Insight into the microbial community of denitrification process using different solid carbon sources: Not only bacteria.

There is a lack of understanding about the bacterial, fungal and archaeal communities' composition of solid-phase denitrification (SPD) systems. We investigated four SPD systems with different carbon sources by analyzing microbial gene sequences based on operational taxonomic unit (OTU) and amplicon sequence variant (ASV). The results showed that the corncob-polyvinyl alcohol sodium alginate-polycaprolactone (CPSP, 0.86±0.04 mg NO3--N/(g·day)) and corncob (0.85±0.06 mg NO3--N/(g·day)) had better denitrification efficiency than polycaprolactone (PCL, 0.29±0.11 mg NO3--N/(g·day)) and polyvinyl alcohol-sodium alginate (PVA-SA, 0.24±0.07 mg NO3--N/(g·day)). The bacterial, fungal and archaeal microbial composition was significantly different among carbon source types such as Proteobacteria in PCL (OTU: 83.72%, ASV: 82.49%) and Rozellomycota in PVA-SA (OTU: 71.99%, ASV: 81.30%). ASV methods can read more microbial units than that of OTU and exhibit higher alpha diversity and classify some species that had not been identified by OTU such as Nanoarchaeota phylum, unclassified_ f_ Xanthobacteraceae genus, etc., indicating ASV may be more conducive to understand SPD microbial communities. The co-occurring network showed some correlation between the bacteria fungi and archaea species, indicating different species may collaborate in SPD systems. Similar KEGG function prediction results were obtained in two bioinformatic methods generally and some fungi and archaea functions should not be ignored in SPD systems. These results may be beneficial for understanding microbial communities in SPD systems.

Novel slow-release carbon source improves anodic denitrification and electricity generation efficiency in microbial fuel cells.

MFC anodic denitrification is more suitable for the coexistence of organic matter and nitrate in actual sewage, but the traditional carbon source has some problems such as high cost and difficulty of dosage control in MFC. Herein, corncob and polycaprolactone (PCL) were mechanically pulverized and mixed in the system of polyvinyl alcohol and sodium alginate, and cross-linked to prepare slow-release carbon source fillers (CPSP), which were added to the MFC anolyte to realize the coupling of solid-phase denitrification and anodic denitrification. Results showed the start-up period of MFC experimental group (MFC-C) with CPSP was slightly longer than the control group (MFC-0), but MFC-C's maximum output voltage (648.4 mV) and power density (2738 mW/m3) could be increased by 5% and 15% higher than that of MFC-0 (P < 0.05). The degradation process of MFC substrate in unit cycle was mainly divided into nitrogen removal stage (0-8 h) and electricity generation stage (8-48 h). The NO3--N and COD degradation and power generation kinetic processes of MFC conformed to the Han-Levenspiel model. Kinetics experiments showed CPSP can improve the affinity and tolerance of MFC to NO3--N, also it can alleviate the pressure of electron competition in anolyte and improve coulombic efficiency. In addition, microbial communities were significantly changed under the effect of CPSP (P < 0.001). Meanwhile, CPSP can promote the synthesis of denitrification functional genes. This study provides a new strategy to improve the performance of MFC by the addition of novel denitrification carbon source.

Effects of antibiotics on corncob supported solid-phase denitrification: Denitrification and antibiotics removal performance, mechanism, and antibiotic resistance genes.

