The level of radioactivity in the soil has been increasing unpredictably due to the human uranium mining exploitation of uranium over the past 100 years. Remediation of metals in actual soil confronts many challenges, remaining poorly understood. This study intends to investigate the concentrations and distributions of U, Cd, Zn, Pb, and Cu in soils surrounded by a uranium mill tailing pond. Furthermore, a phosphorus-modified bio-char was prepared in order to determine its role in immobilizing uranium in soil samples. Results show that the contents of U and Pb are much higher than that of the background values, due to the influence of the uranium mill tailing pond. Phosphorus can enhance the immobilization efficiency of U, Cd, Pb, and Cu in soil samples. The concentration of uranium in the leaching supernatant of phosphorus-modified bio-char group is lower than that of control and unmodified bio-char groups due to the fact that the biosorption occurred in the exterior surface of the biomass, which imply that phosphorus-modified bio-char is a potential immobilization material to reduce the leaching rate of metals. These findings can provide references for remediation technology of metals in natural soil.

The toxic impacts of CuO nanoparticles (NPs) on the marine phytoplankton Nannochloropsis oculata were evaluated by measuring a number of biological parameters. Exposure to different concentrations of CuO-NPs (5–200 mg/L) significantly decreased the growth and content of chlorophyll a of N. oculata. The results showed that CuO-NPs were toxic to this microalga with a half maximal effective concentration (EC50) of 116.981 mg/L. Exposure to CuO-NPs increased the hydrogen peroxide (H₂O₂) content and induced the membrane damages. Moreover, the concentration of phenolic compounds was increased, while the levels of carotenoids were markedly decreased in comparison to the control sample. The activity of catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and lactate dehydrogenase (LDH) enzymes significantly was increased in response to CuO-NPs treatments. These results indicated that CuO-NPs stimulated the antioxidant defense system in N. oculata to protect the cells against the oxidative damages. The Fourier-transform infrared spectroscopy (FTIR) analyses showed that the main functional groups (C=O and C–O–C) interacted with CuO-NPs. The images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the cell membrane damage and the change of cell wall structure which may be contributed to the nanotoxicity. These findings may provide additional insights into the mechanisms of cytotoxicity induced by CuO-NPs.

This article studies the price competition and cooperation in a duopoly that is subjected to carbon emissions cap. The study assumes that in a departure from the classical Bertrand game, there is still a market for both firms’ goods regardless of the product price, even though production capacity is limited by carbon emissions regulation. Through the decentralized decision making of both firms under perfect information, the results are unstable. The firm with the lower maximum production capacity under carbon emissions regulation and the firm with the higher maximum production capacity both seek market price cooperation. By designing an internal carbon credits trading mechanism, we can ensure that the production capacity of the firm with the higher maximum production capacity under carbon emissions regulation reaches price equilibrium. Also, the negotiation power of the duopoly would affect the price equilibrium.

Investigations of deleterious effects on non-target species, including earthworms, have been conducted for a number of pesticides, but there is a need for additional assessments of potential adverse effects. In the present study, the acute toxicity of eight pesticides to the earthworm Eisenia andrei was assessed and compared. The exposures were conducted using the filter paper contact toxicity method. Based on the 48-h LC₅₀ values, one pesticide was classified as supertoxic (combined fungicide containing difenoconazole and fludioxonil), four as extremely toxic (combined herbicide containing pethoxamide and terbuthylazine, combined fungicide containing fluopyram and tebuconazole, fungicide containing pyrimethanil, and combined fungicide containing thiram and carboxin), two as very toxic (combined fungicide containing flutriafol and thiabendazole, and herbicide containing fluroxypyr-meptyl), and one as moderately toxic (insecticide containing thiamethoxam). Additionally, effects of pesticides on the multixenobiotic resistance (MXR) activity were measured. Results showed that four pesticides caused significant effects with a recorded inhibition of the activity, which can consequently lead to a higher toxicity due to longer retention of the pesticides in the cells. Finally, for three chosen pesticides, gene expression of cat, sod, and gst was measured, and significant changes were observed. The obtained results show that earthworms could be significantly affected by pesticides commonly used in agriculture.

