A composite flocculant (PSAS-CS) consisted of cationic starch (CS) and polyaluminum silicate (PSAS) was prepared and used for the flocculation of simulated water samples. The morphology and structure of PSAS-CS were characterized by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. The effect of flocculation conditions such as the flocculant dosage and the simulated water pH were investigated. The turbidity and color removal rates could reach 97.79% and 98.07% at PSAS-CS dosage of 1.5 mL/L and the simulated water pH of 5–9. Furthermore, the flocculation efficiency of PSAS-CS was compared with PSAS, CS and the starch modified polyaluminum silicate at different dosage. The results indicated that PSAS-CS showed the highest flocculation efficiency due to its plentiful of positive charges and extended molecular chain. Moreover, the removal rate of PSAS-CS could remain 85% at a low dosage of 0.2 mL/L.

Wastewater reuse coupled to managed aquifer recharge (MAR) provides a means to store and reuse treated wastewater (TWW) year-round. Determining the fate of nutrients in the subsurface during MAR remains challenging for environmental regulation due to the interaction of the MAR source water with site specific aquifer conditions. To facilitate the understanding of natural treatment processes, this study uses operational monitoring data from a full-scale aquifer storage and recovery (ASR) scheme using TWW to assess nutrient (N and P) transformation and fate. Analysis of median water quality injected into and recovered from the ASR wells for two complete ASR cycles (June 2014 to March 2016) was used to describe the removal of nutrients in an anoxic carbonate aquifer. Total nitrogen (TN) removal was dominated by redox processes, with median removal of 40 to 60% for TN and nitrate (the dominant N species) and higher removal of ammonia (95%) and total Kjeldahl nitrogen (TKN) (70%). Total phosphorous (TP) removal was also observed (~ 90%) due to sorption (filterable reactive phosphorous median removal of ~ 80%). A 40% increase in median salinity was evident within each ASR cycle due to recovery of the entire volume of injected water each year (ambient groundwater is 200% higher in TDS, on average). A reduction in salinity of the recovered water could be achieved by leaving a residual of source water in the aquifer to create a buffer zone between the ambient groundwater and the fresher source water.

Levels of heavy metals and polybrominated diphenyl ethers (PBDEs) were determined in fishes sampled in Jilin Songhua Lake, China. Concentrations and congener profiles of these contaminants varied by fish type. The highest concentrations of Zn, Cu, Mn, and Cd were found in three omnivorous fish (Carassius carassius, Hypomesus olidus, and Hemiculter leucisculus). The highest concentrations of Ni, Cr, and Hg were found in Silurus asotus and Hemibarbus maculatus which are two kinds of carnivorous fish. The minimum total concentration of the seven PBDEs of fish was 0.093 ng/g wet weight (ww) in Ctenopharyngodon idellus, while the maximum, 0.342 ng/g ww, was detected in Aristichthys nobilis. Of all the congeners, BDE 28 and 47 were dominant. The estimated daily intake (EDI) of these metals and PBDEs via consuming the fishes was estimated to be 1.159–10.121 μg/kg bw/day and 0.046–0.597 ng/kg bw/day, respectively. The total hazard quotients (THQs) of both types of pollutants were far below 1, indicating that the health risks of these pollutants were low for the people who consumed the fish species from the Songhua Lake.

Smog pollution deteriorates environmental quality and has severe health risks. This affects the daily lives of people in China, particularly in urban areas. Along with other factors, a large portion for smog comes from transportations, making it dense and more hazardous in urban areas. The Chinese government aims to reduce air pollution by promoting electric vehicles and green modes for mobility along with other environmental protection measures. The study explores the switching intentions of people from motorized vehicles to electric vehicles by integrating push-pull-mooring model and institutional theory. The study incorporates environmental quality, regulative environment, alternative attractiveness, normative environment, self-(decision)efficacy, and willingness to pay into an integrated framework. The study further analyzes the green behavior of consumers by extending switching intentions for electric vehicles. The integrated framework explains mooring as the most influential factor followed by normative environment from pull factors and environmental quality from push factors. The effect of regulative environment remains weak and significant, but the effect of alternative attractiveness remains weak and insignificant. The switching intentions strongly and significantly explain green behavior. Furthermore, mooring moderates the relationship between push factors, some of the pull factors, and switching intentions.

