[Denitrification and Anaerobic Ammonium Oxidation in Soil Nitrogen Migration Process in a Farmland of Wanshandang Lake].

To explore the rate variation and contribution to N loss of denitrification and anaerobic ammonia oxidation (ANAMMOX) in the nitrogen migration process of farmland soils in southern China, we assess the physicochemical characteristics soil samples of different soil layers from farmland and different land use types (farmland, river channel, riparian zone, and lake sediment) in a wheat-rice rotation area of Wanshandang Lake. Illumina MiSeq sequencing and quantitative real-time polymerase chain reaction (qPCR) are used to investigate the microbial community composition and functional gene abundances of the samples. The potential denitrification and ANAMMOX rate (calculated by N2) of each sample was determined by an isotope culture experiment. It was demonstrated that the potential denitrification rate was significantly positively correlated with TOC, NH4+-N, and NO3--N (P<0.05), and with the abundances of nirS, nirK, and nosZ (P<0.05). The denitrification rate of surface soils was (11.51±1.04) nmol·(g·h)-1, which was significantly higher than other soil layers and other land use types (P<0.05). While the ANAMMOX rate in farmland soils was the highest in the 20-30 cm layer and reached (0.48±0.07) nmol·(g·h)-1. In addition, denitrification was the main cause of N loss in surface soils of the studied farmland, accounting for 91.9%-99.7% of overall loss, and ANAMMOX played an important role in the production of N2 in deep soils.

[Insight into the Process of Mn-ANAMMOX in Soils of Agricultural Drainage Ditches].

Anaerobic ammonium oxidation mediated by MnO2 (termed Mn-ANAMMOX) is a newly discovered microbial nitrogen removal pathway. However, few studies have reported on the Mn-ANAMMOX process and related microbial communities in agricultural drainage ditches. In this study, Mn(Ⅳ)-reducing bacteria (MnBR) enrichment cultivation was carried out for 340 days and an isotope tracing technique and high-throughput sequencing technology were used to provide convincing evidence of the occurrence of Mn-ANAMMOX. The results showed that simultaneous NH4+ oxidation and MnO2 reduction occurred during the reaction, and the production of NO2-, NO3-, 30N2, and Mn2+ was detected. Additionally, the average Mn-ANAMMOX rate, ammonium removal rate, and total nitrogen removal rate were 2.88 mg·(kg·d)-1, 20%, and 15%, respectively. Moreover, high-throughput sequencing results showed that after 340 d in the enrichment cultivation experiments, the abundance of MnBR increased from 27% to 70% at the phylum level, and the major genera of MnBR were determined as Acinetobacter and Geothrix, with relative abundances of 26.63% and 4.07%, respectively. Overall, the occurrence of Mn-ANAMMOX was directly proven during the MnBR enrichment cultivation experiments, and it might play an essential role in the pathway of microbial nitrogen removal.

[Insight into the Mechanism of Feammox in the Surface Soils of a Riparian Zone].

Anaerobic ammonium oxidation coupled to iron (Ⅲ) reduction (termed Feammox) is a recently discovered pathway of nitrogen cycling. However, little is known about the pathways of N transformation via the Feammox process in riparian zones. In this study, evidence of Feammox in the riparian zone soil layers (0-20 cm) was demonstrated using the isotope tracing technique and a high-throughput sequencing technology. The results showed that Feammox occurred in the riparian zones in four different soil layers (A:0-5 cm, B:5-10 cm, C:10-15 cm, D:15-20 cm) and the Feammox rates ranged from 0.25 mg·(kg·d)-1 to 0.29 mg·(kg·d)-1. In the B soil sample, the Feammox rate was significantly higher than in the other soil samples (P<0.05). In addition, iron reducing bacteria played an essential role in the Feammox process, and Anaeromyxobacter and Geobacter were detected in all the soil samples. In the B soil sample, the abundance of iron reducing bacteria was significantly higher than in the other soil samples (P<0.05). Overall, the co-occurrence of ammonium oxidation and iron reduction suggest that Feammox can play an essential role in the pathway of nitrogen removal in riparian zones.