This paper investigated the photodegradation of oxytetracycline (OTC) in the presence of dissolved organic matter (DOM) and chloride ions, which is relevant to the estuary environment. The separate effects of chloride ions and DOM on the photodegradation of OTC were first studied, and then, the combined effects were studied. The photodegradation of OTC showed a tendency to decrease with increasing DOM levels: a low concentration of DOM (< 2 mg/L) enhanced the degradation of OTC, and a high concentration of DOM (> 5 mg/L) inhibited it. The addition of chloride ions (10–500 mmol/L) to DOM solutions (20 mg/L) significantly increased the degradation rate of OTC. The observed promotion effects may be a consequence of the participation of reactive chlorine species. Quenching experiments verified that the main active species in the presence of chloride ions and DOM are radicals including Cl•/Cl₂•⁻ and HO•. These results indicate a promotion of OTC degradation in saline water compared with fresh water, and this finding is important to better understand the environmental fate of OTC in estuarine and coastal waters.

Volatile organic compounds (VOC) are air pollutants usually found in urban and industrial areas. Heterogeneous photocatalysis is an interesting technique used to degrade these compounds. Several approaches may enhance this process; some studies have shown higher VOC conversions by adding ozone to the experimental system, once ozone increases the number of reactive radicals in the reaction. In this context, this work studied the conversion of cyclohexane and toluene by heterogeneous photocatalysis in gas phase, in the presence of titanium dioxide (TiO₂), UV light, and different concentrations of ozone. For fixed space times from 13.1 to 48.8 s, an average increase of 9% was reached in cyclohexane conversion when comparing the system with maximum concentration of ozone (0.8%) and the system without it. In addition, difference of less than 2% in the conversion of cyclohexane with different moisture fractions was observed. Toluene photodegradation was also analyzed in the presence of ozone and although the conversion was only about 40% for the space time of 25 s, this result was maintained during 4 h of experiment, with no catalyst deactivation as usually reported in the literature for aromatic compounds. Based on the results, ozone addition is an advantageous technique to improve the photodegradation of VOC.

Crops are the main source of toxic cadmium for humans due to uptake from naturally or anthropogenically polluted soils. Chronic Cd ingestion causes kidney, liver, and skeletal damage along with an increased risk of cancer. Cacao is known to accumulate Cd and may therefore be potentially harmful to human health. Consequently, cocoa production on intensely polluted soils should be avoided. Cocoa products from South America in particular often exceed the limits for Cd, but the factors that drive Cd uptake are as yet poorly studied. In this study, we measured Cd concentrations in defatted cocoa powder from unfermented seeds of 40 different trees on 20 farms in the Huánuco Region, Peru, and associated the Cd levels with the farms’ soil, field management, and nearby vegetation diversity. The mean Cd concentration found in cocoa of the study region was 2.46 mg kg⁻¹ with a range of 0.2–12.56 mg kg⁻¹. The maximum content measured was an order of magnitude higher than the allowed limit of 1.5 mg kg⁻¹ and was the highest reported so far in the literature. Soil Cd content was the most relevant driver of Cd concentration in cacao. In addition, fertilizer use caused significantly higher Cd concentration in cocoa. Higher biodiversity of herbs was positively correlated with Cd contents in cocoa. The study shows that, apart from the known correlation of soil conditions with Cd accumulation in cacao seeds, changes in fertilization and plant composition may be promising measures to counteract Cd contamination in regions with high soil Cd content.

Biotemplating method is a promising way to obtain hierarchical materials with unique morphology and property. In the current work, a novel hierarchically porous ZnAl-CLDH (calcined layered double hydroxides)/FeWO₄ had been successfully synthesized by a facile biotemplated method. The obtained samples were characterized in detail via FESEM-EDX, TEM, XRD, IR, TGA, and BET techniques. The as-synthesized ZnAl-CLDH/FeWO₄ hierarchical microspheres were composed of ZnAl-CLDH nanosheets and FeWO₄ nanoparticles. The obtained sample exhibited both high adsorption and visible-light photocatalytic activity toward Congo Red (CR) in water. It was found that the adsorption process was well described by the pseudo-second-order kinetic model and the Langmuir isotherm model, while the photocatalytic degradation process was well fitted to the first-order kinetics model. The enhanced photocatalytic performance was mainly due to the hierarchically porous structure that could offer more exposed active sites, as well as the unique energy band structure of heterostructures, that facilitated the efficient separation and transfer of photoinduced carriers and enhanced light harvesting. In addition, the as-prepared sample had quickly magnetic response and could be easily separated from water under an external magnetic field after wastewater treatment.

