| Erythromycin(ERY)is a kind of antibiotics which is widely used and frequently detected in environment.In China,erythromycin has been frequently detected in rivers,sediment,soil and even in animals and plants.Erythromycin has resulted in soil and water pollution,even lead to the emergence of resistant bacteria and resistance genes,which may bring about potential health risks to humans.Therefore,it is necessary to study the environmental security of erythromycin.The comprehensive study of the adsorption,desorption and leaching of erythromycin,and its absorption and accumulation in organisms are the foundations to understand the pollution evolution trend of erythromycin reasonably,and to evaluate its environmental security scientifically.Considering that,this paper studied the adsorption-desorption and leaching characteristics of 14C-erythromycin,the law of absorption,concentration,translocation and distribution of erythromycin in plants-soil/water system,and the kinetic of extractable residue and bound residue by using 14C-Iabelled techniques,radioactive quantitative and radionuclide imaging.The aim of this research is to study the fate and bioavailability of ERY in environment comprehensively,and to provide a scientific basis for the evaluation of its environmental security.The main results were as follows:According to the results of adsorption and desorption experiment:the adsorption-desorption of erythromycin in 7 soils fitted well with the Freundlich,Langmiur and linear models,the correlation coefficient R2 values were range from 0.9810 to 0.9999.Soil properties demonstrated significant effects on its adsorption,and the adsorption constant Kfof erythromycin in 7 soils is between 6.86 and 18.38,and roughly followed as S6>S3>S7>S5>S2>S4>S1.Statistical analysis demonstrated that the adsorption of erythromycin by soil was significantly correlated with the soil organic matter content.The free energy variation value for adsorption was less than 40 kJ·mol-1,suggesting that the adsorption of erythromycin to soil was mainly attributed to physical adsorption.In desorption tests,erythromycin showed the obvious hysteresis in all tested soils.The results from the column leaching tests showed that erythromycin had weak leaching ability in soils,with 66.86-92.53%of 14C-erythromycin concentrated in the surface 0-5 cm soil layer.In general,the leaching ability of erythromycin was greatest in S6,which followed by S3,S5 and S7,and was weakest in S1,S2 and S4.It was in accordance with the results from the adsorption test.This study demonstrates that erythromycin has potential risk of accumulating in the surface soil layer,which should be given more attention.Soil-plants cultivation experiments showed:the ERY in soil could be uptake by plants,while the content of ERY in plants were increasing with incubation time,the content of erythromycin in different plants showed a significant difference.After 35 d cultivation,the content of ERY in edible part of pakchoi and water spinach were 27.43±1.16 μg·kg-1 and 13.69±0.36 μg·kg-1 respectively.There was a significant difference(p<0.05)in the content of different parts of the same plant,and the content of ERY in root was much higher than in shoot.The bioconcentration factor(BCF)and translocation factor(TF)of ERY in pakchoi and water spinach were less than 1,suggested that ERY were not readily adsorbed in plant.The Radionuclide imaging result indicated that water spinach could transport the ERY to different parts of plants.C-ERY is mainly concentrated in the new leaves,which suggested that ERY could be transferred in water spinach.During the cultivation period of 35 d.the extractable residue(ER)of ERY in soil decrease over time,while the bound residue(BR)increased over time,and the equilibrium was not reached at 35 d.After 35 d cultivation,the amount of BR of ERY was 6.54%and 5.98%in two soils,respectively.There is no significant difference in the ER and BR of between two soils cultivated different plants.During the whole cultivation period,the percentage of erythromycin bound residue was low all along(3.40%-7.47%),which indicated that erythromycin and its degradation products were not readily to form BR with soil.Water-plants cultivation experiments showed:the ERY in water can be uptake by water spinach,while the content of ERY water spinach were increasing over time.There was a significant difference(p<0.05)in the contents of different parts of hydroponics water spinach.After 21 d cultivation,the content of ERY in root and shoot of water spinach were 6.23±0.57 μg·kg-1 and 1.65±0.17 μg.kg-1,respectively.The BCF and TF of hydroponics water spinach were 1.03 and 0.26,suggesting that ERY could be accumulated in the root of hydroponics water spinach,and it is difficult to translocate to shoot and leaf.The BCF of soil-cultivated water spinach is 0.15,far below 1.03,indicating that ERY in water absorbed and concentrated by water spinach more easily.The human exposure assessment showed that the estimated value of ERY intake by soil-cultivated pakchoi,water spinach and hydroponics water spinach were less than 42 μg/d,suggesting that there is low risk to human health. |
PDF Full Text Request