Uncharacterised microbial pathways are key to understanding large fluxes of biogenic reactive nitrogen gases from agronomic soils
2023 - 2026. Biotechnology and Biological Sciences Research Council BB/X002187/1 (PI: Ryan Mushinski)
Volatile reactive nitrogen oxides (NOy), comprised of NOx and NOz , negatively impact air quality as they are precursors to smog and acid rain, modify climate by enhancing concentrations of tropospheric ozone, and can exacerbate respiratory issues. Very little is known about NOy fluxes from natural sources, even though these sources account for over a half of all atmospheric NOy. Soil is the dominant natural contributor (24%), with this percentage increasing as vehicle and industry emissions decline. As NOy species are relatively short-lived, chemical lifetime ~ 20 mins for nitrous acid and up to 18 hours for nitrogen dioxide, their concentration profiles tend to be localised and consistent depending on the environment. Sources and sinks of NOy are important in addressing air quality and developing reliable policy, where government policy changes may not produce expected result due to these natural sources. Importantly, descriptions of soil NOy emissions in climate models are non-existent, due to a lack of data regarding the mechanisms that control NOy fluxes from soil. Most research on ground-level NOy sources has focused on identifying abiotic mechanisms; however, far less work has been done to elucidate biogenic contributions, resulting in a significant omission in climate models. Agricultural areas have been shown to be major contributors to soil NOy emissions, due to fertiliser use, irrigation, and soil disturbance; however, mechanisms at the plant-soil-microbe interface have yet to be elucidated. By coupling field-based crop trials to robust chemical quantification and molecular analyses, we will test hypotheses regarding how a major agricultural crop, its soil, and associated soil microbes influence NOy fluxes.
Utilising genomics to better understand soil emissions of reactive nitrogen oxides
2022 - 2023. NERC Environmental Omics Facility NEOF1489 (Megan Purchase, Ryan Mushinski)
Volatile reactive nitrogen oxides (NOy) are central to tropospheric cycling of ozone and hydroxyl radical; hence, NOy are extremely important in atmospheric chemistry. However, fluxes of NOy from natural sources, such as soil, to the atmosphere are generally not included in atmospheric models due to lack of mechanistic data. Spatial heterogeneity amongst landscape elements and across population gradients likely influences NOy fluxes due to differences in atmospheric deposition rates and anthropogenic modification to soil – both likely altering microbial and abiotic cycling of NOy; however, this has not been explored in detail. In this work, we will use shotgun metagenomics and RNA-sequencing to link nitrogen cycling microbes, across a gradient of urbanisation and land-use, to NOy gas fluxes from soil. Evidence for biogenic NOy fluxes will be provided if we can show that N-cycling microbes are present and active in soil at the time of sampling. We will further use the data to search for connections between gene expression and soil emissions of NOy that may help support subsequent hypotheses. For example, there may be connections between N-cycle metabolites and other compounds such as reactive oxygen species.
Global change processes in peatlands: A study of the microbiology and biogeochemistry of reactive nitrogen oxides
2022 - 2026. The Central England NERC Training Alliance (Shuaizhi Guo, Niall McNamara, Gary Bending, Ryan Mushinski)
Peatlands in the UK account for 9.5% of land cover and are currently experiencing rapid modifications in response to environmental stimuli such as increased atmospheric nitrogen (N) deposition sourced from human activity. These ecosystems perform a plethora of functions, none more critical than acting as large reservoirs of organic matter (OM). Research has focused on how processes such as N-deposition may transform these OM stocks into sources of greenhouse gases. These studies demonstrate a stimulatory effect of N-deposition on CO2 and CH4 emissions; however, much less attention has been paid to changes in N-cycling associated with enhanced N-deposition.
Net rates of N-cycle processes such as nitrification and denitrification are slow in peatlands. In fact, these process account for less than 5% of N removal from these ecosystems. However, a different group of N-gases, the reactive nitrogen oxides (NOy), are greatly understudied and may actually be emitted at high rates from peatlands, especially under increased N-deposition.
While NOy have been shown to be products of nitrification and denitrification, an under-investigated process involving iron (Feammox) may be extremely important in the cycling of N and subsequent production of NOy in these ecosystems. Feammox is a microbial process that generally occurs under anoxic conditions of saturated soils such as peatlands, where iron oxides can act as an electron acceptor and play a critical role influencing N reactions in the absence of oxygen. However, there has been little research exploring whether this reaction results in NOy production.
Thus, there is a critical need to (1) determine the intrinsic ability of UK peatlands to produce NOy, (2) explore the influence of N-deposition on N-cycle rates in these ecosystems, and (3) differentiate the mechanisms by which N is transformed in peatlands, paying particular attention to microbe-iron mediate processes.
