Elucidating phosphorus removal dynamics in a denitrifying woodchip bioreactor.

Denitrifying woodchip bioreactors (DBRs) are an established nitrate mitigation technology, but uncertainty remains on their viability for phosphorus (P) removal due to inconsistent source-sink behaviour in field trials. We investigated whether iron (Fe) redox cycling could be the missing link needed to explain P dynamics in these systems. A pilot-scale DBR (Aotearoa New Zealand) was monitored for the first two drainage seasons (2017-2018), with supplemental in-field measurements of reduced solutes (Fe, HS/HS) and their conjugate oxidised species (Fe/SO) made in 2021 to constrain within-reactor redox gradients.

Sequential Ammonia and Carbon Dioxide Adsorption on Pyrolyzed Biomass to Recover Waste Stream Nutrients.

The amine-rich surfaces of pyrolyzed human solid waste (py-HSW) can be "primed" or "regenerated" with carbon dioxide (CO) to enhance their adsorption of ammonia (NH) for use as a soil amendment. To better understand the mechanism by which CO exposure facilitates NH adsorption to py-HSW, we artificially enriched a model sorbent, pyrolyzed, oxidized wood (py-ox wood) with amine functional groups through exposure to NH. We then exposed these N-enriched materials to CO and then resorbed NH.

Nitrogen speciation and transformations in fire-derived organic matter.

Vegetation fires are known to have broad geochemical effects on carbon (C) cycles in the Earth system, yet limited information is available for nitrogen (N). In this study, we evaluated how charring organic matter (OM) to pyrogenic OM (PyOM) altered the N molecular structure and affected subsequent C and N mineralization. Nitrogen near-edge X-ray absorption fine structure (NEXAFS) of uncharred OM, PyOM, PyOM toluene extract, and PyOM after toluene extraction were used to predict PyOM-C and -N mineralization potentials.

Fire-derived organic matter retains ammonia through covalent bond formation.

Fire-derived organic matter, often referred to as pyrogenic organic matter (PyOM), is present in the Earth's soil, sediment, atmosphere, and water. We investigated interactions of PyOM with ammonia (NH) gas, which makes up much of the Earth's reactive nitrogen (N) pool. Here we show that PyOM's NH retention capacity under ambient conditions can exceed 180 mg N g PyOM-carbon, resulting in a material with a higher N content than any unprocessed plant material and most animal manures.