations in strength and composition of the wastewater. A biogas yield of 35–45 m³ CH₄/m³ of wastewater and a COD elimination of 80–90% were achieved in bench- and pilot-scale experiments and are achieved in the full-scale biogas plant. The full-scale biogas plant is working stable with a biogas yield of 68 m³ biogas/m³ of wastewater.