| The broad-spectrum antibacterial properties of silver nanoparticles(AgNPs)have promoted the rapid development of AgNPs products.The large-scale use of AgNPs related products will cause them inevitably enter to the ecological environment.In view of the fact that terrestrial invertebrates are important primary consumers in terrestrial ecosystems,their uptake,accumulation and toxicity response to AgNPs have become issues worthy of attention.Soil exposure and food exposure are the main pathways for AgNPs to enter terrestrial invertebrates,but the current biological effects of AgNPs on terrestrial invertebrates are mostly focused on food exposure,and there are few studies on soil exposure.In this thesis we investigated the distribution and accumulation of AgNPs in various tissues of snails,the kinetics of uptake and elimination of AgNPs and snail toxicity response(the growth,oxidative damage and histopathological damage)under soil exposure and food exposure.We found the toxic effects of the exposure pathway and Agforms on snails,which were expected to provide basic data for assessing the ecological risks of AgNPs.The main conclusions were as follows:(1)The exposure pathway of AgNPs has a certain impact on the growth of snails.After exposure to 100 mg kg-1AgNPs for 14 days,the fresh weight of the snails under soil exposure increased significantly(12.5%,p<0.05),but the weight of snails under food exposure did not change significantly(p>0.05),reflecting the inhibition effect of AgNPs on snail growth under food exposure.(2)The exposure pathway significantly affected the absorption and accumulation of Agby snail tissues.Under the same Agconcentration,the Agtranslocation factor in the food exposure was significantly higher than that in the soil exposure group(AgNPs:0.13±0.009 vs.0.089±0.009,Ag+:0.33±0.044 vs.0.17±0.03).The low bioavailability of AgNPs in soil exposure might be due to the low dissolution rate of AgNPs in the soil(0.009-0.301%)and low concentration of free Ag+.Regardless of exposure pathway,AgNPs mainly accumulated in the gastrointestinal tract(3.0-99.9mg kg-1),followed by the digestive gland(0.7-23.7 mg kg-1)and kidney(1.7-33.8 mg kg-1),and in the foot(1.5-9.8 mg kg-1).According to the analysis of uptake and elimination kinetics of AgNPs,the uptake rate of food-phase AgNPs in the gastrointestinal tract of snails was 7.1 mg kg-1 d-1,and the elimination rate was 6.7 mg kg-1 d-1,which was 1.6 times and 0.5 times than that of the soil exposure group,respectively,indicating that food exposure of AgNPs was more likely to cause the accumulation of Agin snails.(3)The exposure pathway significantly affected the toxic response of snails.The toxicity of the food exposure was greater than that of the soil exposure.At the same AgNPs concentration,food exposure resulted the significant increased of LPO levels,CAT and SOD activities in the digestive glands of snails,which were 1.5,1.7 and 2.5times that of the soil exposure group,respectively.In addition,through histopathological analysis,in the food exposre group,the gastrointestinal tract of the snail showed obvious mucosal damage,cell death and shedding,partial cells of kidney tissue necrosis,digestive tubules loosely arranged,part of basement membrane damaged,and part of tissue cells eroded and shed. |
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