Raul Zornoza

Evaluation of carbon and nitrogen dynamics in different soil types amended with pig slurry, pig manure and its biochar by chemical and thermogravimetric analysis

The objective of this study was to assess the short-term changes in soil organic C (SOC) and N pools after incubation of three different soil types (Regosol, Luvisol, and Kastanozem) treated with three amendments differing in organic matter stability (raw pig slurry (PS), manure, and biochar (BC). Both SOC and recalcitrant C (RC) contents increased at the end of incubation with BC applications in all soils. The manure increased SOC in Regosol and Luvisol and decreased the C/N ratio in all soils. PS only increased SOC in Regosol, but decreased C/N in all soils. Thermogravimetric analysis showed that all amendments significantly increased the labile SOC in Regosol, while BC significantly increased the recalcitrant fraction in all soils. Fourier transform infrared (FTIR) spectroscopy suggested that amendments did not involve noticeable qualitative changes in the organic functional groups in any soil, only affecting band intensities. The release of CO2 with PS and manure additions were similar between Regosol, Luvisol, and Kastanozem despite differences in SOC content, suggesting mainly degradation of compounds provided with amendments rather than native SOC. Ammonia volatilization and nitrification of amendments was rapid and intense with the application of labile amendments such as PS and manure, overall in the Regosol. Thus, different soil types behave differently in response to amendment applications, being the Regosol more prone to alter SOC content and stability after applications, but releases more NH3. BC was the only amendment promoting higher SOC concentrations and stability at the end of the incubation in all soils. There is a high interrelationship among chemical, thermal, and spectral data, assessed by regression analysis, suggesting that thermal and spectral analyses are not only complementary but may also replace conventional chemical techniques.

Suitability of Different Mediterranean Plants for Phytoremediation of Mine Soils Affected with Cadmium

Mine residues dumped on the environment as overburden or tailings ponds show environmental and human health hazards by the transfer of heavy metals through erosion or leaching. The objective of this study was to assess the potential use of different Mediterranean plant species for phytostabilization or phytoextraction of cadmium in acidic mine residues. For this purpose, a reclamation strategy was carried out in a mine tailing based on the use of phytoremediation aided with three different amendments (pig slurry, pig manure, and marble waste). –Six Mediterranean species were introduced: Lygeum spartum, Atriplex halimus, Helichrysum stoechas, Dittrichia viscosa, Piptatherum miliaceum, and Limonium cossonianum. Soil and plant samples were collected 24 months after remediation works. Results showed that the characteristics of the mine residue improved with the reclamation developed, with increased pH, organic matter and fertility, and decreased salinity. The extractable and exchangeable fractions of Cd decreased 85 % and 96 %, respectively. The tested species (except for A. halimus and L. cossonianum) may be potential candidates for the objectives of Cd phytostabilization since they showed low translocation and bioaccumulation factors. P. miliaceum was the best candidate owing to its lower translocation and bioaccumulation factors, higher biomass, and higher colonization of the area. A. halimus seems a potential candidate for phytoextraction rather than for phytostabilization of soil Cd, with high translocation and bioaccumulation factors, high biomass, and fast growth.