Processes And Rules Of Inorganic Mercury/Methylmercury Absorption Translocation In Rice

Mercury is a heavy metal contaminant with properties of highly toxic,long-lived,long-range and globally polluting.In recent years,mercury pollution has brought potential threats to the ecological environment and human health.As one of the staple foods of our country's residents,the use of mercury-contaminated rice has become the main route of mercury exposure in our country.In this paper,the migration and transport of mercury in rice is studied.The roots exposure test,leaf exposure test,root exposure test and root overflow test were carried out on rice respectively.The experiment was carried out by means of ICP-MS,total mercury meter,MERX automatic methylmercury analyzer and X-ray fluorescence technology.The main research results are as follows:(1)It has been proved by root-expansion exposure that the concentrations of methylmercury and inorganic mercury in various tissues increases with exposure time,and the concentration of methylmercury in each tissue is greater than that of inorganic mercury,indicating that methylmercury is more easy to accumulate.The presence of methylmercury and inorganic mercury was detected in the unexposed side roots,indicating that both forms of mercury can be transported from the leaves to the roots(reverse transport).X-ray fluorescence scanning results showed that methylmercury is mainly distributed in the central column of the root,and inorganic mercury is mainly distributed in the root surface of the root,indicating that the distribution of different forms of mercury is different.(2)Experiments on root and leaf exposure of rice by different concentrations of methylmercury and inorganic mercury showed that they were transported from the leaf to the root and from the root to the leaf.The kinetic equations then tend to be flat,and the transport dynamics constants increase with increasing exposure concentrations,indicating that the transport rate constants of methylmercury and inorganic mercury are affected by the exposure concentration.At the same concentration of methylmercury and inorganic mercury,the rate constant of methylmercury is greater than inorganic mercury,indicating that methylmercury is more easily transported and accumulated.(3)The mercury content in the blank culture solution was detected in the root overflow experiment.The results showed that no methylmercury was detected in the blank culture solution of the methylmercury leaf exposure test group,but the inorganic mercury exposure group was detected,which showed that inorganic mercury can escape from the roots and methylmercury does not overflow.