Although the Chinese government emphasizes the significance of public transportation development and encourages green travel, no empirical study has examined whether the expansion of public transportation facilitates the mitigation of carbon emissions. To this end, we employ a panel quantile regression to test the endogenous relationship between public transportation scale and carbon emissions. The results suggest that the effect of public transportation scale on carbon emissions is heterogeneous across China’s provinces based on the level of carbon emissions. Even so, the results still support a stable inverted U-shaped relationship between public transportation scale and carbon emissions for provinces with different levels of carbon emissions. That is, when public transportation scale exceeds a threshold value, the relationship between public transportation and carbon emissions will turn from positive to negative. Our findings provide evidence advocating for public transportation development and green travel. It is of great significance for China to respond to climate changes.

In this study, forward osmosis (FO) membranes and fouling solutions were systematically characterized to elucidate the effects of organic fouling on the rejection of two pharmaceutically active compounds, namely, sulfamethoxazole and carbamazepine. Municipal wastewater resulted in a more severe flux decline compared to humic acid and sodium alginate fouling solutions. This result is consistent with the molecular weight distribution of these foulant solutions. Liquid chromatography with organic carbon detection analysis shows that municipal wastewater consists of mostly low molecular weight acids and neutrals, which produce a more compact cake layer on the membrane surface. By contrast, humic acid and sodium alginate consist of large molecular weight humic substances and biopolymers, respectively. The results also show that membrane fouling can significantly alter the membrane surface charge and hydrophobicity as well as the reverse salt flux. In particular, the reverse salt flux of a fouled membrane was significantly higher than that under clean conditions. Although the rejection of sulfamethoxazole and carbamazepine by FO membrane was high, a discernible impact of fouling on their rejection could still be observed. The results show that size exclusion is a major rejection mechanism of both sulfamethoxazole and carbamazepine. However, they respond to membrane fouling differently. Membrane fouling results in an increase in sulfamethoxazole rejection while carbamazepine rejection decreases due to membrane fouling.

During coal mining activities, a lot of coal gangue is produced, which usually contains high mercury (Hg) concentrations as well as the acid mine drainage (AMD) generator of pyrite. In the present study, the total mercury (THg) and methylmercury (MeHg) in gangue, water, sediment, paddy soil, and rice samples, collected from abandoned coal mining areas, were analyzed. Results showed that the THg concentrations ranged from 0.37 to 35 mg/kg (11 ± 8.4 mg/kg) and 0.15 to 19 mg/kg (2.0 ± 3.9 mg/kg) in gangue and sediments, respectively. For paddy soils, the THg concentrations and MeHg varied from 0.16 to 0.91 mg/kg and 0.71 to 11 ng/g, respectively. Rice samples exhibited wide concentration ranges of THg (3.0–22 ng/g) and MeHg (0.71–8.9 ng/g). Sequential extraction of Hg revealed that the nitric acid-extractable state Hg (F4) was the dominant Hg species in gangue and sediment, while humic acids state Hg (F3) was the dominant form in paddy soil. Compared with gangue, higher percentages of F3 and the residual state Hg (F5) in both sediment and soil samples implied the transformation of F4 to F3 and F5 during transportation. Soil n-HAs (the difference between the total organic carbon and humic acids) were positively correlated with both THg and MeHg in soil and rice, indicating that n-HAs enhance Hg bioavailability under acidic conditions. Further studies should be conducted to reveal the factors influencing the transformation of different Hg fractions, providing ideas on decreasing the bioavailability of Hg in coal mining areas.

