The increased applications and production of graphene oxide (GO) make the necessity to study information on the interaction of GO with minerals. In this work, adsorption and desorption were used to study the reversibility of interaction between GO and goethite/kaolinite. Result showed that the pH value, ionic strength, and temperature had significant effects on the adsorption and desorption behavior of GO. Interaction force was stronger between GO and goethite than that of kaolinite. The interaction may be attributed to the electrostatic, hydrogen-bonding, and Lewis acid base interactions. The irreversible interaction between GO and minerals may be a main mechanism for the observed desorption hysteresis. These results are important for evaluating the fate and health risk of GO in the environment.

Heavy metals contamination in agricultural soil has become a worldwide problem, and soil characteristics modulate metal availability in soils. Four field experiments were conducted simultaneously to evaluate concentration and distribution of cadmium (Cd) and lead (Pb) in 39 oilseed rape cultivars at four agricultural locations with different contamination levels of Cd and Pb, as well as the influence of soil characteristics together with soil total and bioavailable Cd and Pb concentration on metal transfer from soil to oilseed rape. Shoot concentrations of Cd and Pb in oilseed rape cultivars ranged from 0.09 to 3.18 and from 0.01 to 10.5 mg kg⁻¹ across four sites. For most cultivars, Cd concentration in root or shoot were higher than pod and lowest in seed, while the highest Pb concentration was observed in root followed by shoot and seed. Stepwise multiple linear regression analysis allows for a better estimation of Cd and Pb concentration in oilseed rape while taking soil properties into consideration. The results demonstrated that Cd and Pb concentration in oilseed rape were correlated with soil organic matter (OM), cation exchange capacity (CEC), available phosphorus (AP), available potassium (AK), sand, soil total and available Cd and Pb concentration, and R² varied from 0.993 to 0.999 (P < 0.05). The Cd and Pb levels found in oilseed rape indicated its phytoextraction potential for Cd and Pb co-contaminated agricultural soils in winter without stopping agricultural activities.

The agricultural land-atmospheric dustfall-plant system around the mining area is at high risks of heavy metal pollution caused by mining-smelting activities. In this study, 118 samples (including rhizospheric soils, background soils, soil-forming parent rocks, crops, vegetables, medicinal plants and atmospheric dustfall) were collected nearby Tongling Cu-Fe-Au mining area, Eastern China. We studied the concentrations, migration, sources, and health risks through consumption of two main crops (corn and rice), six kinds of vegetables, and medicinal plants (Fengdan, Paeonia ostii) for six metal elements (Cu, Zn, Cr, Cd, Pb and Hg). Results revealed Cr and Cd in soils, and Cd, Cr, Pb, Cu and Zn in dustfall showed a relatively high contamination degree. The mean contents of Cr and Pb in corn kernels, as well as Cd, Cr and Pb in rice grains and all vegetables, and Cr in Fengdan cortex moutan exceeded the corresponding food safety limits in China. The transfer capability of Cr in corn kernels and rice grains, Pb in edible vegetables, and Cd in cortex moutan were the strongest, respectively. Health risk assessment results showed Cr had the greatest non-carcinogenic risk, followed by Pb and Cd. The results of pearson's correlation analysis (CA), hierarchical cluster analysis (HCA), and principal component analysis (PCA) indicated Zn-Cr, Pb and Cd-Cu-Hg in the plants might derive from different geochemical end-members. Source apportionment based on lead isotope showed that mining-smelting activities were the major source of Pb in atmospheric dustfall and agricultural soils, with the average contribution rates of 66% and 50%, respectively. Vehicle emissions from diesel fuels (50%–68%) and mining-smelting activities (16%–25%) contributed mainly to Pb accumulation in plants. Hence, our study suggested the accumulations of Pb in plants might be mainly from the direct foliar uptake of atmospheric Pb related to vehicle emissions and mining-smelting activities.

