Chlorine added to drinking water as a disinfectant is a concern of this generation. This is because chlorine reacts with dissolved organic compounds to form polychlorinated complexes that are carcinogenic. Available methods for the removal of chlorine and chlorinated compounds include adsorption, precipitation, electrolysis and ozonation, but some result in the generation of more toxic compounds. This study explored the use of zero-valent bimetals Fe/Zn for the degradation of chlorinated compounds in water which did not generate toxic by-products. The zero-valent bimetallic material was anchored on a polystyrene waste material as a green method of cleaning the environment. It was prepared through nitration, amination, complexation and reduction. The resulting solid material was characterised using Fourier transform infrared (FTIR). The material was also characterised using XPS which confirmed the presence of metals anchored on the material through complexation. The metals were also found to be present upon reduction to zero valence and even after the degradation process of the chlorinated organic compounds. It was then applied for the removal process. Optimization parameters such initial halide concentration, effect of time and bimetal dosage variation were established using synthetic water samples. It was found that the substrate-anchored ZVB material had a degradation capacity of 4.532, 5.362 and 4.513 μmol l⁻¹ for 1,2-dichloroethane, 2-chloro-2-methylpropane and 1-chlorobutane, respectively. The material was then applied on real samples sourced from Nairobi. Quantification of chlorine was done using potentiometric methods and the results confirmed that the degradation was first order. The degradation capacities were found to be 2.37 ± 0.01, 3.55 ± 0.01 and 3.72 ± 0.01 in that order.

This work investigates the behavior of atrazine (AT) and its degradation products deethylatrazine (DEA) and deisopropylatrazine (DIA) in oxisol samples. The study was carried out at different depths of maize culture soil under no-till management for up to 180 days. Additionally, controlled laboratory experiments were performed in open flasks in the absence of sunlight or in closed flasks at 4 °C. Higher AT dissipation occurred in the in the field as compared with the samples evaluated under controlled conditions, which indicated that environmental conditions might degrade AT. Interestingly, DEA and DIA levels were low, which suggested that leaching and runoff processes, formation of other degradation products, or even AT mineralization took place. Residual AT, DEA, and DIA were detected in the oxisol samples after 180 days depending on the initial amount of AT in the soil. This study has shown that straw plays a relevant role in AT retention and significantly contributes to DEA and DIA formation. At 180 days, straw samples contained AT concentrations near 100 μg kg⁻¹ and concentrations of the more leachable DEA and DIA close to 50 μg kg⁻¹ even under the influence of sunlight and rainfall. A preliminary analysis of natural water samples near the investigated region showed that DEA and DIA were absent and that AT concentrations were high, which pointed to the need for more detailed evaluation.

The globalization of agricultural trade has dramatically altered global nitrogen flows by changing the spatial pattern of nitrogen utilization and emissions at a global scale. As a major trading country, China uses a large amount of nitrogen, which has a profound impact on global nitrogen flows. Using data on food production and trade between China and 26 other countries and regions, we calculated nitrogen inputs and outputs in food production ecosystem in each country. We estimated nitrogen flows in international food trade and analyzed their impact on nitrogen pollution in China. We divided nitrogen flows into embodied and virtual nitrogen flows. Embodied nitrogen is taken up by the plant and incorporated into the final food product, whereas virtual nitrogen is lost to the environment throughout the food production process and is not contained in the final food product. Our results show that China mainly imports food products from America and Asia, accounting for 95 % of all imported food. Asia (mainly Japan) and Europe are the main exporters of food from China, with Japan and the EU accounting for 17 and 10 % of all exported food, respectively. Total nitrogen inputs and outputs in food production in China were 55,400 and 61,000 Gg respectively, which were much higher than in other countries. About 1440 and 950 Gg of embodied and virtual nitrogen respectively flow into China through the food trade, mainly from food-exporting countries such as the USA, Argentina, and Brazil. Meanwhile, 177 and 160 Gg of embodied and virtual nitrogen respectively flow out of China from the export of food products, mainly to Japan. China’s net food imports have reduced 720 and 458 Gg for nitrogen utilization and outputs, respectively, which accounted for 1.3 and 0.78 % of total nitrogen inputs and outputs in China. These results suggest that food trade in China has a profound effect on nitrogen flows and has greatly reduced environmental impacts on nitrogen pollution in China.

