Negative pressure irrigation (NPI) is a new water supply technology that can save water and improve fertilizer utilization efficiency. The objective of this study was to determine the effects of different irrigation treatments on the yield and quality of rapeseed, nitrate distribution in soil, and the composition of rhizosphere bacterial communities in a greenhouse. During the entire rapeseed growth period, NPI reduced water consumption by 23 and 23% compared to that reduced by conventional irrigation (CI) and drip irrigation (DI), and NPI improved water use efficiency (WUE) by 67 and 59% more than CI and DI, respectively. Under NPI, the soil water content remained relatively stable within the range of 9.7–11.7%, which was a lower range of variation than that under CI and DI of 8.6–13.3%. NPI significantly improved the yield, quality, and plant nutrients of rapeseed. The NO₃-N content was always lowest at the different sampling times and soil layers under the NPI-L treatment. NPI significantly increased the microbial diversity in the rhizosphere soil of rapeseed and increased the abundance of Actinobacteria while decreasing that of Proteobacteria and Acidobacteria. Simultaneously, the performance of rapeseed was better under the NPI-L fertilizer concentration (0.15%) than under NPI-H (0.20%). Eventually, the combination of the evaluated regimes demonstrated that NPI is the best irrigation technique for saving water and obtaining relatively high rapeseed yields and quality while improving nitrogen utilization and the composition of rhizosphere bacterial communities. The results of this study provide a scientific basis for planting rapeseed in agricultural facilities.

Due to its unique properties, the potential application of graphene oxide (GO) in treating environmental pollution has attracted wide attention. In this study, the UV-light catalyzed photoreduction of Cr(VI) by GO was assessed as well as its adsorption toward Cr(VI), and FTIR and XPS techniques were adopted to reveal the underlying mechanisms. The surfaces of GO were negatively charged across the pH range examined. Therefore, the increase in pH resulted in the decrease in Cr(VI) adsorption due to the enhancement in repulsion between Cr(VI) and GO surfaces. The kinetic studies showed that the Cr(VI) adsorption proceeded quickly during the 0–24 h stage, followed by a slow process until to the end of reaction (96 h). Additionally, the kinetic data could be properly described with the pseudo-first-order rate equation (R² = 0.9754). With the UV-light irradiation, Cr(VI) reduction in the presence of 0.5 g L⁻¹ GO was observed with the concentration of Cr(VI) decreased from 0.1 mM to zero within 12 h at pH 3.0, while which would be suppressed as the pH increased. The addition of EDTA could enhance the photocatalytic Cr(VI) reduction due to the consumption of the photogenerated holes (h⁺), leaving more Cr(III) species present in solution. The generation of h⁺ was further confirmed by the complete photodegradation of 4-CP during 48 h. Moreover, the changes in FTIR and XPS spectrum of GO before and after reaction indicated the oxidization of epoxy and hydroxyl groups by holes or reduction by electrons was involved in the photoreaction. The photoreduction of Cr(VI) could was also observed in an oxisol with the existence of GO, with the disappearance of 0.1 mM of aqueous Cr(VI) at pH 4.40 after 36 h. The results above could enhance our understanding on the essence of photoreactivity of GO, and indicated that the potential release of GO into soil environments would be helpful to eliminate the risk posed by Cr(VI) through the UV-light irradiated photocatalytic reduction.

Carboxymethyl cellulose–stabilized sulfidated nano zerovalent iron (CMC-S-nZVI) was tested for its capacity to the removal of Cr(VI) in this study. The effect of synthesis approaches on morphology and properties of CMC-S-nZVI was studied. Results revealed CMC-S-nZVI prepared by the surface corrosion method had favorable homogeneity and corrosion resistance. The structure and morphology of CMC-S-nZVI particles were investigated by transmission electron microscopy, X-ray powder diffraction, and Fourier-transform infrared spectrometry. Batch experiments showed that the removal efficiency of Cr(VI) by the CMC-S-nZVI particles was influenced by the S/Fe molar ratio, initial pH, initial Cr(VI) concentration, and the reaction temperature. Increasing S/Fe molar ratio from 0 to 0.35 enhanced Cr(VI) removal efficiency from 65.37 to 85.08%. Reducing pH value and improving the reaction temperature have a positive impact on Cr(VI) removal. The removal amount was 535 mg/g (total iron) CMC-S-nZVI with initial Cr(VI) concentration of 50 mg/L. Compared with CMC-nZVI, CMC-S-nZVI had better performance in Cr(VI) removal in a simulated groundwater system. The results indicated that CMC-S-nZVI might be applicable for in situ treatment of the Cr(VI)-containing groundwater.

