Speciation Analysis Of Mercury And Evaluation Of Mercury Environmental Pollutions

Abstract: This thesis includes two parts: review and experiment report.In the review section, the characters, the applications of the mercury and the sources of mercury pollution were introduced. The status of mercury pollution, the effects of mercury on human health and how to prevent and cure the mercury pollution were well documented. Then the analytical methods of total mercury, the speciation analysis of mercury were extensively presented.In the second section, a historical site near Xi'an, Qinshihuang Mausoleum, in Shaanxi province, China and a mill of batteries in Xining, Qinghai province, China were selected to study the effects of ancient and modem human activities on mercury in the natural environment. For Qinshihuang Mausoleum, we studied the distribution and transfer of total mercury in the soil and pomegranate samples collected over and away the burial mound of the Qinshihuang Mausoleum. The study confirmed the records that element mercury was mechanically pumped into the Underground Palace to create the image of flowing rivers. For the nearby area of a mill of batteries in Xining city, we assessed the extent of the mercury contamination of the soil and sediment samples (caused by direct discharge of mercury from the mill of batteries) collected in the vicinity of the mill of batteries. In addition, the sequential selective extraction (SSE) method was used to study the bioavailability and the potential mobility of mercury in soil and sediments. At last, feasible recommendation on how to improve the environmental management of areas in the vicinity of the mill of batteries is proposed. Through the detailed studies reported in this thesis, some main conclusions as follows:1. An abnormal district for mercury over the burial mound of the Qinshihuang Mausoleum was found, and the total mercury values ranged from 91.4～2204 ng/g. The maximum value of 2204 ng/g was 40 times higher than that in the samples collected in the garden far away from the Qinshihuang Mausoleum. Compared with the values observed in forest soil and in the industrial and alluvial soil as well as those in the soil collected in the multi-places in the world, the values observed over the burial mound suggest that the mercury buried thousands years ago in the Underground Palace of the Qinshihuang Mausoleum might still act as a point source of mercury pollution. So we can conclude that the recordation that there was lots of mercury buried in the Qinshihuang Mausoleum was reliable.2. The total mercury concentrations in the pomegranate samples collected over th burial mound of the Qinshihuang Mausoleum ranged from 0.22 to 1.74 ng/g (wet weight) with an average value of 1.09 ng/g. The total concentrations of mercury in the flesh and peel samples, ranged from 0.03 to 0.62 and 0.19 to 1.16 ng/g, respectively. The mercury levels in the flesh (fruit" portion) were generally lower than those in the peel (which is used as a traditional medicine). Although the total mercury concentrations in the pomegranates collected around the center of the burial mound were about two times higher than those observed in the northwest garden and the southeast garden, these values were much lower than the maximum value of 20 ng/g recommended by the Chinese National Standard Agency for food sources. So we can conclude that the mercury buried in the Mausoleum did not pollute the pomegranates grown over the burial mound of the Qinshihuang Mausoleum.3. All the soil samples collected in the nearby area of a mill of batteries in Xining were found to have very high total mercury concentrations ranged from 404 - 5669 ng/g. High values occurred in the near of the mill of batteries, and the maximum value of 5669 ng/g exceeded the soil environmental quality standards of 0.15 mg/kg in China. The lower concentrations of total mercury in the rest soil samples the more far away from the the mill of batteries. The values were 646 and 404 ng/g, respectively. But these values still exceeded the soil environmental quality standards of 0.005 - 0.3 mg/kg in the world and the contents of mercury (0.03 mg/kg) in the earth's crust. Compared these values above we can concluded that the nearby area of a mill of batteries in Xining city was seriously mercury polluted. The total mercury concentrations in the sediment samples collected in the trench of the waste water of the mill of batteries in Xining city ranged from 49.4 to 425.4 ng/g with an average value of 179.3 ng/g, and was at the level of seriously contaminated for mercury, and the special distribution of total mercury was anomalous.4. A five-step sequential selective extraction (SSE) procedure was used to study the bioavailability of mercury in the soil and sediments collected in the nearby area of a mill of batteries in Xining city. The results showed that the mercury in soil existed mainly as element mercury and mercury sulfide, which accounted for 45.2% and 39.4% of the total mercury, respectively. The values of water soluble mercury and human stomach acid soluble mercury were very low, which can be ignored. Although the exchangeable mercury accounted a low percent in the total mercury, it ran the highest risk because it could easily enter into the aquatic system and accumulate in organism. The mercury in surface sediment existed mainly as element mercury, while in the section sediment the mercury existed mainly as mercury sulfide. Moreover, changes in environmental conditions, such as acidification or redox potential, can cause mercury mobilization from the solid to the liquid phase and favour the contamination of the surrounding waters. So we should pay more attention for the mercury pollution of the sediment.