Chromophoric dissolved organic matter (CDOM) in rivers is mainly affected by natural conditions and human activities and can reflect the watershed pollution status to a certain extent. The Yellow River is one of the largest contributors to the global riverine sediment flux from the land to ocean, and there is a paucity of information on how the optical properties of CDOM have the potential to serve as an indicator of water quality for the sediment-laden Yellow River. In this study, a three-dimensional fluorescence parallel factor (PARAFAC) analysis method was applied to investigate the seasonal and spatial variations in CDOM fluorescence components and spectral characteristics from the source region to the estuary in the mainstream of Yellow River. The relationships of CDOM with water quality indicators and trophic state were also analyzed. Six PARAFAC components (C1–C6) were identified and grouped into two categories: humic-like components (C1–C4), which accounted for 85.8 %, and protein-like components (C5 and C6), which accounted for only 14.2 %. The CDOM components, spectral parameters, and their clear correlations with the main ions (Na⁺ and Cl⁻) all indicated that the humic-like components may be primarily derived from nonpoint source erosion, and the protein-like components were mainly derived from point source discharges in the watershed. The combination of the CDOM absorption coefficient at 254 nm (a(254)), spectral slope ratio (SR), specific UV absorbance SUVA₂₅₄, and fluorescence index (FI) had a good predictive ability for the key water quality indicators (total nitrogen (TN), dissolved total nitrogen (DTN), total phosphorus (TP), dissolved total phosphorus (DTP), and chlorophyll a (Chl a)) and trophic state index (TSI). Therefore, some fluorophores and UV spectral parameters of CDOM in the Yellow River can be used for rapid water quality monitoring and pollution source indication, especially pollutants related to nitrogen and phosphorus nutrients in the basin.

The availability of organic matters in vast quantities from the agricultural/industrial practices has long been a significant environmental challenge. These wastes have created global issues in increasing the levels of BOD or COD in water as well as in soil or air segments. Such wastes can be converted into bioenergy using a specific conversion platform in conjunction with the appropriate utilization of the methods such as anaerobic digestion, secondary waste treatment, or efficient hydrolytic breakdown as these can promote bioenergy production to mitigate the environmental issues. By the proper utilization of waste organics and by adopting innovative approaches, one can develop bioenergy processes to meet the energy needs of the society. Waste organic matters from plant origins or other agro-sources, biopolymers, or complex organic matters (cellulose, hemicelluloses, non-consumable starches or proteins) can be used as cheap raw carbon resources to produce biofuels or biogases to fulfill the ever increasing energy demands. Attempts have been made for bioenergy production by biosynthesizing, methanol, n-butanol, ethanol, algal biodiesel, and biohydrogen using different types of organic matters via biotechnological/chemical routes to meet the world’s energy need by producing least amount of toxic gases (reduction up to 20–70% in concentration) in order to promote sustainable green environmental growth. This review emphasizes on the nature of available wastes, different strategies for its breakdown or hydrolysis, efficient microbial systems. Some representative examples of biomasses source that are used for bioenergy production by providing critical information are discussed. Furthermore, bioenergy production from the plant-based organic matters and environmental issues are also discussed. Advanced biofuels from the organic matters are discussed with efficient microbial and chemical processes for the promotion of biofuel production from the utilization of plant biomasses.

Billions of disposable face masks are consumed daily due to the COVID-19 pandemic. The role of these masks as a source of nanoplastics (NPs) and microplastics (MPs) in the environment has not been studied in previous studies. We quantified and characterized face mask released particles and evaluated their potential for accumulation in humans and marine organisms. More than one billion of NPs and MPs were released from each surgical or N95 face mask. These irregularly-shaped particles sized from c. 5 nm to c. 600 μm. But most of them were nano scale sized <1 μm. The middle layers of the masks had released more particles than the outer and inner layers. That MPs were detected in the nasal mucus of mask wearers suggests they can be inhaled while wearing a mask. Mask released particles also adsorbed onto diatom surfaces and were ingested by marine organisms of different trophic levels. This data is useful for assessing the health and environmental risks of face masks.

Chlorinated paraffins (CPs) have been widely used as halogenated flame retardants and plasticizers since the mid-20th century. The prevalence of CPs in soil has been widely reported, but the distribution pattern of CPs in urbanized zones and their association with multiple socioeconomic variables have not been adequately explored. Herein, short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) were investigated in surface soil samples from Tianjin, China, a typical urbanized area. The concentration distributions of SCCPs and MCCPs showed similar trends in different administrative divisions and land use types: urban areas > suburbs > outer suburbs (p < 0.001) and residential areas > greenbelts > agricultural areas (p < 0.001). The CP congeners in residential surface soils mainly included those with longer carbon chains and high degree of chlorination, while the CP congeners in agricultural surface soils mainly consisted of those with shorter carbon chains and fewer chlorine substituents. Multiple statistical approaches were used to explore the association between socioeconomic factors and CP distribution. CP concentration was significantly correlated to population density and gross domestic product (GDP) (p < 0.001), and structural equation models incorporating administrative regional planning showed an indirect impact on the distribution of MCCP concentration due to the influence of regional planning on population density. These results highlight the association between CP contamination and the degree of urbanization, and this paper provides useful information toward mitigating the exposure risk of CPs for urban inhabitants.

