The environmental burden due to industrial activities has been quite observable in the last few years, with heavy metals (HMs) like lead, cadmium, and arsenic inducing serious perturbations to the microbial ecosystem of groundwater. Studies carried out in North China, a region known for interconnection of industrial and groundwater systems, sought to explore the natural mechanisms of adaptation of microbes to groundwater contamination. The results showed that heavy metals permeate from surface increased the diversity and abundance of microbial communities in groundwater, producing an average decrease of 40.84% and 34.62% in the relative abundance of Bacteroidetes and Proteobacteria in groundwater, respectively. Meanwhile, the key environmental factors driving the evolution of microbial communities shift from groundwater nutrients to heavy metals, which explained 50.80% of the change in the microbial community composition. Microbial indicators are more sensitive to HMs pollution and could accurately identify industrial area where HMs permeation occurred and other extraneous pollutants. The phylum Bacteroidetes could act as appropriate indicators for the identification. Significant genera that were identified, being Mesorhizobium, Clostridium, Bacillus and Mucilaginibacter, were found to play important roles in the microbial network in terms of the potential to assist in groundwater clean-up. Notably, pollution from heavy metals has diminished the effectiveness and resilience of microbial communities in groundwater, thereby heightening the susceptibility of these normally stable microbial ecosystems. These findings offer new perspectives on how to monitor and detect groundwater pollution, and provide scientific guidance for developing suitable remediation methods for groundwater contaminated with heavy metals. Future research is essential explore the application of metal-tolerant or resistant bacteria in bioremediation strategies to rehabilitate groundwater systems contaminated by HMs.

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In this study, we examined the aging characteristics of polyethylene (PE) and polylactic acid (PLA) microplastics (MPs), examining the adsorption behaviors and mechanisms concerning Cd(II) and Cr(VI) under both single and binary systems. The results revealed that aging treatment changed the physicochemical properties of MPs. The aging mechanisms of PLA and PE MPs were shown to be similar by the 2D-FTIR-COS study. These mechanisms involve the formation of oxygen-containing functional groups through the combination of carbon chain breakdown and oxygen. Aged MPs had a greater ability to adsorb metal ions than pristine MPs, with PLA MPs outperforming PE MPs. After 30 days of aging, Cd(II) adsorption increased by 40.61 % and 25.49 % for PE and PLA MPs, respectively, while Cr(VI) adsorption increased by 37.50 % and 69.29 %, respectively. The adsorption ability of PE and PLA MPs with Cd(II) or Cr(VI) under binary systems was less than that under single systems, with Cd(II) exhibiting more adsorption competitiveness than Cr(VI). Humic acid (HA), ionic species and strength, solution pH, and adsorption of Cd(II) and Cr(VI) were found to be significantly correlated. Further investigation into the adsorption mechanisms of Cd(II) and Cr(VI) on PE and PLA MPs revealed that pore-filling, electrostatic interactions, complexation, and hydrogen bonding play important roles in the adsorption process. The study's conclusions are crucial for assessing the risk associated with concurrent contamination by metal ions and microplastics.

Salinity, a critical factor, could directly or indirectly affect the microbial community structure and diversity. Changes in salinity levels act as environmental filters that influence the transformation of key microbial species. This study investigates the adaptive characteristics of indigenous microflora in groundwater in relation to external organic pollutants under high salinity stress. A highly mineralized shallow groundwater in Northwest China was conducted as the study area, and six representative sampling points were chosen to explore the response of groundwater hydrochemical parameters and microflora, as well as to identify the tolerance mechanisms of indigenous microflora to combined pollution. The results revealed that the dominant genera found in high salinity groundwater contaminated with organic pollutants possess the remarkable ability to degrade such pollutants even under challenging high salinity conditions, including Halomonas, Pseudomonas, Halothiobacillus, Sphingomonas, Lutibacter, Aquabacterium, Thiomicrospira, Aequorivita, etc. The hydrochemical factors, including total dissolved solids (TDS), sulfide, nitrite, nitrate, oxidation reduction potential (ORP), NH3–N, Na, Fe, benzene series, phenols, and halogenated hydrocarbons, demonstrated a significant influence on microflora. High levels of sulphate and sulfide in groundwater can exhibit dual effects on microflora. On one hand, these compounds can inhibit the growth and metabolism of microorganisms. On the other hand, they can also serve as effective electron donors/receptors during the microbial degradation of organic pollutants. Microorganisms exhibit resilience to the inhibitory effects of high salinity and organic pollutants via a series of tolerance mechanisms, such as strengthening the extracellular membrane barrier, enhancing the synthesis of relevant enzymes, initiating novel biochemical reactions, improving cellular self-healing capabilities, responding to unfavorable environmental conditions by migration, and enhancing the S cycle for the microbial metabolism of organic pollutants.