Solid-phase denitrification (SPD) has been used in wastewater treatment plant effluent to enhance nitrate removal, and antibiotics co-existing in the effluent is a common environmental problem. In this study, it was systematically investigated the effect of single trace sulfamethoxazole (SMX)/trimethoprim (TMP) and their mixture on microbial denitrification performance, the antibiotics removal, and antibiotics resistance genes (ARGs) in corncob supported SPD system. The average denitrification rate was improved by 46.90% or 61.09% with single 50 µg/L SMX or TMP, while there was no significant inhibition with mixed SMX and TMP. The abundance of dominant denitrifiers (Comamonadaceae family and Azospia) and fermentation bacteria (Ancalomicrobium) were consistent with the denitrification performance of different antibiotics groups. Single SMX and TMP achieved relatively higher denitrification gene and enzyme abundance. Mixed SMX and TMP improved the denitrification gene copies, but they reduced the key denitrification enzymes except for EC 1.7.7.2. Additionally, the removal efficiency of TMP (56.70% ± 3.18%) was higher than that of SMX (25.44% ± 2.62%) in single antibiotic group, and the existence of other antibiotics (i.e. SMX or TMP) had no significant impact on the TMP or SMX removal performance. Biodegradation was the main removal mechanism of SMX and TMP, while sludge and corncob adsorption contributed a little to their removal. SMX had the risk of sulfanilamide resistance genes (SRGs) dissemination. Furthermore, network analysis indicated that Niveibacterium and Bradyrhizobium were the potential hosts of SRGs, which promoted the horizontal transmission of ARGs.

Initial carbon release characteristics, mechanisms and denitrification performance of a novel slow release carbon source.

External carbon source addition is one of the effective methods for the treatment of wastewater with low carbon to nitrogen ratio (C/N). Compared with fast-release liquid carbon sources, slow-release solid carbon sources are more suitable for the denitrification process. A novel slow-release solid carbon source (corncob-polyvinyl alcohol sodium alginate- poly-caprolactone, i.e. CPSP) was prepared using corn cob (CC) and poly-caprolactone with polyvinyl alcohol sodium alginate as hybrid scaffold. The physical properties and carbon release characteristics of CPSP and three other carbon sources were compared. CPSP had stable framework and good carbon release performance, which followed the second order release equation. The formic acid, acetic acid, propionic acid and butyric acid released from CPSP accounted for 8.27% ± 1.66 %, 56.48% ± 3.71 %, 18.46% ± 2.69% and 16.79% ± 3.02% of the total released acids respectively. The start-up period of CPSP was shorter than that of the other carbon sources in denitrification experiment, and no COD pollution was observed in the start-up phase (25-72 h) and stable phase (73-240 hr). The composition and structure of the dissolved organic compounds released by CPSP and other carbon sources were analyzed by UV-Vis absorption spectroscopy and three-dimensional fluorescence spectroscopy, which indicated that CPSP was more suitable for denitrification than the other studied carbon sources.

Denitrification and microbial community in MBBR using A. donax as carbon source and biofilm carriers for reverse osmosis concentrate treatment.

In this study, raw Arundo donax (A. donax) pieces were applied as carbon source and biofilm carriers for denitrification in a lab-scale moving bed biofilm reactor (MBBR) for the treatment of reverse osmosis concentrate gathered from local wastewater reuse plant. At stable phase (about 60 days), efficient denitrification performance was obtained with 73.2% ±â€¯19.5% NO3--N average removal and 8.10 ±â€¯3.45 g N/(m3·day) NO3--N average volumetric removal rate. Mass balance analysis showed that 4.84 g A. donax was required to remove 1 g TN. Quantitative real-time PCR analysis results showed that the copy numbers of 16S r-RNA, narG, nirS, nosZ and anammox gene of carrier biofilm and suspended activated sludge in the declination phase (BF2 and AS2) were lower than those of samples in the stable phase (BF1 and AS1), and relatively higher copy numbers of nirS and nirK genes with lower abundance of narG and nosZ genes were observed. High-throughput sequencing analysis was conducted for BF2 and AS2, and similar dominant phyla and classes with different abundance were obtained. The class Gammaproteobacteria affiliated with the phylum Proteobacteria was the most dominant microbial community in both BF2 (52.6%) and AS2 (41.7%). The PICRUSt prediction results indicated that 33 predictive specific genes were related to denitrification process, and the relative abundance of 18 predictive specific genes in BF2 were higher than those in AS2.

