Discussion on the enhancement of denitrification effect of vadose zone through the regulation of organic carbon source

The denitrification of vadose zone is very complex, with organic carbon serving as the main driving factor of its changes, and the denitrification effect of soil can modified through the regulation of soil organic carbon. In this paper, the denitrification rates of many organic carbon sources were compared and the experimental study of denitrification was conducted by adding organic carbon sources in the soil, by selecting the field soil samples, simulation planting soil and field undisturbed infiltration-tank soil and then by inputting nitrate nitrogen and organic carbon source liquid in the test soil or soil samples first or later. The result revealed that the best denitrification effect was achieved in the soil samples with ethanol or sugar added, indicating that it was suitable to be selected as one of the carbon source materials for the regulation of soil denitrification effect. It was shown through comparing the results of the denitrification test that 40.29 g-N was removed from the soil layer where 100 L ethanol solution at 2% (volume ratio) was added into the field undisturbed infiltration-tank soil (1 × 1 × 1.61 m 3 ), 33% larger than that removed from the soil without the addition of ethanol solution. 2.64, 4.38, 5.48 g of nitrogen was removed from the soil by adding 10 g, 20 g and 200 g of sugar in the soil of simulation planting soil (0.8 × 0.4 × 0.3 m 3 ), respectively. It was indicated that the variation of soil denitrification quantity was positively correlated with the addition of organic carbon source, and the change was complex. The soil denitrification effect could be significantly enhanced by adding organic carbon sources, and the guidance for the denitrification purification practice of vadose zone was thus provided.