Ball-milled biochars (BM-biochars) were produced through ball milling of pristine biochars derived from different biomass at three pyrolysis temperatures (300, 450, and 600 °C). The results of scanning electron microscopic (SEM), surface area, hydrodynamic diameter test, and Fourier transform infrared spectroscopy (FTIR) revealed that BM-biochars had smaller particle size (140–250 nm compared to 0.5–1 mm for unmilled biochar), greater stability, and more oxygen-containing functional groups (2.2–4.4 mmol/g compared to 0.8–2.9 for unmilled biochar) than the pristine biochars. With these changes, all the BM-biochar-modified glassy carbon electrodes (BM-biochar/GCEs) exhibited prominent electrochemical properties (e.g., ΔEₚ of 119–254 mV compared to 850 mV for bare GCE). Cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) show that ball-milled 600 °C biochar/GCE (BMBB600/GCE and BMBG600/GCE) had the smallest peak-to-peak separation (ΔEₚ = 119 and 132 mV, respectively), series resistance (RS = 88.7 and 89.5 Ω, respectively), and charge transfer resistance (RCT = 1224 and 1382 Ω, respectively), implying its best electrocatalytic activity for the reduction of Fe(CN)₆³⁻. It is supposed that the special structure (i.e., internal surface area, pore volume, oxygen-containing functional groups, and graphitic structure) facilitates the electron transfer and reduces interface resistance. Economic cost of BM-biochar/GCE was 1.97 × 10⁻⁷ USD/cm², much lower than that of a “low-cost platinum electrode” (0.03 USD/cm²). The results indicate potential application of the novel BM-biochar for low cost and high efficient electrodes. Graphical abstract

Photocatalytic oxidation of formaldehyde (HCHO) is considered as one of the promising ways to resolve indoor air HCHO pollution. TiO₂ has been well known as the most extended application in photocatalysis due to its strong oxidizing ability and stability. Owing to high activity under visible light irradiation, TiO₂ and Bi₂O₃ doping mixed with Bi₂WO₆ was analyzed in this study. The formation of two kinds of heterojunction caused efficient charge separation, leading to the effective reduction in the recombination of photo-generated electron and hole. The special structure and enhanced performance of these catalysts were analyzed. For the first time, the loading of alkali salts was researched for photocatalytic oxidation. In order to understand the reaction mechanism of alkali salts enhanced effects, the catalysts were investigated by using BET, XRD, UV–Vis, FT-IR, SEM, and XPS. The results found more than 2 wt% of Na₂SO₄ loading and the mixed methods with different solutions were key factors affecting the performance of catalysts. Nearly 92% HCHO conversion could be completed over Bi₂WO₆/Bi₀.₁₅Ti₀.₈₅O₂ (Na₂SO₄), and the concentration of HCHO was only 0.07 mg/m³ for 24 h, which was below the limit of specification in China. The results also indicated that the solution mixing method was more favorable to increase the HCHO conversion due to decrease the size of Bi₀.₁₅Tᵢ₀.₈₅O₂ particles. The catalysts with Na₂SO₄ loading provided more surface-adsorbed oxygen that facilitated the desorption of CO₂ and markedly increased the photocatalytic oxidation of HCHO. Graphical abstract Plausible mechanism over W-Bi2WO6/ Bi0.15Ti0.85O2-Na2SO4 (1:4) catalysts

Mercury and lead are deposited in the West Carpathians as long-range transported air pollution. The Alpine accentor (Prunella collaris) was recognized as a cost-effective biomonitor, and used to investigate the bioavailability of contaminants in large alpine areas. The outer tail feathers and blood of the alpine accentors were used for assessment of atmospheric mercury and lead contamination, respectively. Mean mercury levels in feathers of accentors averaged at 1.15 μg/g (SE = 0.105, n = 40). There were no temporal variations in mercury concentrations. Mean blood lead levels were at 5.2 μg/dL (SE = 0.5, n = 27), showing a slight decreasing trend from July to October. Juveniles were not more susceptible to lead accumulation than adults. Bone lead concentrations that increase with age reflect a bioaccumulation effect. A statistically significant negative correlation was found between the length of erythrocytes and the concentration of lead, which may show the first symptoms of microcytosis. In comparison to aquatic ecosystems, the biogeochemical factors that influence methylmercury availability in alpine habitats are not yet completely known and require further investigation. Our findings show that birds in alpine terrestrial ecosystems may contain surprisingly high levels of methylmercury. The mercury levels in the feathers of accentors probably indicate that alpine autotrophs make sufficient amounts of mercury available to the terrestrial food web. The blood lead levels of accentors likely approach the threshold level for further hematological effects. We found a clear tendency in erythrocytes to change their shape from ellipsoid to smaller and rounder with increasing amounts of lead in their blood. The shape of bird erythrocytes appears to be a very sensitive indicator of critical levels of lead in the alpine environment.