Aromatic hydrocarbons (AHs) are known to contaminate groundwater with low indigenous microorganism populations and limited nutrient substrates for degradation reactions, resulting in weak natural remediation abilities of groundwater ecosystems. In this study, we aimed to utilize the principles of AH degradation by microorganisms to identify effective nutrients and optimize nutrient substrate allocation through actual surveys of AH-contaminated sites and microcosm experiments. Building on this, using biostimulation and controlled-release technology, we developed a natural polysaccharide-based encapsulated targeted bionutrient (SA-H-CS) that is characterized by easy uptake, good stability, controllable slow-release migration, and longevity to stimulate indigenous microflora in groundwater to efficiently degrade AHs. Results showed that SA-H-CS is a simple overall dispersion system, and nutrient components diffuse readily through the polymer network. The crosslinking of SA and CS resulted in a more compact structure of the synthesized SA-H-CS, effectively encapsulating the nutrient components and extending their active duration to >20 days. SA-H-CS improved the degradation efficiency of AHs and prompted microorganisms to maintain a high degradation rate (i.e., above 80 %) even in the presence of high concentrations of AHs, particularly naphthalene and O-xylene. Under SA-H-CS stimulation, microorganisms grew rapidly, and the diversity and total number of species of microflora increased significantly, with a notable increase in the proportion of Actinobacteria in the microbial community primarily due to the increased abundance of Arthrobacter, Rhodococcus, and Microbacterium, which are capable of degrading AHs. Concurrently, there was a notable enhancement in the metabolic function of the indigenous microbial communities responsible for AH degradation. SA-H-CS injection facilitated the delivery of nutrient components into the underground environment, improved the conversion ability of inorganic electron donors/receptors in the indigenous microbial community system, and strengthened the co-metabolism mechanism among microorganisms, achieving the goal of efficient AH degradation.

Petroleum hydrocarbon-contaminated groundwater often has a low indigenous microorganism population and lacks the necessary nutrient substrates for biodegradation reaction, resulting in a weak natural remediation ability within the groundwater ecosystem. In this paper, we utilized the principle of petroleum hydrocarbon degradation by microorganisms to identify effective nutrients (NaH2PO4, K2HPO4, NH4NO3, CaCl2, MgSO4·7H2O, FeSO4·7H2O, and VB12) and optimize nutrient substrate allocation through a combination of actual surveys of petroleum hydrocarbon-contaminated sites and microcosm experiments. Building on this, combining biostimulation and controlled-release technology, we developed a biodegradable chitosan-based encapsulated targeted biostimulant (i.e., YZ-1) characterized by easy uptake, good stability, controllable slow-release migration, and longevity to stimulate indigenous microflora in groundwater to efficiently degrade petroleum hydrocarbon. Results showed that YZ-1 extended the active duration of nutrient components by 5–6 times, with a sustainable release time exceeding 2 months. Under YZ-1 stimulation, microorganisms grew rapidly, increasing the degradation rate of petroleum hydrocarbon (10 mg L−1) by indigenous microorganisms from 43.03% to 79.80% within 7 d. YZ-1 can easily adapt to varying concentrations of petroleum hydrocarbon-contaminated groundwater. Specifically, in the range of 2–20 mg L−1 of petroleum hydrocarbon, the indigenous microflora was able to degrade 71.73–80.54% of the petroleum hydrocarbon within a mere 7 d. YZ-1 injection facilitated the delivery of nutrient components into the underground environment, improved the conversion ability of inorganic electron donors/receptors in the indigenous microbial community system, and strengthened the co-metabolism mechanism among microorganisms, achieving the goal of efficient petroleum hydrocarbon degradation.

