Combined Pollution Research Articles

Effects of copper and lead on the sorption and desorption behaviors of benzene onto humic acids and black carbons

ABSTRACT Due to rapid urbanization and industrialization, combined pollution caused by BTEX (benzene, toluene, ethylbenzene, and xylene) and heavy metals has become ubiquitous in soils, which would pose serious health risks to humans. However, the effects of heavy metals on the sorption and desorption behaviors of BTEX have not been fully elucidated. In this study, the effects of Cu2+ and Pb2+ ions on the sorption and desorption of benzene onto humic acids and black carbons were investigated. The results showed that Cu2+ and Pb2+ ions significantly reduced the sorption capacity, slowed down the sorption rate, and made the desorption less hysteretic of benzene on both humic acids and black carbons. Furthermore, the inhibitory effects by Pb2+ were significantly stronger than those of Cu2+. By combining the results of Fourier transform infrared spectroscopy and the site energy distribution model, it can be speculated that the hydration shells of Cu2+ and Pb2+ ions partially cover the surface of humic acids and black carbons, blocking their micropores and shielding sorption sites, consequently inhibiting the sorption of benzene. This study highlights that coexisting metal cations can significantly influence the fate of BTEX in soils.

Simulated Experimental Study on the Removal of Methylene Blue-Cu(II) Composite Pollution by Magnetized Vaterite

The combined pollution of organics and heavy metals represents a significant environ-mental problem that has attracted widespread attention. This explores the treatment of methylene blue (MB) and Cu(II), which are common pollutants in dye wastewater, and the recycling of Cu. A magnetized vaterite (V-M) was synthesized using Bacillus velezensis, and its structure and magnetic performance were investigated. The effects and mechanisms of removing MB-Cu(II) composite pollution using V-M and H2O2 in combination were estimated. The results indicated that V-M is a combination of organic and inorganic substances, with 21.5 wt% organic matter and multiple organic functional groups, including O-H, -SH, and others. The combination of V-M and H2O2 can achieve a maximum removal percentage of 90% for MB-Cu(II) pollution. The analysis showed that MB was oxidized by the ·OH generated from the H2O2-based Fenton-like reaction, and was catalyzed by the Fe3O4 in V-M. The immobilization of Cu(II) by V-M was mostly realized through the binding of the organic substances on the surface of the V-M, multilayer adsorption, and a replacement reaction with Ca(II). Magnetic separation and the addition of diluted HCl were used for the recycling of the Cu(II) enriched by V-M, with a recycling percentage reaching 85%. This study introduced a novel approach to the remediation of MB-Cu(II) composite pollution, and the recycling of Cu(II).

Arsenic Enhances the Degradation of Middle-Chain Petroleum Hydrocarbons by Rhodococcus sp. 2021 Under Their Combined Pollution

The efficient and green remediation of petroleum hydrocarbon (PH) contamination has emerged as a viable strategy for environmental management. Here, we investigated the interaction between arsenic and PH degradation by Rhodococcus sp. 2021 under their combined pollution. The strain exhibited disparate responses to varying concentrations and valences of arsenic. The elevated concentration of arsenic (>100 mg/L) facilitated the degradation of PHs, and there was a positive correlation between arsenic-promoted degradation of PHs and their carbon-chain length. The degradation of PHs changed with arsenic conditions as follows: trivalent arsenic groups > pentavalent arsenic groups > arsenic-free groups (control). Arsenite and arsenate significantly promoted the gene expression of arsenic metabolism and alkane degrading. But unlike arsenite, arsenate also significantly promoted the gene expression of phosphate metabolism. And arsenite promoted the up-regulation of the expression of genes involved in the process of PHs oxidation and fatty acid oxidation. These results highlight the potential of Rhodococcus sp. 2021 in the remediation of combined total petroleum hydrocarbon (TPH) and heavy metal pollution, providing new insights into the green and sustainable bioremediation of combined pollution of organic matters such as PHs and heavy metals/heavy metal-like elements such as arsenic.