Biochar has potential to control the bioavailability and migration of potentially toxic heavy metals in soil by adsorption. Natural ageing in the environment may change the physicochemical properties and adsorption function of biochar over the long-term. The present study compared the effects of different simulated ageing treatments on Cd adsorption of high and low temperature biochar from straw of corn (Zea mays). Fresh and aged biochars were systematically characterized by elemental analysis, FTIR, XPS, Zeta, SEM-EDS, XRD and the composition of their mineral ash. The adsorption of Cd to fresh and aged biochars was then assessed under the influence of pH. Drawing the results together the effects of ageing on the extent and mode of Cd adsorption could be elucidated. The results showed that the adsorption capacity of fresh biochar produced at 650 °C was higher than of biochar made at 350 °C, and that mineral co-precipitation plays a dominant role in Cd sorption. Leaching removed organic and inorganic ash components from biochars, markedly diminishing the capacity of the high temperature biochar to adsorb Cd. The adsorption performance of the low temperature biochar was dependent on surface complexation. The adsorption capacity of low-temperature biochar was markedly enhanced by oxygen-containing functional groups formed through acidification and oxidation. The long-term benefits of biochar in the management of polluted soil require a rethink, considering the contrasting ageing behavior of different temperature biochar and their response to different ageing environments.

Emission inventories are critical to understanding the sources of air pollutants, but have high uncertainties in China due in part to insufficient on-site measurements. In this study, we developed a method of examining, screening and applying online data from the country's improving continuous emission monitoring systems (CEMS) to reevaluate a “bottom-up” emission inventory of China's coal-fired power sector. The benefits of China's current national emission standards and ultra-low emission policy for the sector were quantified assuming their full implementation. The derived national average emission factors of SO₂, NOₓ and particulate matter (PM) were 1.00, 1.00 and 0.25 kg/t-coal respectively for 2015 based on CEMS data, smaller than those of previous studies that may not fully recognize improved emission controls in recent years. The annual emissions of SO₂, NOₓ and PM from the sector were recalculated at 1321, 1430 and 334 Gg respectively, 75%, 63% and 76% smaller than our estimates based on a previous approach without the benefit of CEMS data. The results imply that online measurement with proper data screening can better track the recent progress of emission controls. The emission intensity (the ratio of emissions to economic output) of Northwest China was larger than that of other regions, attributed mainly to its less intensive economy and industry. Transmission of electricity to more-developed eastern provinces raised the energy consumption and emissions of less-developed regions. Judged by 95 percentiles of flue-gas concentrations measured by CEMS, most power plants met the current national emission standards in 2015 except for those in Northwest and Northeast China, while plants that met the ultra-low emission policy were much scarcer. National SO₂, NOₓ and PM emissions would further decline by 68%, 55% and 81% respectively if the ultra-low emission policy can be strictly implemented, implying the great potential of the policy for emission abatement.

The accumulation of phthalate acid esters (PAEs) in the environment has aroused a global concern. Microbial degradation is the most promising method for removing PAEs from polluted environment. Di-n-butyl phthalate (DBP) is one of the most widely used PAEs. In this study, a highly efficient DBP-degrading strain, Enterobacter sp. DNB-S2 was isolated from Mollisol in northeast China, and the degradation rate of 500 mg L⁻¹ DBP reached 44.10% at 5 °C and 91.08% at 50 °C within 7 days. A new intermediate, n-butyl benzoate BP, was detected, implying a new degradation pathway. The complete genome of the strain DNB-S2 was successfully sequenced to comprehensively understand of the entire DBP catabolic process. Key genes were proposed to be involved in DBP degradation, such as esterases, 3,4-dihydroxybenzoate decarboxylase and catechol 2,3-dioxygenase genes. Intermediate-utilization tests and real-time quantitative polymerase chain reaction (RT-qPCR) validated the proposed DBP catabolic pathway. The aboriginal bacterium DNB-S2 is a promising germplasm for restoring PAE-contaminated Mollisol regions at low temperature. This study provides novel insight into the catabolic mechanisms and abundant gene resources of PAE biodegradation.

Photocatalytic degradation is an attractive strategy to purify waste water contaminated by macromolecular organics. Compared with the single-component photocatalysts, heterostructures of different semiconductors have been widely used to improve the photocatalytic performance. In this work, we fabricate a hetero-structured photocatalyst consisting of two-dimensional graphitic carbon nitride (g-C3N4) nanosheets and commercial MoO3 microparticles through a simple mixing and annealing process. The photocatalytic performance was evaluated in various dye degradation reactions, especially Rhodamine (RhB) degradation. The MoO3/g-C3N4 composite shown a significant improvement compared with individual MoO3 or g-C3N4 as well as their physical mixture. By applying electron spin resonance (ESR) spin-trap spectra, radical scavenge experiments and electrochemical analysis, we find that a direct Z-scheme charge transfer between MoO3 and g-C3N4 not only causes an accumulation of electrons in g-C3N4 and holes in MoO3, but also boosts the formation of superoxide radical and hydroxyl radical. The superoxide radical and hole dominate the photocatalytic degradation, while the hydroxyl radical plays a negligible role and its production can be suppressed by lowering the pH value.

