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Abstract According to the novel weapons hypothesis, root exudates are the inhibition factors for native species growth and development through invasive plants. It is hypothesized that antioxidant system (AOS) presents an effective role in plant defense system. The allelopathy indexes of P. multifida gametophyte biomass and sporogonium conversions rates turn negative with the dose and time effects, and the synthetical allelopathic effect index was −55.07% at 100% treatments under root exudates treatments. Under transmission electron microscopy, the cell structures turn burry. Next, AOS and programmed cell death (PCD) were tested in this study. In AOS, strong activities of superoxide dismutase, catalase, glutathione reductase and glutathione S-transferase (GST) were identified in gametophyte cells under the treatments, as well as the contents of glutathione, ascorbic acid and reduced ascorbate, while GPX activity decreased. Based on the input (SOD activity) and the output (GST activity) of antioxidant system, and the decreasing system control would be a reason leading gametophyte death under root exudates. At day 10, PCD would get its peak of 46.93% at 100% root exudates. We found a dynamic balance of PCD and AOS under the exudates treatments. We detected hexadecanoic acid, ethylene glycol and undecane are three major chemicals in root exudates. Our results provide a reference of AOS and PCD working under root exudates treatments in plants and offer novel strategy for the native species protection and invasion plants control in environment science. Graphical abstract fx1 Highlights • PCD and AOS are getting a dynamic balance under the exudates treatments. • PCD and AOS get increase at first then turn steady under root exudates treatments. • Hexadecanoic acid, ethylene glycol and undecane are three major chemicals in root exudates. • The activities of SOD, CAT, GR and GST get stronger, and GPX activity turns decrease under the root exudates treatments. • The contents of glutathione, Ascorbic acid and reduced ascorbate increased under the root exudates treatments. [ABSTRACT FROM AUTHOR]

To facilitate the use of partial nitritation (PN) in nitrogen removal processes for livestock wastewater, this work investigated the inhibitory effects of heavy metals and antibiotics on the nitrifying bacterial activities of the PN processes. Biomass was collected from a continuous-flow internal-loop airlift reactor and cultured with fixed ammonium concentrations of 921 mg N L −1 . Batch activity tests were conducted to determine the specific oxygen uptake rate. The individual and interactive inhibitory effects of Zn 2+ , Cu 2+ , oxytetracycline (OTC) and sulfamethazine (SMZ) were evaluated using an orthogonal test. The results showed that the half maximal inhibitory concentration (IC 50 ) values of Zn 2+ , Cu 2+ , OTC and SMZ on PN sludge were 50.1, 35.4, 447 and 1890 mg L −1 , respectively. The joint toxicities of heavy metals (Zn 2+ and Cu 2+ ) and antibiotics (OTC and SMZ) in the PN mixed culture were generally synergistic, except for between Zn 2+ and Cu 2+ , which was antagonistic. In joint toxicity tests, the significance of the inhibitory effect of Zn 2+ (15.3–164.3 mg L −1 ), Cu 2+ (13.8–90.9 mg L −1 ), OTC (27.0–866.5 mg L −1 ) and SMZ (290–3490 mg L −1 ) on the nitrifying bacterial activity can be ranked in the following order: SMZ > Cu 2+  > Zn 2+  > OTC. Additionally, different exposure times (1 h, 3 h and 24 h) with or without aeration were also comparatively studied. These results show that a greater PN sludge activity loss than when exposure without aeration. [ABSTRACT FROM AUTHOR]

