This study investigated invasive Ambrosia artemisiifolia from five localities with different levels of anthropogenic pollution in order to determine the potential for accumulation of trace metals and metaloids. Physical characteristics of the soil are presented, together with concentrations of As, B, Ba, Ca, Cd, Co, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sb, Sr, and Zn in both plant and soil. The tested samples displayed considerable differences in element concentrations, depending on the level of anthropogenic activities, with the highest concentrations of elements observed in samples from Stolice and Piskanja, the sites with most intensive human influence. A trend of shoot accumulation can be observed in A. artemisiifolia, but without hyperaccumulation, along with lower root concentrations in almost all analyzed samples. This may pose an additional environmental risk, as accumulated elements can spread to other components of the ecosystem. While A. artemisiifolia acumulates a high and even toxic rate of B in shoots regardless of boron concentration in soil, there is a high correlation of Ba, Pb, and Zn concentrations in species shoots with their respective concentration in the soil. Successful colonization of both natural and anthropogenically polluted habitats indicates high tolerance of A. artemisiifolia, which complements its wide environmental amplitude.

This article investigates the effects of real income, trade openness, and energy consumption on the ecological footprint using a panel data of 13 Asian countries over the 1973–2014 period. The empirical findings suggest that the panel variance-ratio test confirms the existence of a long-run equilibrium relationship among ecological footprint real income, trade openness, and energy consumption. Results from panel pooled mean group estimates confirm that the long-run elasticity of real income, trade openness, and energy consumption is 0.16, −0.07, and 0.51, respectively. The real income and energy consumption have a positive impact on the ecological footprint. There are three bidirectional causal relationships that were found between ecological footprint and real income; between energy consumption and ecological footprint; and between trade openness and ecological footprint. In addition, three unidirectional causalities can be found: a unidirectional causality running from real income to trade openness; from real income to energy consumption; and from trade openness to energy consumption. Those causal relationships show that economic indicators are highly related to ecological footprint. The findings recommend that various governments should fund more in renewable energy and efficiency upgrade and continue sustaining their growth without hurting the environment.

An outdoor pot experiment was conducted to study the control effects of zero-valent iron (Fe⁰) on arsenic (As) uptake by rice (Oryza sativa L.) and its relationship with iron (Fe), As, and phosphorus (P) in soil and Fe plaque. The results showed that Fe⁰ reduced total and inorganic As in root, husk, and grain but had no significant effect in straw, and almost all contents of As species in rice plant were decreased by Fe⁰. Total As contents in root, husk, and grain were decreased (54.8%, 39.9%, 30.1%), while reductions of inorganic As were 59.2%, 30.8%, and 30.3%, respectively. The inorganic As in all issues of rice plant was dominated and higher than 70% of total As. The analysis showed that the main mechanisms of Fe⁰ on reduction of As in rice were (i) Fe⁰ stabilized the active As in soil, (ii) Fe⁰ increased the quantity of Fe plaque that hindered the transport of arsenic in soil to rice plant, and (iii) phosphorus adsorbed on the Fe plaque reduced As into rice root by the competitive mechanism between phosphorus and arsenic. Graphical abstract

Microbial fuel cell (MFC) is a green technology that converts the stored chemical energy of organic matter to electricity; therefore, it can be used for wastewater purification and energy production simultaneously. In this study, three kinds of dairy products, including milk, cheese water, and yogurt water, were mixed with Acid orange 7 (AO7) as the model wastewater and used as the anolyte of an MFC. The capability of the system in energy production and dye removal was also investigated. The FESEM images were used to investigate the biofilms attachment to the anodes. Moreover, the polarization curves, electrochemical impedance spectroscopy, cyclic voltammetry (CV), voltage–time profiles, and coulombic efficiency were used to evaluate the electrochemical activity of the MFCs. Based on the CV results, the biofilm formation significantly improved the electrochemical activity of the electrodes. Maximum power density, voltage, and coulombic efficiency were obtained as 44.05 mW.m⁻², 332.4 mV, and 1.76%, respectively, for cheese water + AO7 anolyte, but the milk + AO7 MFC produced a stable voltage for a long time and its performance was similar to the cheese water + AO7 anolyte. Maximum COD removal and decolorization efficiencies were obtained equal to 84.57 and 92.18% for yogurt water + AO7 and cheese water + AO7 anolytes, respectively.