Nocturnal Ozone Enhancement Induced by Sea-Land Breezes During Summertime in Northern Coastal City Qingdao, China

This study investigated the influence of sea–land breezes on nocturnal spatial and temporal distribution of ozone (O3) and its potential effects on particulate nitrate formation in Qingdao, a coastal city in northern China. Observation campaigns were conducted to measure surface air pollutants and meteorological factors during a typical sea–land breezes event from 22 to 23 July 2022. A coherent Doppler lidar (CDL) system was employed to continuously detect three-dimensional wind fields. The results revealed that nocturnal ozone levels were enhanced by a conversion of sea–land breezes. Initially, the prevailing northerly land breeze transported high concentrations of O3 and other air pollutants from downtown to the Yellow Sea. As the sea breeze developed in the afternoon, the sea breeze front advanced northward, resulting in a flow of high O3 concentrations back into inland areas. This penetration of the sea breeze front led to a notable spike in O3 concentrations between 16:00 on 22 July and 02:00 on 23 July across downtown areas, with an average increase of over 70 μg/m3 within 10 min. Notably, a time lag in peak O3 concentration was observed with southern downtown areas peaking before northern rural areas. During this period, combined pollution of O3 and PM2.5 was also observed. These findings indicated that the nighttime increase in O3 concentrations, coupled with enhanced atmospheric oxidation, would likely promote the secondary conversion of gaseous precursors into PM2.5.

Simultaneous removal of vanadium and nitrogen in two-stage vertical flow constructed wetlands: Performance and mechanisms

Vanadium (V(V)) and nitrate, as co-concomitant pollutants in water bodies, pose potential threats to the eco-environment and human health. This study was to reveal the feasibility of simultaneous removal of V(V) and nitrate in the series-wound vertical flow constructed wetlands (CWs) with iron ore (B-CWs)/manganese ore (C-CWs)-wood substrates. The results showed that B-CWs could achieve efficient V(V) and NO3−-N removal with the influent of 2 and 10 mg/L (V(V)/NO3−-N = 1:5), respectively. With the increase of V(V)/NO3−-N ratio (V(V)/NO3−-N = 1:1), B/C-CWs exhibited better combined pollution removal. Even when nitrate was removed (V(V)/NO3−-N = 1:0), the systems could maintain a good capacity for V(V) removal. High V(V) (20 mg/L) significantly inhibited V(V) removal, with a slight recovery of the performance as the decrease of V(V) influent. High NO3−-N concentration (10 mg/L) effectively enhanced V(V) removal and restored C-CWs to the better level. V(IV) precipitates/oxides were the main reducing end-products. High abundance of V(V)-reducing bacteria and iron/manganese cycling pumps ensured efficient V(V) removal.

Contrast of hydraulic conductivity induces transport of combined pollutants in high- and low-permeability systems

The transport process of pollutants in the environment can be influenced by heterogeneous geologic architecture and pollutant interactions. However, there has been a lack of research on co-transport behaviors of combined pollutants in heterogeneous aquifers. In this study, a series of two-dimensional tank experiments were carried out to study the transport behavior of toluene and naphthalene in both homogeneous and heterogeneous aquifers. The results revealed that the coexisting solutes facilitated the transport of toluene and naphthalene in the homogeneous aquifers, potentially due to competitive adsorption between these compounds. In the high- and low-permeability systems, the transport rates for both toluene and naphthalene decreased while exhibiting characteristics such as early arrival, long tails, and multiple peaks. The spatial analysis of pollutant distribution indicated that hydraulic conductivity contrast played a critical role in inducing back diffusion phenomenon. Furthermore, toluene exhibited more pronounced matrix diffusion compared to naphthalene in heterogeneous aquifers, characterized by higher concentrations, wider diffusion range in low-permeability zones. And the β value for toluene is smaller than naphthalene in CTRW model, indicating that the former is more sensitive to the hydraulic conductivity contrast. This study provides novel insights into understanding the co-transport behavior of combined pollutants in heterogenous aquifers.

