Wastewater and stormwater are both considered as critical pathways contributing microplastics (MPs) to the aquatic environment. However, there is little information in the literature about the potential influence of constructed wetlands (CWs), a commonly used wastewater and stormwater treatment system. This study was conducted to investigate the abundance and distribution of MPs in water and sediment at five CWs with different influent sources, namely stormwater and wastewater. The MP abundance in the water samples ranged between 0.4 ± 0.3 and 3.8 ± 2.3 MP/L at the inlet and from 0.1 ± 0.0 to 1.3 ± 1.0 MP/L at the outlet. In the sediment, abundance of MPs was generally higher at the inlet, ranging from 736 ± 335 to 3480 ± 4330 MP/kg dry sediment and decreased to between 19.0 ± 16.4 and 1060 ± 326 MP/kg dry sediment at the outlet. Although no significant differences were observed in sediment cores at different depth across the five CWs, more MPs were recorded in silt compared to sandy sediment which indicated sediment grain size could be an environmental factor contributing to the distribution of MPs. Polyethylene terephthalate (PET) fibres were the dominant polymer type found in the water samples while polyethylene (PE) and polypropylene (PP) fragments were predominantly recorded in the sediment. While the size of MPs in water varied across the studied CWs, between 51% and 64% of MPs in the sediment were smaller than 300 μm, which raises concerns about the bioavailability of MPs to a wider range of wetland biota and their potential ecotoxicological effects. This study shows that CWs can not only retain MPs in the treated water, but also become sinks accumulating MPs over time.

The inconsistency of available methods and the lack of harmonization in current microplastics (MPs) analysis in soils demand approaches for extraction and quantification which can be utilized across a wide variety of soil types. To enable robust and accurate assessment of extraction workflows, PET MPs with an inorganic tracer (Indium, 0.2% wt) were spiked into individual soil subgroups and standard soils with varying compositions. Due to the selectivity of the metal tracer, MPs recovery rates could be quickly and quantitatively assessed using ICP-MS. The evaluation of different methods specifically adapted to the soil properties were assessed by isolating MPs from complex soil matrices by systematically investigating specific subgroups (sand, silt, clay, non-lignified and lignified organic matter) before applying the workflow to standard soils. Removal of recalcitrant organic matter is one of the major hurdles in isolating MPs for further size and chemical characterization, requiring novel approaches to remove lignocellulosic structures. Therefore, a new biotechnological method (3-F-Ultra) was developed which mimics natural degradation processes occurring in aerobic (Fenton) and anaerobic fungi (CAZymes). Finally, a Nile Red staining protocol was developed to evaluate the suitability of the workflow for non-metal-doped MPs, which requires a filter with minimal background residues for further chemical identification, e.g. by μFTIR spectroscopy. Image analysis was performed using a Deep Learning tool, allowing for discrimination between the number of residues in bright-field and MPs counted in fluorescence mode to calculate a Filter Clearness Index (FCI). To validate the workflow, three well-characterized standard soils were analyzed applying the final method, with recoveries of 88% for MPs fragments and 74% for MPs fibers with an average FCI of 0.75. Collectively, this workflow improves our current understanding of how to adapt extraction protocols according to the target soil composition, allowing for improved MPs analysis in environmental sampling campaigns.