The performance and stability of mesophilic codigestion of waste activated sludge (WAS) and food waste (FW) were compared in two parallel, continuously stirred tank reactors using high- and low-magnitude loading increments for the loading regimes. The results indicated that a high methane (CH 4) production of 6.98 L L−1·d−1 was realized without volatile fatty acid accumulation via low-magnitude loading increments at a high loading of 26.5 g-COD·L−1·d−1, and this system was more stable and achieved a higher efficiency than the codigestion system that used high-magnitude loading increments at similar loading and operating conditions. Furthermore, higher CH 4 yields of 258–334 mL-CH 4 ·g-COD−1, TCOD removal efficiencies of 64–79%, conversion ratios of 62–88%, and methanogenic activities of 0.37–0.40 g-CH 4 -COD·g-VS−1·d−1 were consistently maintained via the low-magnitude loading increments during the high-rate period. High abundances of the phyla Firmicutes (63.3%) and genus Methanosarcina (94.5%) contributed to the high rates and stable operating conditions of the mesophilic system for WAS and FW codigestion using low-magnitude loading increments. [Display omitted] • Two CSTR codigestion systems with different incremental loadings were compared. • Low-magnitude loading increments can lead to stable and high rates of codigestion. • A high abundance of Methanosarcina was induced via low-magnitude loading increments. • Low-magnitude loading increments provides an easy-to-apply and promising approach. [ABSTRACT FROM AUTHOR]

Starvation of biomass is common in the biological wastewater industries. To investigate the influence of starvation on the sludge characteristics and reactivation performance of the anaerobic ammonium oxidation (anammox) process, the starvation process of high-activity anammox granules over 50 days and the subsequent reactivation characterization of the granules were evaluated in two upflow anaerobic sludge blanket (UASB) reactors at 20 °C and 4 °C, respectively. The results showed that the starvation temperature had a significant impact on the morphological and physical properties. Anammox granules stored at 4 °C achieved a relatively low decay rate, excellent nitrogen removal capacity, and a low protein-to-polysaccharide (PN/PS) ratio after reactivation. Those results demonstrated that 4 °C was more suitable for the maintenance of structural integrity and granule stability during long-term starvation. The nitrogen removal performance of anammox granules after starvation could be recovered after 4 days of operation, and the anammox activity could be fully restored within 8 days. Furthermore, anammox granules preserved at 4 °C obtained a better recovery performance than those at 20 °C. In summary, anammox granules could be stored up to 50 days without running the risk of losing the integrity of the granules and metabolic potentials. And anammox performance after prolonged starvation could be fully revived. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the substrate ratio on the nitrogen removal performance of the anaerobic ammonium oxidation (Anammox) process was evaluated using an upflow biofilter fed with different ratios of substrates. The influent substrate ratio of nitrite-to-ammonium (R IS) was shown to be a key factor in the Anammox process, and the optimal R IS level was 1.2. When the influent ammonium or nitrite level was relatively high, residual substrate over-consumption was observed. The free ammonia was not significantly inhibitory to the Anammox biomass at a concentration of 17±2mgNL−1; however, a high level of residual nitrite reduced the activity of Anammox bacteria. The activity that was depressed by nitrite inhibition was revived within 5 days following the reduction of the R IS. In this study, the Haldane, Edwards and Aiba models, which were used to simulate nitrite inhibition of the Anammox process, were workable, and the parameters for these models were determined. [Copyright &y& Elsevier]

Abstract: As an important human exposure pathway of contaminants, soil ingestion is of increasing concern for assessing health risk from polycyclic aromatic hydrocarbons (PAHs) in soils. A wide range of total PAH concentrations ranging from 0.112μg g−1 to 27.8μg g−1 in soils collected from different public sites, including gas stations, roadsides, bus stops, a kindergarten, primary and middle schools, a university and residential area, was detected. In general, total PAHs concentrations in soils from traffic areas were significantly higher than that from the other sites, indicating a dominant contribution from motor vehicles. Physiologically based in vitro tests were used to evaluate the oral bioaccessibility of PAHs in surface soil under different land uses in Beijing regarding both gastric and small intestinal conditions. It was found that the oral bioaccessibility of total PAHs in small intestinal condition, ranging from 9.2% to 60.5% of total PAHs in soil, was significantly higher than gastric condition, ranging from 3.9% to 54.9%. The bioaccessibility of individual PAHs in soils generally decreased with the increasing ring number of PAHs in both gastric and small intestinal conditions. However, the ratio of bioaccessibility of individual PAHs in gastric condition to that in small intestinal condition, generally increased with increasing ring number, indicating the relatively pronounced effect of bile extract on improving bioaccessibility of PAHs with relatively high ring numbers characterized by their high K ow values. The observation that bile extract at a level higher than critical micelle concentration could reduce the surface tension of digestive juice substantially, which may cause PAHs to be available for intestinal absorption, calls for more careful establishment of reliable soil criteria for PAHs, especially concerning the health of children who may ingest a considerable amount of PAH-contaminated soil via outdoor hand-mouth activities. [Copyright &y& Elsevier]

