Health impacts of mercury cycling in contaminated environments in China studied by nuclear techniques

In recent decades, the production and using of mercury was reduced, however, the mercury pollution and health impacts are still serious. It is because that China's economy was forging rapidly ahead in the past 20 years. The combustion of fossil fuels, in which of the coal is more than 70% in the total energy consumption, was increasing year after year, especially in some industrial cities. So a co-ordinated research project (CRP), on health impacts of mercury cycling in contaminated environments studied by nuclear techniques, has been supported by the IAEA. In the CRP that contract number is PRC-10874, some research techniques for understanding the behavior of mercury in terrestrial ecosystem were developed, and some problems about mercury pollution in terrestrial ecosystem and their impacts have been probed. The results indicated that because of the increasing of anthropogenic Hg emission, the Hg accumulation in terrestrial ecosystem was increasing with time in the research sites (Chongqing, China), which Hg in wet and dry deposition was sum 195.3 g/km2·yr in urban and 48.5 g/km2·yr in rural area. The bioaccumulation of Hg in plant was related to the concentration of atmospheric Hg and soil Hg. The Hg content of plant increased with the atmospheric Hg increasing. Hg contents in plant leaves increased with the increase of air-Hg, the correlation equation was: y 0.0173x-0.3204 Calculation from this equation showed that the accumulation of Hg in plants stemmed mainly from soil rather than atmosphere when air-Hg was lower than 18.5 ng/m3, however contribution of air-Hg to plant Hg accumulation was increasing with the increase of Air-Hg when its concentration was higher than 18.5 ng/m3. Furthermore, it was found that Hg content in some crops and livestock products had exceeded the limit of FHSV due to Hg accumulation in terrestrial ecosystem increasing gradually with the increasing Hg emission in Chongqing. It should be noted specially that the Hg concentration of milk was higher, some of it was in excess of the limit of Food Health Standard Value (FHSV) because of high Hg accumulation in forages. The investigation data of the mercury in fishpond systems in the research sites indicated that the accumulation of mercury in fishponds in polluted sites was much higher than that in control site. So the content of Hg in fish muscle in polluted sites was higher than in control site. The content of Hg in all the fish muscle in heavy pollution site exceeded the limit of FHSV for Hg in fish (0.3 mg/kg FW). The contents of mercury in muscle of fish from the Yangtze River were lower than the FHSV, but some data from the reservoirs were higher than the FHSV. All the I/O values, the ratios between the input of output of mercury in soil in vegetable land system in different acid deposition areas, in the acid deposition areas were more than 1, it means that there was accumulation of mercury in soil in the regions. The Hg content in surface soil increases average 0.567μg/kg a year in heavy pollution area, but only 0.00907μg/kg in control area. It implies that the Hg accumulated in soil more and more badly in heavy pollution area, it will influence the human health through the food chain. (author)