Mining activities have caused serious environmental problems including acid mine drainage (AMD), the dispersion of mine tailings and dust, and extensive mine waste. In particular, AMD contaminates soil and water downstream of mines and generally contains mainly valuable metals such as Cu, Zn, and Ni as well as Fe and Al. In this study, we investigated the selective recovery of Fe, Al, Cu, Zn, and Ni from AMD. First, the speciation of Fe, Al, Cu, Zn, and Ni as a function of the equilibrium solution pH was simulated by Visual MINTEQ. Based on the simulation results, the predicted pHs for the selective precipitation of Fe, Al, Cu, and Zn/Ni were determined. And recovery yield of metals using simulation is over 99 %. Experiments using artificial AMD based on the simulation results confirmed the selective recovery of Fe, Al, Cu, and Zn/Ni, and the recovery yields of Fe/Al/Cu/Zn and Fe/Al/Cu/Ni mixtures using Na₂CO₃were 99.6/86.8/71.9/77.0 % and 99.2/85.7/73.3/86.1 %, respectively. After then, the simulation results were applied to an actual AMD for the selective recovery of metals, and the recovery yields of Fe, Al, Cu, and Zn using NaOH were 97.2, 74.9, 66.9, and 89.7 %, respectively. Based on the results, it was concluded that selective recovery of dissolved metals from AMD is possible by adjusting the solution pH using NaOH or Na₂CO₃as neutralizing agents.

Biomonitoring offers a valuable tool to estimate the genetic risk as of exposure to genotoxic agents. Here, we intend to assess the potential cytogenetic damage related with occupational exposure to polycyclic aromatic hydrocarbons by evaluating the genetic damages in exfoliated buccal epithelial cells of foundry workers via counting micronucleus (MNs) and other nuclear abnormalities (NAs). This was a cross-sectional study and all study subjects were male . Exfoliated buccal mucosal cells were obtained from 100 subjects involved in either foundry molding or melting processes, and 100 controls matched for sex, age, and smoking from the area of Coimbatore city, Southern India. For each individual, 2000 exfoliated buccal cells were analyzed. Significantly, there was a higher frequency of MN in the exposed workers than in the controls (P < 0.05). Smoking was associated with the increased frequencies of micronuclei and NAs in the buccal epithelium of both the control and the exposed groups. Smoking represented significant factors in terms of increasing the production of MN when the control and the exposed groups were compared (P < 0.05). The results specify that buccal cells of foundry workers display increased levels of genotoxicity and these biomarker responses may be related to the increased cancer risk. These results conclude that the studied individuals are at a risk group and they require periodical biological monitoring and proper care which is essential for them.

Mosquitoes transmit major communicable diseases such as dengue, malaria, filariasis, Japanese encephalitis, chikungunya, and so on. Vector control is important in epidemic disease situations as there is an urgent need to develop new and improved mosquito control methods that are economical and effective yet safe for non-targeted organisms. In the present study, silver nanoparticles (AgNPs) were synthesized from the aqueous leaf extract of neem plant (Azadirachta indica), and their effects on mosquito vectors (Aedes aegypti and Culex quinquefasciatus) were assessed. The synthesised AgNPs were characterized by UV–vis spectroscopy, scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analysis (XRD). The nanoparticles have maximum absorption at 442 ± 1.5 nm with an average size of 41–60 nm. The XRD data showed six well-defined diffraction peaks, corresponding to a relative intensity of the crystal structure of metallic silver 36.42, 100.00, 53.70, 14.20, 16.05, and 6.79, respectively. The FT-IR data showed strong prominent peaks in different ranges, reflecting its complex nature. The mosquito larvae were exposed to varying concentrations of AgNPs synthesized from the neem leaves under investigation (0.07–25 mg/l) for 24 h; this revealed larvicidal activity of AgNPs with LC₅₀and LC₉₀values of 0.006 and 0.04 mg/l for A. aegypti, respectively. Further, the LC₅₀and LC₉₀values were also identified as 0.047 and 0.23 mg/l for Cx. quinquefasciatus, respectively. The result obtained from this study presents biosynthesized silver nanoparticle from A. indica as the biolarvicidal agent with the most potential for mosquito control.

