Study On The Toxicity Of Soil Polluted With Halogenated Flame Retardants And Cadmium To Rice Seedlings

With the wide-scale application of flame retardants tetrabromobisphenol A(TBBPA),dechlorane plus(DP)and the original extensive electronic disassembly activities in China for a long time,the heavy metal Cd,DP and TBBPA are seriously polluted in the soil environment of China's typical e-waste dismantling site.The impact of residues in the soil on crops and the soil ecological environment has attracted much attention.In this study,higher plant rice was used as the test organism and two varieties of Guosetianxiang No.1 and Guosetianxiang No.7were selected.Through the seed germination test and seedling pot experiment,the effects of soil polluted with DP,TBBPA and heavy metal Cd on rice seed germination,shoot and root elongation were studied.The changes of physiological and biochemical indexes during rice seed germination and seedling growth were studied,the effects of halogenated flame retardants and heavy metal cadmium on rice seed germination and seedling growth were determined.The ecotoxicity of pollutants to rice and ecological indicators of pollution were explored.Scientific evidence was provided to assess the environmental risks of composite pollution areas.The main results are as follows:1.DP has a significant dose-effect relationship on the toxicity of two types of rice.The higher of the DP concentration,the more severe of rice seed germination,root and bud growth were inhibited.Under the action of 50 mg·kg-1DP,the seed germination rate and vigor index of Guosetianxiang No.7 decreased by 16.67% and 28.82% compared with the control,respectively.The shoot length and root length inhibition rates of Guosetianxiang No.1 were38.22% and 64.02%,respectively.The vitality index of two types of rice showed a negative correlation with TBBPA concentration.The inhibition rate of root length and shoot length of Guosetianxiang No.7increased with the increase of TBBPA concentration,and the inhibition rate of shoot length of Guosetianxiang No.1 decreased with the increase of TBBPA concentration.The effect of Cd on seed germination of two rice varieties was different.The seed germination growth of Guosetianxiang No.7 increased with the increase of Cd concentration.Guosetianxiang No.1 was more sensitive to Cd at low concentrations(10 and 25 mg·kg-1)in the experimental design.2.Roots of Guosetianxiang No.1 and Guosetianxiang No.7 were more sensitive to DPand TBBPA than shoots.Roots of Guosetianxiang No.1 were more sensitive to Cd than shoots,and shoots of Guosetianxiang No.7 were more sensitive to Cd than roots.3.The two types of rice have different responses to pollutants.Guosetianxiang No.1 is more sensitive to DP than Guosetianxiang No.7 and Guosetianxiang No.1 is more resistant to Cd than Guosetianxiang No.7.4.Exposured to DP,TBBPA and Cd in the soil,two types of rice activate mechanisms to resist adversity in the body.During the germination of rice seeds,the content of proline in rice increased,and the seed root activity increased.During the growth of rice seedlings,the activity of the protection enzyme system in rice was activated,and the activities of SOD,CAT and POD of Guosetianxiang 1 significantly increased.The activities of SOD and CAT of Guosetianxiang No.7 significantly increased,and the POD activity decreased.With the increase of protective enzyme activity,the MDA content and chlorophyll content of the two types of rice increased,the two types of rice were toxic effected by the three pollutants,rice seed germination,root and shoot growthwere inhibited,membrane structure was damaged,and the level of photosynthesis was affected.5.The combined pollution of DP,TBBPA and Cd affected the germination and seedling growth process of two kinds of rice.On the whole,in the seed germination process,from the index of seed germination,seed root vitality,proline content,and protein content,the impact of the three pollutants in combined pollution is greater than that in single pollution.During the growth of seedlings,the combined effects of the three pollutants showed antagonistic effects on MDA content and chlorophyll content.6.Two kinds of rice have a certain bioaccumulation effect on Cd,the accumulation of root is greater than stem,the enrichment Cd of Guosetianxiang No.1 is greater than Guosetianxiang No.7.The combined effect with halogenated flame retardants has different effects on the enrichment capacity of two rice species,and there are differences in varieties...