Soil Slurry Research Articles

Identification of Antimonate Reducing Bacteria and Their Potential Metabolic Traits by the Combination of Stable Isotope Probing and Metagenomic-Pangenomic Analysis.

Microorganisms play an important role in altering antimony (Sb) speciation, mobility, and bioavailability, but the understanding of the microorganisms responsible for Sb(V) reduction has been limited. In this study, DNA-stable isotope probing (DNA-SIP) and metagenomics analysis were combined to identify potential Sb(V)-reducing bacteria (SbRB) and predict their metabolic pathways for Sb(V) reduction. Soil slurry cultures inoculated with Sb-contaminated paddy soils from two Sb-contaminated sites demonstrated the capability to reduce Sb(V). DNA-SIP identified bacteria belonging to the genera Pseudomonas and Geobacter as putative SbRB in these two Sb-contaminated sites. In addition, bacteria such as Lysinibacillus and Dechloromonas may potentially participate in Sb(V) reduction. Nearly complete draft genomes of putative SbRB (i.e., Pseudomonas and Geobacter) were obtained, and the genes potentially responsible for arsenic (As) and Sb reduction (i.e., respiratory arsenate reductase (arrA) and antimonate reductase (anrA)) were examined. Notably, bins affiliated with Geobacter contained arrA and anrA genes, supporting our hypothesis that they are putative SbRB. Further, pangenomic analysis indicated that various Geobacter-associated genomes obtained from diverse habitats also contained arrA and anrA genes. In contrast, Pseudomonas may use a predicted DMSO reductase closely related to sbrA (Sb(V) reductase gene) clade II to reduce Sb(V), which may need further experiments to verify. This current work represents a demonstration of using DNA-SIP and metagenomic-binning to identify SbRB and their key genes involved in Sb(V) reduction and provides valuable data sets to link bacterial identities with Sb(V) reduction.

Organic Matter Causes Chemical Pollutant Dissipation Along With Adsorption and Microbial Degradation

Views on the entry of organic pollutants into the organic matter (OM) decaying process are divergent, and in part poorly understood. To clarify these interactions, pesticide dissipation was monitored in organic and mineral soils not adapted to contaminants for 241 days; in groundwater sediment slurries adapted to pesticides for 399 days; and in their sterilized counterparts with and without peat (5%) or compost-peat-sand (CPS, 15%) mixture addition. The results showed that simazine, atrazine and terbuthylazine (not sediment slurries) were chemically dissipated in the organic soil, and peat or CPS-amended soils and sediment slurries, but not in the mineral soil or sediment slurries. Hexazinone was chemically dissipated best in the peat amended mineral soil and sediment slurries. In contrast, dichlobenil chemically dissipated in the mineral soil and sediment slurries. The dissipation product 2,6-dichlorobenzamide (BAM) concentrations were lowest in the mineral soil, while dissipation was generally poor regardless of plant-derived OM, only algal agar enhanced its chemical dissipation. Based on sterilized counterparts, only terbutryn appeared to be microbially degraded in the organic soil, i.e., chemical dissipation of pesticides would appear to be utmost important, and could be the first response in the natural cleansing capacity of the environment, during which microbial degradation evolves. Consistent with compound-specific dissipation in the mineral or organic environments, long-term concentrations of pentachloroaniline and hexachlorobenzene were lowest in the mineral-rich soils, while concentrations of dichlorodiphenyltrichloroethane (DTT) and metabolites were lowest in the organic soils of old market gardens. OM amendments changed pesticide dissipation in the mineral soil towards that observed in the organic soil; that is OM accelerated, slowed down or stopped dissipation.