Future photovoltaic potential in India: navigating the interplay between air pollution control and climate change mitigation

Abstract India has set ambitious solar energy targets to meet its climate commitments. However, climate change, already evident in the country, poses significant challenges to solar power generation. Therefore, assessing the impact of climate change on future photovoltaic potential in India is essential. This study evaluates the mid-century (2041-2050) solar photovoltaic potential across Indian power grids using CMIP6 models under two scenarios: SSP2-4.5 (moderate climate action with intermediate air pollution) and SSP5-8.5 (weak climate action with strong air pollution control). The results indicate that the nationally averaged photovoltaic potential is projected to decrease by -2.3±0.6% (SSP5-8.5) to -3.3±0.9% (SSP2-4.5) compared to the 1985-2014 baseline, primarily due to reduced radiation and increased temperatures. Additionally, cell temperatures are expected to rise by 1.5±0.13°C (SSP2-4.5) to 2±0.11°C (SSP5-8.5), leading to efficiency losses and additional 18±5 days under SSP2-4.5 (26±3 days under SSP5-8.5) of efficiency de-rating, particularly in solar-rich regions. This translates to a loss of 600±160 GWh under SSP2-4.5 and 840±100 GWh under SSP5-8.5, based on the solar generation status of 2023-24. Overall, SSP5-8.5 projects a smaller reduction in photovoltaic potential, it also predicts greater temperature-induced efficiency losses compared to SSP2-4.5, due to aerosol direct effect and weak climate action. Finally, this assessment highlights the need for combined climate and pollution mitigation efforts to boost India’s photovoltaic potential and secure a sustainable, resilient energy future.

Investigating the inhibitory mechanism of methanogenesis during composting under the combined influence of amoxicillin and copper pollution

This study investigated the effects of different levels of combined amoxicillin and copper (Cu) pollution on the methanogenesis of microbial communities during aerobic composting of dairy manure. Three groups were established: the control group (CK), a low-level combined pollution group (L), and a high-level combined pollution group (H). As the level of pollution increased, carbohydrate metabolism decreased during the thermophilic phase of composting, while signal translation increased. Compared with the initial phase, functional genes related to the acetoclastic pathway decreased significantly in abundance during the thermophilic phase, and cdh had the lowest relative abundance among acetoclastic pathway with a decrease of 81.52%, 81.88%, and 84.73% in groups CK, L, and H, respectively. The cumulative methane emissions in group H decreased by 31.56% and 9.23%, respectively, compared with those from groups CK and L. These results contribute to understanding the effects of combined amoxicillin and Cu pollution on methane emissions during composting.

Response mechanisms of submerged macrophytes and epiphytic biofilms to single and coexisting per-and poly-fluoroalkyl substances and antibiotics stress

Combined pollutants of per- and poly-fluoroalkyl substances (PFAS) and antibiotics are commonly found in aquatic environments. This study aimed to investigate the effects of PFAS (perfluorobutyric acid (PFBA) and perfluorooctanoic acid (PFOA)) and antibiotics (tetracycline (TC) and chloramphenicol (CAP)) on Vallisneria natans (V. natans) and their epiphytic biofilms. The changes in photosynthetic pigments and oxidative damage in V. natans were altered by these pollutants. For example, the total chlorophyll was increased from 4.64 to 8.10 mg/L due to the combined pollutant of PFOA and TC. When exposed to the combined pollutant of PFBA and TC, a concentration of malondialdehyde of 28.4 nmol/g was measured, which was significantly higher than that in the control group. For combined toxicity, the PFAS and antibiotics primarily exhibited antagonistic effects within V. natans. The glycine, serine, and threonine metabolism pathways were mainly affected by the combined stress of PFBA and TC. Single pollutants of TC and CAP were found to inhibit the uptake of nutrients by V. natans, while the coexisting antibiotics enhanced the inhibitory effects of PFBA and PFOA in combined pollutant treatments. The growth of microorganisms in the epiphytic biofilms was significantly promoted by PFBA and PFOA, whereas their growth was notably inhibited by CAP. The composition of biofilms could be altered by single and combined pollutants, with antibiotics being more likely than PFAS to change the microbial communities within the biofilms. When exposed to TC and CAP, the ACE indices decreased from 1171.5 to 466.4 and 703.8, respectively.

Advancing the Effect-Directed Identification in Combined Pollution: Using Pathways to Link Effects and Toxicants.