The sedimentary history of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) over the past 140 years in a lake sediment core from Huixian karst wetland was reconstructed. The total PAHs and OCPs concentrations ranged from 40.0 to 210 ng g⁻¹ and 0.98 to 31.4 ng g⁻¹, respectively. The vertical distribution of PAHs and OCPs in different stages was great consistent with the history of regional socio-economic development and the usage of OCPs. As the indicators of socio-economic development, gross domestic product (GDP), population, energy consumption, highway mileage, and private vehicles correlated with the PAHs concentrations, indicating the impact of human activities on PAHs levels. The PAHs and OCPs concentrations were also affected by environmental changes in the wetland, as reconstructed by total organic carbon (TOC), sand, silt, clay, quartz, and calcite in sediments. Redundancy analysis (RDA) results showed TOC was the dominant factor to explain the concentrations of PAHs and OCPs with the explanation of 86.7% and 43.5%, respectively. In addition, TOC content had significantly positive correlation with PAHs (0.96, p < 0.01) and OCPs (0.78, p < 0.01). In particular, the significantly positive correlation (p < 0.05) between calcite and PAHs and OCPs inferred that karstification might play an important role in the migration of PAHs and OCPs in the karst area. Therefore, the lake in Huixian wetland tended to be a sink more than a source of PAHs and OCPs influenced by the increasing TOC content and karstification under climate warming.

Plastic mulching and straw incorporation are common agricultural practices in China. Plastic mulching is suspected to be a significant source of microplastics in terrestrial environments. Straw incorporation has many effects on the storage of soil organic carbon (SOC) and greenhouse gas emissions, but these effects have not been studied in the presence of microplastic pollution. In this study, 365-day soil incubation experiments were conducted to assess the effects of maize straw and polyethylene microplastics on SOC fractions and carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions in two different soils (fluvo-aquic and latosol). Against the background of straw incorporation, microplastics reduced the mineralization and decomposition of SOC, resulting in a microbially available SOC content decrease by 18.9%. In addition, microplastics were carbon-rich, but relatively stable and difficult to be used by microorganisms, thus increasing the mineral-associated SOC content by 52.5%. This indicated that microplastics had adverse effects on microbially available SOC and positive effects on mineral-associated SOC. Microplastics also decreased coarse particulate SOC (>250 μm), and increased non-aggregated silt and clay aggregated SOC (<53 μm). Furthermore, microplastics changed microbial community compositions, thereby reducing the CO₂ and N₂O emissions of straw incorporation by 26.5%–33.9% and 35.4%–39.7%, respectively. These results showed that microplastics partially offset the increase of CO₂ and N₂O emissions induced by straw incorporation. Additionally, the inhibitory effect of microplastics on CO₂ emissions in fluvo-aquic soil was lower than that in latosol soil, whereas the inhibitory effect on N₂O emissions had the opposite trend.

Chemically oxidative removal of polycyclic aromatic hydrocarbons (PAHs) in soil is related to their occurrence state. Whether the heterogeneity of natural organic matter has an effect on the occurrence of PAHs in soil and, if there is an effect, on the oxidative removal efficiency of PAHs remains unknown. In this study, the removal efficiencies of 16 priority PAHs aged in humic acids (HAs) of different soil aggregate fractions by various oxidants were investigated by combining soil fractionation and microreaction experiments. Results showed that the accumulations of PAHs in particulate HA (P-HA) and microaggregate occluded HA (MO-HA) mainly occurred in the early period of the aging time frame. In contrast, PAH accumulation in non-aggregated silt and clay associated HA (NASCA-HA) was relatively slow and tended to saturate in the late period of the aging time frame. The cumulative contents of PAHs throughout the entire aging period in MO-HA and NASCA-HA were significantly greater than that in P-HA. The aged PAHs in P-HA and NASCA-HA exhibited the highest and lowest removal efficiencies, respectively. This ranking was mainly governed by the molecular size and polarity of HAs. Sodium persulfate and potassium permanganate had the highest removal efficiencies in total PAHs in HAs, with average efficiencies of 85.8% and 79.1%, respectively, in P-HA. Hydrogen peroxide had the lowest degradation efficiency in PAHs. In particular, the degradation efficiency of total PAHs in NASCA-HA was lowered to 31.0%. PAH congeners in HAs showed a large difference in oxidative removal efficiency. Low-ring PAH was more easily degraded than medium- and high-ring PAHs, and in most treatments, fluoranthene and pyrene in the medium ring and benzo[a]pyrene in the high ring demonstrated higher efficiencies than other PAHs with the same number of rings. Our findings are useful in promoting the accurate and green remediation of PAH-contaminated soils.

