Impact and evaluation of potential implications of coastal plains on soil greenhouse gas emissions: Insights from the Sibari Coastal Plain (Calabria, Southern Italy)

The work aims to estimate natural greenhouse gas emissions from soils in the Sibari Coastal Plain (Southern Italy), to understand (i) the contribution in terms of the total amount of CO₂ and CH₄ emitted in non-volcanic areas, (ii) the relationship among emitted gas, land use, organic matter and tectonic structures, and (iii) their potential environmental implications. Data were elaborated with statistical and geostatistical methods to separate the different populations and obtain prediction and probability maps. Methane fluxes had values consistently below the detection limit (0.032 g ∙ m⁻² ∙ d⁻¹) except for three measurement points randomly distributed along the plain. Statistical and geostatistical methods allowed to discriminate three main CO₂ flux populations: (i) high-flux population (Pop. B - mean value of 63.65 g ∙ m⁻² ∙ d⁻¹), located near the mouth of the Crati River and related to the massive presence of buried organic matter in the form of peat; (ii) medium-flux population (Pop. A2 - mean value of 8.37 g ∙ m⁻² ∙ d⁻¹) which is the result of soil respiration, and (iii) low-flux population (Pop. A1 - mean value of 1.85 g ∙ m⁻² ∙ d⁻¹) due to areas where low permeability or increases in saturated aquifer thickness may control the overall flux. In the study area, a total CO₂ emission of about 2671 t ∙ d⁻¹ was calculated, which, if compared to the average total flux expected for simple soil respiration (1284 t ∙ d⁻¹), represents a non-negligible value in the total Carbon balance. Finally, the comparison with representative normalized fluxes from volcanic and non-volcanic areas confirms the critical role of coastal plains in total atmospheric CO₂ emissions. The proposed approach can be applied to areas with comparable or different geological and climatic settings to trace their contribution in terms of greenhouse gas release to the atmosphere.