Selenium (Se) is an essential metalloid element for mammals. Nonetheless, both deficiency and excess of Se in the environment are associated with several diseases in animals and humans. Here, we investigated the interaction of Se, supplied as selenate (Se⁺⁶) and selenite (Se⁺⁴), with phosphorus (P) and sulfur (S) in a weathered tropical soil and their effects on growth and Se accumulation in Leucaena leucocephala (Lam.) de Wit. The P-Se interaction effects on L. leucocephala growth differed between the Se forms (selenate and selenite) supplied in the soil. Selenate was prejudicial to plants grown in the soil with low P dose, while selenite was harmful to plants grown in soil with high P dose. The decreasing soil S dose increased the toxic effect of Se in L. leucocephala plants. Se tissue concentration and total Se accumulation in L. leucocephala shoot were higher with selenate supply in the soil when compared with selenite. Therefore, selenite proved to be less phytoavailable in the weathered tropical soil and, at the same time, more toxic to L. leucocephala plants than selenate. Thus, it is expected that L. leucocephala plants are more efficient to phytoextract and accumulate Se as selenate than Se as selenite from weathered tropical soils, for either strategy of phytoremediation (decontamination of Se-polluted soils) or purposes of biofortification for animal feed (fertilization of Se-poor soils).

The optimisation tests of sodium percarbonate (biocide) with the formula 2Na₂CO₃·3H₂O₂, as a green oxidizing agent for biological deactivation of chicken manure, were carried out. The microbiological analysis of fresh manure which consisted of the enumeration of bacteria, fungi and eggs of intestinal parasites showed that the number of bacteria Enterobacteriaceae, i.e. 8.3 log₁₀CFU/g, and the bacteria E. coli, i.e. 6.96 log₁₀CFU/g, exceeded the required level in organic fertilizers. The Response Surface Methodology for three input parameters (biocide concentration, temperature and time) on the value of E. coli bacteria was applied. The obtained values of the coefficient of the multiple correlation R² and the adjusted coefficient Rₐdⱼ² were 0.90 and 0.75, respectively, which indicate a good fit of the data obtained with the model and the experimental data. It was concluded that a decrease in the count of the analysed microorganisms followed an increase in the sodium percarbonate concentration, an increase in the temperature and a longer time of contact of the manure sample with the biocide. The content of bioavailable macronutrients (P, N, Ca, Mg, K) in water extracts of fresh chicken manure before and after its biological deactivation was determined with the ICP-OES method. The concentration of phosphorous in fresh manure extract was 310 mg/l and decreased after addition of one of the following agents: 7.5 wt.% of sodium percarbonate to 66.9 mg/l or 3.0 wt.% of traditional hygienizing agent, i.e. calcium hydroxide to 5.7 mg/l.. The results of the concentration of N in chicken manure with sodium percarbonate was also higher than in sample with calcium hydroxide, i.e. 1040.0 mg/l and 860.0 mg/l, respectively. While the addition of 2Na₂CO₃·3H₂O₂ decreased the content of Ca, Mg and K in fresh chicken manure.

The work aims to study the removal of crystal violet (CV) using laterite soil with surface modification by surfactant (SML). Surface modification of laterite soil was conducted by pre-adsorption of sodium dodecyl sulfate (SDS) at pH 4 and low ionic strength to enhance removal of CV. The effective conditions for CV removal through adsorption technique using SML were optimized and found to be contact time 60 min, pH 6, adsorbent dosage 5 mg/mL, and 5 mM NaCl as background electrolyte. The highest removal of CV using SML reached to 86.5% under optimum conditions. We used Fourier transform infrared spectroscopy (FT-IR) to evaluate the change of surface vibrational groups of laterite after SDS pre-adsorption and after CV adsorption while the different charged surface was determined by ζ potential measurements. The CV adsorption onto SML increased when increasing ionic strength from 1 to 10 mM. Nevertheless, at high ionic strength, this trend is reversal due to desorption of SDS from laterite surfaces. Adsorption isotherms of CV onto SML at different NaCl concentrations were tried to fit by Langmuir, Freundlich, and a two-step adsorption models. The adsorption kinetics were in good agreement with pseudo-second-order model. The removal efficiency of CV after four regenerations still reached higher than 85%. On the basis of adsorption isotherms, charged surface change by ζ potential and surface modification by FT-IR, we suggest that CV adsorption onto SML was induced by both non-electrostatic and electrostatic interactions. We also demonstrate that SML is a novel, reusable, and low-cost adsorbent for cationic dye removal from aqueous solution.

