Study Of Phytoremediation On Soil Polluted By Nitrobenzene Compounds And Aniline Compounds

Nitro aromatic compounds (NACs) that exist in the current environment are a serious of difficult degraded organic pollutants, because of having low solubility, durability, bio-toxicological and other characteristics, which have caused huge challenges and difficulties to their own environmental pollution control work, nitrobenzene compounds(DNTs) and aniline compounds(DATs) are nitro-aromatic compounds and their derivatives, with NACs’common characteristics, always accompanied by their contamination, showing great harm to the environment. Current domestic and international research shows that a variety of plants can be applied to the NACs remediation of polluted soils, as well as strong pollutants absorption ability, simple equipment operation, low processing costs,combining advantages of landscaping and so on, phytoremediation has gradually become widely accepted treatment technology for soil pollution remediation.This article selected ice grass(Agropyron cristatum) plant to clean up DNTs and DATs pollutants, through the ice grass phytoremediation demonstration test establishment of dinitrotoluene contaminated soil and aniline wastewater irrigated soil, monitoring and analyzing the DNTs and DATs content in soil and grass before and after planting, and products of grass incineration, in order to explore the effect of remediation, the feasibility of aniline wastewater for irrigation and greening and the incineration feasibility of restoration plants, as well as further enriching the technique of phytoremediation, and to provide technical support and practical basis in remediation and improvment of oil polluted by DATs and DNTs. The experimental study concluded as follows:1. The results of ice grass phytoremediation demonstration test on soil contaminated by dinitrotoluene indicated that:(1) DNT had higher removal efficiency under ice grass-soil Combined effects, with a promotion of DNT into DAT; The lower the concentration of DNT, the effect that ice grass-soil better than soil alone is more significant, DNT concentration of0.20mg/kg, the maximum removal efficiency difference were10.8%and11.2%between the ice grass group and the control after120d and150d planting group.(2) DNT in soil can be directly absorbed by ice grass, ice grass bioconcentration factor for DNT has a significant inverse correlation with its surface layer concentration (0.0800mg/kg-2.2000mg/kg range, P<0.01, two-side t test), characterized by low concentration within the promotion of concentration, high concentration within the inhibition of concentration.(3) As for DNT in soil surface layer, after120d, ice grass planting group and non-group removal efficiency reached44.25%～58.34%,33.45%-56.39%respectively, after150d, ice grass planting group and non-group removal efficiency reached58.30%～64.66%,47.10%～59.43%respectively. Speculated that the removal of DNT with the first-year grown ice grass plants was mainly through the promotion of microbial activity to enhance the degradation of DNT, high concentrations of DNT inhibited the metabolic activity of ice grass plants and soil microorganisms.(4) Determining ice grass grown repair cycle on contaminated soil with DNT: wihtin the concentration of0.79mg/kg-3.08mg/kg and3.08mg/kg～5.00mg/kg concentration range, DNT contaminated soil can be reached fixed target limits through two and three ice grass growing period respectively.2. Aniline compounds sewage irrigated soil and ice grass phytoremediation demonstration test results indicated that:(1) Ice grass could absorb DATs and DNTs by roots, than transport to leaf and ear through the stalk; DATs enrichment factor higher than the DNTs enrichment factor in ice grass.(2) For DNTs and DATs, their absorption ability by ice grass were not related to the concentration levels in soil when the soil surface concentration of DATs0.0045mg/kg-0.1400mg/kg, DNTs0.0200mg/kg-0.3000mg/kg.(3) The use of low concentrations of aniline wastewater for irrigation and greening didn’t cause pollution accumulation, sample and reliable, economic, technical, environmental feasible (concentration of DATs=0.0046mg/L, water quantity≈9m3/times/mu, Watering frequency2-5Times/week).3. Natural burning and high-temperature ashing process results indicated that:(1) Using natural incineration approach to deal with the repair plant for harvesting can be reduced to the original quality of about10.8%, plant volume reduction effect is obvious.(2) After harvested ice grass burning, the mean concentration of DATs and DNTs ingredients in the flue gas were calculated within0.0000-0.0006mg/m3and0.0020-0.005lmg/m3range respectively, were much lower than both fugitive emissions monitoring concentration limits to achieve discharge standards, and there was no smoke "secondary pollution" problem.(3)After burning, few DATs and DNTs remained in bottom ash, detected concentrations were0.000432～0.004079mg/kg,0.015681～0.039809mg/kg respect-ively, which were far below the soil remediation limits0.17mg/kg,0.79mg/kg, would not cause soil secondary pollution.(4) High temperature incinerated bottom ashes, at a minimum temperature of500℃conditions chosen, incinerating5minutes, bottom ashes had a very low concentration of two pollutants, which could prove low temperature and short ash time disposal measures were technically feasible.