There has been a growing concern regarding the regulation of environmental pollution in the face of a growing population, global warming, and climate change. Governments around the world have devised various mechanisms and policy strategies to ameliorate the worsening condition of natural environment around the world. Similar to the developed world, in China, the government is also aware of deteriorating environmental conditions. Hence, the existing abatement instruments include pollution discharge fees and several other policy strategies. This research is conducted to investigate the association between pollution intensity and its determinants, i.e., pollutant discharge fees and urban population, third industry structure, and total retail goods consumption. The secondary data of 29 provinces is used for empirical analysis. The principal component analysis is used to develop a single index called pollution intensity, and panel autoregressive distributed lags model (ARDL), or pooled mean group (PMG) analysis, is employed to find long-run and short-run relationship. The empirical findings show that pollution discharge fees negatively affects pollution intensity. Total retail good consumption and urban population increase pollution intensity. However, third industry structure helps to control pollution intensity. These results suggest reforms in the existing environmental regulations policy by targeting more pollutant intensive provinces.

Linda Gehrmann and Helena Bielak contributed equally to this work and are regarded as joint first authors.

Chiral mesoporous silica (SiO₂) with helical structure was synthesized by using anionic surfactants as template. Pre-prepared graphene oxide (GO) was then loaded onto SiO₂ to synthesize composite carrier chial-meso-SiO₂@GO for the immobilization of laccase. The enzyme activity, thermostability, acid stability, and repeatability of the immobilized enzyme were significantly improved after immobilization. The chial-meso-SiO₂@GO-immobilized laccase was then used for the degradation of MXC in aqueous phase. The degradation conditions, including temperature, time, pH, MXC concentration, and the dose of immobilized enzyme for cellulosic hydrolysis, were optimized. The optimum conditions for degradation of methoxychlor were selected as pH 4.5, MXC concentration 30 mg/L, immobilized enzyme dose 0.1 g, the maximum MXC removal of over 85% and the maximum degradation rate of 50.75% were achieved after degradation time of six h at temperature of 45 °C. In addition, the immobilized cellulase was added into the immobilized laccase system to form chial-meso-SiO₂@GO-immobilized compound enzyme with the maximum MXC degradation rate of 59.58%, higher than that of 50.75% by immobilized laccase. An assessment was made for the effect of chial-meso-SiO₂@GO-immobilized compound enzyme on the degradation of MXC in soil phase. For three contaminated soils with MXC concentration of 25 mg/kg, 50 mg/kg, and 100 mg/kg, the MXC removals were 93.0%, 85.8%, and 65.1%, respectively. According to the GC-MS analyses, it was inferred that chial-meso-SiO₂@GO-immobilized compound enzyme had a different degradation route with that of chial-meso-SiO₂@GO-immobilized laccase. The hydrolysis by immobilized cellulase might attack at a weak location of the MXC molecule with its free radical OH and ultimately removed three chlorine atoms from MXC molecule, leading to generating small molecular amount of degradation product.

