| The extensive use of plasticizers containing di-n-butyl phthalate(DBP)and di-(2-ethylhexyl)phthalate(DEHP)results in high residual concentrations in agricultural soil and poses potential risks to human health through the food chain.Studies have been carried out on migration and transformation of organic pollutants in the soil,but most reports have focused on heavy metals(such as Cd and Pb)and polycyclic aromatic hydrocarbons(PAHs).There are a few reports about environmental behavior of phthalic acid esters(PAEs)while most of the papers only focus on residues in the soil section,thus ignoring the mass balance PAEs in different matrixs.Here,two rice cultivars with low(Fengyousimiao)and high(Peizataifeng)PAE-accumulation were grown in leaching columns packed with DBP and DEHP contaminated soils to investigate their transport,fraction distribution and accumulation in soil-rice-water system.In this paper,three fractions including desorbing,non-desorbing and bound fractions of DBP and DEHP in the column soil and its six different particle-size fractions(>180 μm,61~180 μm,30~61 μm,2~30 μm,<2 μm and HA)were investigated using mild extraction and wet sieve precipitation method to explore the influence for residue and bioavailability.The variations in vertical migration and accumulation of DBP and DEHP by the two cultivars implied different adverse effects on the security of groundwater and food.The main results are as follows:(1)Highest concentrations of both DBP and DEHP occurred in the surface soil(0-10 cm),and their concentrations declined with the depth of soil.The residual DBP and DEHP concentrations were significantly different(P < 0.05)among the four treatments.Apparently,at the same layer and sampling time,sterilized treatment showed the highest DBP and DEHP concentrations,followed by non-sterilized treatment without plant.Moreover,the treatments the treatments with rice planted displayed significantly lower DBP and DEHP concentrations(P < 0.05)than the corresponding unplanted treatment,indicating that plants promoted the dissipation of PAEs in soil.(2)Among the three fractions including desorbing,non-desorbing and bound fractions of DBP and DEHP in all soil layers at jointing and ripening stages,the desorbing fractions consisted of the largest portion,followed by non-desorbing and bound residue fractions(except DEHP at ripening stage where desorbing fraction ≈ bound residue >non-desorbing fraction).(3)Among the six soil particle-size fractions of all soil layers at ripening period,DBP concentrations decreased in the order of coarse silt >clay fraction >fine silt ≈ HA >fine sand >coarse sand,while DEHP concentrations decreased in the order of HA >clay fraction >fine silt >coarse silt >fine sand >coarse sand.In this study,soil organic matter content was positively correlated(P < 0.05)with DEHP concentrations while not correlated(P > 0.05)with DBP concentrations in different particle-size fractions.This might be related to the competitive adsorption of DBP and DEHP for occupying simultaneously the active sites on the soil,resulting in a different distribution pattern on soil particle-size fractions.(4)Both DBP and DEHP were detected in all leachate samples at column-draining condition,indicating PAEs could migrate to deeper soil layers under leaching.Importantly,DBP and DEHP concentrations in pore water were positively correlated(P < 0.05)with those in soil at ripening stage.This suggests that once the soil is contaminated,pore water is more likely to be contaminated.(5)Both cultivars Peizataifeng and Fengyousimiao could accumulate PAEs.Overall,the bioconcentration factor(BCF,the ratio of PAE concentrations in rice tissues to environment)of Peizataifeng was higher than that of Fenyousimiao,with significant differences(P > 0.05)for BCFs of roots to soil available fractions,roots(or grains)to soil particle-size fractions as well as roots(or grains)to pore water,indicating that cultivar Peizataifeng had a greater ability to accumulate DBP and DEHP. |
PDF Full Text Request