| Mercyry is known as a toxic and unessential element. Different forms of inorganic Hg that released into water, they will be occur to transfer and transform in the middle of water, sediments and organism and so on, under certain conditions, be converted into MeHg, which is an organic Hg form and is more toxic than inorganic Hg. The organic Hg is accumulated by biota owing to its lipophilic and protein-binding properties and eventually enters the human body through food chains.Therefore, Hg-contaminations from lake pose increasing environmental concerns worldwide.Generally, the mercury concentration in natural water is very low, at the level of 10-9 or 10-12 g.L-1, which makes it difficult to determine exactly. Now, mercury concentrations in national study is only mensurated to ng level, some form mercury can not be determined. And sample quantity is very large in enchiment. This study applied to advanced mercury analysis technique in home and aborad, which afford guarantee for study.As the State Nature Reserve Area, Caohai is one of the largest freshwater lake in Guizhou province. Which has suffered drain project many times since 1958. The main mercury contamination include: industry and the waste residue from refine zinc furnace and so on. But refine zinc furnace let gaseous mercury to atmosphere, which can remote transportation along with airflow and enter into hydrophily-zoology through dry and humid sedimentation, so refine zinc furnace is liked to picking up mercury pollution in Caohai. For making clear contaminated status, the samples is collected from October in 2005 to May in 2006, the samples are include: surface water, layered water, sediments and rainwater. The determined concentrations are include: total mercury, dissolve mercury, particulate mercury, reactive mercury and methylmercury, dissolve methylmercury, particulate methylmercury in water; dissolve mercury and dissolve methylmercury in pore water; total mercury, methylmercury and organic substance in sediments etc. The anlysis methods include: twi-gold-mercury-cold-atom fluorescence spectrum, dissllation-ethylation combined with gas chromatography(GC)-cold vapor atomic fluorescence spectrometer(CVAFS), aqua regia digestion compined with cold vapor atomic fluorescence spectrometer, extraction-ethylation combined with gas chromatography(GC)-cold vapor atomic fluorescence spectrometer(CVAFS), potassium dichromate method and so on. This thesis analyzed the relation of different species mercury, and the effects is discussed of organic substance to methylmerculy. And the diffuse flux is estimated on water-sediment interface. The detailed studies reported in this thesis, some main conclusions were obtained as follows:1. Now, the concentrations of total mercury in surface water were higher than those reported about other undisturbed rivers in North American and Europe, which indicated that Caohai contaminated in terms of mercury in a certain extent. The average concentrations and ranges respectively in surface water were: total mercury was 5.3ng.L-1 and 0.25ng.L-1; dissolve mercury was 3.9ng.L-1, 0.80～6.7ng.L-1; particulate mercury was 1.4ng.L-1, 0.40～3.lng.L-1; reactive mercury was 0.58ng.L-1, 0.06～1.4ng.L-1; total metylmercury was 0.25ng.L-1, 0.11～0.67ng.L-1; dissolve methylmercury was 0.23ng.L-1, 0.07～0.48ng.L-1; particulate methylmercury was 0.05ng.L-1, 0.02～0.26ng.L-1. respectively.The seasonal variety of total mercury and total methylmercury were attributed to rainfall diversification.2. The concentrations of dissolve mercury and particulate mercury in Caohai surface freshwater were evidently correlated with total mercury, it shows that dissolve mercury and particulate mercury are possess on stability characteristic; reactive mercury and dissolve organic carbon were not associated with dissolve mercury, it shows that reactive mercury is difficulty to changing methylmercury; The common effects debased the concentrations of available mercury, and reduced the latency harm to hydrophily-zoology.3. The concentrations of total mercury in Caohai sediment which were higher compared to data reported inother uncontaminated lake, total mercury ranges and average concentrations were 762.7ng.g-1～1014.7ng.g-1, 876.2ng.g-1 respectively; which was higher compared to data reported in other uncontaminated lake(10～35 ng.g-1) and it shows that Caohai lake contaminated in terms of mercury in sediments, the total mercury concentrations were not obvious in terms of space and seasonal variety. Total methylmercury ranges and average concentrations in the whole sediments were 1.1ng.g-1 respectively, the concentrations of methylmercury occurred obviously seasonal variety, higher flux period was higer than low flux period; The methylmercury proportion of mercury was much lower than estuary, ocean and aha lake and hongfeng lake in the same background area, which related to organic substance and hydrophyte.4. Obviously seasonal changes of total mercury and methylmercury in pore water were obtained during the sampling periods, the concentration of inorganic mercury and methylmercury in high flow period were higher than that in low flow period. The main reason was relate to organic substance; The total mercury variety of concentration grads in pore water was not obviouse, but the diversity of distribution is great, the peak value in 10 centimeter, hypo-peak arised in the base sometimes, it may be connect to organic substance and S2-. The methylmercury in pore water column were evidently correlated to that of the sediment(high flow period, r=0.589** n=39, p<0.01; low flow period, r=0.489**, n=40 p<0.01). The diffuse flux was lower to aha lake and hongfeng lake in the same background area, which was effected on organic substance and oxidation condition.
|
PDF Full Text Request