Dietary leucine supplementation alters energy metabolism and induces slow-to-fast transitions in longissimus dorsi muscle of weanling piglets.

Leucine plays an important role in promoting muscle protein synthesis and muscle remodelling. However, what percentage of leucine is appropriate in creep feed and what proteome profile alterations are caused by dietary leucine in the skeletal muscle of piglets remain elusive. In this case, we applied isobaric tags for relative and absolute quantitation to analyse the proteome profile of the longissimus dorsi muscles of weanling piglets fed a normal leucine diet (NL; 1·66 % leucine) and a high-leucine diet (HL; 2·1 % leucine). We identified 157 differentially expressed proteins between these two groups. Bioinformatics analysis of these proteins exhibited the suppression of oxidative phosphorylation and fatty acid ß-oxidation, as well as the activation of glycolysis, in the HL group. For further confirmation, we identified that SDHB, ATP5F1, ACADM and HADHB were significantly down-regulated (P<0·01, except ATP5F1, P<0·05), whereas the glycolytic enzyme pyruvate kinase was significantly up-regulated (P<0·05) in the HL group. We also show that enhanced muscle protein synthesis and the transition from slow-to-fast fibres are altered by leucine. Together, these results indicate that leucine may alter energy metabolism and promote slow-to-fast transitions in the skeletal muscle of weanling piglets.

Global Liver Proteome Analysis Using iTRAQ Reveals AMPK-mTOR-Autophagy Signaling Is Altered by Intrauterine Growth Restriction in Newborn Piglets.

Intrauterine growth restriction (IUGR) impairs fetal growth and development, perturbs nutrient metabolism, and increases the risk of developing diseases in postnatal life. However, the underlying mechanisms by which IUGR affects fetal liver development and metabolism remain incompletely understood. Here, we applied a high-throughput proteomics approach and biochemical analysis to investigate the impact of IUGR on the liver of newborn piglets. As a result, we identified 78 differentially expressed proteins in the three biological replicates, including 31 significantly up-regulated proteins and 47 significantly down-regulated proteins. Among them, a majority of differentially expressed proteins were related to nutrient metabolism and mitochondrial function. Additionally, many significantly down-regulated proteins participated in the mTOR signaling pathway and the phagosome maturation signaling pathway. Further analysis suggested that glucose concentration and hepatic glycogen storage were both reduced in IUGR newborn piglets, which may contribute to AMPK activation and mTORC1 inhibition. However, AMPK activation and mTORC1 inhibition failed to induce autophagy in the liver of IUGR neonatal pigs. A possible reason is that PP2Ac, a potential candidate in autophagy regulation, is significantly down-regulated in the liver of IUGR newborn piglets. These findings may provide implications for preventing and treating IUGR in human beings and domestic animals.

Quantitative proteomics analysis reveals glutamine deprivation activates fatty acid ß-oxidation pathway in HepG2 cells.

Glutamine, a multifunctional amino acid, functions in nutrient metabolism, energy balance, apoptosis, and cell proliferation. Lipid is an important nutrient and controls a broad range of physiological processes. Previous studies have demonstrated that glutamine can affect lipolysis and lipogenesis, but the effect of glutamine on the detailed lipid metabolism remains incompletely understood. Here, we applied the quantitative proteomics approach to estimate the relative abundance of proteins in HepG2 cells treated by glutamine deprivation. The results showed that there were 212 differentially abundant proteins in response to glutamine deprivation, including 150 significantly increased proteins and 62 significantly decreased proteins. Interestingly, functional classification showed that 43 differentially abundant proteins were related to lipid metabolism. Further bioinformatics analysis and western blotting validation revealed that lipid accumulation may be affected by ß-oxidation of fatty acid induced by glutamine deprivation in HepG2 cells. Together, our results may provide the potential for regulating lipid metabolism by glutamine in animal production and human nutrition. The MS data have been deposited to the ProteomeXchange Consortium with identifier PXD003387.