The aim of this study was to determine the distribution of cadmium (Cd) and lead (Pb) in muscle and liver tissue of Haemulopsis axillaris and Diapterus peruvianus from the Eastern Pacific in Mexico and to assess the health risk to consumers. Fish were collected as bycatch on the continental shelf between the coasts of Sinaloa and Guerrero (Eastern Pacific). Cd and Pb were quantified in muscle and liver tissue using graphite-furnace atomic absorption spectrophotometry (GF-AAS).Concentration of Cd was greater in muscle tissue than in liver tissue; with Pb, however, the opposite pattern was found. The highest concentration of Cd (0.177 μg g⁻¹) was found in muscle tissue of H. axillaris from Sinaloa. For Pb, the highest level (0.692 μg g⁻¹) was found in the liver tissue of H. axillaris also from Sinaloa. Levels of Cd and Pb in muscle tissue were both below Mexican Guidelines (0.5, 1.0 μg g⁻¹ wet weight for Cd and Pb respectively) and International Guidelines. The hazard index (HI) for both metals in the edible portion of studied considering metal levels in the edible portion and the rate of fish consumption by the Mexican population (in adults and children) was less than 1 (HI < 1), values which do not represent a health risk to consumers.

The residue concentrations and congener profiles of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) were examined in fly ash and bottom ash released from different thermal industrial processes in Vietnam. PCDD/F concentrations and toxic equivalents (TEQs) in the ash samples varied greatly and decreased in the following order: steel making > aluminum recycling > medical waste incinerator > boilers > municipal waste incinerator > tin production > brick production > coal-fired power plant. Both the precursor and de novo synthesis were estimated as possible formation mechanisms of dioxins in the ash, but the latter pathway was more prevalent. The highest emission factors were estimated for the ash released from some steel-making plants, aluminum-recycling facilities, and a medical waste incinerator. The emission factors of PCDD/Fs in ash released from some steel plants of this study were two to six times higher than the UNEP Toolkit default value. The annual emission amount of ash-bound dioxins produced by 15 facilities in our study was estimated to be 26.2 to 28.4 g TEQ year⁻¹, which mainly contributed by 3 steel plants. Health risk related to the dioxin-containing ash was evaluated for workers at the studied facilities, indicating acceptable risk levels for almost all individuals. More comprehensive studies on the occurrence and impacts of dioxins in waste streams from incineration and industrial processes and receiving environments should be conducted, in order to promote effective waste management and health protection scheme for dioxins and related compounds in this rapidly industrializing country.

In this study, two types of artificial floating islands (AFIs), group A (consists of 1# and 2# traditional AFIs with plant and soil) and group B (consists of 4# and 5# new-type AFIs with plant, substrate, and with luffa sponge and corncob hanging at the bottom), were constructed, respectively. The removal effects and degradation mechanisms of luffa sponge and corncob in group B were compared and investigated. Plant height, root growth, and packing degradation of the two types of AFIs were studied. Temperature, dissolved oxygen (DO), and pH on the decontamination effects of AFI were discussed. The results showed that group A and group B AFIs showed great significant differences in removal of CODCᵣ, TN, NO₃⁻−N, NH₄⁺−N, and TP (p < 0.05). The TP removal of group B was 92.8 ± 0.6%, and the TN removal and NO₃⁻−N removal were significantly higher than that of group A, which was 90.3 ± 0.8% and 96.0 ± 2.2%, respectively; The addition of luffa sponge and corncob could enhance the biodegradability of sewage and the nitrogen and phosphorus removal efficiency of group B. The plant growth height of group B planted with Lythrum salicaria was 2.36 times higher than that of group A. The effect of temperature on TP was significantly greater than that of TN, and both groups of AFIs presented continuous improvement capacities of TN and TP removal when the temperature was above 15 °C. Group B was observed with a lower pH range of 6.69~7.12, which was more suitable for denitrification than group A. The release of carbon source of 5#-corncob AFI was 2.51 times higher than 4#-luffa sponge AFI at the end of the experiment.

