Antibiotics are becoming ubiquitous emerging contaminants in the aquatic environments due to their large amount of production and extensive application, which have received increasing public concern. In this paper, the degradation and mineralization of sulfamethoxazole (SMX) by ionizing radiation in the presence of Fe₃O₄ as Fenton-like catalyst were evaluated, the influencing factors, such as the initial SMX concentration, initial pH, water matrix, and radical scavenger, etc. were examined. The results demonstrated that SMX could be efficiently degraded. The addition of Fe₃O₄ could improve the degradation efficiency of SMX and increased the dose constant at various SMX initial concentrations. More than 98% of SMX was degraded in Fe₃O₄/gamma radiation system at a wide range of pH (about 3.0–11.0). The mineralization of SMX in the presence of Fe₃O₄ was increased by 200%. Adding free radical scavenger (tert-butyl alcohol) inhibited the degradation of SMX. The addition of Fe₃O₄ enhanced the dose constant of ·OH, indicating that Fe₃O₄ promoted the formation of hydroxyl radicals (·OH) and then improved SMX degradation and mineralization. The degradation efficiency of SMX in secondary effluent of WWTP decreased from 100 to 84% in secondary effluent compared with that in deionized water. The intermediate products during the degradation of SMX by ionizing radiation were identified by high-performance liquid chromatography, and a possible pathway of SMX degradation in such a system was tentatively proposed. Graphical abstract Schema illustration of SMX degradation by irradiation in the presence of Fe₃O₄

Thorium (Th) is one of the main sources of natural radiation to ecosystems. However, data regarding Th concentrations in rocks, soil, water and sediments are currently scarce. Accordingly, this study aimed to establish background concentrations and quality reference values (QRVs) for Th in the environmentally impacted Ipojuca River catchment in Brazil, where the weathering of granites releases Th into the environment. Additionally, the study aimed to calculate Th fluxes in water, and both bed and suspended sediment. The mean Th concentration in the study catchment soils was 28.6 mg kg⁻¹. The QRV for Th was estimated to be 21 mg kg⁻¹ and 86.3 Bq kg⁻¹. Bed and suspended sediment–associated concentrations ranged from 2.8 to 32.9 mg kg⁻¹. Suspended sediment–associated discharge (3.42 t year⁻¹) accounted for more than 99% of the total Th flux, while the dissolved phase transport was negligible in comparison. At the downstream cross section in the study catchment, suspended sediment samples exhibited Th concentrations similar to those observed in rivers impacted by mining activities. The discharge of sediment to the ocean from the study area is mainly triggered by soil erosion processes in the hotspot region (middle-inferior course). It is essential to identify Th hotspots before establishing environmental policies regarding human health and environmental protection.

The increasing anthropogenic inputs of Pb and Cd into China’s Nen River (Qiqihar section) owing to rapid urbanization in the past 50 years may pose ecological risks to the river’s aquatic system. To confirm this hypothesis, we determined the Pb and Cd concentrations in the sediments of the Nen River flowing across Qiqihar City by comparing the control group (samplings in the Nen River branch bypassing the city) and bioaccumulation along the food chain. We found significantly higher Pb concentrations in the sediments than in the control group (39.21 mg kg⁻¹ dry weight [dw] vs. 22.44 mg kg⁻¹ dw; p < 0.05). However, the difference between the Cd contents of the two groups was nonsignificant (0.33 mg kg⁻¹ dw vs. 0.30 mg kg⁻¹ dw) (p = 0.07). Accumulated Pb and Cd in the sediments pose a medium risk to the system of Nen River according to the result of risk assessment code analysis. The increased Pb and Cd levels along the food chain had adverse health effects in the species at the top level of the food chain. For example, the feathers of Corvus frugilegus and Sterna hirundo contained 0.28–2.25 mg kg⁻¹ dw of Cd. These values are considered potentially toxic to common avian species. The bone Pb level of C. frugilegus ranged from 4.82 to 7.41 mg kg⁻¹ dw within the increasing Pb range (2–15 mg kg⁻¹ dw) of common water birds. The inputs of Pb and Cd into the local environment should be reduced for the preservation of aquatic system health.

A series of activated carbons (ACs) were prepared by modifying a commercial AC by physical activation using CO₂ during different activation times. The ACs were designated as F, F12, F24, and F40 corresponding to the activation times of 0, 12, 24, and 40 h, respectively. The surface area, total pore volume, micropore volume, and mean micropore width were determined for all the ACs. The textural properties of the modified ACs increased substantially with the activation time, and the capacity of the ACs for adsorbing diclofenac (DCF) was almost linearly dependent upon the surface area of the ACS. The maximum adsorption capacities of F, F12, F24, and F40 carbons towards diclofenac (DCF) from aqueous solution were 271, 522, 821, and 1033 mg/g, respectively. Hence, the adsorption capacities of ACs were considerably enhanced with the activation time, and F12, F24, and F40 carbons presented the highest adsorption capacities towards DCF reported in the technical literature. The F40 adsorption capacity was at least twice those of other carbon materials. The adsorption capacities decreased by raising the pH from 7 to 11 due to electrostatic repulsion between the ACs surface and anionic DCF in solution. The removal of DCF from a wastewater treatment plant (WWTP) effluent was effectively carried out by adsorption on F40. Hence, the capacity of ACs for adsorbing DCF can be optimized by tailoring the porous structure of ACs.