Climate change and human activities are affecting the ecological health of rivers and the economic value of its ecosystem services. Taking water quantity as the intermediate variable, we proposed a quantitative calculation method for the impact of climate change and human activities on the economic value produced by the ecosystem service functions of rivers. The framework mainly consists of three steps: firstly, we quantitatively determined the changes in the amount of water coming from rivers due to climate change and human activities; secondly, combining the theory of resource and environmental economics to calculate the economic value generated by ecological service functions of rivers; finally, we quantitatively identified and analyzed the impact of climate change and human activities on the economic value produced by the ecosystem service functions of rivers. Taking Baoji section of Weihe River (BSWR) as an example, we quantitatively analyzed and calculated the impact of climate change and human activities on the economic value produced by ecosystem service functions of rivers. The main conclusions of this paper are as follows: in recent 52 years, the economic value produced by the ecosystem service functions of rivers decreased by 3.57 billion yuan due to the climate change and human activities; the total economic value has been reduced by an average of 68 million yuan per year. This useful work can not only reveal the impact of climate change and human activities on the economic value of ecosystem services of rivers but also can provide an important basis for the reasonable management model of water resource of ecosystem of rivers watershed.

Environmental sediment dredging is one of the most common methods for the remediation of contaminated sediments in lakes; however, debate continues as to whether the effectiveness of dredging methods contributes to this phenomenon. To determine sediment resuspension and nutrient release following dredging with a variety of dredging methods, four dredging treatments at wind speeds of 0–5.2 m/s were simulated in this study, namely suction dredging (SD), grab dredging (GD), ideal dredging with no residual sediments (ID), and non-dredging (ND). Field sediments from suction and grab dredging areas (including post-dredged and non-dredged sediments) of Lake Taihu were used to assess the release abilities of soluble reactive phosphorus (SRP) and ammonia nitrogen (NH₄⁺-N) from the sediment-water interface. The effects of residual sediments on nutrient concentrations in water were also evaluated. The results reveal that inhibition of resuspension of particulate matter and nutrients released through sediment dredging decreases with increasing levels of residual sediment. Total suspended particulate matter content in the mean water columns of ID, SD, and GD under wind-induced disturbance (1.7–5.2 m/s) decreased by 67.5%, 56.8%, and 44.3%, respectively; total nitrogen and total phosphorus in ID (SD) treatments were 19.8% (12.9%) and 24.5% (11.2%) lower than that in ND treatment. However, there were ~ 1.6 and 1.5 times higher SRP and NH₄⁺-N in the GD treatment compared with the ND treatment at the end of the resuspension experiment (0 m/s). A significant increase in the SRP and NH₄⁺-N release rates at the sediment-water interface was also observed in field sediments from a grab dredging area, indicating that GD may pose a short-term risk of nutrient release to the water body. Hence, dredging methods with less residual sediments both during and after dredging improves the dredging quality.

Biochars from Chinese medicine material residues and furfural residues at 300–600 °C (MBC300–MBC600 and FBC300–FBC600) were used as adsorbents for removing tetracycline (TC) from water. The influence of pH and co-existing of cations or low molecular weight organic acids (LMWOAs) was investigated on TC adsorption. Further, the bulk biochars were treated by ball milling into sub-micron particles, and their properties and adsorption performance toward TC were also characterized. For pristine biochars, TC adsorption was nonlinear and heterogeneous. Heterogeneity of biochars resulted in multiple sorption mechanisms, including H-bonding, π-π interaction, and pore filling. FBC300 and FBC600 had maximum sorption at pH 5–7. Electrostatic repulsion of positively charged biochar surfaces with TCH₃⁺ at pH < 3 or negatively charged biochar surfaces with TCH⁻ and/or TC²⁻ at pH > 7 was not favorable for TC removal. TC sorption decreased with increasing Na⁺ concentrations from 0 to 0.1 mol/L, and bivalent cations (Ca²⁺ and Mg²⁺) showed greater inhibiting effect relative to monovalent ones (Na⁺ and K⁺). The LMWOAs could combine with co-existing cations, thus reducing the inhibitory effect of cations and improving TC sorption. The ball milling caused remarkable size reduction of biochar particles, thus exposing more active surfaces to capture more TC molecules from water. This study provided low-cost and high-efficiency biochar absorbents to remove antibiotics from water and will benefit for understanding the relationship between TC sorption characteristics/mechanisms and biochar properties.

