No abstract

The temperature sensitivity of soil organic matter (SOM) is receiving an increasing interest due to its importance in the global carbon cycle and potential feedbacks to climate change. It constitutes a controversial topic in soil science due to different constrains involving the models employed, together with methodological limitations. It is welcome the introduction of new methods and indicators that can assess the sensitivity to temperature of the SOM macromolecule continuum on a more global basis. Calorimetry can be an attractive alternative if the SOM degradation is studied based on the heat rate under a gradient of temperature. The design of new calorimeters permits to do those measurements in real time through a temperature scan mode. We have applied and designed a preliminary protocol with this new type of calorimeters to calculate the activation energies and Q 10 values of soil samples with different recalcitrance. The calculation was run on short-term basis and continuously through a temperature gradient from 18 to 35°C for 1 week. Results showed fast adaptation of microbial decomposition rates to increasing temperature and enough sensitivity of the method to detect changes in the heat rate involving SOM thermal properties. Labile substrates as carbohydrates showed up as potential rulers explaining E a and Q 10 changes which fitted the rule of thumb connecting both.

No abstract

Self-ignited fires at municipal solid waste (MSW) storage sites are relatively common. The minimization of the phenomenon of self-heating in the waste can reduce the risks for smouldering combustion. The purpose of this work was to develop a method that can be used to measure and characterize the heat production in MSW. The method is based on isothermal heat conduction microcalorimetry (IMC). The heat production in MSW was determined based on sampling from two sites in two different geographical locations in Sweden. Both the original waste and milled/homogenised waste were tested. The heat production was measured at different temperatures together with gas analysis using micro-gas chromatography. The activity in the waste, in terms of its heat flow, increased when the temperature increased up to 60 °C and decreased at higher temperatures, e.g., 70 and 80 °C. The consumption of oxygen and the production of carbon dioxide, together with the heat production, indicated that aerobic metabolism was responsible for the heat production. This is further strengthened by the marginal heat production observed for ultraviolet treated waste. The results showed that IMC is a valuable tool for characterising the self-heating in municipal and industrial waste.

No abstract