Beijing and its surrounding areas implemented a series of stringent measures to ensure good air quality during the Asia-Pacific Economic Cooperation (APEC) summit. These measures included restrictions on traffic, constructions, and industrial activities. The diurnal variations of carbonyls, 24-h PM₂.₅, and its chemical species were investigated before, during, after APEC, and the 2015 summer. The average concentrations of carbonyls, formaldehyde, acetaldehyde, and acetone were decreased by 65.2%, 78.6%, 41.5%, and 55.6% during APEC, respectively. The concentrations of propene equivalent, the ozone formation potential, and the contribution to OH· removal by carbonyls during APEC were approximately 27–33% of those during the preceding interval. The temporal variation of carbonyls during APEC was similar to that of other air pollutants, except for O₃; however, the diurnal variation of carbonyls was consistent with that of O₃, with the highest values at noon and the lowest ones at night during APEC. Large variations in C1/C2 (0.95–9.41) and C2/C3 (5.70–15.71) were observed during the sampling period. The correlations analysis, diagnostical ratios, and diurnal variations of carbonyls indicated that primary sources were not an important source and secondary formation was the dominant source of atmospheric carbonyls during the entire period. The control measures not only reduced primary carbonyl emissions but also dramatically reduced secondary carbonyl precursors, such as NOₓ and volatile organic compounds (VOCs), resulting in the low level of carbonyls during APEC. In addition, the potential health effects of carbonyls were evaluated and the cancer risk from formaldehyde and acetaldehyde was significantly higher before APEC than during the other intervals.

In this study, a new type of composite material, namely modified biochar (MBC), was synthesized by loading the magnetic ferromanganese oxide nanoparticles on pine biochar. BET, SEM, and FTIR were employed to analyze the surface properties and pore structures of MBC. In addition, XRD was adopted to examine the crystal structure of MBC. Characterization results showed that the surface area and porosity of MBC have been greatly improved, and the functional groups have been introduced by ferromanganese oxides. Adsorption experiments of tetracycline hydrochloride (TC) including kinetics, isotherms, thermodynamics as well as the influence of pH, salt ion strength, and the environmental risk of MBC, were evaluated. The results revealed that the experimental data conformed to the pseudo-second-order kinetic model and the Freundlich isotherm model. In the adsorption process, MBC showed excellent adsorption ability (maximum capacity for TC 100.74 mg g⁻¹) to BC (33.76 mg g⁻¹). In isotherm experiments, the maximum adsorption capacity of TC by MBC reached 177.71 mg g⁻¹. Toxicity studies showed that the MBC had no harm to the environment. To conclude, MBC has great potential for applications in removing TC from water.

This study deals with the evaluation of trace element bioaccumulation and histological alterations in the hepatopancreas of the supralittoral amphipod Orchestia montagui Audouin, 1826 due to the exposure to cadmium, copper, and zinc. Orchestia montagui individuals were maintained during 14 days in soils contaminated with different trace elements namely cadmium, copper, and zinc; a control was also prepared. Our results show that the mortality and the body mass vary according to the metal and the nominal concentration used. In general, the mortality increases from the seventh day. However, the body mass shows a decrease with cadmium exposure and an increase with copper and zinc exposures. Furthermore, the concentration factor highlights that this species is considered a macroconcentrator for copper and zinc. The hepatopancreas of unexposed and exposed animals were compared to detect histological changes. Our results show significant alterations in the hepatopancreas of the exposed animals after the experiment. The degree of these alterations was found to be dose-dependent. Among the histological changes in the hepatopancreas in O. montagui, a loss of cell structure was noted, especially cell remoteness and border lyses, the reduction of nuclear volume, an increase in the cytoplasm density with the presence of trace element deposits in both the nucleus and vacuoles, a disorganization and destruction of microvilli, and a condensation of the majority of cell organelles and mitochondria swelling. Through this study, we have confirmed that O. montagui can be a relevant model to assess trace metal element pollution in Tunisian coastal lagoons with the aim of using it in future biomonitoring programs.

