Research Of Characteristic Of Dissolved Organic Mater In Simple Landfill Leachate On Transformation And Migration

In early stage, China had established a large amount of landfill, which landfill methods mainly relied on stacking intensively in the open air or simple landfilling, the measures of seepage control were very humble and crude. These garbage leachate of simple landfill could cause serious threat to the soil and groundwater, and then harm to the growth of plants and animals, and life health of the residents. Therefore.to research the transformation and migration of simple landfill leachate in the soil and groundwater, was the crux matter of the soil and groundwater pollution prevention and control.This study was on the basis of the investigation of the present situation of typical simple landfill, adopting the approach of combination of field observation and indoor simulation, to research the rules of the space-time distribution and distinction of dissolved organic matter (DOM) in simple landfill leachate, as well as their characteristics on transformation and migration in the analog system of aeration zone and groundwater, clarified the mechanism of the coordination of DOM and Pb(Ⅱ), with the aid of fluorescence quenching analysis and soil column simulation technique. Under simulated stress conditions, to explan the toxic effect of landfill leachate and Pb(Ⅱ) on plant development by seed germination and growth experiments. Providing the scientific foundation for the correct evaluation of the disposal of simple landfill leachate and the environmental risk.The main research results are as follows:1. The analysis showed that the fluorescence spectral characteristics and fluorescence peak position and intensity was affected by the landfill ages of leachate DOM. The fluorescence peak position of10a DOM had red shift which move to the long wavelength.Relative to5a landfill leachate DOM, the fluorescence intensity of10a DOM was lower, the degree of aromatization was higher and the structure is more complicated.2. Through the column simulation test and the3DEEM fluorescence spectra technology, the migration characteristics of leachate pollutions and their variation characteristics in the simple landfill were studied.The results indicated that, part of the pollution components of landfill leachate DOM were cleansed on the process of transformation and migration. The thicker of soil layer, the stronger of Purification ability. The degradation of organic pollution components in leachate, mainly relies on the adsorption of soil at earlier stage and relies on the catabolism of microbe at later stage. At the meantime, inorganic pollutions are not easy to intercept by medium and not easy to use by microorganisms and have strong migration ability in soil. In the process of migration and transformation, DOM is influenced by physical, chemical and biological factor leading to the changes of Percent Fluorescence Reponse (Pt,m) of each composition. Under the effect of microbe catabolism, fluorescence peak strength of DOM reduced continually.3. Through the column simulation test and the3DEEM fluorescence spectra technology, the result suggested that Landfill leachate DOM was the efficient organic ligand to Pb(Ⅱ), the proportion of coordination was close to1:1, DOM could greatly promote Pb(Ⅱ) migration in soil. In addition, the migration potential (36.09) and migration rate (0.17) of Pb(Ⅱ) leached by10a landfill leachate DOM was lower than that of5a (43.71,0.19) which revealed that the migration ability of DOM to Pb(Ⅱ) in soil decreased as the extension of landfill age. Furthermore, the total Pb(Ⅱ) mobility during the first12-h elution increased from3.725%to5.75%, when the concentration of DOM in eluting solution increased from32.5mg/L to130mg/L. The above analysis showed that the migration ability of DOM to Pb(Ⅱ) was affected by the concentration, landfill ages, and leaching time of landfill leachate DOM.4. Landfill leachate dissolved organic matter (DOM) showed obvious inhibitory effect on the germination and early development of wheat seeds, evidenced by the decreased germination rate, germination vigor, germination index and vitality index of wheat seeds treated with DOM. Meanwhile, the inhibitory effect increased with the increasing concentrations of DOM. In contrast, the seed germination rate treated with low concentrations of Pb2+(from25mg/L to200mg/L) remained largely unchanged, whereas, high concentrations of Pb2+(≥200mg/L) inhibited the germination of wheat seed. The presence of low concentrations of Pb2+in DOM did not increased but decreased the toxic effect of DOM on wheat seeds, probably duo to the complexation of Pb2+with the functional groups in DOM. In addition, the application of DOM or/and Pb2+unbalanced the synthesis and metabolisms of proline and thus induced the accumulation of free cytosolic proline in wheat cells. Interestingly, DOM and Pb2+showed no superposition of their toxicity effect, but inhibited the toxic effect of each other on the concentration of free proline in wheat cells. Consistently, POD activities of wheat under the stress of DOM and Pb2+increased dramatically as well, while the addiction of low concentrations of Pb2+inhibited the DOM-induced increase of POD activity. Taken together, both DOM and/or Pb2+inhibit the germination and early development of wheat seeds, while the co-presence of them decreases the toxicity effect of each other, which is most likely contributed by the complexation of Pb2+with functional groups in DOM.