The difficulty in associating diverse pollutants with mixture effects has led to significant challenges in identifying toxicants in combined pollution. In this study, pathways were used to link effects and toxicants. By pathways evaluated by the concentration-dependent transcriptome, individual effects were extended to molecular mechanisms encompassing 135 pathways corresponding to 6 biological processes. Accordingly, mechanism-based identification of toxicants was achieved by constructing a pathway toxicant database containing 2413 chemical-pathway interactions and identifying pathway active fragments of 72 pathways. The developed method was applied to two different wastewaters, industrial wastewater OB and municipal wastewater HL. Although lethality and teratogenesis were both observed at the individual level, different molecular mechanisms were revealed by pathways, with cardiotoxicity- and genotoxicity-related pathways significantly enriched in OB, and neurotoxicity- and environmental information processing-related pathways significantly enriched in HL. Further suspect and nontargeted screening generated 59 and 86 causative toxicants in OB and HL, respectively, among which 29 toxicants were confirmed, that interacted with over 90% of enriched pathways and contributed over 50% of individual effects. After upgrading treatments based on causative toxicants, consistent removal of toxicants, pathway effects, and individual effects were observed. Mediation by pathways enables mechanism-based identification, supporting the assessment and management of combined pollution.

Complexity of influences on atrazine phytoremediation of coexisting graphene oxide in water: Mitigating its phytotoxicity while decreasing plant removal contribution

Phytoremediation is an efficient technology for the removal of herbicide atrazine (ATZ) contamination in water bodies, but its ability to reduce ATZ under combined pollution remains unclear, especially ATZ co-existing with the emerging pollutant graphene oxide (GO) that may have potential effects on ATZ fate, plants and microbes. Herein, we investigated the phytoremediation potential of an emergent plant (Iris pseudacorus) for ATZ and the response of bacteria in a hydroponic system with and without GO. The results showed that plants enhanced ATZ dissipation in water with the increased removal rate by a factor of 1.7–4.0. GO restricted ATZ uptake by plants, but favored ATZ bioconcentration in cell walls. The plant contributed most to changes in the bacterial communities, decreasing the alpha diversity, while enriching the functional categories involving in amino acid and carbohydrate metabolisms. These findings indicated that I. pseudacorus can be employed as an effective candidate of phytoremediation for ATZ co-existing with GO at environmentally relevant concentrations, tending to recruit bacteria with plant stress tolerance and growth-promotion activities more than with ATZ degradation activities; GO exerted a mitigating effect on ATZ stress improving the barrier function of cell walls, but decreased the contribution of plants to ATZ removal.

A comparative study on the toxic effects of lead pollution and nanoplastic-lead mixed pollution on red drum and their detoxification strategies

Nanoplastics and heavy metals pose various adverse effects on marine organisms. However, the combined toxicity of nanoplastics and lead pollution to marine fish is not fully understood. This study investigates the toxic effects and detoxification strategies of lead pollution (p07) compared to nanoplastic-lead mixed pollution (m07) in red drum during exposure and recovery phases. Under m07 pollution, the maximum lead content in muscle was 22.61 mg/kg, which was significantly higher than the 15.82 mg/kg observed under p07 pollution. This finding demonstrated that nanoplastics significantly enhance lead accumulation, leading to more severe toxic effects on red drum. Histological analyses revealed that lipid droplets in the liver and epithelial lifting in the gills were the primary lesion types. During the exposure periods, red drum primarily detoxified lead through cellular renewal and the removal of damaged proteins under p07 pollution. Conversely, under m07 pollution, detoxification relied on cellular senescence, apoptosis, endocytosis, and the removal of damaged proteins. In the recovery phases, red drum predominantly recovered through cell proliferation and antioxidant responses under p07 pollution. Under m07 pollution, the focus shifted to functional protein synthesis, apoptosis, endocytosis, and lipid metabolism. This study offers valuable insights into the monitoring and management of combined environmental pollution.