When grown on Cd-contaminated soil, rice typically accumulates considerable Cd in straw, and which may return to the soil after harvest. This work was undertaken to assess the pollution risk of Cd associated to the Cd-contaminated rice straw after incorporating into an uncontaminated soil. With the Cd-contaminated rice straw added at 0, 1, 2, 3, 4 and 5 % (w/w), an incubation experiment (28 days) with non-planting and a followed pot experiment sequent with two planting (rice and Chinese cabbage, transplanted after 28-day incubation) were carried out to investigate the changes of soil Cd speciation and phytoavailability. The results indicated that the Cd-contaminated rice straw addition significantly increased soil pH and dissolved organic carbon during the 28-day incubation. For the high availability of Cd in contaminated rice straw, diethylenetriaminepentaacetic acid (DTPA) extractable Cd significantly increased, and the percentages of acetic acid extractable and reducible Cd in soil significantly enhanced after the addition of Cd-contaminated rice straw. However, the Cd-contaminated rice straw addition inhibited the rice growth and induced the decrease of Cd in rice grain and straw by 12.8 to 70.2 % and 39.3 to 57.3 %, respectively, whereas the Cd contents increased by 13.9 to 84.1 % in Chinese cabbage that planted after rice harvest. In conclusion, Cd associated with Cd-contaminated rice straw was highly available after incorporating into the soil, and thus the Cd pollution risk via the Cd-contaminated rice straw incorporation should be evaluated in the Cd-contaminated paddy region.

The synergistic activity between plants and microorganisms may contribute to the implementation of proactive management strategies in the stabilization of contaminated sites, although heavy metals, such as cadmium (Cd), are potentially toxic to them. The aim of this study was to evaluate the degree of tolerance to Cd contamination (supplying twice 40 mg kg⁻¹ of Cd) in poplar cuttings [clone I-214, P. × euramericana (Dode) Guinier] inoculated or not with two concentrations of Serratia marcescens strain (1 × 10⁷ CFU/g and 2 × 10⁷ CFU/g of potting mix). The response of the plant–bacteria system to excess Cd was investigated with special reference to the structural traits of plants and the functional efficiency of bacteria. Bacterial colonization and substrate components were previously assessed in order to define the best solution for formulating the experimental plant growth media. The tested plant–bacteria association, especially when bacteria were provided in double concentration, stimulated specific tolerance mechanisms to Cd through the promotion of the poplar growth. Inoculated plants produced larger leaves and increased stem diameter, while roots grew longer and wider in Cd-treated plants. The effect of bacterial inoculum on plant growth traits and metal partitioning in plant organs was assessed in order to define the potential of this poplar clone to be a suitable candidate for phytostabilization of Cd-contaminated soil. The final effect of the inoculation with bacteria, which alleviated the metal load and Cd phytotoxicity due to their bioaccumulation ability, suggests promising phytostabilization potential of these plant–bacteria associations.

Rapid economic growth has led to a significant increase in ozone (O₃) precursor emissions in many regions of China. Improved understanding of O₃ formation in response to different precursor emissions is imperative to address the highly nonlinear O₃ problem and to provide a solid scientific basis for efficient O₃ abatement in these regions. A comparative study was conducted in summer using a set of observational data at urban and suburban sites in Nanjing. The results showed that high O₃ concentrations were frequently encountered at both sites. The probability distributions of O₃ in both sites show a fair resemblance to each other, suggesting strong regional mixing over the polluted Nanjing. A distinction between the characteristics of O₃ precursors has been found at different sites. During the observation period, O₃ concentrations varied monthly, reaching a minimum in June and peaking in August. The daily maximum O₃ concentration was found to exceed 80 ppb for 27 days at residential area (RA), whereas it only exceeded 80 ppb for 22 days at industrial area (IA), 16 days at traffic area (TA), and 14 days at commercial area (CA). This pattern suggests a higher continuous ozone exposure risk at RA. The daily maximum O₃ concentrations at different sites were 135.1 ppb (IA), 134.1 ppb (RA), 129.2 ppb (TA), and 110.6 ppb (CA), respectively. The daily maximum O₃ concentration occurred at 16:00 in IA, at 17:00 in TA and CA, and at 18:00 in RA. Nitrogen dioxide (NO₂) and carbon monoxide (CO) showed similar double-peak diurnal cycles. NO₂ showed maximum values in June and minimum values in July. CO showed a similar diurnal variation to NO₂. This effect may be explained by their common sources and the similar chemical losses. During the day, O₃ tended to rapidly increase during the morning, reaching a maximum value of 9–11 ppb h⁻¹. The differences in O₃ and NO₂ between workdays and weekends were small. The CO levels were higher on weekdays than on weekends in urban areas and were higher on weekends than on weekdays in suburban areas. A sensitivity study performed with an observation-based model (OBM) showed alkenes to be the largest contributor to O₃ production. The production of O₃ in the Nanjing area is generally limited by volatile organic compounds (VOCs), whereas high nitric oxide (NO) concentrations suppress O₃ concentrations.

