Seasonal nitrogen fluxes of the Lena River Delta.

The Arctic is nutrient limited, particularly by nitrogen, and is impacted by anthropogenic global warming which occurs approximately twice as fast compared to the global average. Arctic warming intensifies thawing of permafrost-affected soils releasing their large organic nitrogen reservoir. This organic nitrogen reaches hydrological systems, is remineralized to reactive inorganic nitrogen, and is transported to the Arctic Ocean via large rivers. We estimate the load of nitrogen supplied from terrestrial sources into the Arctic Ocean by sampling in the Lena River and its Delta. We took water samples along one of the major deltaic channels in winter and summer in 2019 and sampling station in the central delta over a one-year cycle. Additionally, we investigate the potential release of reactive nitrogen, including nitrous oxide from soils in the Delta. We found that the Lena transported nitrogen as dissolved organic nitrogen to the coastal Arctic Ocean and that eroded soils are sources of reactive inorganic nitrogen such as ammonium and nitrate. The Lena and the Deltaic region apparently are considerable sources of nitrogen to nearshore coastal zone. The potential higher availability of inorganic nitrogen might be a source to enhance nitrous oxide emissions from terrestrial and aquatic sources to the atmosphere.

Cold Adapted Nitrosospira sp.: A Potential Crucial Contributor of Ammonia Oxidation in Cryosols of Permafrost-Affected Landscapes in Northeast Siberia.

Permafrost-affected landscape soils are rich in organic matter and contain a high fraction of organic nitrogen, but much of this organic matter remains inaccessible due to nitrogen limitation. Microbial nitrification is a key process in the nitrogen cycle, controlling the availability of dissolved inorganic nitrogen (DIN) such as ammonium and nitrate. In this study, we investigate the microbial diversity of canonical nitrifiers and their potential nitrifying activity in the active layer of different Arctic cryosols in the Lena River Delta in North-East Siberia. These cryosols are located on Samoylov Island, which has two geomorphological landscapes with mineral soils in the modern floodplain and organic-rich soils in the low-centered polygonal tundra of the Holocene river terrace. Microcosm incubations show that the highest potential ammonia oxidation rates are found in low organic soils, and the rates depend on organic matter content and quality, vegetation cover, and water content. As shown by 16S rRNA amplicon sequencing, nitrifiers represented 0.6% to 6.2% of the total microbial community. More than 50% of the nitrifiers belonged to the genus Nitrosospira. Based on PCR amoA analysis, ammonia-oxidizing bacteria (AOB) were found in nearly all soil types, whereas ammonia-oxidizing archaea (AOA) were only detected in low-organic soils. In cultivation-based approaches, mainly Nitrosospira-like AOB were enriched and characterized as psychrotolerant, with temperature optima slightly above 20 °C. This study suggests a ubiquitous distribution of ammonia-oxidizing microorganisms (bacteria and archaea) in permafrost-affected landscapes of Siberia with cold-adapted AOB, especially of the genus Nitrosospira, as potentially crucial ammonia oxidizers in the cryosols.

Optimisation of bioscrubber systems to simultaneously remove methane and purify wastewater from intensive pig farms.

The use of bioscrubber is attracting increasing attention for exhaust gas treatment in intensive pig farming. However, the challenge is to improve the methane (CH4) removal efficiency as well as the possibility of pig house wastewater treatment. Three laboratory-scale bioscrubbers, each equipped with different recirculation water types, livestock wastewater (10-times-diluted pig house wastewater supernatant), a methanotroph growth medium (10-times-diluted), and tap water, were established to evaluate the performance of CH4 removal and wastewater treatment. The results showed that enhanced CH4 removal efficiency (25%) can be rapidly achieved with improved methanotrophic activity due to extra nutrient support from the wastewater. The majority of the CH4 was removed in the middle to end part of the bioscrubbers, which indicated that CH4 removal could be potentially optimised by extending the length of the reactor. Moreover, 52-86% of the ammonium (NH4+-N), total organic carbon (TOC), and phosphate (PO43--P) removal were simultaneously achieved with CH4 removal in the present study. Based on these results, this study introduces a low-cost and simple-to-operate method to improve CH4 removal and simultaneously treat pig farm wastewater in bioscrubbers.

Biofilter with mixture of pine bark and expanded clay as packing material for methane treatment in lab-scale experiment and field-scale implementation.

Low methane (CH4) emission reduction efficiency (< 25%) has been prevalent due to inefficient biological exhaust gas treatment facilities in mechanic biological waste treatment plants (MBTs) in Germany. This study aimed to quantify the improved capacity of biofilters composed of a mixture of organic (pine bark) and inorganic (expanded clay) packing materials in reducing CH4 emissions in both a lab-scale experiment and field-scale implementation. CH4 removal performance was evaluated using lab-scale biofilter columns under varied inflow CH4 concentrations (70, 130, and 200 g m-3) and corresponding loading rates of 8.2, 4.76, and 3.81 g m-3 h-1, respectively. The laboratory CH4 removal rates (1.2-2.2 g m-3 h-1) showed positive correlation with the inflow CH4 loading rates (4-8.2 g m-3 h-1), indicating high potential for field-scale implementation. Three field-scale biofilter systems with the proposed mixture packing materials were constructed in an MBT in Neumünster, northern Germany. A relatively stable CH4 removal efficiency of 38-50% was observed under varied inflow CH4 concentrations of 28-39 g m-3 (loading rates of 1120-2340 g m-3 h-1) over a 24-h period. The CH4 removal rate was approximately 500-700 g m-3 h-1, which was significantly higher than relevant previously reported field-scale biofilter systems (16-50 g m-3 h-1). The present study provides a promising configuration of biofilter systems composed of a mixture of organic (pine bark) and inorganic (expanded clay) packing materials to achieve high CH4 emission reduction. Graphic abstract ᅟ.