To understand the response characteristics of indigenous microbial community in PAH-contaminated aquifers to the coexistence of microplastics. In this paper, we constructed a groundwater microecosystem using lithologic media collected from the field and subjected it to the stress of a polyethylene microplastics (PE-MPs) concentration gradient. By conducting adsorption experiments and 16S rRNA sequencing, we revealed the growth, structure, metabolism, and resistance mechanisms of the indigenous microbial community in the aquifer lithologic media exposed to varying levels of co-stress from PE-MPs and phenanthrene. Our findings suggest that the adsorption capacity of aquifer lithologic media for phenanthrene is significantly weaker than that of PE-MPs. Additionally, our observations indicated that small particle lithologic media had a greater adsorption capacity for phenanthrene than large particle lithologic media. The presence of PE-MPs was found to increase both the abundance and diversity of microbial communities, although the relationship was not linear with the content of PE-MPs. When exposed to the combined stress of PE-MPs and phenanthrene, the relative abundance of Proteobacteria decreased while that of Bacteroidetes increased. Several genera belonging to Proteobacteria (Aeromonas, Desulfovibrio, Klebsiella, Pantoea, and Microvirgula) and Bacteroidetes (Macellibacteroides and Bacteroides) occupied a central position in the microbial community interaction network and showed significant correlations with other genera. Furthermore, an increase in the proportion of genera capable of degrading various refractory organics was observed. The presence of PE-MPs increased the phenanthrene content in the aquifer lithologic media, thereby intensifying the inhibitory effect on indigenous microbial community in this environment. Despite an increase in the phenanthrene content of aquifer lithologic media due to the presence of PE-MPs, indigenous microbial community in this environment exhibited resistance to the combined inhibition of PE-MPs and phenanthrene through a series of resistance mechanisms. These mechanisms included strengthening the N-cycle process, enhancing metabolic capacity for phenanthrene, improving perception, response, and adaptation to changes in the external environment or intracellular state, modifying the transmembrane transport of the cell membrane to the substrate, and regulating life processes.

In recent decades, microbial-induced carbonate precipitation (MICP) technology has been widely used to treat heavy metal contamination in wastewater. However, the ammonia nitrogen produced by the MICP process and the high pH value of the treated wastewater is the critical drawbacks and challenges in the scientific domains. In this study, MICP was used to treat wastewater containing Cd2+. Thereafter, the treated wastewater is adjusted with phosphoric acid to make the suspension neutral and used for agricultural irrigation to improve soil fertility and promote plant growth by utilizing the ammonia nitrogen as a by-product. Results revealed that Urease - producing flora UB1 screened from soil have rich urea hydrolysis genes (UreA, UreB, UreC, and UreG) and effectively remove more than 90% of Cd2+ whose initial concentration is less than 0.5 mmol/L but its activity was inhibited at higher concentration (Cd2+ >0.5 mmol/L). Besides, cadmium carbonate (CdCO3) formed during the process of Cd2+ removal was confirmed by instrumental analysis (TEM and XRD simultaneously). The simulated irrigation experiment showed that MICP-treated sewage regulated by phosphoric acid can solve the purposes of efficient utilization of sewage water for irrigation and is firmly capable to improve soil fertility and enhance plant growth. This study provides new insights for solving the problems of ammonia nitrogen and high pH in MICP-treated wastewater.

基于氨氮(N H+4-N)污染地下水内在生态恢复机制,利用生态安全型天然矿物材料火山渣负载地下水中土著氮细菌进行NH+4-N污染地下水净化特性研究.结果表明:火山渣负载土著氮细菌生物量约为2.12×107个/g;负载材料在去除地下水中NH+4-N时,可有效去除水化学因子,NH+4-N去除率为83.39％～98.84％,水化学因子去除能力从大到小依次为Fe2+,HCO-3,Ca2+,Mn2+,CO2-3,SO2-4,S2-,Mg2+,其中Fe2+,Mn2+,S2-,SO2-4一定程度上促进NH+4-N净化;CO2-3,HCO-3,Ca2+,Mg2+抑制NH+4-N净化;负载材料的微观结构在净化后表面变平滑,细小突起被覆盖.研究结果为氮污染地下水内在生态调控修复技术研发提供了实验依据.

This study aims to improve soil vapor extraction (SVE) to address its shortcomings in treating halogenated hydrocarbon-contaminated soil. Indoor simulation experiments based on SVE were conducted to provide technical guidance for the remediation of 1,2-DCA-contaminated soil, with the overall intention of soil repair and ecological restoration. A thermal oxidation SVE (TOSVE) system was designed on the basis of SVE technology for application in the remediation of low-permeability soil contaminated with halogenated hydrocarbons from a chemical plant in Northeast China. Laboratory simulation experiments were conducted based on TOSVE technology to study the removal of target pollutants under different organic contents, moisture and air speeds. For the first time, a new material, scoria, was added to the oxidant at different proportions, and its effect on the exhaust gas treatment efficiency was examined. Thermal extraction improved the extraction efficiency of pollutants from low-permeability soil. Moreover, the adsorption–oxidation effect of 0.1–0.25 mm scoria prepared by 20% Na 2 S 2 O 8 on 1,2-dichloroethane (1,2-DCA) in tail gas was higher than that of the oxidant without scoria, indicating that scoria is effective in tail gas treatment.

