Carbon dioxide emissions from a septic tank soakaway in a northern maritime climate

Here, we present the first attempt to quantify long-term and diurnal variations of CO₂ fluxes from a soakaway of an on-site wastewater treatment system serving a single house located in a northern maritime climate (Ireland). An automated soil gas flux chamber system was deployed semi-continuously over a period of 17months, recording hourly flux measurements from the soakaway (F_soak) and a control site (F_control). Soil gas fluxes expressed seasonal and diurnal variations: F_soak and F_control ranged from 0.43 to 100.26μmolCO₂m^-2s^-1 and 0.45 to 19.92μmolCO₂m^-2s^-1 with median fluxes of 6.86 and 5.05μmolCO₂m^-2s^-1, respectively. While temperature, soil water content, and atmospheric pressure were identified as the most significant environmental factors correlated to the release of CO₂ from the control site, fluxes from the soakaway showed weaker correlations in regard to environmental factors. Assuming homogeneous spatial flux distributions, the soakaway emitted 15.0kgyr^-1 more CO₂ into the atmosphere in total compared to a similarly sized control site.