Fluorescent nanoplastics increase the toxic effects of Graphene oxide nanoparticles in freshwater algae Scenedesmus obliquus

The increased usage of Graphene oxide (GO) in various industrial applications led to their entry into freshwater systems. Other secondary contaminants like nanoplastics (NPs) often co-exist with GO in the environment. This study examines the possible role of fluorescent nanoplastics (FNPs) in modifying the toxic effects of GO on freshwater algae Scenedesmus obliquus. Selected concentrations of GO (0.1, 1, and 10 mg L−1) were combined with a fixed concentration of FNPs (1 mg L−1) to perform combinational toxicity tests on algae. FNPs significantly enhanced the toxic effects of GO in the mixtures in comparison with the pristine GO. In addition to the cytotoxic effects, oxidative stress parameters like total ROS generation and malondialdehyde (MDA) production also increased in the case of the combined pollutants. The antioxidant enzymatic activities like catalase (CAT) and superoxide dismutase (SOD) in the cells were also assessed. Algal exposure to the pristine pollutants and their mixture led to a notable decrease in photosynthetic activities in the cells, with the mixed pollutants aggravating the loss of activity. The interactive toxic effects of the contaminants when present in mixtures were evaluated using Abbotts' Independent action modelling. Furthermore, optical microscopic images revealed the morphological changes in the algal cells after exposure to the contaminants both in the pristine and combined forms.

Effects of cyanotoxins on nitrogen transformation in aquaculture systems with microplastics coexposure: Adsorption behavior, bacterial communities and functional genes

Microcystin-LR (MC-LR) and microplastics (MPs) have attracted increasing attention as important new pollutants in freshwater fishery environments. However, there are few reports on the effects of long-term combined MC-LR and MPs pollution on nitrogen transformation and microbial communities in aquaculture ponds, and the resulting risks have yet to be determined. Therefore, in this study, traditional refractory MPs (polystyrene, PS), biodegradable MPs (polylactic acid, PLA) and MC-LR, which are common in freshwater fishery environments in China, were selected as pollutants to construct a microcosm that simulates freshwater aquaculture ponds. MC-LR coexposure to PS and PLA was tested to reveal the effects of these pollutants on nitrogen transformation and microbial communities in aquaculture ponds, as well as to elucidate the potential risks posed by traditional refractory MPs and biodegradable MPs to freshwater aquaculture ecosystems. The results revealed that the MPs had a relatively high adsorption rate for MC-LR and that PS presented a relatively high adsorption capacity, whereas PLA presented a relatively high desorption capacity. Single or combined MPs and MC-LR pollution disrupted the normal nitrogen cycle in the aquaculture system, causing an overall loss of nitrogen in the water, and denitrification and nitrogen fixation in the water were inhibited to a certain extent through the inhibition of nitrogen cycle-related functional genes, with the PS + MC-LR group having the greatest inhibitory effect. In addition, compared with single-pollutant exposure, combined exposure to MC-LR and MPs had a greater effect on the microbial community composition. Analysis of the integrated biomarker response (IBR) index revealed that the risk of combined exposure to MC-LR and PS was greater than that of single exposure, so this phenomenon merits further attention.

Spatial interaction and risk zoning of compound pollutants in farmland soils: Insights from heavy metals and polycyclic aromatic hydrocarbons in Hezhang County, China

The accurate identification and assessment of comprehensive risks associated with compound pollution in agricultural ecosystems remain significant challenges due to the complexity of pollution sources, soil heterogeneity, and spatial variability. In this study, bivariate local indicators of spatial association (LISA) were applied to analyze the spatial interaction between heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in farmland soils in Hezhang County. The results revealed distinct clusters with elevated concentrations of both HMs and PAHs, predominantly in areas affected by long-standing lead-zinc mining and smelting activities. Positive matrix factorization (PMF) was utilized to identify mining and smelting activities, and associated coal consumption as common sources of both pollutants, contributing 53 % and 28 %, respectively. Ecological health risk assessment results indicated that the combined pollution in this area has led to particularly severe ecological and cancer risks, with the pollution coefficient (Pc) exceeding 3.0, and risk values for both adults and children surpassing the threshold of 10−4. Through the integration of advanced bivariate LISA mapping and thorough risk assessment, this study precisely delineated ecological risk zones (33.1 %) and more refined health risk zones (40.1 %) associated with combined pollution. The southwest of Hezhang was identified as a critical hotspot for combined pollution risks, primarily due to intensive mining and smelting activities in the region. Overall, this study underscores the utility of bivariate LISA as a robust approach for delineating spatial clustering patterns caused by combined pollutants. It provides crucial insights for identifying regions with heightened human health and ecological risks in rural settings.