Bisulfite reduction of soil iron for the reductive degradation of trichloroethylene

This study explored the potential reactivities of various reductants in inducing subsurface TCE degradation in natural soils. It was found that bisulfite (HSO3−) exhibited the ability to induce reduction in soil iron minerals, and increase the degradation of TCE in the soil slurry system; however, no TCE degradation occurred in the aqueous system. The role of TCE degradation by soil constituents, such as major soil mineral elements, Fe and humic acid (HA) on HSO3−, was examined in aqueous phase. It was seen that by themselves, the presence of Fe3+, HA, Fe2O3, FeOOH, and Fe3O4 did not result in substantial TCE removals. However, the presence of HSO3− can significantly induce iron reduction, producing a reducing condition that can result in complete TCE degradation. Furthermore, the reductive pathway was identified as the dominant degradation route via electron scavenging with periodate ion. To demonstrate the applicability of HSO3− reduction enhancement, a HSO3−/TCE mixed solution was flushed through a soil column, with gradually increased HSO3− concentrations, at a fixed flow rate, and also with varied flushing rates at a fixed HSO3− concentration. Based on our study, a 10 mM HSO3− solution may be effective for some environmental sites; however, each site requires specific evaluation based on contaminant concentrations and subsurface conditions.

Mathematical Modelling of Azo Blue Dye Degradation by Streptomyces DJP15

Azo dyes are the most well-known synthetic dyes. They have been widely utilized as colorants in various sectors, including textiles, photography/printing, food, medicines, etc. This industry has produced a massive quantity of solid waste, soil slurry, and effluents which are mostly passed into the water bodies or the environments. These dyes tend to compromises the physical, chemical and biological nature of the environments. More so, they have significant health risks on the aquatic life, livestock and the whole environmental biodiversity. Furthermore, they are known to be carcinogenic. In this research, seven (7) different kinetics models, Huang, modified Richards, modified Logistics, modified Gompertz, Buchanan-3-phase, Baranyi-Roberts and von Bertalanffy, were utilized in modeling the growth of Streptomyces DJP15 growth in the degradation of azo blue dye. While all the models show good curve fitting, the von Bertalanffy model was found to be the best model with the lowest RMSE (0.410), AICc (0.58) and has the highest adjR2 (0.983). Thus, this study indicated that the growth of Streptomyces DJP15 on azo blue dye could be described mathematically. Notably, the parameters obtained can be utilized to predict the bioremediation of azo blue dye in the future.

Salt selected for hydrocarbon-degrading bacteria and enhanced hydrocarbon biodegradation in slurry bioreactors

Hydrocarbon and salt contamination of surface and groundwater resources often co-occur from oil production activities. However, salt is often considered as a potential inhibitor of microbial activity. The feasibility of microbiome-based biotechnologies to treat the hydrocarbon contamination is contingent on the ability of the indigenous community to adapt to saline conditions. Here, we demonstrate enhanced hydrocarbon biodegradation in soil slurries under saline conditions of up to ~1 M (5%) compared to non-saline systems and the underlying causes. The mineralization extent of hexadecane was enhanced by salinity in the absence of nutrients. Salinity, similar to nutrients, enhanced the mineralization but through ecological selection. Microbial community analysis indicated a significant enrichment of Actinobacteria phylum and an increase in the absolute abundance of the hydrocarbon-degrading Dietzia genus, but a decrease in the total population size with salinity. Moreover, the in situ expression of alkane hydroxylases genes of Dietzia was generally increased with salinity. The data demonstrate that indigenous halotolerant hydrocarbon degraders were enriched, and their hydrocarbon degradation genes upregulated under saline conditions. These findings have positive implications for engineered biotreatment approaches for hydrocarbons in saline environments such as those affected with produced waters and oil sands tailing ponds.