A novel PSB-EDI system for high ammonia wastewater treatment, biomass production and nitrogen resource recovery: PSB system.

A novel process coupling photosynthetic bacteria (PSB) with electrodeionization (EDI) treatment was proposed to treat high ammonia wastewater and recover bio-resources and nitrogen. The first stage (PSB treatment) was used to degrade organic pollutants and accumulate biomass, while the second stage (EDI) was for nitrogen removal and recovery. The first stage was the focus in this study. The results showed that using PSB to transform organic pollutants in wastewater into biomass was practical. PSB could acclimatize to wastewater with a chemical oxygen demand (COD) of 2,300 mg/L and an ammonia nitrogen (NH4(+)-N) concentration of 288-4,600 mg/L. The suitable pH was 6.0-9.0, the average COD removal reached 80%, and the biomass increased by an average of 9.16 times. The wastewater COD removal was independent of the NH4(+)-N concentration. Moreover, the PSB functioned effectively when the inoculum size was only 10 mg/L. The PSB-treated wastewater was then further handled in an EDI system. More than 90% of the NH4(+)-N was removed from the wastewater and condensed in the concentrate, which could be used to produce nitrogen fertilizer. In the whole system, the average NH4(+)-N removal was 94%, and the average NH4(+)-N condensing ratio was 10.0.

A Novel Data Fusion Strategy of GC-MS and 1H NMR Spectra for the Identification of Different Vintages of Maotai-flavor Baijiu.

Counterfeit Baijiu has been emerging because of the price variances of real-aged Chinese Baijiu. Accurate identification of different vintages is of great interest. In this study, the combination of gas chromatography-mass spectrometry (GC-MS) and proton nuclear magnetic resonance (1H NMR) spectroscopy was applied for the comprehensive analysis of chemical constituents for Maotai-flavor Baijiu. Furthermore, a novel data fusion strategy combined with machine learning algorithms has been established. The results showed that the midlevel data fusion combined with the random forest algorithm were the best and successfully applied for classification of different Baijiu vintages. A total of 14 differential compounds (belonging to fatty acid ethyl esters, alcohols, organic acids, and aldehydes) were identified, and used for evaluation of commercial Maotai-flavor Baijiu. Our results indicated that both volatiles and nonvolatiles contributed to the vintage differences. This study demonstrated that GC-MS and 1H NMR spectra combined with a data fusion strategy are practical for the classification of different vintages of Maotai-flavor Baijiu.

Genome-wide CRISPR screens identify ILF3 as a mediator of mTORC1-dependent amino acid sensing.

The mechanistic target of rapamycin complex 1 (mTORC1) is an essential hub that integrates nutrient signals and coordinates metabolism to control cell growth. Amino acid signals are detected by sensor proteins and relayed to the GATOR2 and GATOR1 complexes to control mTORC1 activity. Here we perform genome-wide CRISPR/Cas9 screens, coupled with an assay for mTORC1 activity based on fluorescence-activated cell sorting analysis of pS6, to identify potential regulators of mTORC1-dependent amino acid sensing. We then focus on interleukin enhancer binding factor 3 (ILF3), one of the candidate genes from the screen. ILF3 tethers the GATOR complexes to lysosomes to control mTORC1. Adding a lysosome-targeting sequence to the GATOR2 component WDR24 bypasses the requirement for ILF3 to modulate amino-acid-dependent mTORC1 signalling. ILF3 plays an evolutionarily conserved role in human and mouse cells, and in worms to regulate the mTORC1 pathway, control autophagy activity and modulate the ageing process.

Seasonal distribution characteristics and ecological risk assessment of phthalate esters in surface sediment of Songhua River basin.

