Transportation Mechanism Of Nitrogen And Heavy Metals From Leachate In An Aquitard

The quality and quantity of municipal waste leachate from landfill are hugely variational; and the leachate has serious contaminative effect on groundwater environment nearby the landfill and has get attention by people increasingly .The paper supported by the National Natural Science Fundation of China (40672154) regards Hefei Longquan Mountain Minicipal Landfill as a case , and it chooses Transportation Mechanism of Nitrogen and Heavy Metals from Leachate in an aquitard as a topic, which has an important theoretical and practical significance.On the basis of consulting international correlative literature, the paper conbines theory study, locale study and simulation experiment in laboratory to monitor and analyse the concentration and its variety of nitrogen and heavy metals systematically. It studies transportation behavior of nitrogen and heavy metals in leachate on aquitard in course of leaching into groundwater, and influence of pH and infiltration altitude. On the basis of the study, mathematics model is applied to simulate transportation of nitrogen and heavy metals. The results of the study can be summarized as follows: (1) nitrogen pollution of landfill leachate is mainly ammonia-nitrogen; (2) heavy metal pollution of landfill leachate is mainly Cd, Pb and Mn; (3) acid condition has no evident influence to nitrogen concentration, ammonia-nitrogen decreases and nitrate-nitrogen increases along with increase of pH in alkaline condition. When pH=12, ammonia-nitrogen does not decrease, and nitrate-nitrogen shows downtrend. When pH is 8.5～9.0, nitrite-nitrogen increases rapidly. When pH oversteps the confine, it decreases rapidly; (4) whole variety of ammonia-nitrogen and nitrite-nitrogen decreases along with increase of infiltration altitude. Infiltration altitude has no evident influence to adorption or degradation of nitrite-nitrogen. At some pH, there have exceptional phenomena at the middle pat of columniation in 30cm: its concentration of ammonia-nitrogen and nitrite-nitrogen are lower than the corresponding concentration at the bottom part of columniation in 40cm; (5) concentration of heavy metals in leachate decrease along with increase of pH. Organism in leachate can make Mn of soil to transportation, so concentration of Mn in effluent of sampling spot is far more than concentration of Cd and Pb; (6) as a whole, concentration of Cd and Pb show downtrend and concentration of Mn show uptrend along with increase of infiltration altitude. Because of adsorption of columniation, concentration of Cd and Pb decrease. And because of organism in leachate can make Mn in soil transportation, the more columniation, the more Mn transportation; (7) solute transportation model is established to simulate concentration of ammonia-nitrogen and Cd. On the basis of experiment data, parameter of model can be caculated. It shows that simulation effect of the model is finer, and the model can be applied to forecast transportation of ammonia-nitrogen and heavy metals in aquitard.The conclusion of this paper provides scientific gist of estimation about quantity of nirogen and heavy metals and controlling and preventing the pollution from landfill leachate to ground water.