Microbial Respiration and Enzyme Activity Downstream from a Phosphorus Source in the Everglades, Florida, USA

Northeast Shark River Slough (NESS), lying at the northeastern perimeter of Everglades National Park (ENP), Florida, USA, has been subjected to years of hydrologic modifications. Construction of the Tamiami Trail (US 41) in 1928 connected the east and west coasts of SE Florida and essentially created a hydrological barrier to southern sheet flow into ENP. Recently, a series of bridges were constructed to elevate a portion of Tamiami Trail, allow more water to flow under the bridges, and attempt to restore the ecological balance in the NESS and ENP. This project was conducted to determine aspects of soil physiochemistry and microbial dynamics in the NESS. We evaluated microbial respiration and enzyme assays as indicators of nutrient dynamics in NESS soils. Soil cores were collected from sites at certain distances from the inflow (near canal, NC (0–150 m); midway, M (150–600 m); and far from canal, FC (600–1200 m)). Soil slurries were incubated and assayed for CO2 emission and β-glucoside (MUFC) or phosphatase (MUFP) activity in concert with physicochemical analysis. Significantly higher TP contents at NC (2.45 times) and M (1.52 times) sites than FC sites indicated an uneven P distribution downstream from the source canal. The highest soil organic matter content (84%) contents were observed at M sites, which was due to higher vegetation biomass observed at those sites. Consequently, CO2 efflux was greater at M sites (average 2.72 µmoles g dw−1 h−1) than the other two sites. We also found that amendments of glucose increased CO2 efflux from all soils, whereas the addition of phosphorus did not. The results indicate that microbial respiration downstream of inflows in the NESS is not limited by P, but more so by the availability of labile C.

Bioaugmentation treatment of polycyclic aromatic hydrocarbon-polluted soil in a slurry bioreactor with a bacterial consortium and hydroxypropyl-β-cyclodextrin

ABSTRACT The aim of the study was to verify the effect of bioaugmentation by the bacterial consortium YS with hydroxypropyl-β-cyclodextrin (HPCD) in a soil slurry. The bacterial consortium YS was enriched from a petroleum-polluted soil using pyrene as sole carbon resource. After 3 weeks, the degradation rate of phenanthrene in CK increased from 22.58% to 55.23 and 78.21% in bioaugmentation (B) and HPCD + bioaugmentation (MB) respectively. The degradation rate of pyrene in CK increased from 17.33% to 51.10% and 60.32% in B and MB respectively in the slurry. The augmented YS persisted in the slurry as monitored by 16S rRNA gene high-throughput sequencing and outcompeted some indigenous bacteria. Enhanced polycyclic aromatic hydrocarbon (PAH) degradation was observed in the addition of HPCD due to the enhanced bioavailability of phenanthrene and pyrene. Additionally, the amount of PAH-degrading bacteria and enzymatic activity in bioaugmentation with HPCD were higher than that in the CK group. The results indicated that bioaugmentation with a bacterial consortium and HPCD is an environmentally friendly method for the bioremediation of PAH-polluted soil.

Highly effective removal of bisphenol A by greigite/persulfate in spiked soil: Heterogeneous soil/water system balance and degradation

The degradation of bisphenol A (BPA) in spiked soil was studied to investigate persulfate (PS) activation by the environment-friendly heterogeneous material greigite for removing organic pollutants from soil. The effects of the PS and greigite doses were investigated, and the BPA degradation rate in the lateritic red soil was lower than that in kaolin. Notably, 500 mg/kg of BPA could be effectively removed by the flower-like greigite (FLG)/PS system in 30 min. The difference in BPA degradation in kaolin and the lateritic red soil was negligible, thus indicating that the contents of components such as total organic matters in the lateritic red soil did not affect the BPA degradation rate of the FLG/PS system considerably. Furthermore, the distribution processes of BPA in the soil and liquid phase were also investigated in detail. The results showed that the water contents were a key factor in the distribution and degradation of BPA. The transfer of BPA from kaolin to the liquid phase was simpler than that from the lateritic red soil to the liquid phase. BPA might be transferred to the liquid phase first and then degraded by the FLG/PS system in that phase. Regarding BPA degradation in the lateritic red soil, BPA was degraded in the soil and liquid phases at the same time. This study proposed a pathway for BPA degradation in soil slurries by heterogeneous material/PS systems for first time, providing a deeper understanding of the degradation mechanism of organic pollutants in soil and new methods for soil remediation.