[New Bromated Phenolic Disinfection Byproducts: Mechanism of Their Decomposition During Chlorination].

Recently, 13 new phenolic halogenated disinfection by-products (DBPs) have been reported in chlorinated drinking water and have been classified into four groups: dihalo-4-hydroxybenzaldehydes, dihalo-4-hydroxybenzoic acid, dihalo-salicylic acids, and trihalo-phenols. In this work, the four fully brominated species (3,5-dibromo-4-hydroxybenzoic acid, 3,5-dibromosalicylic acid, 2,4,6-tribromophenol, and 3,5-dibromo-4-hydroxybenzaldehyde) were selected as representatives, and the decomposition mechanism of these new DBPs during chlorination was studied with the aid of ultra performance liquid chromatography/electrospray ionization triple-quadrupole mass spectrometry (precursor ion scan, multiple reaction monitoring, and product ion scan). Except for 3,5-dibromosalicylic acid, the new DBPs were not stable and could be finally decomposed to haloacetic acids through multistep substitution, hydrolysis, and oxidation. Various decomposition intermediate DBPs were detected, including a new group of halogenated DBPs with cyclic structures (trihalo-hydroxyl-cyclopetene-diones).

[Effect of Elodea nuttallii-Immobilized Nitrogen Cycling Bacteria on the Mechanism of Nitrogen Removal in Polluted River Water].

Surface water, Elodea nuttallii and undisturbed sediment cores from the Qinshui River in Gonghu Bay were collected to carry out a simulation experiment in a laboratory to study the effect of Elodea nuttallii-immobilized nitrogen-cycling bacteria on nitrogen removal mechanisms from the river water. In this study, the transformation and fate of ammonium among four different treatment groups were investigated by using a stable 15 N isotope pairing technique combined with high-throughput sequencing technology[Treatment A:bare sediment, Treatment B:sediment+immobilized nitrogen cycling bacteria (INCB), Treatment C:sediment+E. nuttallii, Treatment D:sediment+INCB+E. nuttallii]. The results of the 15 N mass-balance model showed that there were three pathways to the ultimate fate of nitrogen:precipitated with the sediments, absorbed by E. nuttallii, and consumed by microbial processes[denitrification and anaerobic ammonium oxidation (ANAMMOX)]. The percentages of E. nuttallii assimilated in the 15 NH4+ were 25.44% and 19.79% for treatments C and D. The sediment storage ratio of 15 NH4+ accounted for 7.94%, 5.52%, 6.47% and 4.86% in treatments A, B, C, and D, respectively. The proportion of 15 NH4+ lost as 15 N-labelled gas were 16.06%, 28.86%, 16.93% and 33.09% in the four different treatment groups, respectively. Denitrification and anammox were the bacterial primary processes in N2 and N2O production. The abundance and diversity of microorganisms was relatively higher in the treatment with E. nuttallii-immobilized nitrogen cycling bacteria (E-INCB) assemblage technology applied. Furthermore, the removal rates of 15 NH4+ were 24%, 34.38%, 48.84% and 57.74% in treatments A, B, C and D, respectively. These results show that the E-INCB assemblage technology may improve the capacity for nitrogen removal from the river water.

[Effect of Elodea nuttallii-immobilized Nitrogen Cycling Bacteria on Nitrogen Removal Mechanism in an Inflow River, Gonghu Bay].

Undisturbed sediment cores and surface water from Qinshui River in Gonghu Bay were collected to carry out a simulation experiment in our laboratory. The remediation effect of Elodea nuttallii-Immobilized Nitrogen Cycling Bacteria (INCB) was applied in the polluted inflow river. The denitrification rate, ANAMMOX rate and nitrogen microorganism diversity were measured by ¹5N isotope pairing technology and high-throughput sequencing technology based on 16S rRNA. The TN, NH4⁺-N, NO3⁻-N concentrations were reduced by 72.03%, 46.67% and 76.65% in the treatment with addition of Elodea nuttallii and INCB in our laboratory experiment. Meanwhile, denitrification bacteria and ANAMMOX bacteria had synergistic effect with each other. The denitrification and ANAMMOX rates were increased by 165 µmol (m² · h)⁻¹ and 269.7 µmol · (m² · h)⁻¹, respectively. The diversities of denitrification and ANAMMOX bacteria also increased in our experiment. From the level of major phylum, Proteobacteria, Planctomycetes, Acidobbacteria and Bacteroidetes all increased significantly. The results showed that the Elodea nuttallii-INCB assemblage technology could increase the bio-diversity of nitrogen cycling bacteria and promote the ability of nitrogen removal in Qinshui River.