Abstract: Several soil samples were used to study how the characteristics of natural organic matter (NOM) affect sorption of organic compounds. These soils contains different amounts and types of NOM. Aromaticity of NOM (percentage of aromatic carbons) was determined from solid-state CPMAS [sup 13]C NMR spectra and the soil effective polarity was computed from the equation developed by Xing et al. Naphthalene was used to examine the sorption characteristics of NOM. Both aromaticity and polarity of NOM strongly affected sorption of naphthalene. Old NOM showed higher affinity than that in the surface, young soils. Sorption increased with increasing aromaticity and decreasing polarity. Thus, the sorption coefficients of organic contaminants cannot be accurately predicted without some consideration of NOM characteristics. [ABSTRACT FROM AUTHOR]

To optimize the artificial rumen microorganism sources and develop a stable artificial rumen system, batch and continuous operation were investigated with corn straw and food waste as substrates. The batch trials evaluated the volatile fatty acid (VFA) yield, biogas production, and lignocellulose degradation efficiency. The continuous test evaluated the performance of the artificial cow and sheep rumen systems using a dynamic membrane bioreactor (DMBR) with a stepwise organic loading rate at mesophilic temperature. The anaerobic digestion (AD) of the lignocellulose biomass after rumen fermentation pretreatment and of the permeate from the artificial rumen system were also evaluated for CH 4 production. The results indicated that the cow rumen microorganisms were more suitable than sheep rumen microorganisms for lignocellulosic biomass pretreatment and maximized the CH 4 yield through the AD process without inhibition. After approximately four months of continuous operation, a stable and continuous artificial rumen system for lignocellulosic biomass degradation was achieved with cow rumen fluid as inoculum. Based on analysis of the core lignocellulose-degrading enzyme levels and gel filtration chromatography, the cow rumen microorganisms could secrete more extracellular multienzyme complexes to hydrolyze lignocellulosic biomass than the sheep rumen microorganisms in vitro. During the batch and continuous operations, a high diversity and similar richness of bacteria and fungi demonstrated that the cow rumen microorganisms can be used as a preferred inoculum for the artificial rumen system. The use of an artificial cow rumen system with a DMBR is a promising way to construct a stable and continuous artificial rumen system to biodegrade lignocellulosic biomass for biogas production. Unlabelled Image • Rumen fermentation enhanced the AD efficiency of corn straw and food waste. • Stable and continuous operation of artificial rumen system in a DMBR was conducted. • Artificial cow rumen system is a promising way to degrade lignocellulosic biomass. • Artificial cow/sheep rumen fermentation compared in batch and continuous operations. [ABSTRACT FROM AUTHOR]