Hydrogen peroxide decomposition into oxygen in different soils: Kinetic analysis, mechanism and implication in catalyzed hydrogen peroxide propagations

Rapid hydrogen peroxide (H2O2) decomposition in soils is one of the most important barriers standing in front of catalyzed H2O2 propagations (CHP) for soil and groundwater remediation, and the rates depend greatly on soil components. However, there are lack of indicators to quantitatively evaluate the processes in various soils. Different from previous studies focusing on H2O2 decomposition, O2 production kinetics are more valuable due to the direct relationship with H2O2 utilization. In this contribution, O2 production during H2O2 decomposition in the soil slurry was in situ detected using a fiber-optic oxygen transmitter. A kinetic model of O2 production was developed, which can be fitted well by the measured data of 18 soil samples. A kinetic constant on O2 production (kO2) ranging from 0.001 min−1 to 0.057 min−1 was obtained from the model, which represents the diverse catalytic activity of the soils. The constant kO2 is correlated with the contents of manganese, iron as well as inorganic carbon in the soils, and Mn mineral is the dominant factor. Three types of soils were selected to investigate the effect of acid-washing and stabilizer phosphate addition on phenol oxidation in CHP. Acid-washing can greatly suppress O2 production, while phosphate addition is not desirable for the highly active soils. Phenol slightly inhibits O2 production in the soils with higher kO2 values, which are inverse with those of phenol degradation. Acid-washing can remove Mn minerals but retain most of Fe components, and accordingly increase phenol degradation. Both hydroxyl radicals and superoxide radicals contribute to phenol degradation, and the latter ones display a more significant role. This work increases the understanding of the mechanism of H2O2 decomposition in the soils and provides a parameter (kO2) to guide CHP technologies in soil remediation.

Cometabolic Vinyl Chloride Degradation at Acidic pH Catalyzed by Acidophilic Methanotrophs Isolated from Alpine Peat Bogs.

Remediation of toxic chlorinated ethenes via microbial reductive dechlorination can lead to ethene formation; however, the process stalls in acidic groundwater, leading to the accumulation of carcinogenic vinyl chloride (VC). This study explored the feasibility of cometabolic VC degradation by moderately acidophilic methanotrophs. Two novel isolates, Methylomonas sp. strain JS1 and Methylocystis sp. strain MJC1, were obtained from distinct alpine peat bogs located in South Korea. Both isolates cometabolized VC with CH4 as the primary substrate under oxic conditions at pH at or below 5.5. VC cometabolism in axenic cultures occurred in the presence (10 μM) or absence (<0.01 μM) of copper, suggesting that VC removal had little dependence on copper availability, which regulates expression and activity of soluble and particulate methane monooxygenases in methanotrophs. The model neutrophilic methanotroph Methylosinus trichosporium strain OB3b also grew and cometabolized VC at pH 5.0 regardless of copper availability. Bioaugmentation of acidic peat soil slurries with methanotroph isolates demonstrated enhanced VC degradation and VC consumption below the maximum concentration level of 2 μg L-1. Community profiling of the microcosms suggested species-specific differences, indicating that robust bioaugmentation with methanotroph cultures requires further research.

Variable influences of soil and seed-associated bacterial communities on the assembly of seedling microbiomes.

Plants grown in distinct soils typically harbor distinct microbial communities, but the degree of the soil microbiome influence on plant microbiome assembly remains largely undetermined. We also know that the microbes associated with seeds can contribute to the plant microbiome, but the magnitude of this contribution is likely variable. We quantified the influence of soil and seed microbiomes on the bacterial community composition of seedlings by independently inoculating seeds from a single cultivar of wheat (Triticum aestivum) with 219 unique soil slurries while holding other environmental factors constant, determining the composition of the seed, soil, and seedling bacterial communities via cultivation-independent methods. Soil bacterial communities exert a strong, but variable, influence on seedling bacterial community structure, with the extent of the soil bacterial contribution dependent on the soil in question. By testing a wide range of soils, we were able to show that the specific composition of the seedling microbiome is predictable from knowing which bacterial taxa are found in soil. Although the most ubiquitous taxa associated with the seedlings were seed derived, the contributions of the seed microbiome to the seedling microbiome were variable and dependent on soil bacterial community composition. Together this work improves our predictive understanding of how the plant microbiome assembles and how the seedling microbiome could be directly or indirectly manipulated to improve plant health.

