Silicon (Si) is a beneficial element which was proven to enhance the tolerance of plants to excess metal in a given growth medium. However, the efficacy of Si in mitigating Cu toxicity in plants can vary between plant species and with the amount of copper (Cu) present in the soil/medium. An experiment was performed to investigate the role of Si in alleviating Cu toxicity in Tanzania guinea grass (Panicum maximum cv. Tanzania). The experimental design consisted on complete random blocks with tree replicates containing three Si rates (0, 1, and 3 mmol L⁻¹) and four Cu rates (0.3, 250, 500, and 750 μmol L⁻¹). The grass was grown for 62 days in a greenhouse under hydroponic conditions, with a total of 36 pots. Thirteen days after sowing, seedlings were transplanted to pots and grown for further 25 days, and then exposed to the set Cu rates for 7 days. The plants were also evaluated more for 30 days after the first harvesting. The results confirmed that the Si supply to Tanzania guinea grass can alleviate the effects of excessive Cu. Plant yield increased with Si supply and decreased with the increment of Cu rates in both growth periods. Copper concentration in diagnostic leaves (DL) and in roots, and Cu content in shoots and roots were higher in plants exposed to Cu of 750 μmol L⁻¹ with no Si application than in other combinations. Besides reducing Cu concentration in plant tissues, the most important Si role was reducing the transport of Cu from roots to shoots, which allowed successive harvesting. Graphical abstract

To regulate the water level and minimize the occurrence of water eutrophication in shallow lakes, dams and gates are often constructed in rivers. However, this practice may result in a deterioration of water quality in some estuaries. In the present study, using the correction of Nemerow pollution index (CNPI) and a redundancy analysis (RDA), water samples from different dammed rivers around Taihu Lake were compared to assess the pollution risk and identify the factors responsible for water eutrophication. The average total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC) concentrations, and chemical oxygen demand (CODMₙ) were 2.45 ± 2.28, 0.08 ± 0.06, 43.01 ± 18.75, and 10.78 ± 4.86 mg L⁻¹, respectively. The CNPI values indicated that approximately 76.47% of the estuarine water was moderately polluted (1 < CNPI < 7.28). A positive correlation was observed between dam construction and nutrient concentrations (e.g., rTN = 0.38, p < 0.05; rTP = 0.89, p < 0.01). Under the effects of dam construction, land use change, estuary shape, and meteorological conditions, there was a clear spatial variation of the TN concentrations. Dams that were closed all year round accelerated the TN accumulation in the water around them. The pollution risk in a trumpet-shaped estuary was higher than that in other regions (t = 2.92, p = 0.02). Endogenous release of pollutants was an important factor that may have a priming effect on algal blooms and should be given more attention. In Wuli Lake, exogenous pollution was the dominant pollutant source. A total of 74.49% of the nitrogen losses with the runoff into the estuarine water in 2018 were derived from urban domestic sewage and constructed land, with the load being 4.40 times higher than in 2000. The RDA results revealed that dam construction was the main factor (43.70%) affecting water quality, while meteorological conditions, land use types, estuary shape, and other factors contributed 56.30%. Scientific regulation and control of dam operation is important to protect the water environment of Taihu Lake.

2,2′,4,4′-Tretrabromodiphenyl ether (BDE47) is known as a typical polybrominated diphenyl ethers (PBDEs) due to its high environmental abundance, ecological toxicity, and bioaccumulation. In this study, the influences of three typical surfactants (CTAB, SDS, and TX-100) on BDE47 solubilization and degradation by the polyanionic cellulose–stabilized Pd/Fe (PAC-Pd/Fe) nanoparticles were investigated. The results showed that BDE47 solubilities increased linearly when surfactant concentrations were above their critical micelle concentrations (CMCs), and the solubilization capacities of surfactants for BDE47 followed the order of TX-100 > CTAB > SDS. The appropriate dosages of surfactants were favorable for BDE47 degradation due to enhancing solubilization and accelerating mass transfer, while excessive surfactants inhibited BDE47 degradation due to excessive and thicker micelles formed, but still higher than no surfactant. The influences of various factors (PAC-Pd/Fe nanoparticle dosage, solution pH, and temperature) on BDE47 degradation in TX-100 solution were also tested. The results showed that BDE47 degradation followed the pseudo first-order kinetics model. The degradation rates of BDE47 increased as PAC-Pd/Fe nanoparticle dosage and temperature increased. Weak acidic condition (pH 5.5) was favorable for BDE47 degradation with 96.8% BDE47 was removed within 7.5 min, while alkaline condition (9.0) was not conducive to the degradation of BDE47. The degradation of BDE47 by PAC-Pd/Fe nanoparticles was a catalytic reductive debromination process via active H-species attack, wherein the sequential debromination was the dominant reaction. This study suggests that in the presence of moderate surfactant, PAC-Pd/Fe nanoparticles may be potentially employed to eliminate BDE47 in contaminated water.