[Preparation of Nanocomposite Hydrogel and Its Adsorption of Heavy Metal Ions].

An acylamino and hydroxyl functionalized hydrogel [p(HMAm/HEA)] was newly prepared by the 60 Co-γ-induced polymerization of N-hydroxymethyl acrylamide (HMAm) and 2-hydroxyethyl acrylate (HEA). Then the copolymer p(HMAm/HEA) hydrogel was utilized for in situ nanosized hydrous manganese dioxide (HMO) loading to prepare nanocomposite hydrogel HMO-p(HMAm/HEA) for Pb2+ and Cu2+ removal. The nanocomposite hydrogel was characterized by SEM, TEM and FTIR, showing that p(HMAm/HEA) hydrogel was indeed a copolymer of HMAm and HEA monomers, and the loading of HMO nanoparticles onto p(HMAm/HEA) was successful. Various influencing parameters on heavy metal ions removal by HMO-p(HMAm/HEA), such as initial pH, temperature, initial heavy metal concentration, contact time and competing Ca2+ and Na+, were estimated. The results showed that the adsorption process was temperature-independent, pH-sensitive, Langmuir monolayer adsorption and followed a pseudo-second-order rate equation. The presence of high concentrations of competing Ca2+ and Na+ had no significant effect on the adsorption process. The XPS spectra analyses further indicated that Pb2+ and Cu2+ were adsorbed via the ion exchange of -OH groups. Moreover, HMO-p(HMAm/HEA) could be regenerated by 0.05 mol·L-1 of HCl, and obtained excellent repeated use.

[Nitrogen uptake and denitrification study on the joint treatment of aquatic vegetation and immobilized nitrogen cycling bacteria in Taihu Lake].

Undisturbed sediment cores were collected from Meiliang Bay, Taihu Lake. Immobilized nitrogen cycling bacteria (INCB), Elodea nuttallii were added to four groups of restoration incubation chambers respectively to explore the nitrogen removal mechanism in different restoration treatments. uN tracer and isotope pairing technique were used to determine the rates of plant uptake and denitrification in different treatments. The results showed that denitrification rates were significantly different among the treatments, while cores with addition of both INCB and Elodea nuttallii achieved the highest denitrification rate of 99.35 µmol · (m2 · h)( -1) and plant uptake rate of 36.55 µg · (m2 · h) -1. Elodea nuttallii in the cores could assimilate nitrate itself and enhance coupled nitrification- denitrification. Compared with plant uptake, denitrification was the main pathway of nitrogen removal. The results also showed that the combination of Elodea nuttallii and INCB could promote benthic nitrogen removal and purification of water body.

[Denitrification study of Elodea nuttallii-nitrogen cycling bacteria restoration in Meiliang Bay, Taihu Lake].

Undisturbed sediment cores were collected from Meiliang Bay, Taihu Lake, and the integrated Elodea nuttallii-nitrogen cycling bacteria technology was applied as a restoration method. The effects of the Elodea nuttallii-nitrogen cycling bacteria technology on sediment denitrification was observed by isotope pairing technique. The highest denitrification rate of 104.64 micromol x (m2 x h)(-1) was achieved in sediments with Elodea nuttallii-nitrogen cycling bacteria assemblage. The abundance of nirS, nirK and nosZ genes involved in denitrification processes in the sediments (within 2 cm below the water-sediment interface) were measured by real-time quantitative PCR (RT-qPCR). The abundance of nirS and nosZ genes in the sediments with restoration treatments was increased, which was more than one order of magnitudes higher than that in bare sediments. The results indicated that the presence of macrophyte and nitrogen cycling bacteria could increase benthic nitrogen removal by facilitating coupled nitrification-denitrification and uncoupled nitrification-denitrification.