Eco-environmental responses of Eichhornia crassipes rhizobacteria community to co-stress of per(poly)fluoroalkyl substances and microplastics

The stabilization of rhizobacteria communities plays a crucial role in sustaining healthy macrophyte growth. In light of increasing evidence of combined pollution from microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs), Selecting typical floating macrophyte as a case, this study explored their impacts using hydroponic simulations and 16S rRNA high-throughput sequencing. A total of 31 phyla, 77 classes, 172 orders, 237 families, 332 genera, and 125 rhizobacteria species were identified. Proteobacteria (16.19% to 57.70%) was the dominant phylum, followed by Bacteroidota (12.34% to 44.48%) and Firmicutes (11.31% to 36.36%). In terms of α-diversity, polystyrene (PS) MPs and PFASs significantly impacted community abundance (ACE and PD-tree) rather than evenness (Shannon and Pielou) compared to the control. βMNTD and βNTI analyses revealed that PS MPs enhanced deterministic assembly processes driven by F-53B and GenX, while mitigating those induced by PFOA and PFOS. Contamination treatments narrowed the ecological niche breadths at both the phylum (5% (PS) to 49.91% (PS & PFOA)) and genus levels (8% (PS) to 63.96% (PS & PFOA)). Functionally, MPs and PFASs decreased the anaerobic capacity and ammonia nitrogen utilization of rhizosphere bacteria. This study enhances our understanding of the microecological responses of macrophyte-associated bacteria to combined MP and PFAS contamination and offers insights into ecological restoration strategies and mitigating associated environmental risks.

The combined toxicity of polystyrene microplastic and arsenate: From the view of biochemical process in wheat seedlings (Triticum aestivum L.)

Microplastics (MPs) are important carriers of various toxic metals and can alter their toxicity pattern in agricultural soil, leading to combined pollution, therefore posing new challenges to soil pollution management and environmental risk assessment. In this study, we observed the internalization of MPs in plants and conducted incubation experiments to evaluated the effects of arsenate (As(V)) alone and in combination with polystyrene (PS) MPs on wheat seedlings (Triticum aestivum L.). Under As(V) alone and combined with PS-MP exposure, dose-dependent toxicity in terms of root and stem elongation and biomass accumulation was observed. Compared with As(V) alone, the presence of PS-MPs reduced the accumulation of As in wheat roots by 11.43–58.91%, but PS-MPs intensified the transport of As to the aboveground parts of wheat, increasing As accumulation in wheat stems by 27.77–1011.54%. This causes more serious mechanical damage and oxidative stress to plant cells, increasing the accumulation of reactive oxygen species and lipid peroxidation in wheat roots and upregulating the activities of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD). In addition, the co-exposure of As(V) and PS-MPs disrupts the photosynthetic system of wheat leaves and the secretion activities of roots. Therefore, the combination of As(V) and PS-MPs caused greater damage to wheat growth. Our findings contribute to a more comprehensive assessment of the combined toxicity of MPs and heavy metal to crops.

Regulation of the co-transport of toluene and dichloromethane by adsorbed phase humic acid under different hydro-chemical conditions

The transport behavior of combined organic pollutants in soil and groundwater has attracted significant attention in recent years. Research on the influence of humic acid (HA) on organic pollutant transport behavior mainly focuses on the study of the mobile phase HA, with less research on the adsorbed phase HA, especially regarding its interaction with combined pollutants. To enhance understanding of the regulation of co-transport and retention of combined pollutants by adsorbed phase HA, in this study, tests were conducted to investigate how toluene (TOL) and dichloromethane (DCM) are transported in the presence of adsorbed phase HA at different pH levels and ionic strengths. As the proportions of HA-coated sand increased, so did its adsorption capacity for TOL and DCM, which can be attributed to adsorbed phase HA providing more adsorption sites compared to plain sand, thereby reducing the transport potential of the pollutants. The presence of both TOL and DCM facilitated their mutual transportation due to competitive adsorption controlled by the adsorbed phase HA content in the porous medium. Furthermore, it was observed that pH levels influenced the transport behavior of TOL and DCM when adsorbed phase HA was present since adsorbed phase HA transformation into mobile phase was regulated by pH levels. The transport patterns can be effectively simulated using the chemical nonequilibrium two-site sorption model in HYDRUS-1D, accurately reflecting the retardation coefficients and transport distances based on model parameters. This work sheds new light on the regulatory role of adsorbed phase HA in TOL and DCM transport under diverse hydrochemical conditions, with implications for accurately depicting the behavior of combined pollutants, optimizing the remediation strategies and improving remediation efficiency in contaminated sites.

