施用生物质炭对红壤中硝态氮垂直运移的影响及其模拟

为研究在红壤中施用生物质炭后硝态氮的垂直运移规律，采用室内土柱模拟的方法，分别按照炭土比为0、2.22%(5 t·hm^-2)、4.45%(10 t·hm^-2)、8.95%(20 t·hm^-2)、13.37%(30 t·hm^-2)和17.80%(40 t·hm^-2)设置混合土壤，并采用CXTFIT 2.0模型对试验结果进行拟合.结果表明： 在饱和条件下，不同生物质炭添加比例下，硝态氮运移的穿透曲线发生明显变化.不同处理的硝态氮相对浓度(C/C_o)峰值、淋溶速率和累积淋失量随生物质炭添加量的增加而显著降低.各穿透曲线尾部均存在一定的拖尾现象，且随生物质炭添加量的增加拖尾现象越显著.对硝态氮穿透曲线的影响因素分析可知，生物质炭影响了土壤的容重、有机碳、孔隙度、阳离子交换量(CEC)等物理性质，进而导致各处理硝态氮穿透曲线发生了变化.采用CXTFIT 2.0数学模型模拟硝态氮在土壤中的运移，硝态氮的穿透曲线拟合值与实测值呈显著正相关，相关系数均>0.850，能够很好地对土壤硝态氮运移和运移参数进行预测，试验结果可为预测生物质炭施用对地下水体环境硝态氮的影响提供科学依据.

Effects of biochar application on the vertical transport of NO3-N in the red soil and its simulation.

Soil column experiments in laboratory were conducted to determine the effect of biochar application on the vertical transport of NO₃-N in red soil. Biochar was mixed thoroughly with soil at rates of 0, 5, 10, 20, 30 and 40 t·hm^-2, i.e., biochar/soil ratios of 0, 2.22%, 4.45%, 8.95%, 13.37% and 17.80%. The CXTFIT 2.0 model was used to simulate the breakthrough curve of NO₃- N. The results were as follows: the breakthrough curve of NO₃-N varied remarkably with the increase of biochar application rate under saturated condition. The peak values of relative concentration (C/C_o), leaching rate and cumulative loss of NO₃-N all significantly decreased with the increasing biochar application rate. There existed a certain prolongation of the breakthrough curves among all treatments. The more the biochar was applied, the more obviously the breakthrough curve was prolonged. According to the correlation analysis between the NO₃-N breakthrough curves and soil properties, biochar affected the bulk density, organic carbon, total porosity, CEC of red soil, which would exert an effect on the breakthrough curves. The simulation value and the actual obtained value of the breakthrough curves were positively correlated with the correlation coefficients being over 0.850 in all breakthrough curves, which indicated the CXTFIT 2.0 model could best fit the prediction of nitrate N transport and relative infiltration. These results could provide a scientific basis for predicting the effect of biochar on nitrate N in underground water after biochar incorporation into field.