[Preparation of a novel modified hydrogel and study of its adsorption performance].

A novel copolymer hydrogel poly(Hydroxyethyl methacrylate/N-Vinylformamide) [p (HEA/NVF)] was prepared by 60Co-gamma induced copolymerization, using low-temperature radiation technique. Triethylenetetramine(TETA) was applied to modify the prepared hydrogel into an ammoniated hydrogel poly (Hydroxyethyl methacrylate/N-Vinylformamide) -TETA [p (H/V) -T]. The two hydrogels prepared were characterized by using FTIR spectrometry and the p (HEA/NVF) was scanned by SEM. Moreover, the p (H/V) -T hydrogels were analyzed by XPS before and after adsorption. The adsorption capacities of Pb2+, Cd2+ on p (HEA/NVF) and p (H/V)-T were investigated. And the effects of pH, time and initial metal ion concentration on the adsorption of Pb2+, Cd2+ by p (H/V)-T were examined in batch experiments. SEM photos showed that p (HEA/NVF) hydrogel is a macroporous polymer material. Compared to the p (HEA/NVF) hydrogel, the adsorption capacities of Pb2+, Cd2+ on p(H/V)-T increased by 700% and 600%, respectively. The adsorption behaviors for Pb2+ and Cd2+ confirmed that the adsorption on p(H/V)-T followed the pseudo-second-order rate equation and was fitted to both Langmuir and Freundlich adsorption model (R2 > 0.95). Besides, the adsorption capacities of p (H/V)-T increased with increasing pH values. The FTIR spectra verified that p (HEA/NVF) was indeed a copolymer of HEA and NVF monomers, and the multi-amine groups have been successfully grafted to the surface of the copolymer hydrogel. The XPS analysis concluded that the mechanism of Pb2+ and Cd2+ by p (HEA/MALA) could be the chelation between -NH2 and metal ions.

[Applied study of the submerged macrophytes bed-immobilized bacteria in drinking water restoration].

The effect of submerged macrophytes bed-immobilized bacteria technology which applied in drinking water restoration was studied. Ammonifying bacteria, nitrobacteria, nitrosobacteria and denitrifying bacteria which isolated from Taihu Labe was immobilized to the porous carries, combined with the submerged macrophytes bed technology, we applied the new equipment in water restoration of gonghu bay, this equipment has good ability to resist storm, the denitrifying bacteria number increased from 5.4 x 10(2)-2.7 x 10(3) to 3.9 x 10(5)-9.1 x 10(5), N2O flux of experimental plot was 3-24 microg x (m2 x h)(-1), it's more than the contrast group obviously, TN concentration reduced 19% - 74%, while NO3- concentration reduced 24% -81% after the equipment running a period of time; The experimental data of 120 days showed that this technology is suitable for drinking water restoration, as it can control eutrophication.

[Immobilized ammonia-oxidizing bacteria Comamonas aquatic LNL3 and its partial nitrification characterization].

A new kind of ammonia-oxidizing bacteria (AOB)-Comamonas aquatic LNL3 was screened out and immobilized by Poly (HEA)-Poly (HEMA) copolymer carrier using irradiation techniques. Four kinds of impact factors on short-cut nitrification, including temperature, pH, DO and free ammonia (FA) concentration had been investigated. The result showed that AOB-Comamonas aquatic LNL3 had short-cut nitrification capability and the optimal temperature, pH, DO and FA concentration were 30 degrees C, 8.5, 4.03 mg/L and 9 mg/L respectively. Corresponding to above results, ammonia nitrogen removal rate and short-cut nitrification efficiency were 93.52%, 94.73%; 79.74%, 94.67%; 91.17%, 94.66% and 90%, 94.4% respectively.

[Ecological engineering experiment for Jinshan Lake in Zhenjiang base on techniques of immobilized nitrogen cycling bacteria].