Dissimilatory iron reduction and potential methane production in Chagan Lake wetland soils with carbon addition

Dissimilatory iron reduction is increasingly becoming recognized as an influential process in freshwater sediments, coupling with carbon cycling. To evaluate the influence of organic matter addition on the reduction rates and dynamics of Fe(III) in wetland soils in Chagan Lake, soil slurry and microbial anaerobic incubation studies were conducted by adding a soluble and redox-active quinone (anthraquinone-2,6-disulphonate, AQDS), glucose and sodium pyruvate. In soil slurry experiment, glucose was added as a single doze and a pulsed input over time. Pulsed glucose addition promoted DIR, particularly in the later incubation stage. The addition of different forms of carbon significantly affected DIR in the inoculation experiment, and the addition of pyruvate increased DIR more than that of glucose in the wetland soil. The AQDS dramatically stimulated the potential DIR by 480-fold. A negative relationship was observed between pH and DIR. Besides, potential methane production was inhibited by the addition of ferrihydrite. These findings provide insight into the connection between iron and carbon input and emission.

Rapid treatment of high-water-content dredged slurry using composite flocculant and PHD-facilitated vacuum

Flocculation by chemicals can adequately reduce the clogging effect, and the bending effect of prefabricated vertical drains can be eliminated by laying a prefabricated drain in the horizontal direction. Various settling column tests with different contents of chemicals, polyacrylamide (PAM) and hydrated lime (Ca(OH)2), were initially conducted to find the optimum dose for the fastest settling. Then, the combined effect of using both PAM and lime on the dewatering behavior of dredged clay slurry is studied using a prefabricated horizontal drain (PHD) and vacuum pressure of 80 kPa. Initially, sedimentation and self-weight consolidation with the optimum dose of PAM and lime are allowed to occur, and then further vacuum preloading is carried out. The combined effect of lime and PAM is very effective in increasing the dewatering rate, taking only 207 hours in comparison to 247 hours for the soil slurry treated with only PAM and 411 hours for the soil slurry without any chemicals. After the treatment, the shear strength substantially increases to 58.5 kPa for the soil with lime and PAM in comparison to 42.8 kPa for the soil with PAM only and 16 kPa for the soil without any chemicals.

Degradation Potentials Of Tropical Soil Bacteria On Detergents

Detergents are chemicals of high environmental importance owing to their production volumes. They are mainly released into the environment through wastewater pathway and it could severely affect the soil environment. In this study, we examined the degradation potentials of soil bacteria in liquid culture media induced with detergents. Using conventional enrichment methods, via contaminated soil slurry enrichment with selected alkyl-benzene sulphonates (detergents), we obtained pure bacteria species capable of using alkyl-benzene sulphonates as the sole source of carbon and energy. From the morphological and biochemical characterization and comparison with respect to the standard reference organisms, the bacteria isolates were presumably Corynebacterium, Pseudomonas, and Bacillus species. Different concentrations 5.0, 10.0 15.0, and 20.0 w/v of the branded detergents were prepared as sole carbon and energy and screened against our bacteria species to determine their physiological gradient fluxes after 96hours of incubation. Data obtained showed an increase in Optical density (OD) as well as increases in pH flux values. The mean OD data obtained ranged between 0.017- 0.818, with a pH of 7.47-8.95. From this study, tropical soils possess unique bacteria species capable of utilizing alkyl-benzene sulphonates (detergents).