In an electrocoagulation process, controlling various parameters, such as temperature, pH, and conductivity, increases the performance of the process. In this study, fuzzy logic algorithms were used to control the temperature of the electrocoagulation system for the removal of pollutants from textile wastewater. In the experimental part, we used a reactor with a cooling jacket to control the temperature, and the flow rate of the cooling water was a variable that we could manipulate. Also, we investigated the use of a single-variable fuzzy control process and a multivariable fuzzy control process to control the dynamic behavior of the system. In the single variable control process, the effect of temperature was investigated at chosen original temperatures, i.e., 17.2 °C, 20 °C, and 23 °C. In the multivariable control, the temperature-pH and temperature-conductivity pairs were controlled separately in different processes. When the removal efficiencies were determined for the two control approaches, it was observed that the temperature-pH control process outperformed the temperature-conductivity control process, and its removal efficiencies for COD, color, and turbidity were about 74.6%, 85.2%, and 91.0%, respectively. Thus, the results obtained from this study will be useful for other investigators in the field. Graphical abstract .

Making good environmental damage caused by industrial accidents and restoring impaired ecosystems may be associated with high costs. The European Environmental Liability Directive requires that environmental damage is prevented or remediated and confers financial liability on operators responsible for the activities that caused the damage. The directive encourages adoption of financial risk instruments for environmental liability, ensuring that operators stand up for their responsibilities. We analyse the risk financing instruments for environmental liability in Italy, with emphasis on waste treatment and disposal plant management in Venice Metropolitan City, where financial guarantees and environmental insurance are mandatory. The regional legislation obliges operators of waste treatment plants to seek financial protection through financial guarantees and environmental insurance. We have conducted online survey and in-depth interviews with both suppliers and users of financial protection instruments. On national level, the relatively high environmental consciousness is countered by a low perception of risk and subsequently very low penetration of financial security instruments. Among the identified barriers, we have singled out a limited knowledge of cumulative and long-lasting impacts of industrial activities on environment and ecosystems. Financial and insurance are well developed, but a deep support for specific risk identification and coverage lacks. A closer cooperation between public and private sector can be an opportunity to foster the adoption of these instruments and to improve the coverage of public costs for environmental restoration, due to unattended liability.

The Caspian Sea is the largest land-locked lake in the world that includes numerous endemic species. Because of its enclosed nature, the pollutants entering this water body become entrapped. The present paper examines the influence of human activity and beach morphology on the abundance and distribution of stranded plastic debris along the Caspian Sea coastlines. It would be possible by relating some characteristics of these beaches (population, urbanization, substrate type, and slope of beaches) with the abundance of plastic debris through a PCo analysis. The results showed that in our study area, the most effective factors on plastic debris distribution were urbanization and population followed by the slope and substrate of beaches. Three size classes of plastic debris were defined as “large microplastic” (1 to < 5 mm), “mesoplastic” (5 to < 25 mm), and “macroplastic” (> 25 mm). The density of the large microplastic, mesoplastic, and macroplastic materials on the Caspian Sea coastline was 8.43 ± 0.54, 8.74 ± 0.42, and 7.53 ± 0.30 particles/m², respectively. Foam was the most abundant microplastic debris along the study area (47.58%), followed by resin pellets (33.93%) and fragments (16.30%), respectively. We also selected the Boujagh National Park with limited accessibility as an appropriate area for the study of marine debris as one sampling station. Cigarette butts and film pieces displayed a different distribution pattern compared to other debris types in the Boujagh National Park station likely due to their distinct buoyancy specification.

Crop straw is an abundant renewable resource whose usage is limited due to its high cellulose, hemicellulose, and lignin contents. Here, Trichoderma viride, Saccharomyces cerevisiae, and Musca domestica were used to transform crop straws, and we investigated their impact on housefly rearing performance and optimized their utilization. The weights of cellulose, hemicellulose, and lignin in fermented crop straw diets significantly decreased after bioconversion by M. domestica larvae. The highest bioconversion rate was recorded in corn straw diet (16.19%), followed by wheat straw diet (10.31%) and wheat bran diet (8.97%). Similarly, high larval weight (yield) and pupation rate and fecundity and fertility rate were recorded in fermented crop straw diets composed of corn straw and wheat bran in 1:1 proportions. These results indicated that fermenting crop straw with T. viride and S. cerevisiae represented an efficient strategy that enhanced crop straw bioconversion and improved the rearing capacity of the housefly larvae. The resulting larvae could further be used as proteinaceous feed in poultry and aquaculture industries. Graphical abstract