The farmland irrigation with the sewage is a common and better pathway to save the resource of groundwater in Northern China. The investigation was conducted in the farmland along the Fuhe River to explore characteristics of heavy metals in soils and grains of wheat and maize from a long-term sewage-irrigated area of Baoding region. The results showed that the topsoil with long-term sewage irrigation accumulated more Cd, Pb, and Hg compared with that of soil irrigated with groundwater and their corresponding natural background values. Cd concentrations in 48% of sewage-irrigated soil samples exceeded the Chinese safety limitation at 0.6 mg/kg, but less Cd accumulated in crop grains and did not pose the potential health risk. On the contrary, Pb levels in soils irrigated with sewage were lower than the safety limitation but Pb concentrations in 24% of wheat grain samples exceeded the Chinese national safety limit. Long-term sewage irrigation did not increase As, Cr, and Ni concentrations in soils or crop grains. The target hazard quotient (THQ) of heavy metals in edible grains of crops was selected to assess their risk to human health. Total THQ values were higher than 1.0 for the wheat samples from sewage-irrigated area and both sewage-irrigated and smelter-impacted areas, and As is the main contributor to the total THQ and posed the potential risk to human health. Therefore, the accumulation of Cd, Pb, Hg, and As in soils and crops in sewage-irrigated area should be monitored continuously to ensure food safety and security.

Organophosphorus pesticides are effective, cheap, and used extensively but can harm aquatic organism and human health. Here, water quality criteria (WQCs) for dichlorvos (DDVP) and malathion (MAL) were derived. Nine aquatic organisms native to China were used in toxicity tests. Published toxicity data for aquatic organisms native and non-native to China were also analyzed. DDVP and MAL WQCs were derived using (log-normal model) species sensitivity distributions. Species sensitivity distribution curves indicated native and non-native species have different sensitivities to DDVP. The sensitivities of native and non-native species to MAL were not different because non-native species data for fewer than eight genera were available, so further research is required. The results indicated that native species need to be considered when deriving WQCs. The criteria maximum concentration (CMC) and criteria continuous concentration (CCC) were 1.33 and 0.132 μg/L, respectively, for DDVP, and 0.100 and 0.008 μg/L, respectively, for MAL. The CMCs for DDVP and MAL derived using ETX 2.0 software and species sensitivity ranks were different from the CMCs obtained using the SSD method because of parameter uncertainties. The DDVP and MAL WQCs were significantly lower than Chinese surface water quality standard thresholds. The results provide basic data for revising these thresholds.

Fenton’s reaction-based chemical oxidation is in principle a method that can be utilized for all organic fuel residues thus making it a potential all-purpose, multi-contaminant, in situ application for cases in which storage and distribution of different types of fuels have resulted in contamination of soil or groundwater. Since peroxide breakdown reactions are also expected to lead to a physical transport of the target compound, this secondary physical removal, or rebound concentrations related to it, is prone to be affected by the chemical properties of the target compound. Also, since soil conditions are seldom optimal for Fenton’s reaction, the balance between chemical oxidation and transport may vary. In this study, it was found that, with a high enough hydrogen peroxide concentration (5 M), methyl tert-butyl ether–spiked groundwater could be treated even under suboptimal conditions for chemical mineralization. In these cases, volatilization was not only contributing to the total removal but also leading to rebound effects similar to those associated with air sparging techniques. Likewise for diesel, temporal transport from soil to the aqueous phase was found to lead to false positives that outweighed the actual remediation effect through chemical mineralization.

An ultra-fast non-conventional waste management protocol was being designed and applied to recycle and reuse industrial coal fly ash (CFA) waste to generate highly pure nanozeolite X. Both microwave heating–assisted hydrothermal treatment method and ultrasonic waves–assisted hydrothermal method have been successfully used for the fast valorization of power plant CFA waste, and the results were compared with conversional valorization method for CFA conversion to zeolite. While conventional methods like hydrothermal treatment using sodium hydroxide took up to 4 days in valorization of the solid CFA waste into a useful zeolitic X material; the non-conventional methods using microwave irradiation of frequency 2.45 GHz and ultrasound irradiation of frequency 20 kHz took 90 min and 20 min respectively to fast-valorize the solid waste into highly pure zeolite material with high cation–exchanged capacity. The unconventional techniques, therefore, can be used in the large-scale valorization of solid waste recycling and reuse to yield highly pure zeolite.