Phthalic acid esters (PAEs) are typical industrial chemicals used in China. PAEs have received considerable attention because of their ubiquity and potential hazard to humans and the ecology. The spatiotemporal distributions of six PAEs in the surface sediments of the Songhua River in the spring (March), summer (July), and autumn (September) are investigated in this study. The total concentration of phthalic acid esters (∑6PAEs) ranges from 1.62 × 102 ng g-1 dry weight (dw) to 3.63 × 104 ng g-1·dw, where the amount in the spring is substantially higher (p < 0.01) than those in the autumn and summer. Seasonal variations in PAEs may be due to rainfall and temperature. The ∑6PAEs in the Songhua River's upper reaches are significantly higher than those in the middle and lower reaches (p < 0.05). Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) are the two most abundant PAEs. The ecological hazard of five PAEs is assessed using the hazard quotient method. DBP and DEHP pose moderate or high ecological risks to aquatic organisms at various trophic levels. PAEs originate primarily from industrial, agricultural, and domestic sources. Absolute principal components-multiple linear regression results indicate that agricultural sources are the most dominant contributor to the ∑6PAEs (53.7%). Guidelines for controlling PAEs pollution in the Songhua River are proposed.

Lysine crotonylation regulates leucine-deprivation-induced autophagy by a 14-3-3ε-PPM1B axis.

Lysine crotonylation as a protein post-translational modification regulates diverse cellular processes and functions. However, the role of crotonylation in nutrient signaling pathways remains unclear. Here, we find a positive correlation between global crotonylation levels and leucine-deprivation-induced autophagy. Crotonylome profiling identifies many crotonylated proteins regulated by leucine deprivation. Bioinformatics analysis dominates 14-3-3 proteins in leucine-mediated crotonylome. Expression of 14-3-3ε crotonylation-deficient mutant significantly inhibits leucine-deprivation-induced autophagy. Molecular dynamics analysis shows that crotonylation increases molecular instability and disrupts the 14-3-3ε amphipathic pocket through which 14-3-3ε interacts with binding partners. Leucine-deprivation-induced 14-3-3ε crotonylation leads to the release of protein phosphatase 1B (PPM1B) from 14-3-3ε interaction. Active PPM1B dephosphorylates ULK1 and subsequently initiates autophagy. We further find that 14-3-3ε crotonylation is regulated by HDAC7. Taken together, our findings demonstrate that the 14-3-3ε-PPM1B axis regulated by crotonylation may play a vital role in leucine-deprivation-induced autophagy.

KAT7-mediated CANX (calnexin) crotonylation regulates leucine-stimulated MTORC1 activity.

Amino acids play crucial roles in the MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) pathway. However, the underlying mechanisms are not fully understood. Here, we establish a cell-free system to mimic the activation of MTORC1, by which we identify CANX (calnexin) as an essential regulator for leucine-stimulated MTORC1 pathway. CANX translocates to lysosomes after leucine deprivation, and its loss of function renders either the MTORC1 activity or the lysosomal translocation of MTOR insensitive to leucine deprivation. We further find that CANX binds to LAMP2 (lysosomal associated membrane protein 2), and LAMP2 is required for leucine deprivation-induced CANX interaction with the Ragulator to inhibit Ragulator activity toward RRAG GTPases. Moreover, leucine deprivation promotes the lysine (K) 525 crotonylation of CANX, which is another essential condition for the lysosomal translocation of CANX. Finally, we find that KAT7 (lysine acetyltransferase 7) mediates the K525 crotonylation of CANX. Loss of KAT7 renders the MTORC1 insensitivity to leucine deprivation. Our findings provide new insights for the regulatory mechanism of the leucine-stimulated MTORC1 pathway.Abbreviations: CALR: calreticulin; CANX: calnexin; CLF: crude lysosome fraction; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; ER: endoplasmic reticulum; GST: glutathione S-transferase; HA: hemagglutinin; HEK293T: human embryonic kidney-293T; KAT7: lysine acetyltransferase 7; Kcr; lysine crotonylation; KO: knockout; LAMP2: lysosomal associated membrane protein 2; LAMTOR/Ragulator: late endosomal/lysosomal adaptor: MAPK and MTOR activator; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; PDI: protein disulfide isomerase; PTM: post-translational modification; RPS6KB1/p70S6 kinase 1: ribosomal protein S6 kinase B1; RPTOR: regulatory associated protein of MTOR complex 1; SESN2: sestrin 2; TMEM192: transmembrane protein 192; ULK1: unc-51 like autophagy activating kinase 1.

