Due to its wide range of hazardous hydrocarbons and even heavy metal ions, oily sludge has become a great environmental challenge which must be dealt with quite quickly. As a result, ther have been numerous efforts during recent years to develop an efficient method for sludge recovery. The current research studies the effectiveness of solvent extraction with toluene and Fe2O3 nanoparticles for recovery and upgrading of oily sludge. Having employed Design of Experiment (DOE), it has found optimum conditions for sludge recovery with solvent extraction, namely a temperature of 55°C and mixing time of 17 minutes with solvent to sludge ratio of 6.4/4.2. Under these conditions, the sludge recovery has been 37%, which is the maximum available with toluene. Furthermore, it has studied the effectiveness of Fe2O3 nanoparticles for improvement of sludge pyrolysis efficiency in order to upgrade the oily sludge, wherein it has been observed that nanoparticles can significantly decrease the temperature and time of reaching maximum conversion during sludge pyrolysis process. The temperature and time of reaching to the maximum conversion, by means of gamma Fe2O3 nanoparticles, is about 200°C and 1200 s, respectively, which is lower than the condition in which pure sludge is being pyrolyzed.

Pyrolysis is an applicable method that has been widely used to recover hydrocarbons from Used Lubricating Oil (ULO). However, large-scale application of this approach has been limited by its noticeably energy and time consuming nature. In the present research, it has been attempted to modify the energy and time requirements of ULO pyrolysis using the catalytic effects of metal oxide nanoparticles (NPs). The impacts of γ-Al2O3, γ-Fe2O3 and ZnO NPs on the kinetic features of ULO pyrolysis were studied using thermogravimetric analysis (TGA). The kinetic parameters of the pyrolysis process were calculated based on Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozava (FWO) models. The activation energy of virgin ULO pyrolysis had been calculated to be 161.505 and 162.087 kJ/mol using KAS and FWO models, respectively. However, in the present work, utilization of γ-Fe2O3 NPs significantly reduced the activation energy of ULO pyrolysis to 133.511 and 138.289 kJ/mol through KAS and FWO models, respectively. The catalytic effect of ZnO NPs was not as noticeable as that of γ-Fe2O3 NPs, resulting in activation energies of 155.568 and 158.501 kJ/mol using KAS and FWO models, respectively. Moreover, based on the results of this study, γ-Al2O3 NPs had no significant impact on the kinetics of ULO pyrolysis.

Radiology and photography films are mainly made of silver halides, which are very sensitive to light. The developer-fixing solution reduces silver salt crystals and turns them into black metallic silver on film and a stable and clear image appears on the film. After several uses of the fixing solution, its efficiency is reduced due to the decrease in the concentration of sodium thiosulfate and finally, it cannot be used since there is not enough awareness regarding its harm, so it enters the environment through wastewater. In this study, the recovery of fixing solution waste has been investigated. The recovery of the solution waste, silver extraction, and direct synthesis of nanoparticles have been performed by chemical reduction method from the waste. The obtained samples were analyzed and studied by EDX, XRD, and SEM techniques. The results showed that the fixing solution waste and silver metal were recovered properly with a purity of 99.81%. Also, AgNPs were synthesized by chemical reduction. Recovery of the fixing solution waste -for the first time- and metallic silver, as well as the synthesis of AgNPs by chemical reduction method, is an economical method and free of any contamination.