The Mugan Plain is the most productive area in the Republic of Azerbaijan, but a previous study confirmed trace metal and metalloid (TM&M) contamination with Cr, Ni and Pb, and the potential ecological risk of As was estimated. However, no industrial activity was previously reported in this area; thus, a source apportionment model using positive matrix factorization (PMF) was employed to identify pollution sources, and a human health risk assessment was conducted to evaluate noncarcinogenic and carcinogenic risks. Surface soil samples were collected from 349 sites, and six major elements (Si, Ca, Cl, P, S and Sr) and 8 TM&Ms (As, Cd, Cr, Co, Cu, Ni, Pb and Zn) were analyzed by X-ray fluorescence and employed for further apportionment and risk assessment. As a result, the PMF model showed 7 factors, assigned to natural activity (12.9%), dry riverbed (13.6%), surface accumulation (3.1%), desalinization activity (3.2%), residential activity (12.3%), fossil fuel combustion (35.5%) and agricultural activity (19.3%). The PMF model characterized certain areas with desalinization activity in the previous Soviet period and with surface accumulation of salt, and these findings were confirmed by additional field surveys and historical Landsat satellite images. The risk assessment results showed that there was no risk for the adults, while for children, there was a noncarcinogenic risk, but no carcinogenic risk. Dermal contact was estimated to be the primary pathway, and Ni and As were identified as the most problematic TM&Ms for noncarcinogenic and carcinogenic risks, respectively. According to the results, fossil fuel combustion associated with heating and vehicle transportation was estimated to be the main source of pollution, contributing 42.6% of the noncarcinogenic and 48.0% of the carcinogenic risks. These results can provide scientific guidance to understand and prevent the risk of TM&Ms on the Mugan Plain.

A highly efficient, eco-friendly and relatively low-cost catalyst is necessary to tackle bottlenecks in the treatment of industrial wastewater laden with heavy metals and antibiotic such as livestock farm and biogas liquids. This study investigated co-oxidative removal of arsenite (As(III)) and tetracycline (TC) by iron nanoparticles (Fe NP)-impregnated carbons based on heterogeneous Fenton-like reactions. The composites included Fe NP@biochar (BC), Fe NP@hydrochar (HC), and Fe NP@HC-derived pyrolysis char (HDPC). The functions of N and S atoms and the loading mass of the Fe NP in the Fe NP@BC in heterogeneous Fenton-like reactions were studied. To sustain its cost-effectiveness, the spent Fe NP@BC was regenerated using NaOH. Among the composites, the Fe NP@BC achieved an almost complete removal of As(III) and TC under optimized conditions (1.0 g/L of dose; 10 mM H₂O₂; pH 6; 4 h of reaction; As(III): 50 μM; TC: 50 μM). The co-oxidative removal of As(III) and TC by the Fe NP@ BC was controlled by the synergistic interactions between the Fe NPs and the active N and S sites of the BC for generating reactive oxygen species (ROS). After four consecutive regeneration cycles, about 61 and 95% of As(III) and TC removal were attained. This implies that the spent carbocatalyst still has reasonable catalytic activities for reuse. Overall, this suggests that adding technological values to unused biochar as a carbocatalyst like Fe NP@BC was promising for co-oxidative removal of As(III) and TC from contaminated water.

Uranyl carbonate (UC(VI)) is a stable form of uranyl (U(VI)) that widely coexists with amorphous colloidal silica (ACSi) and humic acid (HA) in carbonate-rich U-contaminated areas. In this context, the cotransport behavior and mechanism of UC(VI) with ACSi (100 mg L⁻¹) and HA colloids in saturated porous media were systematically investigated. It was found that the ACSi and strip-shaped HA have a strong adsorption capacity for UC(VI), and their adsorption distribution coefficient (Kd) is 4–5 orders of magnitude higher than that of quartz sand (QS). In the ternary system, UC(VI) was mainly existing in the colloid-associated form at low UC(VI) concentration (4.2 × 10⁻⁶ M). Compared with the individual transport of UC(VI), the presence of ACSi and strip-shaped HA in the binary system promotes the transport of low-concentration UC(VI) (4.2 × 10⁻⁶ M) but shows a hindering effect when UC(VI) = 2.1 × 10⁻⁵ M. When ionic strength (IS) increased from 0 to 100 mM, the individual transport of UC(VI) and ACSi was weakened owing to the masking effect and the compression of the electrical double layer, respectively; this weakening effect is more pronounced in the binary (UC(VI)–ACSi) system. Notably, the transport of UC(VI) and ACSi in the ternary system is independent of the changes in IS due to the surface charge homogeneity strengthening the electrostatic repulsion between HA and QS. The Derjaguin–Landau–Verwey–Overbeek theory and retention profiles reveal the co-deposition mechanism of ACSi and UC(VI) in the column under different hydrochemical conditions. The nonequilibrium two-site model and the mathematical colloidal model successfully described the breakthrough data of UC(VI) and ACSi, respectively. These results are helpful for evaluating the pollution caused by UC(VI) migration in an environment rich in HA and formulating corresponding effective control strategies.

