The properties of nanoparticles and their increased use have raised concerns about their possible harmful effects within the environment. Most studies on their effects have been in aqueous systems. Here we investigated the effect of TiO(2) and ZnO nanoparticles on wheat growth and soil enzyme activities under field conditions. Both of the nanoparticles reduced the biomass of wheat. The TiO(2) nanoparticles were retained in the soil for long periods and primarily adhered to cell walls of wheat. The ZnO nanoparticles dissolved in the soil, thereby enhancing the uptake of toxic Zn by wheat. The nanoparticles also induced significant changes in soil enzyme activities, which are bioindicators of soil quality and health. Soil protease, catalase, and peroxidase activities were inhibited in the presence of the nanoparticles; urease activity was unaffected. The nanoparticles themselves or their dissolved ions were clearly toxic for the soil ecosystem.

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A series of pulverized semi-coke combustion experiments were carried out to investigate the characteristics of fuel-N transformation and the effect of operating conditions in a circulating fluidized bed (CFB) and a down-fire combustor (DFC) on fuel-N transformation. The fuel-N transformation takes place in two stages: first, the fuel-N in pulverized semi-coke is partly converted to N 2 and NH 3 in a circulating fluidized bed; second, the fuel-N in preheated semi-coke and NH 3 is converted to NO x or N 2 in a down-fire combustor. The fuel-N in the preheated semi-coke and the NH 3 concentration in the syngas both decreased with increasing λ CFB in the preheating process. The distribution of the secondary air determined the paths of NH 3 conversion in the reducing zone. The air staging of the tertiary air promoted NH 3 , which was generated for fuel-N, converting to N 2 in a complete combustion process. With this process, the NO x emissions were effectively limited. The lowest NO emission from combustion of pulverized semi-coke was 50 mg/m 3 (about 60 mg/m 3 NO x ) (at 6 vol % free O 2 ), which satisfied the emission standard of air pollutants for thermal power plants in China.