One of the serious environmental problems that society is facing today is mine tailings. These byproducts of the process of extraction of valuable elements from ores are a source of pollution and a threat to the environment. For example, mine tailings from past mining activities at Giant Mines, Yellowknife, are deposited in chambers, stopes, and tailing ponds close to the shores of The Great Slave Lake. One of the environmentally friendly approaches for removing heavy metals from these contaminated tailing is by using biosurfactants during the process of soil washing. The objective of this present study is to investigate the effect of sophorolipid (SL) concentration, the volume of washing solution per gram of medium, pH, and temperature on the efficiency of sophorolipids in removing heavy metals from mine tailings. It was found that the efficiency of the sophorolipids depends on its concentration, and is greatly affected by changes in pH, and temperature. The results of this experiment show that increasing the temperature from 15 to 23 °C, while using sophorolipids, resulted in an increase in the removal of iron, copper, and arsenic from the mine tailing specimen, from 0.25, 2.1, and 8.6 to 0.4, 3.3, and 11.7%. At the same time, increasing the temperature of deionized water (DIW) from 15 to 23 °C led to an increase in the removal of iron, copper, and arsenic from 0.03, 0.9, and 1.8 to 0.04, 1.1, and 2.1%, respectively. By increasing temperature from 23 to 35 °C, when using sophorolipids, 22% reduction in the removal of arsenic was observed. At the same time while using DI water as the washing solution, increasing temperature from 23 to 35 °C resulted in 6.2% increase in arsenic removal. The results from this present study indicate that sophorolipids are promising agents for replacing synthetic surfactants in the removal of arsenic and other heavy metals from soil and mine tailings.

Wastewater stabilization ponds (WSPs) are commonly used to treat municipal wastewater in Arctic Canada. The biological treatment in the WSPs is strongly influenced by climatic conditions. Currently, there is limited information about the removal of fecal and pathogenic bacteria during the short cool summer treatment season. With relevance to public health, the objectives of this paper were to determine if treatment in arctic WSPs resulted in the disinfection (i.e., removal of fecal indicator bacteria, Escherichia coli) and removal of selected human bacterial pathogens from the treated effluent. The treatment performance, with focus on microbial removal, was assessed for the one-cell WSP in Pond Inlet (Nunavut [NU]) and two-cell WSP in Clyde River (NU) over three consecutive (2012–2014) summer treatment seasons (late June-early September). The WSPs provided a primary disinfection treatment of the wastewater with a 2–3 Log removal of generic indicator E. coli. The bacterial pathogens Salmonella spp., pathogenic E. coli, and Listeria monocytogenes, but not Campylobacter spp. and Helicobacter pylori, were detected in the untreated and treated wastewater, indicating that human pathogens were not reliably removed. Seasonal and annual variations in temperature significantly (p < 0.05) affected the disinfection efficiency. Improved disinfection and pathogen removal was observed for the two-cell system in Clyde River as compared to the one-cell system in Pond Inlet. A quantitative microbial risk assessment should be performed to determine if the release of low levels of human pathogens into the arctic environment poses a human health risk.

This study investigated the levels of persistent toxic substances, such as 16 polycyclic aromatic hydrocarbons (Σ16PAHs) and heavy metals (Cu, As, Cd, Zn, Pb, Ni, Mo, and Cr) in biochars produced from crop residues (walnut shell, corn cob, corn straw, rice straw, and rice husk) at different heat treatment temperatures (HTTs, 250, 400, and 600 °C). The levels of Σ16PAHs in different biochars were 0.47–7.11 mg kg⁻¹, with naphthalene and phenanthrene contributing the most. The Σ16PAHs had the positive correlations with H/C and (O + N)/C, but had negative correlations with biochar surface areas. This finding indicates the increasing hydrophobic π-π interactions between the PAHs and the aromatic sheets of biochars and even the trapping of PAHs within the micropores with the increase of HTTs. The levels of heavy metals in rice residue-derived biochars were significantly higher than those in other biochars. The heavy metals had positive correlations with ash contents in the biochars, indicating the enrichment of heavy metals in the ash. The potential ecological risks of PAHs and heavy metals (dosage: 1%, w/w; frequency: 1) were minimal according to the risk quotient of negligible concentrations (RQNCₛ: 2.50–47.40, << 800) and maximum permissible concentrations (RQMPCₛ: 0.02–0.48, << 1) for PAHs and the potential ecological risk indexes (PERI: 0.01–0.28, << 150) for heavy metals.