To enhance the degradation of wheat straw (WS) and corn straw (CS) in rumen fermentation, characterization of degradation and ruminal microorganisms of monosubstrate (WS/CS) groups and a cosubstrate strategy with food waste (FW) group was performed. The cellulose, hemicellulose, and lignin degradation efficiency of WS and CS; soluble chemical oxygen demand; volatile fatty acid yields; and activity of ligninolytic, cellulolytic, and hemicellulolytic enzymes for the cosubstrate group were improved compared with those for the corresponding monosubstrate groups. An accurate and a good of fit of the Weibull kinetic model, decreased crystallinity index values, and characteristic absorbance bands in the Fourier transform-infrared spectra further confirmed that cosubstrate addition with FW decreased the resistance of cellulose and hemicellulose to biodegradation. High-throughput sequencing results suggested that the bacterial diversity in CS rumen fermentation and fungal diversity and richness in WS rumen fermentation were promoted with FW as a cosubstrate. The cosubstrate addition with FW significantly affected the composition of the ruminal bacteria and fungi in rumen fermentation. The relative abundances (RAs) of rumen bacteria were increased in the cosubstrate CS/WS and FW fermentation conditions, and the enhancement of CS degradation with FW supplementation was stronger than that of WS rumen fermentation with FW supplementation. The RAs of the ruminal fungal genera Ustilago and Fusarium were promoted in CS and WS fermentation with FW, respectively. Moreover, the fermentation properties and rumen flora in the FW rumen fermentation also provided some evidence to suggest an enhancement of the cosubstrate strategy compared with the monosubstrate strategy. Image 1 • Food waste (FW) increased alkalinity and improved VFAs yield in rumen fermentation. • Wheat/corn straw (WS/CS) rumen degradation was enhanced by cosubstrate with FW. • Lignocellulases and bacterial diversity in CS and FW fermentation were improved. • Fungal diversity and richness in WS fermentation were promoted with FW addition. [ABSTRACT FROM AUTHOR]

Rumen fermentation is known to be effective for lignocellulosic-wastes biodegradation to certain extent but it is still unclear if there exists a termination of the microorganisms' action to further degrade the bio-refractory fractions. In order to illuminate the related microbiological characteristics, experiments were conducted in a prolonged duration of rumen fermentation of mechanically ruptured wheat straw, with inoculation of cow rumen microorganisms in vitro. Although the organic wastes could not be biodegraded quickly, continuous conversion of the lignocellulosic contents to volatile fatty acids and biogas proceeded in the duration of more than three months, resulting in 96–97% cellulose and hemicellulose decomposition, and 42% lignin decomposition. X-ray diffraction and Fourier transform infrared spectroscopy further demonstrated the characteristics of lignocellulosic structure decomposition. Under the actions of cow rumen microorganisms, stable pH was maintained in the fermentation liquid, along with a steady NH 4 +-N, volatile fatty acids accumulation, and a large buffering ability. It was identified by enzyme analysis and Illumina MiSeq sequencing that the rich core lignocellulolytic enzymes secreted by the abundant and diverse rumen bacteria and fungi contributed to the persistent degradation of lignocellulosic wastes. Members of the Clostridiales order and Basidiomycota phylum were found to be the dominant lignocellulolytic bacteria and fungi, respectively. It could thus be inferred that the main lignocellulose degradation processes were a series of catalytic reactions under the actions of lignocellulolytic enzymes secreted from bacteria and fungi. The dominant hydrogenotrophic methanogens (Methanomassiliicoccus , Methanobrevibacter , Methanosphaera , and Methanoculleus) in the rumen could also assist CH 4 production if the rumen fermentation was followed with anaerobic digestion. Unlabelled Image • High WS decomposition was achieved by the persistent action of cow rumen microflora. • Degradation characteristics of raw WS subject to rumen fermentation were analysed. • Rich core lignocellulolytic enzymes were secreted by the rumen bacteria and fungi. • Firmicutes and Basidiomycota were the dominant lignocellulolytic bacteria and fungi. • Degradation mechanisms for the in vitro rumen fermentation of WS were elucidated. [ABSTRACT FROM AUTHOR]