Development of a non-reactive flux chamber system to measure pollutant gases
2022 - 2023. The Royal Society Research Grant, RGS\R2\212146 (PI: Ryan Mushinski)
We are interested in the chemical reactions and biological processes that impact air pollution, climate, and health. The long-term goal of our work is to improve our understanding of the sources and sinks of pollutant nitrogen gases from land surfaces - enabling more accurate representation of these gases in predictive models used to understand the climate system and to protect human health from the effects of air pollution. We seek to understand the fundamental chemical mechanisms and processes responsible for how these trace gases behave in the environment. Up to this point, we have exclusively used laboratory experiments to inform our understanding of pollutant nitrogen gases from natural sources, such as soil; however, true environmental conditions are crucial to validate or disprove observations made in the laboratory. Due to the highly reactive chemistry of these compounds, all surfaces within measurement systems are made of nonreactive materials. Further, the chamber system is equipped with ancillary sensors, including temperature, humidity, and light intensity. These chambers have been multiplexed to enhance spatial coverage of gas emissions.
An isotope ratio mass spectrometry system to enhance interdisciplinary research at the University of Warwick
2021 - 2022. The University of Warwick Academic Equipment Fund (PI: Ryan Mushinski; Co-I's: Gary Bending, Hendrik Schaefer, Kevin Purdy)
This project funds the acquisition of an isotope ratio mass spectrometer with various peripherals, enabling elemental and isotopic quantification of light elements in solids, liquids, and gases. These instruments provide unique analytical capabilities at the forefront of environmental science. This system will support gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS), elemental analysis isotope ratio mass spectrometry (EA-IRMS), and pre-concentration gas chromatography combustion isotope ratio mass spectrometry (PreCon-GC-C-IRMS). The GC-C-IRMS peripheral enables compound-specific isotope determinations from complex organic mixtures - allowing on-line analysis of 𝛿¹³C in GC-separated carbon-containing compounds, including alkanes, lipids, and alcohols. The EA-IRMS component enables high temperature pyrolysis for elemental concentrations of oxygen and hydrogen and corresponding isotope ratios (𝛿¹⁸O and 𝛿D), as well as high temperature combustion and subsequent chromatography for elemental and isotopic determination of carbon (𝛿¹³C), nitrogen (𝛿¹⁵N), and sulfur (𝛿³⁴S). The PreCon-GC-C-IRMS enables isotopic analysis of atmospheric greenhouse gases. This system uses cryogenic pre-concentration followed by chromatography and chemical trapping to analyse trace concentrations of CO2 (𝛿¹³C and 𝛿¹⁸O), N2O (𝛿¹⁵N and 𝛿¹⁸O), N2 (𝛿¹⁵N), and CH4(𝛿¹³C). Combined this suite of IRMS systems will catalyse new avenues for the environmental, plant and crop, and biotechnology research themes at Warwick..
Environmental microbes and gas fluxes: A systematic study of volatile reactive nitrogen oxides
2021 - 2025. The Central England NERC Training Alliance (Megan Purchase & Ryan Mushinski)
A range of pollutant gases, and especially nitrogen (N) compounds (NO, NO2, etc.) are emitted to the atmosphere from terrestrial sources, including agriculture and natural ecosystems. These gases are extremely important for a myriad of reason including their contribution to climate change and urban air pollution. Common agricultural practices such as fertilisation and irrigation will continue to increase, likely resulting in high emissions. In natural ecosystems, atmospheric deposition of N has become increasing prevalent, also stimulating emissions from soil. However, N-gas forecasts from terrestrial sources are hampered by a lack of field-based measurements and an incomplete understanding of the processes associated with production and consumption of these gases. This project aims to better quantify N-gas fluxes from terrestrial systems as well as map the various mechanisms associated with emission and consumption in soil.
Unravelling the global microbiome of crop plants to improve sustainability and food security
2020 - 2024. The Central England NERC Training Alliance (Anna Lazar, Ryan Mushinski, Christopher Quince, & Gary Bending)
Understanding and harnessing interactions between plants and microbes has enormous importance for devising sustainable agricultural systems while ensuring food and energy security and mitigating the threats posed by climate change and land degradation. In collaboration with an international team of scientists we are investigating the composition of crop microbiomes, the factors which shape the assembly of microbiomes, and specific functional traits within microbiomes that impact crop growth and yield. The programme is part of a global initiative to profile microbiomes from key crops including wheat, maize, rice, cotton, and potato.