PFKP facilitates ATG4B phosphorylation during amino acid deprivation-induced autophagy.

ATG4B facilitates autophagy by promoting autophagosome maturation through the reversible lipidation and delipidation of LC3. Recent reports have shown that phosphorylation of ATG4B regulates its activity and LC3 processing, leading to modulate autophagy activity. However, the mechanism about how ATG4B phosphorylation is involved in amino acid deprivation-induced autophagy is unclear. Here, we combined the tandem affinity purification with mass spectrometry (MS) and identified the ATG4B-interacting proteins including its well-known partner gamma-aminobutyric acid receptor-associated protein (GABARAP, a homolog of LC3) and phosphofructokinase 1 platelet isoform (PFKP). Further immunoprecipitation assays showed that amino acid deprivation strengthened the interaction between ATG4B and PFKP. By genetic depletion of PFKP using CRISPR/Cas9, we uncovered that PFKP loss reduced the degradation of LC3-II and p62 due to a partial block in autophagic flux. Furthermore, MS analysis of Flag-tagged ATG4B immunoprecipitates identified phosphorylation of ATG4B serine 34 residue (S34) and PFKP serine 386 residue (S386) under amino acid deprivation condition. In vitro kinase assay validated that PFKP functioning as a protein kinase phosphorylated ATG4B at S34. This phosphorylation could enhance ATG4B activity and p62 degradation. In addition, PFKP S386 phosphorylation was important to ATG4B S34 phosphorylation and autophagy in HEK293T cells. In brief, our findings describe that PFKP, a rate-limiting enzyme in the glycolytic pathway, functions as a protein kinase for ATG4B to regulate ATG4B activity and autophagy under amino acid deprivation condition.

[Release Mechanisms of Carbon Source and Dissolved Organic Matter of Six Agricultural Wastes in the Initial Stage].

As carbon sources for the denitrification process, agricultural wastes have some problems, such as excess release of organic carbon; unclear release characteristics of nitrogen, phosphorus, and colorimetric substances; and unclear components, release mechanisms, and potential effects of the released dissolved organic matter (DOM) in the start-up period. To resolve those problems, rice straw, wheat straw, corn stalk, corncob, soybean stalk, and soybean hull were selected as denitrification carbon sources to investigate the release mechanisms and potential influences of the organic matter, secondary pollutants, and DOM. The results showed that the six agricultural wastes could be used as the denitrification carbon source. The carbon content in the wheat straw was the highest and the secondary pollution risk from the corncob was the lowest. For the six carbon sources, the second-order kinetic equation and Ritger-Peppas equation were followed during the 1-120 h carbon release process. The fitting results demonstrated that corncob was more suitable for use as the denitrification carbon source because of its moderate cm value and longer t1/2 value, and the release mechanisms of the six types of carbon sources were mainly controlled by the diffusion process. The NH4+-N, TN, and TP contents in the immersion water of the rice straw were higher than those of the five other agricultural wastes, and there was heavy chromaticity in the immersion water of the wheat straw and corn stalk. The amounts of nitrogen, phosphorus, and chromatic substances released from the corncob were the lowest. The leachates of the corncob and soybean hull had higher biodegradability and lower risks of secondary pollution than those of the other sources. The aromaticity and molecular weight of DOM increased as the reaction time increased, and the humification of DOM was low. Five components were identified by PARAFAC. The main component was protein-like matter, which was mainly composed of tyrosine-like and tryptophan-like substances. There was less humic acid-like matter in the immersion water. The component characteristics of DOM might have had an adverse effect on the subsequent water treatment process. These results could provide theoretical support for the impact on effluent water quality and risk assessment when the agricultural wastes are used as an additional denitrification carbon source at the start-up stage.