An efficient lab-scale soil bioreactor for the removal of chromium (Cr) and arsenic (As) contaminated soil using co-culture

ABSTRACT Heavy metal pollution has become a serious global threat in recent times which are mostly caused by anthropogenic activities. Bioremediation is cost-effective and eco-friendly technique. In the present study, bioremediation of the co-metal was performed by isolating chromium (Cr) and arsenic (As) resistant bacterial strains and its optimisation of different environmental parameters such as pH, temperature, carbon sources, nitrogen sources and vari+ous concentrations of chromium and arsenic were studied. The isolated co-culture bacterial strains were identified with biochemical and molecular identification using 16s RNA sequencing. Further, a lab-scale soil bioreactor was set up and mineralisation of chromium and arsenic was observed using different heavy metal contaminated soil samples. About 51.1% Chromium was mineralised by the co-culture, 26.7% in cycle 2, 22% in cycle 3 and 34.2% in cycle 4 respectively. The Arsenic mineralisation was 16.7%,23.7%,35.4% and 35.8% at the end of 4 cycles. The final mineralised concentration was analysed by Inductively coupled plasma optical emission Mass spectrometry (ICP-MS) resulting in 29.9 of Chromium and Arsenic 0.083 mg/L respectively. The physico-chemical parameters, such as pH, temperature, TS, TDS, BOD and COD were monitored for the mineralisation study in the soil slurry bioreactor. The study proved that there was effective mineralisation of the co-metals with the cocultures of the isolated bacterial strains from the metal contaminated site.

Removal of organochlorine insecticide endosulfan in water and soil by Fenton reaction with ascorbic acid and various iron resources.

An assortment of Fenton (or Fenton-like) reaction treatment systems using various iron resources such as ferrous sulfate, ferric nitrate, commercial zerovalent iron (mZVI), or self-made ZVI (Fe-nanowire) were evaluated to effectively remove α- and β-isomers of endosulfan (ED) from contaminated water and soil. Ascorbic acid (AA) was added as a chelation reagent to maintain the aqueous reaction of soluble iron. In the aqueous experiment, a combined treatment of 1% mZVI, 0.01 M AA, and 0.1 M H2O2 was determined to be the most effective method, showing 98-100% of ED removal within 24 h. The mZVI/AA/H2O2 treatment method was finally applied to ED-contaminated soil samples, and the application removed significant ED residues from both soil slurries (65-73%) and immobile soils containing small amount of moisture (64-66.2%). Overall results showed that the mZVI/AA/H2O2 treatment can be utilized as a potential technique to remediate both water and soil contaminated with ED.

Visual experimental study on development of mud film in slurry shield excavation face based on transparent soil technology

In order to solve the problems of grouting diffusion and invisible formation process in shield slurry film forming test, transparent soil and transparent slurry were introduced to carry out shield mud film test based on shield grouting model. Using laser imaging combined with CCD camera (high-speed industrial camera) rapid capture photography technology, through a series of visible physical model tests of slurry diffusion and mud film development under different working conditions, the temporal and spatial conditions of slurry diffusion were observed and recorded in real time to explore the slurry diffusion law and the formation mechanism of mud film in slurry shield excavation face.The phenomenon shows that the smaller the grouting pressure is, the more favorable the formation of mud film is.The mud penetration distance is generally proportional to the grouting pressure.The infiltration distance of the grout increases with time, and the infiltration distance of the grout is similar at each moment under the same grouting pressure. The leachate volume and time show a quadratic function roughly under the same density and mud pressure, and the increase rate of the leachate volume begins to slow down with time.

A Constitutive Model Incorporating Mixed Soil Slurry for Interface

In projects, mixed soil slurry between cut-off wall and coarse-grained soil always exists. It may influence on or change mechanical properties of interface between coarse-grained soil and structure. The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under mixed soil slurry. The significant dilatancy and stress-strain softening can be achieved through the results, which also indicate that the cement content play an important role in the shear strength of the interface. The peak strength and the position when the dilatancy occurs are related to both normal stress and cement content. An elasto-plastic constitutive model for interface considering mixed soil slurry was formulated in the framework of generalized potential theory. The entire model parameters can be identified by experimental tests. Finally, the predictions of the model have been compared with experimental results, and results show the model is reasonable and practical.

