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The aim of this study was to explore a novel method to immobilize heavy metals (HM) in composting through increasing the combination of these with humic substances. An electric-field assistant technique was applied to strengthen biomass biodegradation and assess the impact on the humification process and HM immobilization in composting. Results demonstrated that the application of an electric field enriched bacterial abundance and enhanced bacterial metabolism. Humic substance and humic acid (HA) contents in compost product were significantly increased by 19 and 69%, respectively. The HA-complexed Cu, Zn, As, Cd contents were increased by 34, 41, 29 and 135.1%, respectively, which was attributed to the promotion of HA formation since a positive correlation between HA and HA-complexed HM (R2 = 0.60-0.87) was established. The evidence presented here supports the future development of electric field implementation as an intrinsic bioremediation technique for HM immobilization.

Grazed grassland systems are an important component of the global carbon cycle and also influence global climate change through their emissions of nitrous oxide and methane. However, there are huge uncertainties and challenges in the development and parameterisation of process-based models for grazed grassland systems because of the wide diversity of vegetation and impacts of grazing animals. A process-based biogeochemistry model, DeNitrification-DeComposition (DNDC), has been modified to describe N(2)O emissions for the UK from regional conditions. This paper reports a new development of UK-DNDC in which the animal grazing practices were modified to track their contributions to the soil nitrogen (N) biogeochemistry. The new version of UK-DNDC was tested against datasets of N(2)O fluxes measured at three contrasting field sites. The results showed that the responses of the model to changes in grazing parameters were generally in agreement with observations, showing that N(2)O emissions increased as the grazing intensity increased.