The Translocation And Biotransformation Process Of Short Chain Chlorinated Paraffins In Pumpkin And Soybean Seedlings

Emerging persistent organic pollutants,short chain chlorinated paraffins(SCCPs),are complex mixtures of n-chloroalkanes with characteristics of long-range environmental migration,persistence,bioaccumulation and high biotoxicity.At the eighth meeting of the Stockholm Convention on Persistent Organic Pollutants in the year of 2017,SCCPs were included in the list of controlled POPs in Annex A into the Convention.Plants,as the producers of ecosystems,play an important role in the environmental fate and geochemical cycles of various organic pollutants.However,the knowledge about the interaction between plants and SCCPs is very limited till now.Pumpkin has a high enrichment capacity for many organic pollutants such as PBDEs and DDT.Soybean has also been reported to be able to absorb and translocate chlordane,chlorobenzene and 8:2 fluorotelomer alcohol.Therefore,in this study,pumpkin(Cucurbita maxima x C.moschata)and soybean(Glycine max L.Merrill)were selected as the model plants.The absorption,translocation and biotransformation of SCCPs in different plants were studied by a relatively simple hydroponic exposure system.The main contents are as follows:(1)SCCPs can be absorbed by soybean and pumpkin seedlings through roots and leaves,and translocate within plants.The bi-directional translocation includes translocation from the roots to the leaves and from the leaves to the roots.In the exposusre group,the SCCPs were absorbed through the roots.The translocation from roots upwards to the stems and leaves was dominant,and the SCCPs can be emitted into the atmosphere through the stomata.While in the blank controls,airborne SCCPs were absorbed by stem and leave.The translocation down to the roots was predominant.In pumpkin plants,the amount of parent chemicals acculumated in roots were largest,which was larger than 23%.(2)The uptake,translocation and phytovolatilization of SCCPs in soybean and pumpkin plants were affected by the carbon chain length and the number of chlorine atoms.When SCCPs contain the same number of carbon atoms,the content and velocity of the SCCPs accumulated in the plants increased with the increasing of the number of chlorine atoms.When the SCCPs contained the same number of chlorine atoms,the accumulation increased with the increasing number of carbon atoms.The SCCP congeners with shorter carbon chain length and less chlorine atoms were more easily translocated within plants and phtovolatilized,as well as tend to stay in the air.(3)It was found that the high chlorinated SCCP congeners could be dechlorinated to the low chlorinated congener mediated by the pumpkin and soybean seedlings.The chlorine atom rearrangement and the carbon chain cleavage process of SCCPs were also found in the pumpkins and soybeans.(4)The abilities of different plant species to translocate and transform SCCPs are different.The soybean has significantly weaker translocation ability for SCCPs than that of pumpkin,but has significantly higher biotransformation ability for SCCPs.This work studied on the environmental behaviors of SCCPs in intact plants for the first time,and provided important results for understanding the fate,the environmental and health risk of SCCPs in the ecosystems.