Electronic waste (e-waste) has been widely studied by scholars all over the world, but the research topics and development trends in this field are still unclear. This study aimed to explore the status quo, hot topics, and future prospects in the field of e-waste. Data of publications were downloaded from the Web of Science Core Collection. We used CiteSpace V, Histcite, and VOSviewer to analyze literature information. A total of 2800 papers in e-waste research were identified, and the number of publications increased rapidly after 2004. Six thousand five hundred seventy-three authors participated in the e-waste research, but 70.01% of the authors published only 1 article. The most productive country in this field was China (1146 publications), and the most productive institution was the Chinese Academy of Sciences (370 publications). The Waste Management (225 publications) was the most productive journal, and Environment Science & Technology (9704 co-citations) was the most co-cited journal. The main hot topics in e-waste field were management and recycling of e-waste in developing countries, health risk assessment after exposure to organic pollutants, degradation and recovery of waste metal materials, and impact of heavy metals on children’s health. The frontier topic was degradation.

Triclosan (TCS) is a potential endocrine-disrupting compound (EDC), which produces an adverse impact on aquatic life and human beings. Wastewater discharge is considered as the primary source of triclosan in water bodies. The study is aimed to investigate the occurrence and environmental risk of triclosan released by municipal wastewater treatment plants (WWTP). An analytical protocol was developed and validated to determine the presence of TCS in the samples through offline solid-phase extraction (SPE) and liquid chromatography - electron spray ionization (ESI)—quadrupole mass spectrum (LC/ESI/MS). The limit of detection and quantification of protocol was estimated as 2.8 ng/L and 6.25 ng/L, respectively. The season-wise influent and effluent samples from two WWTP in Chennai, India, were monitored. The TCS concentrations in samples were found in the range of 443 to 1757 ng/L. The Risk Quotient (RQ) method was performed to evaluate the environmental (ecotoxicological and human health) risk associated with the exposure of TCS-containing wastewater. The results of the study revealed that primary producer (algae) was highly vulnerable to exposure of TCS in the aquatic environment. The estimated daily intake of TCS was much lower than the reference dosage, and this indicates that TCS did not produce any considerable risk to human health. Also, it suggested that additional treatment was required for complete removal of triclosan residues.

In this study, organoclay and clay-biopolymer composites were evaluated for the adsorption process of an anionic red dye, Allura Red (AR), in aqueous solution. For this purpose, the cationic exchange capacity (CEC) of a natural bentonite was calculated, and it was modified with the cationic surfactant hexadecyltrimethylammonium bromide (OB). Furthermore, a commercial montmorillonite modified with dimethyldialkyl ammonium (OM) was also employed. These organo-modified clays were used for the synthesis of two series of composites, with alginate as the polymer matrix, and were identified as OBC and OMC, respectively; composites were obtained in the wet (W) and dry (D) states. The adsorbent materials were characterized by means of infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and dispersive energy spectroscopy (EDS). Afterwards, kinetics and isotherms studies were performed in batch systems, with dye solutions of different concentrations, without pH adjustment. Some parameters were evaluated, such as the variation of the pH value of the solution and the concentration of the dye with the organoclays and composites. Chemisorption was considered as the main mechanism that follows the adsorption processes of AR. Results demonstrated that the pseudo-second order was the kinetics model that best described the adsorption process of the AR dye, with both, hydrated and dry composites. Finally, the Freundlich and the Langmuir–Freundlich isotherms were the best models that described the hydrated and dry composites behavior, respectively.

The objective of this study is to identify the feasibility of using rhamnolipid biosurfactant to remediate heavy metals contained in manganese nodules collected from the Clarion-Clipperton Fracture Zone, Pacific Ocean. Deep-sea manganese nodules may represent one of the most important future natural resources for heavy metals due to the depletion of resources on land. Since international marine environment guidelines for deep-sea mining will be set up by international organisations in the 2020s, remediation technologies are urgently required for deep-sea mining tailings. We show that rhamnolipid biosurfactant is an environmentally friendly substance and can be successfully used for the remediation of heavy metals in deep-sea mining tailings under various reaction conditions. Rhamnolipids therefore represent a useful extracting agent for heavy metals in deep-sea mining tailings. The removal of nickel (Ni), copper (Cu), and cadmium (Cd) would be enhanced in the presence of rhamnolipids with specific reaction times and concentrations. Future actual remediation technologies should be developed using rhamnolipid biosurfactant on the basis of these results.