The resistance mechanism of microbial communities in contaminated groundwater under the combined stress of sulfonamide antibiotics (SAs), NH4+, and Fe-Mn exceeding the standard levels was studied in an agricultural area along the Songhua River in Northeast China with developed livestock and poultry breeding. Representative points were selected in the study area to explore the response of environmental parameters and microbial communities, and microscopic experiments with different SA concentrations were conducted with background groundwater. The results showed a complex relationship between microbial communities and environmental factors. The environmental factors SM, SM2, SMX, DOC, NO3-, Fe, Mn, and HCO3- significantly affected the microbial community, with SMX, DOC, and Mn having the greatest effect. Three types of antibiotics with similar properties had different effects on the microbial community, and these effects were not simply additive or superimposed. After adding SAs, Proteobacteria with multi-resistance (99.85%) became the dominant phylum, and Acinetobacter (98.68%) became the dominant genus with SA resistance. SAs have a significant influence on bacterial chemotaxis, transporters, substance transport, and metabolism. Microorganisms resist the influence of SAs via a series of resistance mechanisms, such as enhancing the synthesis of relevant enzymes, generating new biochemical reactions, and reducing the transport of harmful substances through cell membranes. We also found that the proportion of exogenous compound degradation and metabolism-related functional genes in the presence of high SA concentrations increased significantly, which may be related to the degradation of SAs by microorganisms.

The environmental conditions at a contaminated site will impact on the indigenous microbial communities, with implications for the removal of pollutants. An analysis of the characteristics of microbial communities in petroleum-contaminated groundwater can give insights into the relationships between microbial community and environmental factors, and provide guidance about how microbes can be used to remediate and regulate petroleum-contaminated groundwater. This study focuses on two petroleum-contaminated sites in northeast China, the physico-chemical-biological changes in petroleum-contaminated groundwater were analyzed, the response relationship between hydro-chemical indicators and microbial communities was characterized, and the bioindicator that can reflect the petroleum contamination status were established for environmental monitoring and management. The results showed that Proteobacteria was the dominant bacteria in petroleum-contaminated groundwater, with a relative abundance of 42.45%-91.19%. pH, TDS, DO, NO3-, NO2-, SO42-, NH4+, Al, and Mn have significant effects on microbial community. The effect of petroleum pollutants on microbial communities is not only related to the concentration and composition of the pollutants themselves, but also could indirectly affect microbial communities by changing the content of inorganic electron acceptor components such as iron, manganese, sulfate and nitrate in groundwater, and this indirect effect is significantly greater than the direct impact of pollutants on microbial communities. In petroleum-contaminated groundwater, the dominant genera (Polaromonas, Caulobacter) and microbial metabolic functions (methanol oxidation, methylotrophy, ureolysis, and reductive biosynthesis) of the indigenous microbial community can be used as bioindicators to indicate petroleum contamination status. The higher abundance of these bioindicators in petroleum-contaminated groundwater, the more serious petroleum pollution in groundwater.

The resistance mechanism of microbial communities in contaminated groundwater under combined stresses of aromatic hydrocarbons (AHs), NH4+, and Fe-Mn exceeding standard levels was studied in an abandoned oil depot in Northeast China. The response of environmental parameters and microbial communities under different pollution levels in the study area was discussed, and microscopic experiments were conducted using background groundwater with different AHs concentrations. The results showed that indigenous microbial community were significantly affected by environmental factors, including pH, TH, CODMn, TFe, Cr (VI), NH4+, NO3-, and SO42-. AHs likely had a limited influence on microbial communities, mainly causing indirect changes in the microbial community structure by altering the electron donor/acceptor (mainly Fe, Mn, NO3-, NO2-, NH4+, and SO42-) content in groundwater, and there was no linear effect of AHs content on the microbial community. In low- and medium-AHs-contaminated groundwater, the microbial diversity increased, whereas high AHs contents decreased the diversity of the microbial community. The microbial community had the strongest ability to metabolize AHs in the medium-AHs-contaminated groundwater. In the high-AHs-contaminated groundwater, microbial communities mainly degraded AHs through a complex co-metabolic mechanism due to the inhibitory effect caused by the high concentration of AHs, whereas in low-AHs-contaminated groundwater, microbial communities mainly caused a mutual transformation of inorganic electron donors/acceptors (mainly including N, S), and the microbial community's ability to metabolize AHs was weak. In the high-AHs-contaminated groundwater, the microbial community resisted the inhibitory effect of AHs mainly via a series of resistance mechanisms, such as regulating their life processes, avoiding unfavorable environments, and enhancing their feedback to the external environment under high-AHs-contaminated conditions.

