TY - JOUR

T1 - Optical Chemical Sensors for Soil Analysis

T2 - Possibilities and Challenges of Visualising NH3 Concentrations as well as pH and O2 Microscale Heterogeneity

AU - Merl, Theresa

AU - Hu, Yihuai

AU - Pedersen, Johanna

AU - Zieger, Silvia Elisabeth

AU - Bornø, Marie Louise

AU - Tariq, Azeem

AU - Sommer, Sven Gjedde

AU - Koren, Klaus

PY - 2023

Y1 - 2023

N2 - Agricultural nitrogen (N) application to soils is the main source of atmospheric ammonia (NH3). Ammonianegatively impacts the environment on a large scale. However, emissions of NH3 are affected byspatiotemporal heterogeneities of soil parameters on a microscale. Some key parameters controllingprocesses of the N cycle are soil oxygen (O 2) and pH. To better understand biogeochemical soilprocesses, NH3 emissions and the interconnection of the ecospheres, we propose the application ofoptical chemical sensors (optodes) in and above soils. The use of optodes in soil science is in its infancy.In this laboratory-based study, we investigated the possibilities and challenges of using optodes in non-waterlogged soils with the extended application of a recently developed NH3 optode along with pH andO2 optodes in two different soils and with different fertilisers. Our intention is to help expand the use ofoptodes in soil science. Our results demonstrated the possibility to visualise reductions of NH 3concentrations by 76% and 87% from the incorporation of sludge compared to the surface application ofsludge. We showed from 2D measurements how soil pH and fertiliser composition correlate with NH3volatilisation. Our measurements demonstrated that pH optodes can have advantages over conventionalmethods when measuring pH in soils in situ but are challenged by the limited dynamic range (typically 3pH units) compared to pH electrodes. Finally, we investigated the spatiotemporal dynamics of O2 atdifferent soil water contents and discuss potential challenges, which can lead to measuring artifacts.

AB - Agricultural nitrogen (N) application to soils is the main source of atmospheric ammonia (NH3). Ammonianegatively impacts the environment on a large scale. However, emissions of NH3 are affected byspatiotemporal heterogeneities of soil parameters on a microscale. Some key parameters controllingprocesses of the N cycle are soil oxygen (O 2) and pH. To better understand biogeochemical soilprocesses, NH3 emissions and the interconnection of the ecospheres, we propose the application ofoptical chemical sensors (optodes) in and above soils. The use of optodes in soil science is in its infancy.In this laboratory-based study, we investigated the possibilities and challenges of using optodes in non-waterlogged soils with the extended application of a recently developed NH3 optode along with pH andO2 optodes in two different soils and with different fertilisers. Our intention is to help expand the use ofoptodes in soil science. Our results demonstrated the possibility to visualise reductions of NH 3concentrations by 76% and 87% from the incorporation of sludge compared to the surface application ofsludge. We showed from 2D measurements how soil pH and fertiliser composition correlate with NH3volatilisation. Our measurements demonstrated that pH optodes can have advantages over conventionalmethods when measuring pH in soils in situ but are challenged by the limited dynamic range (typically 3pH units) compared to pH electrodes. Finally, we investigated the spatiotemporal dynamics of O2 atdifferent soil water contents and discuss potential challenges, which can lead to measuring artifacts.

U2 - 10.1039/d3va00127j

DO - 10.1039/d3va00127j

M3 - Journal article

VL - 2

JO - Environmental Science: Advances

JF - Environmental Science: Advances

SN - 2754-7000

IS - 9

ER -