| 其他摘要 | Abstract: Mercury is known as a toxic and nonessential heavy metallic element, which can be transported over the global scale. The transport of mercury in the atmosphere plays a vital role in the biogeochemistry of mercury in the environment. In the late 1980s and early 1990s, long-range transport of mercury in the atmosphere had caused serious mercury pollution problems in fishes from lakes in Northern Europe and Northern America, in which there were no anthropogenic and natural emission sources. China is regarded as the largest mercury emission source in the world and this probably result in the high level of mercury species in the atmosphere and high deposition flux of mercury. However, there is still a less of long-term observations of atmospheric mercury species and deposition fluxes, to our best knowledge, have been made in China.
During May 2005 and May 2007, measurements of total gaseous mercury (TGM), reactive gaseous mercury (RGM), and total particulate mercury (TPM) were carried out in Mt. Gongga area by using an automatic and high time resolution atmospheric mercury analyzer, KCl coated denuders, and Mini particulate matters sampling traps, respectively. Moreover, precipitation samples, foliar leaves, and stream-water samples were also collected in Mt. Gongga area, to study mercury deposition fluxes and elucidate the input and output of mercury in this upland area. Some conclusions are as follows:
（1） The two-year concentrations of total gaseous mercury in the Mt. Gongga atmospheric baseline station were averaged to be 3.94±1.16 ng m-3, and this value is much higher than those observed from remote areas in Europe and Northern America, but it is comparable to those observation results in the remote areas in Asia. The TGM concentration in Mt. Gongga area is much lower than those observed from some urban areas in China, but it is slightly higher than the result obtained in Mt. Changbai. The distribution of TGM in ambient air in Mt. Gongga suggests the air in China and even Asia are mercury polluted because of anthropogenic emissions.
（2） Average RGM and TPM concentrations in Mt. Gongga were 6.2±3.9 and 30.7±32.1 pg m-3, respectively. The RGM and TPM concentration in Mt. Gongga area are quite consistent with those observed from remote areas in other countries, and this differs significantly with the distribution of TGM. Higher deposition fluxes and restricted transport ability of RGM and TPM were the main reasons attributed to the lower RGM and TPM concentrations in this area.
（3） TGM concentrations showed a clear spatial distribution pattern on the descending order: urban areas (8.63~22.5 ng m-3) >towns (4.74 ng m-3) >villages (2.55~8.83ng m-3) >regional background sites (1.65~3.57 ng m-3), and TGM concentrations in these four environmental function zones especially in heating season were all elevated compared to the global average TGM concentration in remote areas.
（4） Great anthropogenic emissions in Southwestern China contributed significantly to the elevated atmospheric concentrations in Mt. Gongga area. Besides, regional emission sources including non-ferrous metal smelting activities, human activities in some population centers (eg. Urban areas) also played important roles.
（5） Total gaseous mercury and total particulate mercury showed a remarkable seasonal distribution pattern: winter, autumn, spring, and summer, listed in the descending order; while reactive gaseous mercury was observed on the descending order of spring, autumn, summer, and winter. Seasonal variations of emission sources, meteorological parameters especially wind direction, photochemical reactions, and dry deposition velocity of atmospheric mercury played important roles in the seasonal variations of TGM and TPM in ambient air; while the seasonal distribution of RGM in ambient air might be attributed to the seasonal variations of photochemical reactions and wet scavenge processes.
（6） The wet deposition fluxes of mercury in Mt. Gongga area at 1600 and 3000 meters above sea level were 9.1 and 26.1 μg m-2 yr-1, respectively, and wet deposition flux in forest ecosystem reached 57.0 μg m-2 yr-1. Average dry deposition flux of mercury was calculated to be 51.9 μg m-2 yr-1, and 15.9 μg m-2 yr-1 of which was attributed to the mercury deposition of litterfall.
（7） Mt. Gongga area acted as a great sink of atmospheric mercury, and the annual deposition flux of mercury in Luding County reached about 142 kg. Moreover, most (more than 95%) of the deposited mercury from atmosphere entered into forest ecosystem, while output and input of mercury in deforested area in Luding County were just balanced. |
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