A large amount of tetracycline (TC) persists in water, soil, food, and feed due to the overuse of antibiotics, causing serious environmental problems such as damage to ecosystems and posing risks to human health. Thus, there is an urgent need to find a method to detect TC that is practical, rapid, sensitive, and offers ready visualization of TC levels so that adequate remediation measures can be immediately implemented. Herein, we report a fluorescent and colorimetric dual-mode nanosensor for the detection of TC based on reduced state carbon dots (r-CDs). In the presence of TC, the emission fluorescence of r-CDs was quenched by the Förster resonance energy transfer mechanism to achieve high-sensitivity detection of TC with a low limit of detection (LOD) of 1.73 nM. Moreover, TC was also detected by r-CDs via a noticeable color change of the solution (from colorless to red) with the naked eye, having an LOD of 0.46 μM. Furthermore, r-CDs have excellent selectivity and sensitivity in detecting TC in wastewater, and therefore, have practical applications in wastewater treatment. The fluorescent and colorimetric dual-mode proposed in this work may offer a unique idea for the detection of TC, with great prospects for environmental wastewater applications.

Forest fires significantly affect the wildlife, vegetation, composition and structure of the forests. This study explores the potential of partially burnt wood recovered in the aftermath of a recent Canadian forest fire incident as a feedstock for generating hydrogen-rich syngas through hydrothermal gasification. Partially burnt wood was gasified in hydrothermal conditions to study the influence of process temperature (300–500 °C), residence time (15–45 min), feed concentration (10–20 wt%) and biomass particle size (0.13 mm and 0.8 mm) using the statistical Taguchi method. Maximum hydrogen yield and total gas yield of 5.26 mmol/g and 11.88 mmol/g, respectively were obtained under optimized process conditions at 500 °C in 45 min with 10 wt% feed concentration using biomass particle size of 0.13 mm. The results from the mean of hydrogen yield show that the contribution of each experimental factors was in the order of temperature > feed concentration > residence time > biomass particle size. Other gaseous products obtained at optimum conditions include CO₂ (3.43 mmol/g), CH₄ (3.13 mmol/g) and C₂–C₄ hydrocarbons (0.06 mmol/g).

An increase in polycyclic aromatic hydrocarbon (PAH) pollution poses significant challenges to human and ecosystem health in the Three Gorges Reservoir (TGR) of the Yangtze River. Based on the combination of PAH analysis with qPCR and high-throughput sequencing of bacteria, 32 topsoil samples collected from 16 sites along the TGR were used to investigate the distribution and biodegradation pathways of PAHs in the water-level-fluctuation zone (WLFZ). The results indicated that the concentrations of PAHs were 43.8–228.2 and 30.8–206.3 ng/g soil (dry weight) under the high- and low-water-level (HWL and LWL) conditions, respectively. The PAH concentration in urban areas was higher than that in rural areas. Under both the HWL and LWL conditions, the abundance of the bamA gene, a biomarker of anaerobic PAH biodegradation, was significantly higher than that of the ring-hydroxylating-dioxygenase (RHD) gene, a biomarker of aerobic PAH biodegradation. The abundance of the bamA gene was significantly positively correlated with PAHs (R² = 0.8), and the biodegradation percentage of PAHs incubated anaerobically was greater than that in the aerobically incubated microcosm experiments. These data implicated a key role of the anaerobic pathway in PAH biodegradation. Co-occurrence network analysis suggested that anaerobic Anaerolineaceae, Dechloromonas, Bacteroidetes_vadin HA17 and Geobacter were key participants in the biodegradation of PAHs. The diversity analysis of functional bacteria based on the bamA gene and microcosm experiments further demonstrated that nitrate was the primary electron acceptor for PAH biodegradation. These findings provide a new perspective on the mechanism of PAH biodegradation in the TGR and knowledge that can be used to develop strategies for environmental management.