Due to the rapid growth in the heavy metal-based industries, their effluent and local dumping have created significant environmental issues. In the past, typically, removal of heavy metals was handled by reverse osmosis and ion exchange techniques, but these methods have many disadvantages. Therefore, extensive work into the development of improved techniques has increased, especially for heavy metal removal. Many countries are currently researching new materials and techniques based on nanotechnology for various applications that involve extracting heavy metals from different water sources such as wastewater, groundwater, drinking water and surface water. Nanotechnology provides the possibility of enhancing existing techniques to tackle problems more efficiently. The development in nanotechnology has led to the discovery of many new materials such as magnetic nanoparticles. These nanoparticles demonstrate excellent properties such as surface-volume ratio, higher surface area, low toxicity and easy separation. Besides, magnetic nanoparticles can be easily and efficiently recovered after adsorption compared with other typical adsorbents. This review mainly emphasises on the efficiency of heavy metal removal using magnetic nanoadsorbent from aqueous solution. In addition, an in-depth analysis of the synthesis, characterisation and modification approaches of magnetic nanoparticles is systematically presented. Furthermore, future opportunities and challenges of using magnetic particles as an adsorbent for the removal of heavy metals are also discussed.

With increasing attentions on climate change, solid wastes, over-tourism, and improved environmental awareness worldwide, eco-tourism has been widely promoted worldwide. This requires that governmental agencies at different levels should prepare appropriate policies to facilitate eco-tourism and local communities should take necessary actions to preserve their natural resources, protect their environment, and support sustainable tourism. Academically, literatures on eco-tourism have increased faster with an annual growth rate of 10–30% during the recent years. Under such a circumstance, it is important to conduct a comprehensive review so that research progress on eco-tourism can be summarized and future research directions can be identified. Based on 1771 publications published during 2001–2018, a systematic method combining bibliometric analysis and network analysis is applied in this study to uncover the dynamic trends, academic collaboration, and research hotspots related with eco-tourism. Results show that the total number of relevant publications has gradually increased. Key journals include Journal of Hospitality and Tourism Management, Annals of Tourism Research, Conservation Biology, and Biological Conservation. Authors from USA have the most publications and international co-authorships, while the most influential institution is the Chinese Academy of Science. Moreover, research keywords have been identified, including eco-tourism, management, biodiversity, national park, sustainability, and sustainable tourism. Research findings of this study provide valuable insights to further improve eco-tourism research so that this emerging research field can be proactively fostered.

The contents of total arsenic (tAs), inorganic arsenic (iAs), Cd, Cr, Cu, Mn, Ni, Pb, Sb, and Zn in 135 rice grain samples from Zijiang River basin were determined, and the probabilistic distribution of noncarcinogenic and carcinogenic risks associated with ingesting locally produced rice was determined by Monte Carlo simulation. Further, multivariate statistical analysis was used to analyze the potential sources of the heavy metals in rice grains. The average concentrations of the heavy metals in rice grains were ranked as follows: Mn (17.314 mg/kg) > Zn (16.043 mg/kg) > Cu (2.013 mg/kg) > Ni (1.332 mg/kg) > Cr (0.571 mg/kg) > Cd (0.283 mg/kg) > tAs (0.241 mg/kg) > Pb (0.145 mg/kg) > Sb (0.027 mg/kg). These heavy metals were significantly enriched in some rice grain samples. The analysis of potential sources indicated that As, Pb, Sb, and Zn were mainly derived from mining and smelting and agricultural activities; Cd, Cu, Mn, and Ni were mainly derived from the agricultural activities; Cr were mainly derived from the natural source. The results of Monte Carlo simulation indicated that ingestion of rice grown in the area may pose health risks for children, adult males, and adult females. The noncarcinogenic risks were mainly from As, Cd, Mn, Ni, and Sb, and the carcinogenic risk was mainly from As, Cd, and Ni. This study could provide basic information for land management and rice intake in the study area.