Distribution characteristics of nitrogen and the related microbial community in the surface sediments of the Songhua River.

Nitrogen in surface sediments is becoming an ecological risk to the river environment and it is essential to clarify the relationship between the different forms of nitrogen and related microorganisms. A survey was conducted to analyze the distribution characteristics of the nitrogen and related microbial community in the sediments of the Songhua River during normal season and dry season. In the surface sediments of the Songhua River, no total nitrogen (TN) pollution risk was observed according to the U.S. EPA assessment criteria (1000 mg kg-1) for sediment contamination, but TN in several sampling sites (554.9-759.7 mg kg-1) exceeded the alert values (550 mg kg-1) should be concerned according to the guidelines issued by the Ministry of Environment and Energy of Ontario, Canada. The average TN, NH4 +-N, NO3 --N and total organic nitrogen (TON) in the surface sediments of the Songhua River during normal season were higher than those in the dry period. TON was the main form of nitrogen in the sediment of Songhua River, NO2 --N content was lowest and no obvious difference was observed between normal and dry seasons. The highest average NH4 +-N of both seasons occurred in the Nenjiang River, and the highest average NO3 --N of both seasons were found in the main stream of the Songhua River. The community abundance of AOB genes (1.1 × 107 to 2.5 × 108 copies per g soil in normal season, 7.2 × 105 to 3.3 × 108 copies per g soil in dry season) was higher than that (1.2 × 106 to 9.7 × 107 copies per g soil in normal season, 6.6 × 104 to 3.2 × 107 copies per g soil in dry season) of AOA genes in both normal and dry seasons. The denitrifying nirS genes were predominant in both seasons, and their abundance (1.8 × 106 to 8.0 × 108 copies per g soil) in dry season was higher than that (9.7 × 105 to 4.6 × 108 copies per g soil) in normal season. Moreover, the moisture concentration, pH, dissolved oxygen and different formation of nitrogen were key factors affecting the variation of nitrogen-transformation microorganisms during normal and dry seasons. This research could help to explain the relationship between nitrogen transformation and the related microbial community in the surface sediment, which could provide a scientific basis for water ecological restoration and water environment improvement of Songhua River.

Release Mechanism, Secondary Pollutants and Denitrification Performance Comparison of Six Kinds of Agricultural Wastes as Solid Carbon Sources for Nitrate Removal.

Agricultural wastes used as denitrification carbon sources have some drawbacks such as excessive organic carbon release and unclear release characteristics of nitrogen, phosphorus, and chromatic substances, which can cause adverse effects on the effluent quality during the denitrification process. The composition and surface characteristics, carbon release mechanisms, and secondary pollutant release properties of six kinds of agricultural wastes, i.e., rice straw (RS), wheat straw (WS), corn stalk (CS), corncob (CC), soybean stalk (SS), and soybean hull (SH) were studied and analyzed in this research. The denitrification performance of these agricultural wastes was also investigated extensively by batch experiments. The results showed that the carbon release basically followed the second-order reaction kinetic equation and Ritger-Peppas equation in the 120 h reaction, and it was mainly controlled by the diffusion process. The kinetic equation fitting results and bioavailability test suggested that the potential risk of excessive effluent COD of CC was the lowest due to the appropriate amount and degradability of its released carbon. The NH4+-N, TN, and TP in the leachate of RS were higher than those of the other five agriculture wastes, and the chroma in the leachate of WS and CS was heavier than that of the others. CC released the lowest pollutants, which resulted in slight fluctuations of effluent quality in the start-up period (1-11 d), and it had the best nitrogen removal capacity in the denitrification experiment. The average NO3--N removal of CC was 5.12 mg for each batch in the stable period (11-27 d), which was higher than that of others, and less NO2--N, NH4+-N, and COD were accumulated in the CC effluent during the whole denitrification process.