Pesticides constitute an integral part of high-intensity European agriculture. Prior to their authorization, a highly elaborated environmental risk assessment is mandatory according to EU pesticide legislation, i.e., Regulation (EC) No. 1107/2009. However, no field data-based evaluation of the risk assessment outcome, i.e., the regulatory acceptable concentrations (RACs), and therefore of the overall protectiveness of EU pesticide regulations exists. We conducted here a comprehensive meta-analysis using peer-reviewed literature on agricultural insecticide concentrations in EU surface waters and evaluated associated risks using the RACs derived from official European pesticide registration documents. As a result, 44.7 % of the 1566 cases of measured insecticide concentrations (MICs) in EU surface waters exceeded their respective RACs. It follows that current EU pesticide regulations do not protect the aquatic environment and that insecticides threaten aquatic biodiversity. RAC exceedances were significantly higher for insecticides authorized using conservative tier-I RACs and for more recently developed insecticide classes, i.e., pyrethroids. In addition, we identified higher risks, e.g., for smaller surface waters that are specifically considered in the regulatory risk assessment schemes. We illustrate the shortcomings of the EU regulatory risk assessment using two case studies that contextualize the respective risk assessment outcomes to field exposure. Overall, our meta-analysis challenges the field relevance and protectiveness of the regulatory environmental risk assessment conducted for pesticide authorization in the EU and indicates that critical revisions of related pesticide regulations and effective mitigation measures are urgently needed to substantially reduce the environmental risks arising from agricultural insecticide use.

The present study was conducted to assess the impact of gibberellic acid on growth and yield of sunflower in hexavalent chromium [Cr(VI)]-contaminated soil in the presence as well as absence of pressmud. Seeds of sunflower were sown in potted soil amended with pressmud as an organic amendment and contaminated with different levels of Cr(VI) (12, 18, and 24 mg kg⁻¹) by using K₂Cr₂O₇ salt. Gibberellic acid (10⁻⁴ M) was applied at time of seedling emergence in the rhizosphere. The results showed that Cr(VI) stress significantly reduced the growth and yield of sunflower. However, application of gibberellic acid and pressmud reversed the toxic effects of Cr(VI) and improved the growth and yield of sunflower. Combined application of gibberellic acid and pressmud further improved growth and yield compared to their separate application in Cr(VI) stress. Moreover, gibberellic acid and pressmud decreased the uptake of Cr and stabilized it in the soil.

A mesophilic alkali-tolerant bacterial consortium belonging to the Bacillus genus was evaluated for its ability to biodegrade high free cyanide (CN⁻) concentration (up to 500 mg CN⁻/L), subsequent to the oxidation of the formed ammonium and nitrates in a continuous bioreactor system solely supplemented with whey waste. Furthermore, an optimisation study for successful cyanide biodegradation by this consortium was evaluated in batch bioreactors (BBs) using response surface methodology (RSM). The input variables, that is, pH, temperature and whey-waste concentration, were optimised using a numerical optimisation technique where the optimum conditions were found to be as follows: pH 9.88, temperature 33.60 °C and whey-waste concentration of 14.27 g/L, under which 206.53 mg CN⁻/L in 96 h can be biodegraded by the microbial species from an initial cyanide concentration of 500 mg CN⁻/L. Furthermore, using the optimised data, cyanide biodegradation in a continuous mode was evaluated in a dual-stage packed-bed bioreactor (PBB) connected in series to a pneumatic bioreactor system (PBS) used for simultaneous nitrification, including aerobic denitrification. The whey-supported Bacillus sp. culture was not inhibited by the free cyanide concentration of up to 500 mg CN⁻/L, with an overall degradation efficiency of ≥99 % with subsequent nitrification and aerobic denitrification of the formed ammonium and nitrates over a period of 80 days. This is the first study to report free cyanide biodegradation at concentrations of up to 500 mg CN⁻/L in a continuous system using whey waste as a microbial feedstock. The results showed that the process has the potential for the bioremediation of cyanide-containing wastewaters.

The increasing sludge generated in wastewater treatment plants poses a threat to the environment. Based on the traditional processes, sludge dewatered by usual methods was further dewatered by hydraulic compression and the filtrate released was treated by anaerobic fermentation. The difficulties in sludge dewatering were associated with the existence of sludge flocs or colloidal materials. A suitable CaO dosage of 125 mg/g dry sludge (DS) could further decrease the moisture content of sludge from 82.4 to 50.9 %. The filtrate from the dewatering procedure was a potential substrate for biohydrogen production. Adding zero-valent iron (ZVI) into the anaerobic system improved the biohydrogen yield by 20 %, and the COD removal rate was lifted by 10 % as well. Meanwhile, the sludge morphology and microbial community were altered. The novel method could greatly reduce the sludge volume and successfully treated filtrate along with the conversion of organics into biohydrogen.