Bioscrubber treatment of exhaust air from intensive pig production: Case study in northern Germany at mild climate condition.

Treatment by field-scale bioscrubber of exhaust air, including ammonia (NH3) and the greenhouse gases methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2), from 13 intensive pig production houses located in northern Germany were investigated in 2013 and 2015. NH3 removal efficiencies varied between 35 and 100% with an overall average value of 79% under the NH3 inlet fluctuations from 34 to 755 g d-1 m-3 in both 2013 and 2015. Results of the electron microscopic analyses demonstrated that the bacteria Nitrosomonas sp. and methanotrophs type I were the dominant NH3 and CH4 oxidizers, respectively. However, overall average removal efficiencies of CH4 was approximately zero, which means CH4 is hard to remove in bioscrubbers under normal operation. The pH of recirculation water in the bioscrubber varied from 6.1 to 8.1, and the bioscrubbers with low pH values (<7.0) had high NH3 removal efficiencies (>79%). Electrical conductivity was commonly used to diagnose the bioscrubbers' performance; in the present study, electrical conductivity presented a significant linear relationship with dissolved inorganic nitrogen, which indicates the performance stability of the 13 selected bioscrubbers.

Performance evaluation and optimization of field-scale bioscrubbers for intensive pig house exhaust air treatment in northern Germany.

The treatment of exhaust air from three intensive pig houses in northern Germany by field-scale bioscrubbers (BS.1, BS.2, and BS.3) were evaluated monthly in 2015. The simultaneous removal of NH3 and CH4 was investigated by connecting a second bioscrubber (BS.2-2) to one of the three bioscrubbers (BS.2) to create a two-series connected bioscrubber (BS.2+BS.2-2). Additionally, whether isolated methanotrophic bacterial inoculation in BS.2-2 intensified CH4 removal was examined. Average NH3 removal efficiencies of 86%, 80%, and 77% were observed for BS.1, BS.2, and BS.3, respectively, under fluctuate NH3 inlet concentrations (variation of 22%-54%) throughout the study year. However, average CH4 removal efficiencies were lower than 10% in the three bioscrubbers. The pH of the recirculation water, which ranged from 5.7 to 8.1, was demonstrated to be an important factor for NH3 removal and negatively correlated with NH3 removal and NH4+-N concentration in the recirculation water. The dominant NH3-oxidizing and methanotrophic bacteria in the bioscrubbers, analysed by transmission electron microscopy, were Nitrosomonas sp. and Type I methanotrophs, respectively. NH3 removal efficiency reached 100% in the two-series connected bioscrubber, however, CH4 removal was still low (average of 2%). After inoculating isolated methanotrophic bacteria into BS.2-2, the average CH4 removal was enhanced to 35%, offering a great option for bioscrubbers application to intensify CH4 removal. Therefore, a two-series connected bioscrubber inoculated with methanotrophic bacteria would be an option for simultaneous removal of NH3 and CH4 from the exhaust air of animal houses.

Immunocytochemical localization of membrane-bound ammonia monooxygenase in cells of ammonia oxidizing bacteria.

The intracellular location of the membrane-bound ammonia monooxygenase (AMO) in all genera of ammonia oxidizing bacteria (Nitrosomonas, Nitrosococcus and Nitrosospira) was determined by electron microscopic immunocytochemistry. Polyclonal antibodies recognizing the two subunits, AmoA- and AmoB-proteins, were used for post-embedding labeling. Ultrathin sections revealed that the AmoB-protein was located in all genera on the cytoplasmic membrane. In cells of Nitrosomonas and Nitrosococus additional but less AmoB-labeling was found on the intracytoplasmic membrane (ICM). In contrast to the detection of AmoB-protein, the AmoA-antibodies failed to detect the AmoA-protein. Based on quantitative immunoblots the extent of ICM in Nitrosomonas eutropha was correlated with the amount of AmoA in the cells. The highest extent of ICM and amount of AmoA was found at low ammonium substrate concentrations.

Moderately thermophilic nitrifying bacteria from a hot spring of the Baikal rift zone.

Samples from three hot springs (Alla, Seya and Garga) located in the northeastern part of Baikal rift zone (Buryat Republic, Russia) were screened for the presence of thermophilic nitrifying bacteria. Enrichment cultures were obtained solely from the Garga spring characterized by slightly alkaline water (pH 7.9) and an outlet temperature of 75 degrees C. The enrichment cultures of the ammonia- and nitrite oxidizers grew at temperature ranges of 27-55 and 40-60 degrees C, respectively. The temperature optimum was approximately 50 degrees C for both groups and thus they can be designated as moderate thermophiles. Ammonia oxidizers were identified with classical and immunological techniques. Representatives of the genus Nitrosomonas and Nitrosospira-like bacteria with characteristic vibroid morphology were detected. The latter were characterized by an enlarged periplasmic space, which has not been previously observed in ammonia oxidizers. Electron microscopy, denaturing gradient gel electrophoresis analyses and partial 16S rRNA gene sequencing provided evidence that the nitrite oxidizers were members of the genus Nitrospira.