Bioavailability Of Phthalic Acid Esters In Different Types Of Soil-plant Systems

Phthalic acid esters (PAEs) are widely used for plastic plasticizer and softener in industrial, which increase the plasticity and toughness of plastics and improve strength of plastic. PAEs are poisoning animals and people. As the mass production and the widespread use in human society, phthalates become the planet's most widespread environmental pollutants, which can be detected in phthalate pollutants existence in the atmosphere, water, soil and other environmental mediaOrganic soil environmental quality standards (GB 15618) only give a total amount of standards (such as DDT with four kinds of derivatives, the natural soil background value (<0.05 mg/kg) shall be first-degree standards.), But not establishing the standards of pollutants following a variety of derivatives and isomers under different soil conditions.In this research, it is selected the green leafy vegetables-Brassica campestris which is generally grown in Jiangsu Province, the representative types of PAEs compounds:di-butyl phthalate and di(2-ethylhexyl) phthalate and the yellow brown soil and the red soil as two representative types of the regional soils as the research object. The toxicological effects of plant growth were studied under different pollution levels of PAEs and different types of soils, combined with the results of soil aging test. It also estimated the critical concentration of PAEs based on the ecological effects.Aging tests showed that the adsorption capacity of DBP and DEHP in the soils increased with the aging time. Aging rate was faster at the beginning (0～10 d), then (10～30 d) decreased and the total adsorption quantity stabilized with the aging time. And it also showed the aging degree of DBP and DEHP in the yellow brown soil were higher than their performance in the red soil;either in the yellow brown soilor red soil the aging degree of DEHP was higher than DBP in the same soil.The results of pot experiment showed that the levels of DBP/DEHP (DBP: 0.576～2.750 mg/kg; DEHP:9.369～33.256 mg/kg) in plants grown in the red soil were positively related to the concentration of PAEs in contaminated soils, biomass and the concentration of PAEs in contaminated soils had negatively correlation. The biomass of Brassica campestris did not change with the increasing amount of DBP/DEHP added in the yellow brown soil. The content of DBP/DEHP (DBP:0.212～0.401 mg/kg; DEHP: 0.421～0.490 mg/kg) in plants grown in the yellow brown soil was far lower than the same concentration of polluted treatment in the red soil. The BCF values of DBP/DEHP in yellow brown soil-Brassica campestris system ranged between 0.061～1.041. The BCF values were greater than 1.0 (ranging between 1.175～15.695) in red soil, with a certain degree of bioconcentration effect. This study also estimated the critical concentration of DBP/DEHP in the red soil, which was between 6.932～11.718 mg/kg,for the establishment of early warning indicators of the ecological effects.It lacks the accumulated features of PAEs in agricultural soils, especially in soil-plant systems at home and abroad. This study investigated the levels of PAEs in soils and crops in the typical agricultural areas along the Yangtze River in Jiangsu Province, found the distribution features of PAEs in soil-crop systems. The polluted level of PAEs was discussed in order to lay the basis for assessing the environmental quality of soils.The results of Sampling along the Yangtze River in Jiangsu Province showed that DBP and DEHP were detected in all samples in soils and plants. The concentration of DBP in the soils was detected between 0.305～0.871 mg/kg, an average of 0.462 mg/kg. All samples were over the U.S. PAEs soil control standards. The total amounts of DEHP were between 0.012～1.111 mg/kg, an average of 0.269 mg/kg, were lower than U.S. soil PAEs control standards. Overall, the levels of DBP were generally higher than the levels of DEHP in agricultural soils. The concentrations of PAEs were different in different areas, which were between 0.437～0.969 mg/kg in different regions. Whatever the concentrations of DBP and DEHP, or totalΣPAEs in the area of Wuxi city, were higher than the other regions. Different soil use types have different concentrations of PAEs, according to the concentration order:rape>maize≈wheat≈soybean.In addition to the concentrations of PAEs in the soils which cultivated rape could see slightly higher, the contents of PAEs in the soils which cultivated wheat, soybeans and corn were similar,which were nearly in the 0.5 mg/kg.DBP and DEHP were detected in the grain, straw and roots of wheat, which both had the highest concentrations in wheat grain, between 0.777～2.217 mg/kg and between 0.311～0.818 mg/kg respectively. DBP and DEHP could be transferred from the soil to the plant and accumulated in the grain. In all sampling points, the concentration of DBP was higher than the level of DEHP.DBP had the highest concentrations in rape seeds (1.512～3.328 mg/kg), but the highest concentrations of DEHP were in the rape roots (2.487～8.091 mg/kg). Clearly, DBP transfered to the rape and accumulated in the grain easily; rape roots had higher levels of DEHP, which might be due to a large amounts of DEHP in soil adsorbed on the root surface.DBP and DEHP had the highest concentration in the roots of soybean and corn, the concentrations between 0.669～2.288 mg/kg and between 0.467～2.241 mg/kg respectively. Other parts had the lower concentration of PAEs, most under 0.5 mg/kg.The concentrations of DBP and DEHP in all parts of wheat, rape, soybean and maize were higher than the soils, showing that PAEs had a certain biological accumulation. But specific to different crops, there were different laws of its accumulation.