Research On Analytical Method And Environmental Behavior Of PAEs In Vegetable Greenhouse

In recent years scientists have become increasingly concerned about the phthalic acid esters(PAEs) which is one of the environmental endocrine disruptors.The aim of this paper was to evaluate the safety of the pollution of PAEs in the greenhouse vegetables.In this paper, vegetable bases of Horticulture Institute of Shandong Agriculture University and Shouguang of Shandong Province was regarded as the research object;a new analytical method based on matrix solid phase dispersion(MSPD) coupled to liquid and gas chromatography with mass spectrometric detection was developed for the determination of PAEs.The paper studied the distribution of PAEs in air,soil and vegetables in greenhouses and the absorption law of PAEs in vegetables.Sorption/desorption behaviour of PAEs on soil and its organic matter fractions was also discussed in the paper which gave us a deep understanding of the mechanism of sorption of PAEs.The main research contents and achievements are as follows.1.A new analytical method based on MSPD coupled to LC-MS and GC-MS,which required florisil as dispersant sorbent,graphitizand carbon black as purificant and ethyl acetate as eluting solvent,was first developed for the determination of PAEs in vegetables and soil.The method which required no special instruments was convenient and fast with good accuracy and repeatability,it also had good correlation coefficient and detection limit good for trace analysis.2.It first systematicly analysised the law of PAEs distribution in air,soil and vegetables. The results showed that:DBP and DEHP were the main PAEs pollutants,while DMP and DEP had the lower concentration;PAEs contents varied with the source of plastics film and the contents of the plasticizer.The total contents of PAEs in soil and vegetables ranged from 7.35 mg/kg to 33.39 mg/kg and from 0.85 mg/kg to 2.50 mg/kg respectively.The content of PAEs in vegetables was far beyond the standard which was made by WHO for the PAEs in the water.3.Experiments of vegetables cultivated in pot indicated that:DBP and DEHP at different pollution levels could all be detected in rhizome,stalk and leaf of carrot,cucumber and tomato;moreover,the higher concentration of PAEs,the higher content in the vegetables,the content of DBP was higher than DEHP at different pollution levels,some experts consider that this phenomenon may be related with absorption and transportion of PAEs in vegetables and the physics and chemistry properties of PAEs,such as molecular weight,Kow and volatility.DBP can be easily absorpted and transported by vegetables because of smaller molecular weight and lower Kow than that of DEHP,most of which retains in the rhizome because DEHP is difficult to be transported to the stalk and leaf of vegetables.4.Sorption experiments indicated that:A notable nonlinear absorption behavior of original soils for DEP and DBP was found.The nonlinearity of DBP was higher than that of DEP in the homologous soil and K_oc of DBP is 6～12 times of that of DEP at three concentration levels.5.The nonlinearity of sorption of DEP increased in the order of humic acid,original oils, base-treated soils.K_oc of DEP in base-treated soils was higher than that in humic acid and original soils at three concentration levels.6.The results of ¹³C NMR and isothermal sorption indicated that:A notable nonlinear sorption behavior of humic acid for DEP was found with the increase of aromatic structure and decrease of fatty structure.This mean that the sorption of fatty structure for DEP follows distribution mechanism,while romatic structure follows nonnlinearity mode.7.Contributions of humic acid and base-treated soils to the sorption of original soils were quantitied and the results indicated that:More than 60 percent of whole sorption of original soils were contributed by base-treated soils.Thus,base-treated soils played the dominant role in whole sorption of original soils and were main cause of nonlinear sorption.With increase of equilibrium concentration,K_oc of base-treated soils decreased more quickly than that of humic acids because base-treated soils had stronger nonlinearity,then the Contribution from base-treated soils would reduced.8.The results of sorption/desorption indicated:Hysteresis index of original oil,which was larger than that of humic acid,had an increasing trend with the decrease of the proportion of humic acid in TOC.This mean that humic acid was the main cause of nonlinear sorption.9.When the SOM contents were above 50%,SOM in soil surface would block organic pollutants into the SOM of inner soil,which resulted the decrease of the absorption ability of original soil.