Arsenic (As) and antimony (Sb) are considered as priority environmental pollutants and their accumulation in crop plants particularly in rice has posed a great health risk. This study endeavored to investigate As and Sb contents in paired soil-rice samples obtained from Xikuangshan, the world largest active Sb mining region, situated in China, and to investigate As speciation and location in rice grains. The soil and rice samples were analyzed by coupling the wet chemistry, laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), synchrotron-based micro X-ray fluorescence mapping (μ-XRF) and micro X-ray absorption near-edge structure (μ-XANES) spectroscopy. The results of field survey indicated that the paddy soil in the region was co-polluted by Sb (5.91–322.35 mg kg−1) and As (0.01–57.21 mg kg−1). Despite the higher Sb concentration in the soil, rice accumulated more As than Sb indicating the higher phytoavailability of As. Dimethylarsinic acid (DMA) was the predominant species (>60% on average) in the rice grains while the percentage of inorganic As species was 19%–63%. The μ-XRF mapping of the grain section revealed that the most of As was distributed and concentrated in rice husk, bran and embryo. Sb was distributed similarly to As but was not in the endosperm of rice grain based on LA-ICP-MS. The present results deepened our understanding of the As/Sb co-pollution and their association with the agricultural-product safety in the vicinity of Sb mining area.

In this study, a series of BUC-21/titanate nanotube (BT-X) composites were facilely fabricated via ball-milling of 2-dimensional (2D) metal-organic framework (MOF) BUC-21 and titanate nanotubes (TNTs). The BT-X composites were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), UV–visible diffuse-reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectrometer (XPS) and high resolution transmission electron microscopy (HRTEM). Both the photocatalytic reduction from Cr(VI) to Cr(III) and adsorptive removal of formed Cr(III) of BT-X composites were systematically investigated under different conditions including pH values and co-existing inorganic ions. It was found that BUC-21 (100 mg)/TNTs (100 mg) (BT-1) composites demonstrate remarkable ability of photocatalytic Cr(VI) reduction and adsorptive Cr(III) removal, as well as good reusability and stability. It is believed that the introduction of TNTs could capture the formed Cr(III) from the surface of BUC-21, which provided more active sites exposed to enhance the Cr(VI) reduction.

Urban wastewater effluents bring large amounts of nutrients, organic matter and organic microcontaminants into freshwater ecosystems. The effects of this complex mixture of pollutants on freshwater invertebrates have been studied mainly in temperate rivers and streams with high dilution capacities. In contrast, Mediterranean streams and rivers have lower dilution capacities especially during the seasonal drought, and are therefore exposed to high concentrations of pollutants. Here, we assess the effects of urban wastewater pollution on invertebrate communities from Mediterranean streams under different hydrological conditions. Specifically, we assessed the invertebrates taxonomic composition and functional biological traits in 12 streams, differing in stream and substrate size (sand or cobbles), under low (2 surveys) and baseflow (1 survey) conditions. In each stream, we selected reaches both upstream and downstream of the wastewater discharge point. Our results indicate that urban wastewater pollution favours the most tolerant invertebrate taxa and homogenises functional trait composition over time. Changes in functional traits were more evident during the seasonal drought, when the low flow conditions at the upstream and downstream sites were more severe and, pollutant concentrations downstream were at their highest. However, the effects of urban wastewater pollution were not uniform in the downstream sites; as local invertebrate communities differed in according to the river substrate and stream size (i.e., width and discharge). Overall, urban pollution caused by wastewater enhanced both, taxonomic and functional differences between the invertebrate communities. Such an absence of homogenisation among wastewater pollution impacted sites was probably related to the relevant role of stream substrate-size as well flow conditions in the rivers receiving the impact. These are attributes that need to be considered when setting the pollutant discharge limits in rivers and streams receiving effluents.