Microbial bioremediation of heavy metals contamination from water and wastewater has been adopted as a key tool to cope up with the harmful effects of metals. Literature reveals that materials adsorption methods and microbial mineralization were frequently used for the remediation of heavy metals in wastewater and shown their respective advantages and disadvantages. In order to give full play to the advantages of both materials and microbial methods and to avoid the disadvantages of the two methods, this study enriched a group of high efficiency urease bacteria (UF1) and loaded it on the surface of scoria to synthesize a novel microbial adsorbent (Scoria@UF1) to adsorb Pb2+ and Cd2+ ions in contaminated water. Microbial experiments showed that UF1 had the maximum biomass and urease activity for 24 h at 20-35 degrees C with initial pH value was 6-9. Moreover, UF1 could maintain normal microbial activity at initial concentration of Pb2+ and Cd2+ < 1 mmol/L. Metagenomic analysis showed that the UF1 community was mainly composed of Proteobacteria (46.81%) and Firmicutes (37.6%), and the addition of Pb2+ and Cd2+ ions decrease the community diversity of UF1 (ACE value decreased from 2316 to 2011 and 1893, respectively). The adsorption of Pb2+ and Cd2+ by Scoria@UF1 reached equilibrium in 20 h, and the adsorption process satisfied the pseudo-first-order adsorption kinetics model (R-2 > 0.97). The theoretical maximum adsorption capacities of Scoria@UF1 for Pb 2+ and Cd2+ were 0.078 and 0.054 mmol/g at 25 degrees C, respectively. The adsorption behavior of Scoria@UF1 for Pb2+ and Cd2+ was consistent with Langmuir isothermal model (R-2 > 0.98) and follow the spontaneous endothermic process (Delta G(0) < 0; Delta H-0 > 0). Similarly, control experiment shows that the fixation of selected heavy metal ions by Scoria@UF1 includes the process of scoria adsorption and urease microbial mineralization, and the two ways have continuous and non-overlapping adsorption time periods (scoria: 0-8 h, microbe: 8-14 h). Scanning electron microscopy and elemental analysis showed that microorganisms were successfully attached to the surface of scoria before the reaction, and heavy metal elements formed irregular precipitation on the surface of scoria after the reaction. This study provides a theoretical basis for the application of Scoria@UF1 in treating Pb2+ and Cd2+ in contaminated water.

Sulfonamide antibiotics are potentially harmful to the ecological environment and human health, and control of pollution with these compounds has received much attention. In this study, removal of the four sulfonamides sulfamethoxazole, sulfamethazine, sulfamethazine, and sulfamethoxamine from the water was investigated using a composite material prepared from peanut shells and sulfonamide-degrading bacteria. Adsorption-degradation of the sulfonamides with the composite material was investigated using orthogonal static experiments and dynamic experiments. Scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and other microscopic detections and analytical techniques were used to explore the mechanism of action. When the sulfonamide concentration was 0.5 mg/L, the removal rates (%) of sulfamethoxazole, sulfamethazine, sulfamethazine, and sulfamethoxamine by the peanut shell composite were 89.69%, 78.39%, 71.38%, and 88.55%, respectively. The optimum conditions for preparation of the composite material were 50 mL of basic medium, a peanut shell:bacteria ratio of 1.5 g/2.5 mL, and a fixation time of 36 h. The dynamic experiments showed that the composite material performed well for removal of sulfonamides present at the low (0.05 mg/L) and high (5.0 mg/L) concentrations, with average removal rates of 79.89% and 61.53%, respectively. The removal of sulfonamides in water by the composite material occurred mainly by physical and chemical adsorption and biodegradation. Physical and chemical adsorption occurred through the porous structure and active functional groups (C-O, -OH, N=C-O, CH, C=O, -CH3 , and -CH2-) of the peanut shell composite. Biodegradation mainly involved metabolism by sulfonamide-degrading bacteria immobilized on the peanut shells.