This study is the first attempt to investigate the drivers of Chinese industrial SO₂ and NO ₓ emissions from both periodic and structural perspectives through a decomposition analysis using the logarithmic mean Divisia index (LMDI). The two pollutants’ emissions were decomposed into output effects, structural effects, clean production effects, and pollution abatement effects. The results showed that China’s industrial SO₂ discharge increased by 1.14 Mt during 2003–2014, and the contributions from the four effects were 23.17, − 1.88, − 3.80, and − 16.36 Mt, respectively. Likewise, NO ₓ discharge changed by − 3.44 Mt over 2011–2014, and the corresponding contributions from the four effects were 2.97, − 0.62, − 1.84, and − 3.95 Mt. Thus, the output effect was mainly responsible for the growth of the two discharges. The average annual contribution rates of SO₂ and NO ₓ from output were 14.33 and 5.97%, respectively, but pollution abatement technology presented the most obvious mitigating effects (− 10.11 and − 7.92%), followed by the mitigating effects of clean production technology (− 2.35 and − 3.7%), and the mitigation from the structural effect was the weakest (− 1.16 and − 1.25%, respectively), which meant pollutant reduction policies related to industrial structure adjustment should be a long-term measure for the two discharges. In addition, the sub-sectors of I20 (manufacture of raw chemical materials and chemical products), I24 (manufacture of non-metallic mineral products), and I26 (smelting and pressing of non-ferrous metals) were the major contributors to both discharges. Thus, these sub-sectors should be given priority consideration when designing mitigation-related measures. Last, some particular policy implications were recommended for reducing the two discharges, including that the government should seek a technological discharge reduction route.

In recent years, the treatment of wastewater treatment plant (WWTP) effluent has gained increasing attention. However, researches on the relationships between nitrogen forms and nitrogen removal efficiency are very limited. Based on the fact that the nitrogen forms in the WWTP effluent may vary as the season changes, the nitrogen removal efficiencies of an integrated ecological floating bed (IEFB) was studied under different influent nitrogen forms. In addition, the effects of sediments in the system were also quantified during the experiment. Results showed that the total nitrogen (TN) removal rates of the IEFB were 25.61 ± 5.72% and 60.03 ± 7.00%, respectively, when the main influent nitrogen forms are nitrate and ammonia. The sediments in the system also played vital roles in the removal processes: when the sediments were covered with a polyethylene membrane, the total nitrogen (TN) removal rate of the system dropped from 27.86 ± 5.53% to 14.78 ± 4.97%, and the total phosphorus (TP), from 58.77 ± 6.20% to 33.51 ± 25.52%.

A novel quaternary ammonium polyethylene nonwoven fabric for removing chromium ions from water was prepared via radiation-induced grafting of glycidyl methacrylate and further modification with N,N′-dimethylethylenediamine. The structural and morphological characteristics of the adsorbent were analyzed using Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential thermogravimetry (TG/DTG), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The influences of several principal factors, including pH value, initial Cr(VI) concentration, contact time, and coexisting anions (including SO₄²⁻, CO₃²⁻, NO₃⁻, PO₄³⁻, and Cl⁻), on adsorption performance were investigated via batch tests. The results showed that the optimum removal efficiency was 99.2% at pH 3 and the maximum adsorption quantity for Cr(VI) at 25 °C was 336 mg/g. The adsorption kinetic parameters were better fitted with the pseudo-second-order kinetic model, and the equilibrium data were described very well by the Freundlich isotherm model. Furthermore, the as-synthesized adsorbent exhibited excellent regeneration and recyclability while maintaining high adsorption performance after five adsorption/desorption cycles.

The paper investigates the linkage of carbon dioxide (CO₂) emissions, per capita real output, share of non-fossil electricity consumption, and trade openness in South Korea from 1971 to 2013. The empirical results indicate that the environmental Kuznets curve (EKC) is supported by autoregressive distributed lag (ARDL) test. Both short- and long-run estimates indicate that increasing non-fossil electricity consumption can mitigate environmental degradation, and increasing trade aggravates carbon dioxide emissions. By Granger causality, long-run causalities are found in both equations of CO₂ emissions and trade openness, as well as exports and imports. In the short-run, evidence indicates feedback linkage between output and trade, unidirectional linkages from trade to emissions, from emissions to output, and from output to non-fossil electricity use. Therefore, South Korea should strengthen the sustainable economy, consume clean energy, and develop green trade.