Research on the removal efficiency and membrane fouling analysis of nanofiltration membranes under the combined pollution of emerging contaminants

Based on the research background of five emerging contaminants (ECs)— sulfadiazine (SD), sulfamethoxazole (SMZ), malathion, hexachlorobenzene (HCB), and bisphenol A (BPA)—which can be detected in trace amounts in a river basin in southern China, a spiking experiment was conducted to effectively address the potential impact risks of these contaminants. The experiment aimed to investigate the removal efficiency and membrane fouling of nanofiltration membranes (NF) under the combined pollution of these ECs. The experimental results show that under the combined pollution of these ECs, the NF exhibits good removal efficiency for all five ECs, with removal rates of approximately 83 ± 2 %, 84 ± 3 %, 76 ± 3 %, 73 ± 6 %, and 80 ± 5 % for SD, SMZ, malathion, HCB, and BPA, respectively. Additionally, NF also has high efficiency in removing other pollutants, with removal rates for chromaticity, CODMn, and total hardness at 80 ± 2 %, 60 ± 3 %, and 62 ± 2 %, respectively, and over 80 % of fluorescent substances were removed. Analysis of the key operating indicators of the NF under the combined pollution of ECs revealed that the membrane flux decreased slightly faster compared to without the combined pollution of ECs, and both the membrane fouling index and membrane resistance increased to a certain extent. Furthermore, the analysis of the NF chemical cleaning solutions showed that these ECs can be detected in both alkaline and acid cleaning solutions. Analysis of membrane dissection on NF revealed that severe cake layer contamination formed on the membrane surface both under and without the combined pollution of ECs, the presence of ECs is worse than the absence of ECs.

Removal of enrofloxacin as well as nutrients in mariculture water by Sesuvium portulacastrum system: Insights for biodegradation, ecotoxicity of enrofloxacin

Antibiotic contamination and eutrophication in mariculture have become problems that cannot be ignored, and enrofloxacin (ENR), as an example, is especially widely used in mariculture. This study firstly revealed that Sesuvium portulacastrum, a plant with world-wide distribution in coastal zones, with its rhizosphere microorganisms, could remove ENR as well as nutrients. The S. portulacastrum system could degrade ENR to small-molecule products 1,2,3,4-tetrahydroquinolin-4-ol and (2,4-dihydroxyphenyl)-cyclopropylamine. And there were 81.3–39.2 % removals of ENR with 0.01-100 mg/L. Although ENR significantly influenced functions of rhizosphere microbial community, like decreasing nitrogen fixation, shifting trophic strategies from phototrophy to chemoheterotrophy, nutrients (NH4+-N, NO2−-N, NO3−-N and total dissolved phosphorus) removal of S. portulacastrum system was essentially unaffected at low ENR concentration (< 1 mg/L). The removal mechanism of S. portulacastrum system was explored. Neither of the isolated root exudates and rhizosphere bacteria could degrade ENR, however, without rhizosphere bacteria, ENR removal rate would decrease. Root proteins including oxidase, decarboxylase, dehydrogenase, such as laccase, isocitrate dehydrogenase, delta-1-pyrroline-5-carboxylate dehydrogenase were overexpressed. Additionally, endocytosis is a pathway for antibiotics to enter S. portulacastrum. This study demonstrated that S. portulacastrum system could be used for remediation of antibiotics-nutrients combined pollution, and deepened understanding the antibiotic removal mechanism of macrophytes in mariculture, moreover, provided new macroplant species and a theoretical basis for antibiotics removal in aquatic systems.