The zeta potential of hydrous manganese dioxide (HMO) may significantly influence its adsorption towards heavy metals. The effect of zeta potential of HMO on adsorption efficiency of three heavy metal ions, Pb(II), Cd(II), and Ni(II), was investigated. The zeta potential values decreased with decreasing Mn²⁺/MnO ₄ ⁻ ratio in the HMO synthesis. The larger adsorption capacity was observed for HMO with more negative zeta potentials, and its zeta potential values increased after the adsorption of Pb(II), Cd(II), and Ni(II). The adsorption equilibrium of HMO at 303.15 K could be well described by Langmuir isotherm equation with qₘₐₓ value of 502.85 mg/g for Pb(II), 155.11 mg/g for Cd(II), and 87.52 mg/g for Ni(II), respectively. Higher initial heavy metal concentration and solution pH both favored the enhancement of adsorption capacity. The pseudo-second-order equation could best fit the adsorption process. Furthermore, the Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that Pb(II), Cd(II), and Ni(II) may form inner-sphere complex on HMO surface. In addition, HMO adsorbent can be regenerated readily by treating with 50% KMnO₄ solutions. After five rounds, the zeta potential value decreased to − 50.6 mV and the Pb(II) removal efficiency is 91% as compared to previous HMO removal efficiency of 93%. These findings revealed that the surface zeta potential of HMO adsorbent might be used as a parameter to determine its performance for the removal of heavy metals from contaminated water.

Literature on prevalence of concentrated flow paths (CPFs) in agricultural fields are limited at field scale with only few studies that address occurrence of CFPs at large geographic extent. This study used high-resolution Light Detection and Ranging (LiDAR) data to identify CFPs in agricultural fields and calculate the percentage of the fields drained by CFPs at a county scale. In 389 agricultural fields across Jackson County, southern Illinois, this study also investigated the association between field characteristics and CFP formation using multiple regression and CART analysis. The mean number of CFPs in a field was 5 with a minimum of 0 and maximum of 17 CFPs. The majority of the CFPs fell under the large category for CFP length and drainage area that corresponds with high mean percent (81%) of field area drained by the CFPs. Further, 85% of the fields had more than 70% of their area drained by CFPs. The multiple regression and CART analysis showed slope as an important factor influencing CFP characteristics such as number of CFPs and CFP length. Both analyses also indicated physical soil properties such as bulk density, soil erodibility factor, saturated hydraulic conductivity, LS factor, organic matter, and percent sand were also predictors of the CFP characteristics. However, these factors explained only 2 to 12% of the variation observed. The significant presence of CFP’s has important implications for water quality since current conservation practices such as riparian buffers were not designed to address concentrated flow from agricultural fields.

After the tsunami caused by the Great East Japan Earthquake, marine sediment was taken from the sea bottom and deposited over local agricultural fields. The marine sediment already contained an unknown amount of heavy metals, due to anthropogenic activities prior to the tsunami, which might affect plants, animals, and humans. Furthermore, soil salinity in tsunami-inundated land greatly increased. Three different amounts of steel slag were employed as pretreatment agent in order to improve agricultural soil quality. The soil samples treated with 2% of steel slag present a remarkable increase of A. thaliana biomass production with low BCF and TF values for most of the heavy metals. It was concluded that steel slag pretreatment used in the tsunami-inundated agricultural lands produced a noteworthy improvement in soil quality which lead to a positive stimulative effect on plant growth, and the slag addition treatment proved to be a promising treatment that might be used for phytostabilization of slightly contaminated soils.

Metsulfuron-methyl is a common active ingredient recommended for use in pre- and post-emergence control of annual grasses and broadleaf weeds in crops, usually applied with mineral oil as adjuvant to enhance its efficiency. Despite the increasing use of this herbicide, there are no information on its ecotoxicity effects to soil fauna. Avoidance and lethality tests were performed with earthworms and collembolans using tropical artificial soil contaminated with formulated products Ally® (600 g L⁻¹ metsulfuron-methyl) and Assist® (756 g L⁻¹ mineral oil) as adjuvant. Lethality test with earthworms showed no difference when tested with or without adjuvant. When Ally® was tested alone, it caused avoidance behavior only at high concentrations (5000 and 10,000 times field predicted dose). However, Assist® addition changed the response of soil invertebrates increasing the avoidance even at field predicted doses. The toxicity of the adjuvant was confirmed in tests exposing collembolans and earthworms to Assist® alone resulting in avoidance behavior. The results clearly show that the addition of mineral oil enhanced the ecotoxicity of metsulfuron-methyl. This study provides an important contribution to the knowledge on the toxicity of metsulfuron-methyl and indicates that adjuvants should be considered in risk assessment of pesticides, considering that under field conditions, these products are applied together.

Ethanol is a renewable fuel and it is considered an alternative to gasoline in Otto-cycle engines. The present study evaluated the behavior of exhaustion gas carbon monoxide (CO) and total hydrocarbons (THC) according to the levels of anhydrous ethyl alcohol (AEA) added to gasoline in different proportions (E0, E10, E20, E27, that is, pure gasoline and its blends with AEA at 10, 20, and 27% v/v) in the use of non-road single cylinder engines of different powers (13 and 6.5 hp), to the loads applied to engine-generators and the air-fuel ratio (A/F) admitted to the engine cylinders. Also, the performance of engine-generators was verified in terms of mass, specific and energetic consumption and efficiency of the evaluated systems for the same blends and loads. The results showed that an increase in the AEA content in the blend resulted in significant drops in CO and THC concentrations for both engine-generators, while fuel consumption showed a slight upward trend; the increases in applied loads resulted in an increase in CO and THC concentrations and fuel consumption. In general, a higher AEA content (oxygenated) in the blends had a greater effect on gaseous emissions compared to the effect on consumption and system efficiency.