In recent decades, industrial emissions have been reduced in many countries, which provides an opportunity for the recovery of polluted ecosystems. However, our knowledge of the rate and factors facilitating the recovery of local bird populations after pollution abatement is incomplete. Long-term (1989–2021) annual observations on nest-box populations of a passerine bird, Ficedula hypoleuca, were used to analyze temporal dynamics of breeding parameters following a 50-fold reduction of industrial emissions from the Middle Ural copper smelter (MUCS) according to pollution zone, habitat, air temperature, and breeding density. In the heavily polluted (impact) zone (1–2 km of MUCS), egg and fledgling production were strongly impaired compared to the moderately polluted (buffer zone, 4–8 km of MUCS) and unpolluted control zone (16–27 km of MUCS). During the study period, the laying date advanced along with increasing spring air temperatures. The clutch size increased in the impact zone by 26%, in the buffer zone by 10%, and in control by 5%. The number of fledglings increased in the impact zone by 102% and the buffer zone by 17%. In the most recent year (2021), mean laying date, clutch size, fledgling production, and the frequency of nests with unhatched eggs in the impact zone did not reach the control level, whereas the frequency of nests with perished chicks did not differ among zones. Breeding parameters of birds in the impact zone improved slowly, likely due to the slow recovery of habitats. We conclude that bird reproduction may require many decades to recover fully in the heavily polluted zone.

The contributions of contaminant sources are difficult to resolve in the sediment record using concentration gradients and flux reconstruction alone. In this study, we demonstrate that source partitioning using lead isotopes provide complementary and unique information to concentration gradients to evaluate point-source releases, transport, and recovery of metal mining pollution in the environment. We analyzed eight sediment cores, collected within 24 km of two gold mines, for Pb stable isotopes, Pb concentration, and sediment chronology. Stable Pb isotope ratios (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁴Pb) of mining ore were different from those of background (pre-disturbance) sediment, allowing the use of a quantitative mixing model. As previously reported for some Arctic lakes, Pb isotope ratios indicated negligible aerosol inputs to sediment from regional or long-range pollution sources, possibly related to low annual precipitation. Maximum recorded Pb flux at each site reached up to 63 mg m⁻² yr⁻¹ in the period corresponding to early years of mining when pollution mitigation measures were at a minimum (1950s–1960s). The maximum contribution of mining-derived Pb to these fluxes declined with distance from the mines from 92 ± 8% to 8 ± 4% at the farthest site. Mining-derived Pb was still present at the sediment surface within 9 km of Giant Mine more than ten years after mine closure (5–26 km, 95% confidence interval) and model estimates suggest it could be present for another ∼50–100 years. These results highlight the persistence of Pb pollution in freshwater sediment and the usefulness of Pb stable isotopes to quantify spatial and temporal trends of contamination from mining pollution, particularly as concentrations approach background.

Average nitrogen (N) deposition across Europe has declined since the 1990s. This resulted in decreased N inputs to forest ecosystems especially in Central and Western Europe where deposition levels are highest. While the impact of atmospheric N deposition on forests has been receiving much attention for decades, ecosystem responses to the decline in N inputs received less attention. Here, we review observational studies reporting on trends in a number of indicators: soil acidification and eutrophication, understory vegetation, tree nutrition (foliar element concentrations) as well as tree vitality and growth in response to decreasing N deposition across Europe. Ecosystem responses varied with limited decrease in soil solution nitrate concentrations and potentially also foliar N concentrations. There was no large-scale response in understory vegetation, tree growth, or vitality. Experimental studies support the observation of a more distinct reaction of soil solution and foliar element concentrations to changes in N supply compared to the three other parameters. According to the most likely scenarios, further decrease of N deposition will be limited. We hypothesize that this expected decline will not cause major responses of the parameters analysed in this study. Instead, future changes might be more strongly controlled by the development of N pools accumulated within forest soils, affected by climate change and forest management.

Current pesticide registration guidelines call for short-term testing of plants; long-term effects on vegetative parts and reproduction remain untested. The aims of our study were to determine level of recovery and recovery times for plants exposed to the sulfonylurea herbicide chlorimuron ethyl using data collected from single species, dose–response greenhouse experiments. The nine terrestrial and eight wetland species tested showed variable levels of recovery and recovery timeframes. Many species (six terrestrial and five wetland) were vegetatively stunted at sublethal doses and were reproductively impaired. Full recovery did not occur at all doses and maximum recovery times varied from 3 to 15 weeks in this controlled environment. In a complex community, affected species may be displaced by tolerant species, through interspecific competition, before they fully recover. It is plausible that individual populations could be diminished or eliminated through reduced seedbank inputs (annuals and perennials) and asexual reproduction (perennials).