Incorporation of biochar into soil has been proposed as a strategy for enhancing soil fertility and rice production. A pot trial was carried out to investigate the effects of the dissolvable fraction of biochar in the Yangtze River estuary, China. Soil in plastic pots was incorporated with straw biochar at five different rates: 0%, 5%, 10%, 15%, and 20% (w/wet weight). The rice height, tiller number, and grain yield were recorded; soils and surface water were sampled, and key chemical properties were investigated. Rice grain yield was improved by 29.1–34.2%, and the grain-to-straw ratio was promoted by 8.0–26.1% in the treatments with 10–15% biochar incorporated compared with the control. Soil total organic carbon and total nitrogen contents increased 65.7–242.8% and 22.9–75.3% in the biochar-amended treatments, respectively. Meanwhile, the soil dissolved organic carbon contents increased by 13.4–25.3% in biochar-amended treatments. Higher amounts of added biochar resulted in increased soil electrical conductivity but had no significant effect on soil pH. The major anion was Cl⁻, and the main cations were K⁺ and Na⁺ in the mudflat soil. Addition of 10–15% straw biochar to soil for agronomic purposes is a potentially sustainable ecologically technology.

Heavy metals in food are non-intentional pollutants such as lead (Pb), cadmium (Cd), and mercury (Hg). Pb, a neurotoxic substance, is classified as a possible carcinogen for humans (group 2B) by the International Agency for Research on Cancer (IARC) under the World Health Organization (WHO). Cd, a substance that causes kidney damage, is classified as a substance that causes human cancer (group 1). In this study, inductively coupled plasma atomic emission spectrometry (ICP-AES) and a mercury analyzer (MA) were used to identify the concentrations of heavy metals (Pb, Cd, Hg) in fishery products and to assess the effects of chronic human exposure to heavy metals via fisheries consumption. Food consumption data were obtained from the Korea National Health and Nutrition Examination Survey (KNHANES 2010–2015), and the mean exposure concentrations for Pb, Cd, and Hg were 0.0067 μg/kg bw/day, 1.1277 μg/kg bw/month, and 0.0872 μg/kg bw/week, respectively. Exposures to Pb, Cd, and Hg using the 95th percentile of the consumption data were 0.0183 μg/kg bw/day, 4.0230 μg/kg bw/month, and 0.2268 μg/kg bw/week, respectively, corresponding to 3, 16, and 6% of the human exposure safety standard. Safe guidelines for the intake of fishery products are proposed to reduce the exposure to and accumulation of heavy metals in humans.

Two superior adsorbents, namely bentonite and graphene oxide (GO), were hybridised to study the removal of copper and nickel ions from synthetic and industrial wastewater. The as-synthesised GO, bentonite/GO and bentonite were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and N₂ adsorption-desorption analysis. The factors influencing the adsorption behaviours including contact time, initial solution pH, ionic strength, initial concentration of metal ions, temperature and adsorbent dosage were systematically investigated by batch equilibrium method. The adsorption equilibrium for copper and nickel onto bentonite was attained in 90 min while equilibrium was reached in 60 min on bentonite/GO. The adsorption of copper and nickel was pH-dependent in the range from pH 2 to pH 7 and from pH 2 to pH 8. Pseudo-first-order kinetic model excellently described the adsorption of copper and nickel onto bentonite and bentonite/GO. The equilibrium adsorption data was well described by the Langmuir isotherm model and the maximum adsorption capacity was 248.9 mg/g, 558.4 mg/g, 215.8 mg/g and 402.5 mg/g for bentonite-copper, bentonite/GO-copper, bentonite-nickel and bentonite/GO-nickel adsorption systems, respectively. The bentonite/GO composite exhibited a higher adsorption capacity of both cations from synthetic wastewater than pure bentonite owning to the synergistic effect between bentonite and GO. In all adsorption studies, copper was more efficiently removed than nickel due to its higher tendency to form bond with adsorbent surfaces. The adsorption of copper and nickel on bentonite/GO was mainly due to cation exchange, intermolecular and electrostatic interactions and physisorption dominated the adsorption processes. The practical application of bentonite/GO on adsorption of copper was investigated using real wastewater and its removal efficiency was beyond 98%. The excellent adsorption performances of composites for the copper and nickel removal from wastewater demonstrated its significant potential for pollution mitigations.

