Peat Soil Burning in the Mezzano Lowland (Po Plain, Italy): Triggering Mechanisms and Environmental Consequences

The effects of peat burning on organic‐rich agricultural soils of the Mezzano Lowland (NE Italy) were evaluated on soil profiles variously affected by smoldering. Profiles were investigated for pH, electrical conductivity, bulk density, elemental and isotopic composition of distinct carbon (and nitrogen) fractions. The results suggest that the horizons affected by carbon loss lie at depths 10–70 cm, where the highest temperatures are developed. We suggest that the exothermal oxidation of methane (mediated by biological activity) plays a significant role in the triggering mechanism. In the interested soils we estimated a potential loss of Soil Organic Carbon of approximately 110 kg m−2 within the first meter, corresponding to 580 kg CO2 m−3. The released greenhouse gas is coupled with a loss of soil structure and nutrients. Moreover, the process plausibly triggers mobility of metals bound in organometallic complexes. All these consequences negatively affect the environment, the agricultural activities and possibly also health of the local people. Plain Language Summary Peat soils are formed by accumulation of organic matter and represent a carbon sink. Unfortunately, they are often affected by burning as the organic matter can fuel combustion for a long time, ultimately releasing carbon dioxide and other greenhouse gases, and particulate matter (PM). It is not clear how peat burning ignite and spread. This study investigates the trigger mechanisms and effects of peat burning in the Mezzano Lowland (NE Italy). For this purpose, pH, electrical conductivity, bulk density and carbon elemental and isotopic compositions of Mezzano soil profiles variously affected by peat burning have been investigated. The results suggest that the burning doesn't propagate from surface and that the horizons affected by carbon loss lie at depths 10–70 cm, with temperatures up to 750°C. The process appears spontaneous, probably due to multiple factors such as drying, biological activity and exothermal oxidations. We estimated a loss of soil carbon of approximately 110 kg for square meter, corresponding to a release of 580 kg of CO2 for cubic meter of burnt soil. This carbon loss and the consequent release of gas and PM negatively affect the environment, the agricultural activities and possibly also the health of the local people. Key Points Peat burning in the Mezzano Lowland is a process active since wetland reclamation and variously affects the soil structure and carbon content T