Effect of Biochar layer on Break Through curve on porous media and nitrate distribution profile

Many processes amplify the nitrate contamination in the groundwater. In addition to economic losses caused by further utilization of nitrate fertilizers, nitrate leaching from agricultural lands imposes irreparable damages to the environment .Biochar has been recently used as an optimal method to decrease the leaching of soil nutrients. To meet this purpose, the present study was carried out to investigate the effect of using Biochar on the decrease of nitrate leaching from soil as well as the effect of changes (including increase and decrease) of dispersivity coefficient and absorption isotherm coefficient on the break through curve and nitrate distribution profile. The HYDRUS-1D model was used to simulate the variations of the break through curve (BTC) and nitrate distribution profile in different points of the soil depth Biochar hydraulic parameters were measured in the lab. The results showed that increasing the value of Biochar adsorption isotherm decreases the output nitrate concentration and causes the nitrate BTC moves to the right side (Retardation). The results also showed that the increase of the Biochar dispersivity coefficient decreases the reduction rate of output nitrate concentration and causes nitrate BTC moves to the left side. The results also showed that the presence of the Biochar layer can decrease the content of nitrate distributed at the end of the column by about 61%. The transfer velocity of pollutants into the soil depth also decreased with the increase of the Biochar adsorption and decrease of dispersivity coefficient meaning that the solutes exit later and less from the soil column when the biochar layer is used. The results of momentum analysis showed that the value of output pollutant mass from the column in the case of non-Biochar is 15.36 (mg/cm3×h) while in the case of using Biochar is 13.78 (mg/cm3×h) indicating a 10.3% reduction of output pollutant from the column. In all treatments, this value was lower than the control treatment meaning that the Biochar, can absorb contaminants in all conditions from the aquatic environment and reduce the contaminant percolation to the soil depths.