It is very necessary to produce bio-activated carbon for special use with easy procedure and low cost. One kind of huge surface area microporous bio-material was successfully prepared from agricultural residues (peanut shell, Arachis hypogaea Linn.) and beneficially applied to control elemental mercury (Hg⁰) in simulated coal-fired flue gas in this study. The possible effects of experimental factors including activator, reaction temperature, and flue components were investigated. The physicochemical properties of the prepared adsorbents were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDX), and X-ray photoelectron spectroscopy (XPS). The results indicated that the peanut shell activated carbon presented excellent Hg⁰ removal efficiency near 90% at 150 °C. The characterization analysis indicated that the removal characteristics were governed by both physical adsorption and chemical adsorption. The chemisorbed mercury on the activated carbon was mainly distinguished into mercuric chloride (HgCl₂) and mercuric oxide (HgO). The presence of C-Cl and O* promoted Hg⁰ into HgCl₂ and HgO. Zinc chloride could not only improve the micropore quantity of activated carbon but also have remarkably positive effects on the elemental mercury removal. This study provided a practical and easy preparation method of bio-activated carbon for Hg⁰ removal with low cost. Graphical Abstract

The percentage of agricultural land cover effect on water quality in Culiacan River basin is studied in this research. The basin contains only intensive cropland as primary economic activity with 60% of the total area. Mathematical relationships between percentages of cropland and total phosphorus (TP) and total nitrogen (TN) concentrations were established. Sampling sites in middle and lower basin and water quality information during 2013–2018 were considered, and percentages of cropland were obtained by geospatial methods including variable area buffers. During rainy season, coefficients of determination were less than 0.2, although quantified nutrient concentration was higher, related to point sources of pollution in the basin. During dry season, coefficients of determination were higher than 0.76 and 0.90 for TN and TP, respectively, with an exponential mathematical trend. Results suggest that intensive agriculture practices generate accelerated loss of soil consolidation, which is transported to water bodies. These soils are in continuous contact with fertilizers and pesticides, mostly organophosphates which have been transported by runoff and underground flows. Using the information generated will help to establish environmental management plans, and to improve environmental diagnosis and effect in countries where there is not enough historical cartographic information and/or water quality data.

This study investigates the relationship between environmental performance and the comparative advantage of crude oil by incorporating the role of institutional quality in 28 oil-producing countries from 2002 to 2014. Using dynamic panel data analysis, the results show that environmental performance and institutional quality along with the conventional factors for comparative advantage are key determinants of the comparative advantage of crude oil. Specifically, while environmental performance negatively affects the comparative advantage of crude oil, it is also negatively associated with the comparative advantage of crude oil. These results are in support of the pollution haven hypothesis in resource-based industry, and it shows a bidirectional relationship between environmental performance and comparative advantage of producing crude oil. Further, the results revealed a vital role played by institutional quality in enhancing the comparative advantage of crude oil and environmental performance. More so, the environmental Kuznets curve (EKC) hypothesis is validated in our result. Finally, a substantial difference in the results between OPEC and non-OPEC countries is confirmed by a set of dummy variables.

The aim of this work consists on the synthesis of a nanomaterial for heavy metal ion removal from aqueous solutions. Al-doped ZnO (ZnO:Alx%) nanopowders with 0 to 5% Al content are prepared via an amended sol-gel method. The morphology and microstructure of the prepared ZnO:Alx% are probed by means of scanning electron microscopy (SEM), X-ray particles diffraction (XRD) analysis, energy dispersive X-ray spectroscopy (EDS) and elemental mapping. The findings reveal the prevalence of the hexagonal wurtzite ZnO structure with increasing crystallite size (45 to 60 nm) as a result of Al doping. SEM images show nearly spherical nanoparticles with considerable aggregation. EDS and elemental mapping analysis confirm the incorporation of Al within ZnO host lattice. The relatively large surface area as estimated from N₂ adsorption makes the nanopowders very favorable for the uptake Cd(II), Cr (IV), Co (II) and Ni(II) from aqueous solution. The ZnO:Alx% with 1 wt% Al exhibits the highest uptake rate of heavy metal ions. The adsorption process has been found to be spontaneous and endothermic and obey Langmuir adsorption model. The high tendency of the prepared nanoparticles to eliminate heavy metal ions renders them suitable candidates for environmental remediation. Desorption studies with 0.1 M NaOH indicate that ZnO:Alx% can be regenerated effectively.