Scalable 3D printing method for the manufacture of single-material fluidic devices with integrated filter for point of collection colourimetric analysis

Assembly and bonding are major obstacles in manufacturing of functionally integrated fluidic devices. Here we demonstrate a single-material 3D printed device with an integrated porous structure capable of filtering particulate matter for the colourimetric detection of iron from soil and natural waters. Selecting a PolyJet 3D printer for its throughput, integrated filters were created exploiting a phenomenon occurring at the interface between the commercially available build material (Veroclear-RGD810) and water-soluble support material (SUP707). The porous properties were tuneable by varying the orientation of the print head relative to the channel and by varying the width of the build material. Porous structures ranging from 100 to 200 μm in thickness separated the sample and reagent chambers, filtering particles larger than 15 μm in diameter. Maintaining the manufacturing throughput of the Polyjet printer, 221 devices could be printed in 1.5 h (∼25 s per device). Including the 12 h post-processing soak in sodium hydroxide to remove the solid support material, the total time to print and process 221 devices was 13.5 h (3.6 min per device), with a material cost of $2.50 each. The applicability of the fluidic device for point of collection analysis was evaluated using colourimetric determination of iron from soil slurry and environmental samples. Following the reduction of Fe3+ to Fe2+ using hydroxylammonium chloride, samples were introduced to the fluidic device where particulate matter was retained by the filter, allowing for particulate-free imaging of the red complex formed with 1,10-phenanthroline using a smartphone camera. The calibration curve ranged from of 1–100 mg L−1 Fe2+ and good agreement (95%) was obtained between the point of collection device and Sector Field ICP-MS.

Contingent Effects of Liming on N2O-Emissions Driven by Autotrophic Nitrification

Liming acidic soils is often found to reduce their N2O emission due to lowered N2O/(N2O + N2) product ratio of denitrification. Some field experiments have shown the opposite effect, however, and the reason for this could be that liming stimulates nitrification-driven N2O production by enhancing nitrification rates, and by favoring ammonia oxidizing bacteria (AOB) over ammonia oxidizing archaea (AOA). AOB produce more N2O than AOA, and high nitrification rates induce transient/local hypoxia, thereby stimulating heterotrophic denitrification. To study these phenomena, we investigated nitrification and denitrification kinetics and the abundance of AOB and AOA in soils sampled from a field experiment 2–3 years after liming. The field trial compared traditional liming (carbonates) with powdered siliceous rocks. As expected, the N2O/(N2O + N2) product ratio of heterotrophic denitrification declined with increasing pH, and the potential nitrification rate and its N2O yield (YN2O: N2O-N/NO3–-N), as measured in fully oxic soil slurries, increased with pH, and both correlated strongly with the AOB/AOA gene abundance ratio. Soil microcosm experiments were monitored for nitrification, its O2-consumption and N2O emissions, as induced by ammonium fertilization. Here we observed a conspicuous dependency on water filled pore space (WFPS): at 60 and 70% WFPS, YN2O was 0.03-0.06% and 0.06–0.15%, respectively, increasing with increasing pH, as in the aerobic soil slurries. At 85% WFPS, however, YN2O was more than two orders of magnitude higher, and decreased with increasing pH. A plausible interpretation is that O2 consumption by fertilizer-induced nitrification cause hypoxia in wet soils, hence induce heterotrophic nitrification, whose YN2O decline with increasing pH. We conclude that while low emissions from nitrification in well-drained soils may be enhanced by liming, the spikes of high N2O emission induced by ammonium fertilization at high soil moisture may be reduced by liming, because the heterotrophic N2O reduction is enhanced by high pH.