Hydrilla verticillata-Sulfur-Based Heterotrophic and Autotrophic Denitrification Process for Nitrate-Rich Agricultural Runoff Treatment.

Hydrilla verticillata-sulfur-based heterotrophic and autotrophic denitrification (HSHAD) process was developed in free water surface constructed wetland mesocosms for the treatment of nitrate-rich agricultural runoff with low chemical oxygen demand/total nitrogen (C/N) ratio, whose feasibility and mechanism were extensively studied and compared with those of H. verticillata heterotrophic denitrification (HHD) mesocosms through a 273-day operation. The results showed that the heterotrophic and autotrophic denitrification can be combined successfully in HSHAD mesocosms, and achieve satisfactory nitrate removal performance. The average NO3--N removal efficiency and denitrification rate of HSHAD were 94.4% and 1.3 g NO3--N m-3·d-1 in steady phase II (7-118 d). Most nitrate was reduced by heterotrophic denitrification with sufficient organic carbon in phase I (0-6 d) and II, i.e., the C/N ratio exceeded 4.0, and no significant difference of nitrate removal capacity was observed between HSHAD and HHD mesocosms. During phase III (119-273 d), sulfur autotrophic denitrification gradually dominated the HSHAD process with the C/N ratio less than 4.0, and HSHAD mesocosms obtained higher NO3--N removal efficiency and denitrification rate (79.1% and 1.1 g NO3--N m-3·d-1) than HHD mesocosms (65.3% and 1.0 g NO3--N m-3·d-1). As a whole, HSHAD mesocosms removed 58.8 mg NO3--N more than HHD mesocosms. pH fluctuated between 6.9-9.0 without any pH buffer. In general, HSHAD mesocosms were more stable and efficient than HHD mesocosms for NO3--N removal from agricultural runoff during long-term operation. The denitrificans containing narG (1.67 × 108 ± 1.28 × 107 copies g-1 mixture-soil-1), nirS (8.25 × 107 ± 8.95 × 106 copies g-1 mixture-soil-1), and nosZ (1.56 × 106 ± 1.60 × 105 copies g-1 mixture-soil-1) of litter bags and bottoms in HSHAD were higher than those in HHD, which indicated that the combined heterotrophic and autotrophic denitrification can increase the abundance of denitrificans containing narG, nirS, and nosZ, thus leading to better denitrification performance.

Distributions, compositions, and ecological risk assessment of polycyclic aromatic hydrocarbons and phthalic acid esters in surface sediment of Songhua river, China.

The distribution, composition, and ecological risk of 16 types of polycyclic aromatic hydrocarbons (PAHs) and 6 types of phthalic acid esters (PAEs) in the surface sediment of Songhua river, northeast China, were investigated. The total weight of the PAHs (∑16PAHs) varied from 226.70 to 7086.62 ng/g dry weight (dw), whereas that of the PAEs (∑6PAEs) ranged from 819.44 to 24,035.39 ng/g dw. The dominant PAHs were four-membered ring PAHs, which varied from 18.65% to 78.10% of the total PAHs. The most abundant PAEs was di-2-ethylhexyl phthalate ester (DEHP), which accounted for 65.02-99.07% of the total PAEs, followed by di-n-butyl phthalate ranging from 1.50 to 55.43%. Pyrolytic origin was the dominant PAH source. Approximately 12.70% target PAHs in the Songhua river sediment exhibited moderate ecological risk with 23.49-1404.09 ng/g carcinogenic toxicity equivalent. DEHP in 80.95% of the sediment samples exceeded the effects range low, indicating its potential harmfulness to the aquatic environment.