Study On Influence And Mechanisms Of Nanoparticles On Transfer Of Typical Pesticides In Soil Plant System And Its Bioavailability

In this study,nanoparticles and pesticides were simultaneously added into soils to explore the influence and mechanism of nanoparticles on the transfer of pesticides from soil to vegetables and the bioavailability of pesticides in the soil.Firstly,a series of concentrations(0,10,100 and 1000 mg/kg)of environmental friendly nanoparticles(nano carbon)and a common utilized pesticide(pentachloronitrobenzene,PCNB 1000 ng/g)were simultaneously added into the soil to cultivate pakchoi.The concentrations of PCNB in roots and leaves of pakchoi were measured at different sampling time.Compared to the individual PCNB treatment group,the concentration of PCNB in the roots of pakchoi in the combined treatment group significantly increased,but when the concentration of nano carbon reached 1mg/g,the concentration of PCNB in the leaves of pakchoi was the lowest.The results showed that nano carbon could promote pakchoi to absorb PCNB.Meanwhile,it was found that the high concentration of na no carbon(1000 mg/kg)could inhibit this process,which may be due to that the high concentration of nano carbon would block the vessel of plants,inhibit the transfer of nano carbon adsorbed with PCNB to the leaves of plants,thus inhibiting the transfer of PCNB to the leaves.In another experiment,a series of concentrations of nano Cu O(10,50,100mg/kg)and a common utilized pesticide(bifenthrin,200 ng/g)were simultaneously added into the soil to cultivate rape.The concentrations of Cu²⁺and bifenthrin in the roots and leaves of rape were measured at different sampling times.Compared to individual bifenthrin treatment group,the concentration of bifenthrin in the roots and leaves of rape did not significantly increase when adding low concentration of nano Cu O(10,50 mg/kg).However,when the concentration of nano Cu O reached 100mg/kg,the concentration of bifenthrin in the roots and leaves of rape significantly increased.The results showed that high concentration of nano Cu O would bring oxidative damage to rape roots,however,nano Cu O and bifenthrin would have no influence on the growth of rape.Low concentration of nano Cu O would not promote bifenthrin to enter into the plant root,while high concentration of nano Cu O would promote bifenthrin to enter into the plant root.The reason may be that the high concentration of nano Cu O will destroy the plant root cells,so that bifenthrin would extra enter into the plant body.In addition,bifenthrin could also migrate to leaves under the force of transpiration,however,Copper in plants will not affect this behavior.As for the influence and mechanism of nanoparticles on the bioavailability of pesticides in soil,firstly,earthworms were utilized to be cultivated in soil to study the bioavailability of two pesticides(pentachloronitrobenzene or tolclofos-methy).Earthworms were exposed to artificial soils containing a series of different concentrations of(0.01,0.1,1,10 mg/kg)of pesticides.On day 1,3,7 and 14,the concentrations of pesticides and biomarkers(active oxygen radicals,superoxide dismutase,malondialdehyde)in earthworms were measured.The results showed that the concentration of pesticides in earthworm would represent the bioavailability of pollutants.Meanwhile,after exposure for a period of time,the changes of ROS,SOD,MDA and other biomarkers in earthworms were correlated with the concentration of pesticides in soil and earthworms,which indicated that these indicators could reflect the toxic bioavailability of pesticides.The relationship between environmental bioavailability and toxicity bioavailability showed that earthworm culture experiment could be utilized to represent the bioavailability of pesticides.Then,nano particles(nano Cu O or nano Zn O)with different concentrations(10,50,250 mg/kg)and bifenthrin(100?g/kg)were added into the soil to cultivate earthworms for 21 days.The concentrations of heavy metals,bifenthrin and biomarkers in earthworms were measured on day 7,14,and 21.When the concentration of nano Cu O and nano Zn O reached 250 mg/kg,the concentration of bifenthrin reached 23.2?g/g and 28.9?g/g in binary treatment groups,which were2.65 and 3.32 times of that in individual bifenthrin treatment group.The results showed that the accumulation of bifenthrin in earthworms was enhanced by nano particles,however,the adsorption test results exhibited that this phenomenon could not be explained by“carrier effect”of nano particles.The ex vivo toxicity test indicated nanoparticles would bring damage to cells of earthworm body cavity.Earthworms would absorb hydrophobic chemicals(bifenthrin)through the body cavity,so extra bifenthrin would enter into earthworms through the injured body cavtiy.The increased of Cu²⁺or Zn²⁺accumulation in earthworms in the binary treatment groups reversely supported this hypothesis.In in vivo toxicity test,bifenthrin and nanoparticles brought the oxidative damage to earthworm,and the toxicity of binary pollutants was higher than that of individual pollutants.At last,nano particle(nano Cu O or nano Zn O)with different concentrations(10,50,250 mg/kg)and PCNB(100?g/kg)were simultaneously added into soils to cultivate earthworms.The concentrations of heavy metals,PCNB and biomarkers in earthworms were measured on day 7,14 and 21.Compared to the individual PCNB treatment group,the concentration of PCNB in the combined treatment group with nano particles significantly increased.It was also observed that when the concentration of nano Zn O and nano Cu O reached 250 mg/kg,the concentration of PCNB in the combined treatment group reached 21.7?g/g and 27.5?g/g,which were2.47 and 3.13 times of that in individual PCNB treatment group.It was also observed that the existence of nanoparticles(nano Zn O and nano Cu O)enhanced the accumulation of PCNB in earthworms,thus increasing the bioavailability of PCNB in the soil.The damage of nanoparticles and PCNB to the coelomolyte cells of earthworm was caused by excessive ROS.In individual experiments,nanoparticles and PCNB caused oxidative damage to earthworms,resulting in the increase of ROS content in pollutant treatment group.Therefore,it is hypothesized that the existence of nanoparticles would bring toxicity to earthworms and damage the body cavity of earthworms,thus increasing the concentration of PCNB in earthworms.In the past,most of the researches related to the influence and mechanism of nano particles on the transfer and transformation of organic pollutants in the environment-plant system and the bioavailability in the environment focusd on the hydroponic experiment or the water environment.This experiment innovatively simulated the transfer and transformation of pesticides under the actual planting conditions(soil planting).The scientific significance of this study are the two following aspects:(1)To explore the influence of nanoparticles on pesticide accumulation in plants and earthworms,and to reveal the mechanism of nanoparticles on bioavailability of pesticides in soil.(2)The relationship between the concentration of nanoparticles and pesticides in plants and earthworms was established to provide a novel insight for the comprehensive assessment of binary compound pollutants in the environment.