Study On Migration And Accumulation Of Octachlorodipropyl Ether In Soil-vegetable Systems

The analytical methods and dynamics of Octachloropropyl ether residues in soil andvegetables （bitter chrysanthemum, lettuce, potherb mustard, pakchoi cabbage and swampcabbage） were studied in this dissertation. The sensitivity, accuracy and precision of themethods were investigated. The migration and accumulation of OCDPE in differentsoil–vegetable systems were studied in laboratory experiment. The main results weresummarized as following:1. The analytical methods for OCDPE residues in soil and vegetablesSoil samples were extracted with ethyl acetate by ultrasonic. Quantification analysiswas performed by gas chromatography with an electron capture detector. Recoveries andRSDs of OCDPE in soil (the concentrations of OCDPE fortified in soil were0.01to1.00mg·kg^-1) were83.4%to95.5%and3.7%to8.6%, respectively.Vegetable samples were extracted with acetonitrile by ultrasonic and purified byFlorisil cartridge. Quantification analysis was performed by gas chromatography with anelectron capture detector.Recoveries and RSDs of OCDPE in stems and leaves of lettuce(the concentrations of OCDPE fortified were0.01to0.50mg·kg^-1) were92.7%to106.4%and1.3%to6.9%, respectively; Recoveries and RSDs of OCDPE in stems and leaves ofbitter chrysanthemum (the concentrations of OCDPE fortified were0.01to0.50mg·kg^-1)were86.3%to103.6%and1.8%to5.1%, respectively; Recoveries and RSDs of OCDPEin stems and leaves of potherb mustard (the concentrations of OCDPE fortified were0.01to0.50mg·kg^-1) were90.2%to110.1%and1.6%to2.7%, respectively; Recoveries andRSDs of OCDPE in stems and leaves of pakchoi cabbage (the concentrations of OCDPEfortified were0.01to0.50mg·kg^-1) were95.4%to105.5%and2.2%to4.2%, respectively;Recoveries and RSDs of OCDPE in stems of water spinach (the concentrations of OCDPEfortified were0.01to0.50mg·kg^-1) were82.4%to108.8%and1.9%to3.8%, respectively;Recoveries and RSDs of OCDPE in leaves of water spinach (the concentrations of OCDPEfortified were0.01to0.50mg·kg^-1) were85.2%to92.0%and4.6%to6.7%, respectively.Root samples were extracted with acetonitrile by ultrasonic and purified by Florisilcartridge. Quantification analysis was performed by gas chromatography with an electroncapture detector. Recoveries and RSDs of OCDPE in roots of lettuce (the concentrations ofOCDPE fortified were0.01to1.00mg·kg^-1) were90.7%to101.0%and4.3%to7.2%, respectively; Recoveries and RSDs of OCDPE in roots of bitter chrysanthemum (theconcentrations of OCDPE fortified were0.01to1.00mg·kg^-1) were83.0%to96.5%and2.9%to8.8%, respectively; Recoveries and RSDs of OCDPE in roots of potherb mustard(the concentrations of OCDPE fortified were0.01to1.00mg·kg^-1) were92.4%to103.5%and2.7%to8.2%, respectively; Recoveries and RSDs of OCDPE in roots of pakchoicabbage (the concentrations of OCDPE fortified were0.01to1.00mg·kg^-1) were84.8%to96.7%and5.5%to9.7%, respectively; Recoveries and RSDs of OCDPE in roots of waterspinach (the concentrations of OCDPE fortified were0.01to1.00mg·kg^-1) were89.2%to107.2%and6.8%to9.1%, respectively.The accuracy, precision and sensitivity of this validated method were suitable foranalysis of OCDPE residue in soil and vegetables.2. Migration and accumulation of OCDPE in different soil-vegetable systemsIn soil concentration of1.0mg·kg^-1, there was difference in accumulation of OCDPEbetween stems and leaves of five vegetables. It cost about9d to achieve peak value for theabsorption of OCDPE from soil to stems and leaves