Presence of industrial dyes and heavy metal as a contaminant in environment poses a great risk to human health. In order to develop a potential technology for remediation of dyes (Reactive remazol red, Yellow 3RS, Indanthrene blue and Vat novatic grey) and heavy metal [Cu(II), Ni(II), Cd(II), Zn(II), Cr(VI) and Pb(II)] contamination, present study was performed with entomopathogenic fungi, Beauveria bassiana (MTCC no. 4580). High dye removal (88–97%) was observed during the growth of B. bassiana while removal percentage for heavy metals ranged from 58 to 75%. Further, detailed investigations were performed with Pb(II) in terms of growth kinetics, effect of process parameters and mechanism of removal. Growth rate decreased from 0.118 h⁻¹ (control) to 0.031 h⁻¹, showing 28% reduction in biomass at 30 mg L⁻¹ Pb(II) with 58.4% metal removal. Maximum Pb(II) removal was observed at 30 °C, neutral pH and 30 mg L⁻¹ initial metal concentration. FTIR analysis indicated the changes induced by Pb(II) in functional groups on biomass surface. Further, microscopic analysis (SEM and atomic force microscopy (AFM)) was performed to understand the changes in cell surface morphology of the fungal cell. SEM micrograph showed a clear deformation of fungal hyphae, whereas AFM studies proved the increase in surface roughness (RSM) in comparison to control cell. Homogenous bioaccumulation of Pb(II) inside the fungal cell was clearly depicted by TEM-high-angle annular dark field coupled with EDX. Present study provides an insight into the mechanism of Pb(II) bioremediation and strengthens the significance of using entomopathogenic fungus such as B. bassiana for metal and dye removal.

While essential to food production, nitrogen (N) fertilizers in agricultural ecosystems are also important sources of environmental pollution nationally and globally. The environmental impact of three N fertilization levels (30, 60, and 90 kg ha⁻¹) plus a non-N control (0 kg ha⁻¹) in growing three rice cultivars (cv. Hashemi, cv. Alikazemi, and cv. Khazar) were assessed for 2 years in northern Iran, with the methodology of the life cycle assessment (LCA). The impact categories evaluated in this study were global warming, acidification, terrestrial eutrophication, and depletion of fossil, phosphate, and potassium resources. Over cultivars, no use of N fertilizer provided the lowest grain yield (2194 kg ha⁻¹), whereas the N rates of 60 and 90 kg ha⁻¹ increased grain yield by 52.9 and 66.9%, respectively. Over N rates, cv. Khazar produced the highest grain yield (3415 kg ha⁻¹) and cv. Hashemi the lowest (2663 kg ha⁻¹). On-farm (foreground) emissions were higher than off-farm (background) emissions in most impact categories. The maximum value of environmental index (1.33) was observed for cv. Hashemi with 90 kg N ha⁻¹, while the minimum value (0.38) was observed for cv. Khazar without N fertilization. Moreover, cv. Khazar showed the lowest resource depletion index (0.44) with 90 kg N ha⁻¹, whereas cv. Hashemi with no use of N showed the maximum value (0.96). Over cultivars, high N rates imposed drastic impact to the categories acidification and terrestrial eutrophication. However, selection of high-yielding cultivars significantly alleviated the impact to most categories. Fertilization that enables optimal yields, in accordance with the nutrient requirements of crops, ensures the most efficient land use and sustainable rice production.

The most commonly used method of operating landfills more sustainably is to promote rapid biodegradation and stabilization of municipal solid waste (MSW) by leachate recirculation. The present study is an application of computational fluid dynamics (CFD) to the 3D modeling of leachate recirculation in bioreactor landfills using vertical wells. The objective is to model and investigate the hydrodynamic and biochemical behavior of MSW subject to leachate recirculation. The results indicate that the maximum recirculated leachate volume can be reached when vertical wells are set at the upper middle part of a landfill (H W/H T = 0.4), and increasing the screen length can be more helpful in enlarging the influence radius than increasing the well length (an increase in H S/H W from 0.4 to 0.6 results in an increase in influence radius from 6.5 to 7.7 m). The time to reach steady state of leachate recirculation decreases with the increase in pressure head; however, the time for leachate to drain away increases with the increase in pressure head. It also showed that methanogenic biomass inoculum of 1.0 kg/m³ can accelerate the volatile fatty acid depletion and increase the peak depletion rate to 2.7 × 10⁻⁶ kg/m³/s. The degradation-induced void change parameter exerts an influence on the processes of MSW biodegradation because a smaller parameter value results in a greater increase in void space.