Accumulation Of Silver Nanoparticles In Soybean And Its Risk Assessment In The Food Chain

With the widespread use of AgNP in consumer products,their release into the environment is unavoidable.The release of AgNP would have potential risks on biologys.Therefore we have the necessity to research the environmental behavior of exposure to AgNPs.In this study,we synthesized the stable and monodispersed AgNP;the effects of AgNP on soybean in the process of photosystem Ⅱ,and the bioaccumulation and translocation of AgNP on soybean by different exposure pathway were investigated.Then we studied the trophic transfer behavior of AgNP in the food chain transfer of lettuce-snail,the accumulation of AgNP of waterborne exposure,and based on these results,the biodynamic modeling was established.In addition,the exposure experiments of 109 AgNP and Ag2S-NPs were carried out.The main research results are shown as follows:(1)Soybean was exposured to AgNP and AgNO3 of hydroponics,and the concentration were 0,1,5,10 mg·L-1 and 0,0.1,0.5,1 mg·L-1 respectilely.The effects of AgNP and AgNO3 on soybean biomass were determined;The effects of AgNP and AgNO3 on photosystem Ⅱ(PSⅡ)activity of soybean were analyzed by chlorophyll fluorometer;The content of chlorophyll was determined by spectrophotometry.The results showed that the aboveground and underground biomass of high concentration AgNP and AgNO3 treatment were reduced 36.8%,40.5% and 32.8%,36.6% than that of control,respectively;chlorophyll a and chlorophyll b of high concentration AgNP and AgNO3 treatment were reduced 25.2%,22.8% and31.5%,23.3%,respectively.Meanwhile,the efficiency of PS II and the reaction center density were decreased by AgNP and AgNO3 exposured.(2)We investigated the bioaccumulation and translocation of AgNP on soybeans(Glycine max L.xudou16)by foliar,root and their combined exposure pathway.results showed that the accumulation of total silver of new leaves were 0.06-1.03 μg·g-1,and the accumulation of total silver of roots were 1.07-1.47 μg·g-1 by foliar exposure pathway.These results demonstrated that AgNP could be taken up and translocated within soybean.Furthermore,the transfer efficient of AgNP with foliar exposure was lower than that with root exposure(0.002 vs.0.28);as with all exposure route,the transfer efficient of AgNO3 exposure was higher than that of AgNP exposure(0.002-0.28 vs.0.011-0.71).So in addition to the influence of exposure pathway,the forms of Ag(i.e.AgNP or AgNO3)also affected the accumulation of Ag in soybean leaves.Therefore,when assessing the risk of Ag on the growth of crops,we should consider the exposure pathway and the forms of Ag.(3)The bioaccumulation in snails after dietborne and waterborne exposure was investigated.The results showed that the assimilation efficiencies of Ag NP and Ag NO3 were 73.3% and 76%,respectively;Food ingestion rates were 0.11 ± 0.03 g·g-1·d-1 and 0.07 ± 0.02 g·g-1·d-1 for AgNP and AgNO3 treatment.For snails of waterborne exposure,the uptake rate constant from water for AgNP treatment was much lower than that of AgNO3(2 ×10-4 vs.0.12 L·g-1·d-1).The biodynamic modeling were established on the basis of dietborne and waterborne exposure,and the model showed that dietary uptake was the dominant uptake pathway for AgNP in most circumstances(Rfood>90%),and there may have some potential risk of food chain transfer in the terrestrial ecosystem.(4)Soybean exposured the same concentration of foliar exposure(0.2 mg·L-1)of 109 AgNP and at the same time by different concentrations(10,20,50 mg·L-1)of root exposure of Ag2S-NPs.The accumulation of 109 Ag and 107 Ag in different parts of soybean were calculated,investigated the relative contribution of foliar exposure and root exposure to AgNP accumulation in plants.Then we deigned the leaves of high concentration treatment as food to feed snails.Results showed that the ratio of 109 Ag were 90.9 to 95% in the foliar exposed leaves,and 28.4 to 43.9% in the unexposed leaves,however,the ratio of 109 Ag was 3% in the roots.Transfer efficiency showed that the 107 Ag by root exposed mainly accumulated in the roots,and the 109 Ag by foliar exposed mainly transferred to the underground.The ratio of 107 Ag changed from 79.0% to 71.6% in the food chain,which indicated 107 Ag had more advantages in the transmission process.