The Effect of Soil Texture and Transmission Distance on The Nitrate Dispersivity in Sandy Soil Using Brigham, Fried-Combernous Models and CXTFIT code

Increased use of nitrogen fertilizers due to high dynamics of soil nitrate is a serious threat to groundwater and as a result for human health. The purpose of this study is evaluation of nitrate dispersivity values in the sandy soils of coarse, medium and fine-distance transmission at 80, 40 and 20 cm in laboratory conditions with three models including, Brigham, Fried-Combernous and CXTFIT code. For this purpose, pure potassium nitrate salt solution as sustainable contaminant under the steady regim with concentration of 16 was added to the soil column. In order to obtain the required parameters for the three models, output nitrat concentration were measured in the different nolum porosity and Breakthrough curves were plotted for each column. The results showed that in all three models with a moderate increase in transmission distance of medium and coarse sand, the amount of nitrate dispersivity increased. At various distance of transportation, dispersivity values were measured for fine sand from 0.09 to 3.06 cm,0.23 to 1.6 cm for medium sand and 0.43 to 2.18 cm for coarse sand, respectively. But the Brigham and CXTFIT models showed that the dispersivity of fine sand increases when the distance increases. It was also found that for the fine sand with reduction of transport distance, Brigham model and CXTFIT code showed better results.