This study investigates the performance of a sequential pyrite-Fenton and biological process for the treatment of 2-chlorophenol (2-CP) containing wastewater using pyrite-Fenton process as a pretreatment stage. Pyrite was tested as a catalyst material in Fenton reaction due to its low cost and high abundance in the environment. All experiments were run in batch mode. The biodegradation experiments were performed under aerobic conditions using glucose as the co-substrate with untreated or Fenton-pretreated 2-CP. Despite the 100% removal of 2-CP in batch pyrite-Fenton reactors, the total organic carbon (TOC) removal only approached 70%, implying the transformation of 2-CP into some chemically stable intermediate reaction by products during pyrite-Fenton oxidation. In systems with no pyrite-Fenton pretreatment, a combined effect of biotic and abiotic processes including biological degradation, sorption, and volatilization played a significant role on 2-CP removal. The pyrite-Fenton pretreatment of 2-CP significantly improved the performance of aerobic biological reactor relative to system with no pyrite-Fenton pretreatment by (1) reducing the toxicity of 2-CP on aerobic microbial cells and (2) enhancing cell growth. Overall, this study shows that pyrite-Fenton pretreatment coupled with aerobic biological degradation could provide a cost-effective solution for the treatment of wastewater containing low-biodegradable toxic compounds such as chlorophenols.

Phytoremediation is considered one of the well-established and sustainable techniques for the removal of heavy metals and metalloids from contaminated sites. The metal extraction ability of the plants can be enhanced by using suitable organic materials in combination with metal-tolerant plants. This experiment was carried out to investigate the phytoextraction potential of Mentha piperita L. for nickel (Ni) with and without citric acid (CA) amendment in hydroponic experiment. The experiment was performed in controlled glass containers with continuous aeration in complete randomized design (CRD). Juvenile M. piperita plants were treated with different concentrations of Ni (100, 250, and 500 μM) alone and/or combined with CA (5 mM). After harvesting the plants, the morpho-physiological and biochemical attributes as well as Ni concentrations in different tissues of M. piperita plants were measured. Results revealed that Ni stress significantly decreased the plant agronomic traits, photosynthesis in comparison to control. Nickel stress enhanced the antioxidant enzymes activities and caused the production of reactive oxygen species (ROS) in M. piperita. The CA treatment under Ni stress significantly improved the plant morpho-physiological and biochemical characteristics when compared with Ni treatments alone. The results demonstrated that CA enhanced the Ni concentrations in roots, stems, and leaves up to 138.2%, 54.2%, and 38%, respectively, compared to Ni-only-treated plants. The improvement in plant growth with CA under Ni stress indicated that CA is beneficial for Ni phytoextraction by using tolerant plant species. Graphical abstract

Following the global alertness and consciousness over the increasing warming and heating on the ground of climate change, over 200 countries including Nigeria have committed themselves in reducing this global phenomenon. Nigeria being among the countries placed with individual country’s task and also known as a one-economy operating county because of its oil and gas gifting is subject to investigation of its efforts and result in decarburization of its economy and environment. The oil and gas sector of Nigeria has been identified as the major sector where the heavy utilization of energy is centered on through mining and exploration activities of these foreign companies who have investments and stakes in the main stream sector. This is the major reason of adopting FDI as a major variable to test the performance of the environmental condition of the country. To effectively carry this research, the authors, adopt, cointegration test and the linear ARDL test to unveil the true picture of the foreign investors impact on carbon emission reduction. Among the findings is the positive but not significant interaction between economic growth and carbon emission which infers the capability of the economic operation to initiate the degradation in the environment via pollutant emission. Energy use depicts inducement to carbon emission with positive association with carbon emission. FDI established both negative and positive relationship with carbon emission at initial stage and lag 1 respectively. All the variables point towards carbon emission increase in the country which call for serious attention towards decarburization of the country to fall in line with the agreed policy of Paris formation.