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| Experimental analysis of preferential flow and its effect on nitrate nitrogen migration in soil of farmland at Changping district in Beijing |
| (1.School of Soil and Water Conservation, Beijing Forestry University, 100083, Beijing, China; 2.Beijing Soil and Water Conservation Project Consulting Co., Ltd., 100055, Beijing, China; 3.Yanqing Soil and Water Conservation Work Station, 102200, Beijing, China) |
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Abstract In order to investigate the principles of the farmland soil water and solute migration under the influence of preferential flow, a comparison was studied between undisturbed and packed soil columns which represented for non-balancing and balancing infiltration respectively. With the methods, the effect of preferential flow on nitrate nitrogen migration was studied in the agricultural land at Changping district. The results showed that nitrate nitrogen migrated in higher rates and in greater numbers under the promotion of soil preferential flow, and tailing was also a vital appearance in the preferential flow’s Break Through Curve. The water flow rate with preferential flow in soil appeared larger degree of volatility, and was 1.48-2.69 times of that of balancing infiltration. Since the nitrate ions are non-absorptive, the migration of nitrate nitrogen was characterized with higher rates and greater numbers as influenced by preferential flow. The breakthrough time of undisturbed soil column was 12h with a 57% reduction compared to the packed one, and the leachate volume of undisturbed soil column was 0.36 times of Pore Volume when the nitrate ions penetrated which was 0.73 times of that of the packed one. In addition, the preferential flow of NO-3 in undisturbed soil column accounted for 43.83% of total flux, but resulted to a 97.60% accumulative lechate mass for NO-3 in total mass. These results indicated that the preferential flow with limited ratio in total flux could lead to a large proportion of NO-3 migration. Tailing was an important phenomenon in the preferential flow’s BTC and was a unique feature of the curve, it may be caused by the disproportion of preferential flow to matrix flow on penetration rate in the infiltration progress.
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Received: 27 November 2012
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