Silver@graphene oxide nanocomposite was synthesized through an efficient approach, characterized by FTIR, EDX, and TEM instruments and then was used as adsorbent for imidacloprid removal from water in batch procedure. Effective variants such as contact time, pH, adsorbent dosage, and initial concentration of imidacloprid on procedure by two methods, one at a time and experimental design methods, were studied. Results in optimum conditions based on one at a time experiments is removal of 63% of the pesticide from 50 mL water containing 10 mg/L of imidacloprid by 0.03 g of the adsorbent at pH = 6.6 after 60 min while, experimental design method predict similarity results, 66% uptake of the poison by 0.06 g of the adsorbent in pH = 8. Kinetics and isotherm for adsorption processes follows Freundlich and pseudo-second-order models. Results confirm that Ag@graphene oxide nanocomposite can be applicable for removal of imidacloprid from real polluted water.

Quasi-cryogelation technique is a simple yet effective technique for improving the adsorptive efficiency of biopolymer-based adsorbent materials. In this work, a biopolymer-based adsorbent material, graphene oxide alginate quasi-cryogel beads are reported. Alginate biopolymer was crosslinked and frozen at − 21 °C in order to obtain a gel with cryogel-like microstructure. Graphene oxide was included in the bead formulation in order to enhance the adsorptive characteristics. Beads were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and swelling experiments. Removal of the model cationic dye, methylene blue, was studied by batch adsorption method. It is found that the adsorption follows the Freundlich isotherm model and pseudo-first order kinetics with reaching an adsorption capacity of 122.26 mg/g in 60 min. Results indicate that the physisorption might be due to the π–π interactions between graphene oxide and methylene blue, in addition to electrostatic interactions. Moreover, quasi-cryogelation technique significantly improved the dye removal properties.

CoFe₂O₄/Zn₂SnO₄ composite was synthesized using a simple two-step process and applied as a novel-efficient photocatalyst for the rhodamine B degradation from aqueous solution. Characterization techniques such as X-ray diffraction (XRD), N₂ adsorption-desorption isotherms, scanning electron microscopy (SEM), EDS analysis, and diffuse reflectance spectroscopy were employed in order to investigate the physical and chemical properties of composite. Higher values of the specific surface area, pore volume and diameter, and a smaller band-gap energy promoted a greater catalytic activity of CoFe₂O₄/Zn₂SnO₄ composite when compared to Zn₂SnO₄. A rapid decolorization of dye solution was observed at 40 min of reaction using the CoFe₂O₄/Zn₂SnO₄ catalyst, being 2.5 times faster than the Zn₂SnO₄ alone. Therefore, the CoFe₂O₄/Zn₂SnO₄ composite shows extraordinarily high photocatalytic activity toward the degradation of rhodamine B dye from aqueous solution.

A new synergistic method was proposed to remove Escherichia coli by using high-gradient magnetic separation (HGMS)-ultraviolet titanium oxide photocatalysis (UV/TiO₂). Compared with sole HGMS, UV radiation, UV/TiO₂, and HGMS-UV, the combined HGMS-UV/TiO₂ significantly increased the bacterial removal rate. After treatment of 6 min, bacterial removal rate for HGMS-UV/TiO₂ was 5.25 log, and E. coli was unlikely to photoreactivate or dark repair. In addition, HGMS-UV/TiO₂ treatment led to rapid increase of malondialdehyde (MDA) concentration, severe inhibition of superoxide dismutase (SOD) activity, and massive leakages of intracellular K+ and protein, proving the process caused more damage to E. coli cell structure. For HGMS-UV/TiO₂ treatment, seawater turbidity did not significantly affect the bacterial removal rate, and 10 mg L⁻¹ humic acid could largely reduce the bacterial removal rate. Totally, the HGMS-UV/TiO₂ could be effectively employed to treat ballast water with less organic matter. Despite the limitation, this novel method has many potential applications in the treatment of ballast water.

The purpose of this study was to clarify the kinetic bioaccumulation potential of herbicides in the earthworm, Pheretima spp., the most common earthworms throughout Asia, and Eisenia spp., litter-feeding earthworms included in the test species recommended by the Organization for Economic Co-operation and Development. The kinetic bioaccumulation factors of trifluralin and pendimethalin were estimated from an uptake test for 10 or 12 days and from an elimination test for 10 days. The time required to reach a steady state following herbicide exposure was 7 days for both herbicides in Eisenia spp. and 1 day in Pheretima spp. The uptake rate constant (g-soil/g-worm/day) and elimination rate constant (per day) for trifluralin were 2.1 and 0.23 in Eisenia spp. and 0.42 and 0.45 in Pheretima spp., respectively, and those for pendimethalin were 1.5 and 0.26 in Eisenia spp. and 0.27 and 1.0 in Pheretima spp., respectively. Kinetic bioaccumulation factors of both herbicides were relatively close to bioaccumulation factors in steady state and were higher in Eisenia spp. (8.9 for trifluralin and 5.7 for pendimethalin) than in Pheretima spp. (0.95 and 0.26). These results demonstrated that the herbicide bioaccumulation risk is lower for Pheretima spp. than for Eisenia spp. because of the lower uptake rate and higher elimination rate in Pheretima spp.