Indoor air pollution significantly influences personal exposure to air pollution and increases health risks. Nitrogen dioxide (NO₂) is one of the major air pollutants, and therefore it is important to properly determine indoor concentration of this pollutant considering the fact that people spend most of their time inside. The aim of this study was to assess indoor and outdoor concentration of NO₂ during each season; for this purpose, passive sampling was applied. We analyzed homes with gas and electric stoves to determine and compare the concentrations of NO₂ in kitchen, living room, and bedroom microenvironments (MEs). The accuracy of passive sampling was evaluated by comparing the sampling results with the data from air quality monitoring stations. The highest indoor concentration of NO₂ was observed in kitchen ME during the winter period, the median concentration being 28.4 μg m⁻³. Indoor NO₂ levels in homes with gas stoves were higher than outdoor levels during all seasons. The concentration of NO₂ was by 2.5 times higher in kitchen MEs with gas stoves than with electric stoves. This study showed that the concentration of NO₂ in indoor MEs mainly depended on the stove type used in the kitchen. Homes with gas stoves had significantly higher levels of NO₂ in all indoor MEs compared with homes where electric stoves were used.

Lignin-derived methoxyphenols (MPs) with Fe³⁺-reducing activity were used as potential mediators to increase the decolorization of dyes by classical Fenton (Fe²⁺/H₂O₂) and Fenton-like reactions (Fe³⁺/H₂O₂). In this study, several MPs such as vanillin, vanillic alcohol, syringaldehyde, ferulic, vanillic, and syringic acids were evaluated. The results showed that all MPs displayed similar prooxidant activities in the decolorization of methylene blue, chromotrope 2R, methyl orange, and phenol red. For example, the reaction performed with Fe³⁺/H₂O₂ decolorized 27 % of chromotrope 2R, whereas the treatments with Fe³⁺/H₂O₂/MP decolorized around 70 % of the same dye after 60 min. For Fe²⁺/H₂O₂ systems, two stages of decolorization were visibly observed. In the first stage, the MPs inhibited the treatments, and then they increased the decolorization rate in the second stage. Prooxidant and antioxidant properties were observed for decolorization of methylene blue performed in the presence of low and high concentrations of vanillin, respectively. Overall, the MPs increased dye decolorization without increasing the consumption of H₂O₂.

Textile wastewater was treated by adsorption in batch and column systems using electrochemically modified montmorillonite clay and activated carbon. Textile wastewater was obtained from a denim manufacturing process; according to the characterization of wastewater, non-biodegradable organic matter was found and it limits the application of biological treatments, and then an alternative method was evaluated. The adsorption process was performed with natural and modified materials; iron-modified montmorillonite was prepared at pH 7 using iron electrodes and activated carbon was treated with copper electrodes at pH 2, and 10–12 % of iron and copper respectively were found in the modified materials. Adsorption kinetics and isotherms of chemical oxygen demand (COD), color, and total organic carbon (TOC) were evaluated; the adsorption capacities for color were 50, 37, and 44 U PtCo/g for natural clay, activated carbon, and iron-modified clay, respectively. Adsorption kinetics of COD, color, and TOC data were best adjusted to Elovich model and isotherms data to Freundlich model, indicating chemisorption on heterogeneous materials. The regeneration of materials was performed in the presence and absence of hydrogen peroxide. Continuous systems were evaluated for color and TOC. Fe-modified clay was the best adsorbent, and data were best adjusted to Thomas and Yoon-Nelson models.