Global warming is drastically altering the climate conditions of our planet. Soils will be among the most affected components of terrestrial ecosystems, especially in contaminated areas. In this study we investigated if changes in climate conditions (air temperature and soil moisture) affect the toxicity of historically metal(loid)-contaminated soils to the invertebrate Folsomia candida, followed by an assessment of its recovery capacity. Ecotoxicity tests (assessing survival, reproduction) were performed in field soils affected by metal(loid)s under different climate scenarios, simulated by individually changing air temperature or soil moisture conditions. The scenarios tested were: standard conditions (20°C + 50% soil water holding capacity-WHC); increased air temperature (daily fluctuation of 20–30°C + 50% WHC); soil drought (20°C + 25% WHC); soil flood (20°C + 75% WHC). Recovery potential was assessed under standard conditions in clean soil. Increased temperature was the major climate condition negatively affecting collembolans performance (decreased survival and reproduction), regardless of metal(loid) contamination. Drought and flood conditions presented less pronounced effects. When it was possible to move to the recovery phase (enough juveniles in exposure phase), F. candida was apparently able to recover from the exposure to metal(loid) contamination and/or climate alterations. The present study showed that forecasted climate alterations in areas already affected by contamination should be considered to improve environmental risk assessment.

Numerous studies have sought to address the extraction of metals from printed circuit boards by employing bioleaching process. However, separation and recovery of the bioleached metals have always been a bottleneck. Herein, we demonstrate effective recovery of bioleached Au and Cu via selective separation using ion exchange resins. pH-edge experiments revealed high affinity of Amberjet™ 4200 resin towards Au (adsorption capacity > 98%) over the entire pH range from pH 2–10, whereas Amberlite IRC-86 resin recorded very high Cu adsorption at around pH 5. Therefore, a two-step sequential process was designed for the effective separation and recovery of Au and Cu. In the 1st step, Au was completely recovered by using the Amberjet™ 4200 at the natural pH of 7.5. Subsequently, the Au-free solution was adjusted to pH 5 and Cu was recovered by using Amberlite IRC-86 (2nd step). Consequently, 98.7% Au and 78.9% Cu were successfully recovered. Therefore, this study provides a technical guideline for the selective recovery of Au and Cu from bioleached wastewater, which promotes effective waste minimization and efficient resource recovery.

Deposition of reactive nitrogen (N) is a major threat to terrestrial ecosystems associated with impacts on ecosystem properties and functions including carbon (C) and nutrient stocks, soil water quality and nutrient retention. In the oceanic-alpine Racomitrium heath habitat, N deposition is associated with moss mat degradation and a shift from bryophyte to graminoid dominance. To investigate the effects of moss mat decline on C and N stocks and fluxes, we collected Racomitrium heath vegetation/soil cores from sites along a gradient of N deposition in the UK. Cores were maintained under controlled conditions and exposed to scenarios of current (8–40 kg N ha⁻¹ y⁻¹), reduced (8 kg N ha⁻¹ y⁻¹) and elevated (50 kg N ha⁻¹ y⁻¹) N deposition. Cores from high N deposition sites had smaller aboveground C and N stocks and, under current conditions, leached large amounts of inorganic N and had low soil water pH compared with low N deposition sites. With reduced N deposition there was evidence for rapid recovery of soil water quality in terms of reduced N leaching and small increases in pH. Under high N deposition, cores from low N deposition sites retained much of the applied N while those with a history of high N deposition leached large amounts of inorganic N. Carbon fluxes in soil water and net CO₂ fluxes varied according to core source site but were not affected by the N deposition scenarios. We conclude that C and N stocks and cycling in Racomitrium heath are strongly affected by long-term exposure to N deposition but that soil water quality may improve rapidly, if N deposition rates are reduced. The legacy of N deposition impacts on moss mat cover and vegetation composition however, mean that the ecosystem remains sensitive to future pulses in N input.