The long-term and large-scale utilization of fertilizers and pesticides in facility agriculture leads to groundwater pollution. However, the coexistence and interactions between organic fertilizers (i.e., organic matter), toxic metals, and pesticides in shallow groundwater have seldom been studied. Thus, the study sought to characterize said interactions via fluorescence, ultraviolet–visible spectroscopy (UV–Vis), and Fourier-transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy and chemometric techniques. The results indicated that groundwater DOM was comprised of protein-, polysaccharide-, and lignin-like substances derived from organic fertilizers. Protein-like substances accounted for the binding of Co, Ni, and Fe, while polysaccharide- and lignin-like substances were mainly responsible for Cr and Mo complexation. Moreover, lignin- and polysaccharide-like substances played a key role in the binding of pesticides (i.e., dichlorodiphenyltrichloroethane [DDT], endosulfan, γ-hexachlorocyclohexane [γ-HCH], monocrotophos, chlorpyrifos, and chlorfenvinphos), rendering the conversion of γ-HCH to β-hexachlorocyclohexane (β-HCH) and the degradation of DDT to dichlorobenzene dichloroethylene (DDE) ineffective. However, the presence of protein-like substances in groundwater benefited the degradation and conversion of γ-HCH and α-endosulfan. Redundancy analyses showed that lignin- and polysaccharide-like matter had the most impacts on the coexistence of DOM with toxic metals and pesticides. Image 1 • Interactions between DOM and toxic metals/pesticides in groundwater were analyzed. • Groundwater DOM comprised protein-, polysaccharide-, and lignin-like substances. • DOM functional groups bonded with toxic metals and pesticides. • Groundwater DOM was found to affect the degradation and conversion of pesticides. Lignin- and polysaccharide-like matter had the most impacts on the coexistence of DOM with toxic metals and pesticides. [ABSTRACT FROM AUTHOR]

The inhibitory action and possible damage mechanism of dibutyl phthalate (DBP) on the red tide algae Karenia brevis were investigated. The results showed that the algae experienced oxidative stress after exposure to 5 mg L −1 DBP. Malondialdehyde (MDA) peaked after 72 h, with a value approximately 2.3 times higher than that observed for untreated cells. The superoxide dismutase (SOD) and catalase (CAT) activities significantly increased as an adaptive reaction after 48 h. DBP induced the overproduction of reactive oxygen species (ROS), the OH concentration showed a peak of 33 U mL −1 at 48 h, and the highest H 2 O 2 content was approximately 250 nmol/10 7 cells at 72 h; these latter two values were 2.5 and 4.4 times higher than observed for the control, respectively. TEM images showed that a number of small vacuoles or apical tubers were commonly found around the cell membrane, and the membrane structure was ultimately disintegrated. Further experiments were carried out to locate the original ROS production sites following DBP exposure. The activity of CuZn-SOD (a mainly cytosolic isoform, with some also found in chloroplasts) under DBP exposure was approximately 2.5 times higher than the control, whereas the Mn-SOD (mitochondrial isoform) activity was significantly inhibited. No significant difference was observed in the activity of Fe-SOD (chloroplastic isoform). In addition, dicumarol (an inhibitor of the electron transport chain in the plasma membrane) stimulated DBP-induced ROS production, whereas rotenone (an inhibitor of the mitochondria electron transport chain complex I) decreased DBP-induced ROS production. These results suggested that mitochondria could be the main target sites for DBP attack. [ABSTRACT FROM AUTHOR]

Hexylene-bridged periodic mesoporous polysilsesquioxanes (HBPMS) are a promising new class of adsorbent for the removal of organic contaminants from aqueous solutions. These hybrid organic-inorganic materials have a larger BET surface area of 897 m2·g-1 accessible through a cubic, isotropic network of 3.82-nm diameter pores. The hexylene bridging group provides enhanced adsorption of organic molecules while the bridged polysilsesquioxane structure permits sufficient silanols that are hydrophilic to be retained. In this study, adsorption of phenanthrene (PHEN), 2,4-Dichlorophenol (DCP), and nitrobenzene (NBZ) with HBPMS materials was studied to ascertain the relative contributions to adsorption performance from (1) direct competition for sites and (2) pore blockage. A conceptual model was proposed to further explain the phenomena. This study suggests a promising application of cubic mesoporous BPS in wastewater treatment.