External carbon source was usually added to enhance denitrification efficiency for nitrogen removal in wastewater treatment. In this study, waster sludge alkaline fermentation liquid was successfully employed as an alternative carbon source for biological denitrification. The denitrification performance was studied at different C/Ns (carbon-to-nitrogen ratios) and HRTs (hydraulic retention times). A C/N of 7 and an HRT of 8 h were the optimal conditions for denitrification. The nitrate removal efficiency of 96.4% and no obvious nitrite accumulation in the effluent were achieved under the optimal conditions with a low soluble chemical oxygen demand (SCOD) level. The sludge carbon source utilization was analyzed and showed that the volatile fatty acids (VFAs) were prior utilized than proteins and carbohydrates. The excitation-emission matrix (EEM) spectroscopy with fluorescence regional integration (FRI) was adopted to analyze the compositional and variations of dissolved organic matters (DOM). Moreover, a high denitrification rate (VDN) and potential (PDN) with low heterotroph anoxic yield (YH) was exhibited at the optimal C/N and HRT condition, indicating the better denitrification ability and organic matter utilization efficiencies.

For remediating polluted soils, phytoextraction of metals received considerable attention in recent years, although slow removal of metals remained a major constraint in this approach. We, therefore, studied the effect of selected organic and inorganic amendments on the solubility of zinc (Zn), cadmium (Cd), and lead (Pb) in polluted soil and enhancing the efficacy of phytoextraction of these metals by Indian mustard (Brassica juncea cv. Pusa Vijay). For this purpose, a greenhouse experiment was conducted using a metal-polluted soil to evaluate the effect of amendments, viz. green manure (T2), EDTA (T3), sulfur (S)+S oxidizing bacteria (Thiobacillus spp.) (T4), metal-solubilizing bacteria (Pseudomonas spp.) (T5), and green manure + metal-solubilizing bacteria (T6), on solubility and bioavailability of Zn, Cd, and Pb. Distribution of metals in different soil fractions revealed that Cd content in water soluble + exchangeable fraction increased to the extent of 34.1, 523, 133, 123, and 75.8% in T2, T3, T4, T5, and T6 treatments, respectively, over control (T1). Cadmium concentrations in soil solution as extracted by Rhizon sampler were recorded as 3.78, 88.1, 11.2, 6.29, and 4.27 μg L⁻¹in T2, T3, T4, T5, and T6, respectively, whereas soil solution concentration of Cd in T1 was 0.99 μg L⁻¹. Activities of Cd (pCd²⁺) in Baker soil extract were 12.2, 10.9, 6.72, 7.74, 7.67, and 7.05 for T1, T2, T3, T4, T5, and T6, respectively. Cadmium contents in shoot were recorded as 2.74, 3.12, 4.03, 4.55, 4.68, and 4.63 mg kg⁻¹ in T1, T2, T3, T4, T5, and T6 treatments, respectively. Similar trend in Zn and Pb content with different magnitude was also observed across the different amendments. Cadmium uptake by shoot of mustard was enhanced to the extent of 125, 62.5, 175, 175, and 212% grown on T2-, T3-, T4-, T5-, and T6-treated soil, respectively, over T1. By and large, free ion activity of metals as measured by Baker soil test proved to be the most effective index for predicting Zn, Cd, and Pb content in shoot of mustard, followed by EDTA and DTPA. Among the metal fractions, only water soluble + exchangeable metal contributed positively towards plant uptake, which explained the variation in shoot Zn, Cd, and Pb content to the extent of 74, 81, and 87%, respectively, along with other soil metal fractions. Risk to human health for intake of metals through the consumption of leafy vegetable (mustard) grown on polluted soil in terms of hazard quotient (HQ) ranged from 0.64 to 1.10 for Cd and 0.11 to 0.34 for Pb, thus rendering mustard unfit for the human consumption. Novelty of the study mainly consisted of the use of natural means and microorganisms for enhancing solubility of metals in soil with the ultimate aim of hastening the phytoremediation.