of bitter chrysanthemum, lettuce andpakchoi cabbage, and it cost14d to stems and leaves of water spinach, while it was3d topotherb mustard. OCDPE residues of stems and leaves of bitter chrysanthemum up to0.5232mg·kg^-1was16times more than stems and leaves of potherb mustard which hasminimum residual. The results showed that the most likely to accumulate OCDPE wasstems and leaves of bitter chrysanthemum.OCDPE residues of stems and leaves decreasedafter gradually accumulated to maximum over time.There was difference in accumulation of OCDPE between roots of five vegetables. Itcost about5d to achieve peak value for the absorption of OCDPE from soil to roots ofbitter chrysanthemum and pakchoi cabbage, while it cost14d to stems and leaves of waterspinach and bitter chrysanthemum, the maximum were0.3215mg·kg^-1,0.3163mg·kg^-1,0.4004mg·kg^-1and0.3462mg·kg^-1. It was weak in accumulation of OCDPE for roots oflettuce, the maximum was just0.0521mg·kg^-1.3. Degradation of OCDPE residues in different soil-vegetable systemsOCDPE residues in soil were gradually decreased with time in five soil-vegetablesystems. The dynamic equations of OCDPE in soil which separately planted bitterchrysanthemum, lettuce, potherb mustard, pakchoi cabbage and water spinach wereC_t=0.476e^-0.059t（R²=0.824）, C_t=0.995e^-0.062t（R²=0.972）, C_t=0.825e^-0.066t（R²=0.954）, C_t=0.600e^-0.052t（R²=0.805）, C_t=0.813e^-0.082t（R²=0.974）, respectively; half-life （T1/2） was11.75d,11.18d,10.50d,13.33d and8.45d, respectively. There was difference indegradation of OCDPE between five different soil-vegetable systems.4. OCDPE residues in different part of vegetableOCDPE accumulation in different part of water spinach had been studied. The resultsshowed the order of residues in different part of water spinach was: root> stem> leaf. Theroot’s BCF of pakchoi cabbage was32while its stem and leaf’s BCF was16; the root’sBCF of potherb mustard was40while its stem and leaf’s BCF was3; the root’s BCF ofwater spinach was35while its stem’s BCF was13and leaf’s BCF was10.It indicated atrend that root’s BCF＞stem and leaf’s BCF, which means the root ability of OCDPEaccumulation was higher than stem and leaf’s in vegetable.5. Migration and accumulation of OCDPE in soil-vegetable systems in differentconcentrationMigration and accumulation of Octachlorodipropyl ether in soil-pakchoi cabbagesystem in different concentrations had been studied. The stem and leaf’s BCFs of pakchoicabbage were11,16and26in soil concentration of0.1,1.0,10.0mg·kg^-1, repectively. Itshowed that stem and leaf’s BCF of pakchoi cabbage and soil pollution concentrationshowed positive correlation. While the root’s BCF of pakchoi cabbage were41,32and32in soil concentration of0.1,1.0,10.0mg·kg^-1, repectively. It indicated a trend the root’sBCF decreased as the concentration increased. The time which root and stem and leaf ofpakchoi cabbage accumulated OCDPE to maximum needed didin’t changed because of achange in concentration, it was5d and9d, respectively. It showed soil pollutionconcentration didin’t affect the speed pakchoi cabbage accumulated OCDPE.The dynamic dissipation of OCDPE in soil of soil-pakchoi cabbage system followedan apparent first-order kinetic model. Dealing with different concentrations of0.1,1.0,10.0mg·kg^-1, the dynamic equation of OCDPE was C_t=0.051e^-0.059t（R²=0.704）,C_t=0.600e^-0.052t（R²=0.805）, C_t=8.542e^-0.110t（R²=0.955）, and the dissipation half-life （T1/2）were11.71d,13.33d,6.30d, respectively. It indicated a trend of the higher theconcentration, the shorter half-life.