Volatile organic compounds (VOCs) decomposition by non-thermal plasma (NTP) has been receiving increasing attention from the scientific communities due to its advantages of easy operation, high efficiency, energy saving, and non-secondary pollution. But most of the researches are doing experiments and existing experiment methods cannot observe the micro physical and chemical processes. In order to make up for the deficiency of the experiment, herein, a numerical method was developed to analyze the decomposition behavior of HCN, C₃H₃N, C₃H₈, C₃H₆, CO, and NO in the VOCs treatment by NTP. Results indicated that increasing electron density or energy was beneficial to VOCs decomposition, but when the electron density and energy was too high, the promotion would be weakened. The influences of initial concentration of O₂ and H₂O on different VOCs decomposition were totally different. The increase of initial concentration of oxygen was beneficial to the decomposition of HCN, C₃H₈, CO, and NO, but the high concentration of oxygen could promote to generate C₃H₆ at the initial reaction stage. The decomposition of HCN and C₃H₃N are not restricted by dry or wet conditions, but the increase of the concentration of water vapor is advantageous to the decomposition of C₃H₈, CO, and NO. Graphical Abstract ᅟ

We conducted a field experiment to determine whether application of biosolids (municipal sewage sludge) to degraded areas of the Brazilian Atlantic rainforest had the potential to contaminate native forest species with trace metals in the sandy soils of the region. Treatments consisted of 0, 2.5, 5, 10, 15, and 20 dry Mg biosolids ha⁻¹, with nine native pioneer, secondary, and climax tree species assessed for metal uptake: capixingui, aroeira-pimenteria, canafístula, cedro-rosa, mutamba, angico-vermelho, copaíba, jatobá, and jequitibá. Biosolid application did not have a statistically significant effect on metal concentrations in soil, and Cd was the only metal with increased availability. No increased metal uptake was seen in tree foliage sampled at 6 and 12 months after application. Additional longer-term study is recommended; however, the results of this study indicate biosolids could be used in Atlantic rainforest reclamation in degraded sandy soils with little impact on soil accumulation and tree uptake of trace metals.

This study evaluated the seed germination and dry mass accumulation of five plant species (Brassica napus L., Brassica rapa L., Celosia cristata L., Tagetes erecta L., and Calendula officinalis L.) grown in five mine tailings collected from Zacatecas, Mexico. Sampled mines were El Bote, Noria de San Pantaleon, Noria de Angeles, Vetagrande, and El Bordo-El Lampotal, in which Pb (3.9–69.7 mg kg⁻¹), As (0.7–26.2 mg kg⁻¹), Hg (0.05–0.10 mg kg⁻¹), and Au (0.01–0.02 mg kg⁻¹) were detected. The most abundant elements at each mine site were as follows: Pb and Au (3.9 and 0.023 mg kg⁻¹, respectively) for El Bote; As, Pb, and Hg (7.4, 6.1, and 0.10 mg kg⁻¹, respectively) for the Noria de San Pantaleon; Pb, As, and Hg (69.7, 26.2, and 0.08 mg kg⁻¹, respectively) for Noria de Angeles; Pb (20.8 mg kg⁻¹) for Vetagrande; and Pb (5.3 mg kg⁻¹) for El Bordo-El Lampotal. Both Noria de Angeles and Vetagrande mine tailings had high values of sodium, sulfates, and electrical conductivity, chemical properties that impaired seed germination and dry mass accumulation. Regardless the mining tailings, B. napus showed high seed germination (66 %), tolerance, growth, and total dry mass accumulation (0.041 g). Either B. napus or C. cristata has good potential for stabilizing or recovering metals from mine tailings.

Accumulation of divalent manganese (Mn) and its toxicity in the green alga Scenedesmus quadricauda was studied at circumneutral pH (6.5). A comparison of two applied concentrations (10 or 100 μM) of MnCl₂, MnSO₄, and Mn(NO₃)₂ indicated that mainly sulfate evoked higher Mn accumulation. On the other hand, nitrate rather depleted antioxidative enzyme activities (APX, CAT, SOD), leading to an increase in ROS formation as proven by fluorescence microscopy. Subsequent experiments revealed that increase in pH (from 4.5 to 9.5) increased also Mn content but typically depleted amounts of reduced glutathione and phytochelatin 2. We also measured the size of particles formed from the manganese salts at pH 9.5. Competitive experiment between Ca/K salts (CaCl₂, CaSO₄, Ca(NO₃)₂, KCl, K₂SO₄, KNO₃) and Mn (as Mn sulfate) showed a negative relation between Ca and Mn amount but KNO₃ stimulated Mn accumulation. Microscopy revealed that mainly K salts elevated plasma membrane damage (Acridine orange staining). Data indicate that not only pH but also accompanying anion affects Mn accumulation and that Ca salts may affect Mn toxicity.