Rural household energy consumption is an important component of national energy consumption. This paper explores the rural household energy consumption status and influencing factors on different sources of rural household energy consumption in western China. Using data from a survey of 240 households conducted in 2017, this study finds that rural households’ energy consumption structure in the study area is a combination of traditional biomass energy and commercial energy sources. Fuelwood is the most commonly used fuel in the study area, while modern energy sources only occupy a low proportion. Rural household energy consumption is influenced by various factors. Individual perceptions of climate change, social trust and networks, and households’ socio-economic and demographic factors (gender, age, education, income per capita, household size, household location, and number of household appliances) are identified as having significant effects on rural households’ consumption of biomass and commercial energies. The research results provide implications for policy makers to formulate related rural energy policies to improve the rural energy consumption structure and future energy policy design in China and other developing countries.

Sources of renewable energy have received wide attention in the literature because of serious threats to the environment. However, some renewable resources, including biomass energy role is debatable in the energy economics literature. This empirical work focuses to analyze the role of biomass energy in carbon dioxide (CO₂) emissions using the framework of the environmental Kuznets curve (EKC) in Pakistan over the period from 1980 to 2015. The bound testing approach suggests there is cointegration among study variables. The study uses an auto-regressive distributed lag model (ARDL) with a structural break in the series. To summarize the findings of the study, it can be inferred that biomass energy increase CO₂ emissions. In addition, biomass energy helps to form a U-shaped relationship between income and CO₂ emissions that support the EKC hypothesis. Also, the feedback hypothesis is found between biomass energy and CO₂ emissions. The findings would guide policymaker with practical guidelines to formulate policies to utilize a high amount of biomass energy in a sustainable manner.

The distribution of emerging organic contaminants in drinking water sources in Africa is a subject with very scanty data and information. In order to fill knowledge gaps, we report here the distribution and potential ecological risks of three phenolic compounds (bisphenol A (BPA), 4-nonylphenol (NP), and 4-tert-octylphenol (OP)), which have been previously identified to have the potential of endocrine disrupting activity, in surface water and sediment of the New Calabar River. The compounds were quantified using GC-MS. At all sampling sites, a similar concentration pattern of BPA > NP > OP was recorded, with the exception of Choba sampling station in which the levels of these endocrine disrupting compounds were low or undetectable. The levels of BPA in surface water ranged from 1.20 to 63.64 μg/L, whereas those of NP and OP ranged from < 0.20 to 2.15 μg/L and from < 0.10 to 0.68 μg/L, respectively. For sediments, measured levels were from 1.20 to 66.57 μg/kg for BPA, from < 0.35 to 3.37 μg/kg for NP, and from < 0.13 to 0.90 μg/kg for OP. Risk quotients (RQs) assessed for some sensitive organisms (algae, Daphnia magna, and fish) were above 1 for BPA and NP, whereas RQs for OP were below 1. This implies that BPA and NP at the levels detected could have potential risks to the sensitive organisms considered, but low risk for OP.

The Baltic Sea is known to be severely polluted by a range of chemicals, one group of which being PCBs. Although the use and production of PCBs were limited or banned in many countries in the 1970s, their presence is still observed in the environment. The aim of this study was to evaluate PCBs concentration in four species of diving sea ducks, interspecies and tissues differences, and in the case of game species, comparison of the obtained results with maximal residue levels (MRLs) and tolerable weekly intake (TWI). The level of Σi-PCBs was noted in most examined samples (liver, muscle, fat tissue) at levels ranging between < LoD and 2315.45 ng/g lw. The dominant congener was PCB 153, followed by PCB 180 and 138. The mean dl-PCB-TEQ value in the muscles of the tested tufted ducks and common pochards was 0.31 and 0.71 pg-TEQ/g lw, respectively, which is 8–25 and 18–57% of the TEQ maximum limit (ML) value for farm animal muscles. The average decrease in i-ΣPCB concentration in the fat tissue of ducks wintering in the Baltic Sea southern coast was found to be 2.9–3.3%/year. The analysis of PCB residues indicates that the common pochard and tufted duck are not suitable for consumption due to high Σi-PCB concentrations. However, the regular consumption of muscle and liver of game birds does not result in an unacceptable intake of dl-PCBs, i.e., above the TWI value.

The original publication of this paper contain typographical mistakes. ‘Michael Bell’ mentioned in this paper should be corrected as ‘Michelle L. Bell’.

The aim of this meta-analysis was to synthesize the effects of biochar amendment on soil enzyme activities (SEAs) related to carbon (C), nitrogen (N), and phosphorus (P) cycling. Based on 401 paired comparisons from 43 published studies, the SEAs and main influential factors were analyzed in response to biochar characteristics, soil properties, and experiment conditions. Results showed that biochar additions to soils overall increased the N- and P-cycling SEAs by 14 and 11%, respectively. The enhancement of the N- and P-cycling SEAs was mainly attributable to the microbial stimulation by biochar properties (i.e., nutrient content and porosity) and soil nutrients (e.g., soil organic C and total N). The enhancement was the most significant under the conditions with biochars produced at low temperatures and using feedstock materials with high nutrient content, and biochar applications in acidic or neutral soils, coarse or fine soils, and farmland soils. Biochar additions to soils overall reduced the C-cycling SEAs by 6.3%. The C-cycling SEAs were greatly suppressed under the conditions with low and very high biochar loads, biochars produced at high temperatures and with feedstock materials of herb and lignocellulose, and biochar applications in alkaline, fine, and forest soils. The results were mainly related to the adsorption and inhibition effects of biochars and soil properties (e.g., liming effect, high biochar porosity and aromatic C content) on fungi and the enzymes. Biochar feedstock, C/N and load, and soil total N were the main influential factors on the SEAs. The results from this study demonstrate that biochar amendment is beneficial to improving soil N and P cycling and C sequestration.