| Mercury is a global pollutant. Hg0 is the predominant form of atmospheric Hg, which has a long residence time in the atmosphere from 0.5 to 2 years. The global cycle of mercury is controlled by the atmospheric circumfluence and it can be transported to everywhere on the earth. Recently the concentration of global atmospheric mercury is increasing and mercury pollution continues to increase. Thereby, the global releasing of mercury causes more and more attention.This research was studied in the Jiaozhou Bay. The mercury and the other heavy metasl in seawater were investigated to learn the pollution level of metals. The species of mercury and their diunal variances were studied. The sea-air flux of mercury was measured and estimated using model, thus the influencing factors and machenism were analyzed further.The results indicate that:In October 2008 the average content of particulate mercury was 146.9ng/L and dissolved mercury was 15.8ng/L, so the particulate mercury was the main form. The content of As, Cu and Cd was lower, and the polution of Pb was serious.The average ratio of the reactive mercury to dissolved mercury was about 0.50. The variation range of methylmercury concentration on November 19th was small compared with December 22nd. The concentration peaks occured at about 14:00. The methylmercury concentration changes little within 2.5m depth, and the concentration is higher at the bottom. At the day time, the concentration of DGM decreased after the sunrise on November 19th; however on December 22nd it increased at first and then decreased. The DGM concentration correlated with the reactive mercury/dissolved mercury significantly (P<0.01), and DGM had negative correlation with DOC, but not significant. The significant positive correlation (P<0.05) with UV radiation indicated that photoreduction played a crucial role in the formation of DGM. The profile distributions of DGM changed obviously and the concentration was higher at the bottom.The flux of mercury from the seawater to the atmosphere was-0.78-1.72ng/(m2·h) measured at field and the average was 0.26ng/(m2·h) on November 19th, which showed obvious bimodal diurnal variations. The small peak occoured after sunrise and the second appeared at 11:10. There was evasion of mercury from the water to the atmosphere before 14:00 and after 14:00 the emission was small or negative. The estimated emission flux of mercury on the same day using a gas exchange model was 0.14-1.52ng/(m2-h), which had similar diurnal variation characteristics and has highly significant correlation (P<0.01) with the field result. The average flux modeled was 0.63ng/(m2-h). On December 22nd, the modeled sea-air flux was 0.23-2.26ng/(m2-h), and the average was 0.85ng/(m2-h), which increased at first and then decreased.The UV radiation affected the emission flux by influencing the concentration gradient of sea-air and, it was a major factor. The temperature of surface water and wind speed affected the emission flux by influencing the transfer velocity (K) of DGM. |
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