Microplastics (MPs), as a new type of environmental pollutant, pose a serious threat to soil ecosystems. The activities of soil extracellular enzymes produced by microorganisms are the potential sensitive indicators of soil quality. However, little is known about the response mechanism of enzyme activities toward MPs on a long-term scale. Moreover, information on differences in enzyme activities across different soil aggregates is lacking. In this study, 150 days of incubation experiments and soil aggregate fractionation were combined to investigate the influence of MPs on extracellular enzyme activities in soil. 28% concentration of polyethylene with size 100 μm was adopted in the treatments added with MPs. The results show that MPs inhibited enzyme activities through changing soil nutritional substrates and physicochemical properties or through adsorption. Moreover, MPs competed with soil microorganisms for physicochemical niches to reduce microbial activity and eventually, extracellular enzyme activity. Enzyme activities in different aggregate-size fractions responded differently to the MPs exposure. The catalase in the coarse particulate fraction and phenol oxidase and β-glucosidase in the micro-aggregate fraction exerted the greatest response. With comparison, urease, manganese peroxidase, and laccase activities showed the greatest responses in the non-aggregated silt and clay fraction. These observations are believed to stem from differences in the key factors determining the enzyme activities in different aggregate-size fractions.The inhibitory pathway of microplastics on activities of extracellular enzymes in soil varies significantly across different aggregate fractions.

Alprazolam, clonazepam and diazepam are drugs belonging to the benzodiazepine class. These drugs might be important environmental contaminants in aquatic media. A total understanding of behavior and fate of drugs in aquatic environment is not available for these and other drugs. Thus, in this work, a complete optimization of sample treatment and extraction of analytes from sediments and water was described, as well a study of sediment/water distribution comparing it with sample characteristics. Ultrasound for 10 min and 3 steps using 3 mL of extraction solvent were chosen as the stirring form for extraction. A methanol/water (1:1) solution pH 12 was the best extraction solvent. Aiming to eliminate interferences, an addition of 10 μL of NaCl 3.06 mol L⁻¹ was necessary after each step of extraction. Sediment and water samples were characterized, presenting different values on physical-chemical parameters. Six distinct sample sets of water and sediments were spiked with each benzodiazepine and analyzed. Kd values varied from 1.4 to 9.2 L kg⁻¹ for clonazepam, 1.8–11.5 L kg⁻¹ for alprazolam and 2.31–12 L kg⁻¹ for diazepam. A principal component analysis showed high dependence on Kd with sample characteristics mainly related to sediments. In the systems, whose sediments presented high levels of clay, silt and organic matter, the drugs presented a great interaction with the solid part of the system, increasing the Kd value. Koc values varied from 149.25 to 634.13 L kg⁻¹ for clonazepam, 186.57–852.48 L kg⁻¹ for alprazolam, and 194.68–1189.81 L kg⁻¹ for diazepam.

The presence of Per-, Poly-fluoroalkyl substances (PFASs) in aquatic ecosystems has drawn broad concerns in the scientific community due to their biological toxicity. However, little has been explored regarding PFASs' removal in phytoplankton-dominated environments. This study aimed to create a simulated bacteria-algae symbiotic ecosystem to observe the potential transportation of PFASs. Mass distributions showed that sand (63–2000 μm), silt & clay (0–63 μm), the phycosphere (>3 μm plankton), and the free-living biosphere (0.22–3 μm plankton) contained 19.00, 7.78, 5.73 and 2.75% PFASs in their total mass, respectively. Significant correlations were observed between carbon chain lengths and removal rates (R² = 0.822, p < 10⁻⁴). Structural equation models revealed potential PFAS transportation pathways, such as water-phycosphere- free-living biosphere-sand-silt&clay, and water-sand-silt&clay (p < 0.05). The presence of PFASs decreased the bacterial density but increased algal density (p < 0.01) in the planktonic environment, and PFASs with longer carbon chain lengths showed a stronger enhancement in microbial community successions (p < 0.05). In algal metabolisms, chlorophyll-a and carotenoids were the key pigments that resisted reactive oxygen species caused by PFASs. PFBA (perfluorobutyric acid) (10.38–14.68%) and PFTeDA (perfluorotetradecanoic acid) (10.33–15.96%) affected bacterial metabolisms in phycosphere the most, while in the free-living biosphere was most effected by PFPeA (perfluorovaleric acid) (13.21–13.99%) and PFDoA (perfluorododecanoic acid) (10.04–10.50%). The results of this study provide new guidance measures for PFAS removal and management in aquatic environments.

