GreenCad

Impact of cadmium on agricultural greenhouse gas emissions

01.03.2019 bis 28.02.2022

Agricultural soils are a major contributor to global greenhouse gas emissions, as they release about 2 gigatons
of CO2-equivalents per year to the atmosphere. Methane (CH4) and nitrous oxide (N2O) are highly potent
greenhouse gases, and their respective microbially-produced emissions make up approximately 50% and 20%
of the total agricultural global warming potential today. To take measures to decrease agricultural greenhouse
gas emissions, biogeochemical models are used to simulate field greenhouse gas production under a variety
of environmental perturbations such as climate change or agricultural land management. However, these
models do not consider the presence of soil contaminants in agricultural soils stemming from industrial inputs
and present-day fertilizer use. Owing to its toxicity and presence in phosphate mineral fertilizers, cadmium
(Cd) is particularly threatening. In addition, it is critical that these models consider that the bioavailability of
contaminants, like Cd, in the soil varies with climate, which could affect greenhouse gas emissions. For
example, an increase in temperature might enhance Cd desorption or Cd-bearing mineral dissolution so that
more Cd partitions into the soil solution, where it has a higher potential to interact with the greenhouse gasproducing
microbial community. In such a case, Cd contamination may (1) reduce greenhouse gas emissions
by exhibiting toxicity effects on the microbiome and/or (2) shift total emissions of either CO2, CH4 or N2O
depending on if certain chemical or metabolic transformations are favoured over others. The proposed project
for the Baden-Württemberg Stiftung plans to investigate how the major soil contaminant Cd in combination
with different climatic conditions, namely elevated temperature and increased atmospheric CO2, will impact
biogeochemical processes and specifically microbial CO2, CH4 and N2O emissions in agricultural soils. Total
and temporally resolved greenhouse gas emissions will be linked to climate data and Cd fractionation between
soil solids and solution. Detailed mineralogical (Cd binding environment to soil minerals) and microbiome
investigations will be undertaken through X-ray-based synchrotron and omics approaches to probe how these
two environmental stressors affect microbial dynamics and linked greenhouse gas production and feedback
loops. The overarching goal of this project is to develop a mechanistic understanding of how soil contamination
affects microbial greenhouse gas emissions in agricultural landscapes, in hopes of better equipping models to
predict greenhouse gas emissions based on agricultural management strategies.