Nitrogen cycling bacteria, including ammonifying, nitrobacteria, nitrosobacteria and denitrifying bacteria were screened, carrier was made and immobilized nitrogen cycling bacteria (INCB) was prepared. The results demonstrated that ammonifying, nitrobacteria, nitrosobacteria and denitrifying bacteria were increased markedly in the experimental areas and root zone of aquatic plants by releasing of INCB. The results also showed that the average removal efficiencies for total N (TN), NH4(+) -N, NO3(-) -N and NO2(-) -N were 44.70%, 67.17%, 31.79% and 74.21%, respectively. Furthermore, NH4(+) -N, total N (TN) reached the National Standard II and IV for surface water, respectively. With INCB, local lake water quality could improve. Therefore, the technique of INCB could play an important role for remedying and rehabilitating in desertification water.

[Stability of short-cut nitrification using immobilized ammonia-oxidizing bacteria].

The ammonia-oxidizing bacteria were immobilized by copolymer with cell proliferation technology. The effects of NH(4+) -N load, HRT, free ammonia (FA) and organic matter on short-cut nitrification process were studied. The results showed that when influent NH(4+) -N load were 100 mg/L, 150 mg/L and 200 mg/L respectively, effluent NH(4+) -N concentration was less than 10 mg/L. When the system run for 3 h, 6 h and 12 h, corresponding to influent NH(4+) -N concentration of 25.8 mg/L, 51.1 mg/L and 93.3 mg/L respectively, NH(4+) -N concentration was low in effluent with high short-cut nitrification efficiency. The HRT could be adjusted to optimize the system operation with variation of influent NH(4+) -N concentration. The results also indicated that the ammonia-oxidizing bacteria were restrained while free ammonia concentration was over 9 mg/L. The activity of the ammonia-oxidizing bacteria could be enhanced under existence of low-molecular-weight organic compounds, but the short-cut nitrification efficiency was little affected. In addition, the short-cut nitrification and denitrification could be realized with existence of organic compounds during the experiment.

In-situ nitrogen removal from the eutrophic water by microbial-plant integrated system.

OBJECTIVE: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get insight into different mechanisms involved in nitrogen removal. METHODS: The aquatic macrophytes used include Eichhornia crassipes (summer-autumn floating macrophyte), Elodea nuttallii (winter-growing submerged macrophyte), and nitrogen cycling bacteria including ammonifying, nitrosating, nitrifying and denitrifying bacteria isolated from Taihu Lake. The immobilization carriers materials were made from hydrophilic monomers 2-hydroxyethyl acrylate (HEA) and hydrophobic 2-hydroxyethyl methylacrylate (HEMA). Two experiments were conducted to evaluate the roles of macrophytes combined with INCB on nitrogen removal from eutrophic water during different seasons. RESULTS: Eichhornia crassipes and Elodea nuttallii had different potentials in purification of eutrophic water. Floating macrophyte+bacteria (INCB) performed best in improving water quality (during the first experiment) and decreased total nitrogen (TN) by 70.2%, nitrite and ammonium by 92.2% and 50.9%, respectively, during the experimental period, when water transparency increased from 0.5 m to 1.8 m. When INCB was inoculated into the floating macrophyte system, the populations of nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 2 orders of magnitude compared to the un-inoculated treatments, but ammonifying bacteria showed no obvious difference between different treatments. Lower values of chlorophyll a, COD(Mn), and pH were found in the microbial-plant integrated system, as compared to the control. Highest reduction in N was noted during the treatment with submerged macrophyte+INCB, being 26.1% for TN, 85.2% for nitrite, and 85.2% for ammonium at the end of 2nd experiment. And in the treatment, the populations of ammonifying, nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 3 orders of magnitude, as compared to the un-inoculated treatments. Similar to the first experiment, higher water transparency and lower values of chlorophyll a, COD(Mn) and pH were observed in the plant+ INCB integrated system, as compared to other treatments. These results indicated that plant-microbe interaction showed beneficial effects on N removal from the eutrophic waterbody.