Condensed organic matters (COM) with black carbon-like structures are considered as long-term carbon sinks because of their high stability. It is difficult to distinguish COM from general organic matter by conventional chemical analysis, thus the contribution by and interaction mechanisms of organo-mineral complexes in COM stabilization are unclear and generally neglected. Molecular markers related to black carbon-like structures, such as benzene polycarboxylic acids (BPCAs), are promising tools for the qualitative and quantitative analysis of COM. In this study, one natural soil and two cultivated soils with 25 y- or 55 y-tillage activities were collected and the distribution characteristics of BPCAs were detected. All the investigated soils showed similar BPCA distribution pattern, and over 60% of BPCAs were detected in clay fraction. The extractable BPCA contents were substantially increased after mineral removal. The ratios of BPCA contents before and after mineral removal indicate the extent of COM-mineral particle interactions, and our results suggested that up to 73% COM were protected by mineral particles, and more stronger interactions were noted on clay than on silt. The initial cultivation dramatically decreased COM-clay interactions, and this interaction was recovered only slowly after 55-y cultivation. Kaolinite and muscovite are important for COM protection. But a possible negative correlation between BPCAs and reactive iron oxides of the cultivated soils suggested that iron may promote COM degradation when disturbed by tillage activities. This study provided a new angle to study the stabilization of COM and emphasized the importance of organo-mineral complexes for COM stabilization.

Hard coal is the predominant energy source in Poland. The unavoidable consequence of coal combustion is the production of huge amounts of ash which can be concentrated in radionuclides. The ashes from coal combustion are utilized or stored and may affect the quality of the environment. Therefore, the estimation of radionuclides in hard coal and by-products is of crucial importance. The analyzed samples included ashes produced in ash furnaces, power plants and individual home furnaces operating in the Upper Silesian Industrial Region, Southern Poland, during the hard coal burning. This paper presents radioactivity concentrations of ²²⁸Ra, ²²⁶Ra and ⁴⁰K in hard coal, bottom and fly ash samples from Polish coal-fired power plants obtained during various technological coal combustion processes and generated in individual domestic furnaces, determined using the HPGe gamma spectrometry technique. The measurements of ²³⁴,²³⁸U concentrations were performed after sample preparation using alpha-particle spectrometer. The concentrations of the obtained radionuclides differ greatly in the fly and bottom ash samples. The lowest concentrations of ²²⁶Ra, ²²⁸Ra, ²³⁴U, ²³⁸U were observed in bottom ashes from the co-firing of hard coal and biomass in a fluidized-bed furnace, whereas the highest concentrations of ²²⁶Ra (163 ± 6 Bq/kg), ²²⁸Ra (100 ± 2 Bq/kg) isotopes were found in the ashes from individual household furnaces. This means that both the feed coal type and combustion techniques have a direct impact on the concentration of radionuclides in ash. Hard coal silt samples may be enriched in radionuclides and the radioactive equilibrium between ²²⁶Ra and ²³⁸U even in the case of coal is not always achieved. The concentrations of the analyzed isotopes in ashes are 5-7-fold higher than in feed coal. Given that combustion by-products are utilized as construction products, it should be noted that for some ash samples, the radiological hazard indices approach or exceed the maximum permitted levels.