| 其他摘要 | Under the influence of Himalayan movement, Yunnan-Guizhou Plateau is a special environmental unit which has great grads and complicated landforna structure. This region is influenced by Southwest monsoon and Southeast monsoon. The chemical species and compounding features of carbon, nitrogen and phosphorus in lake sediments of Yunnan-Guizhou Plateau can reflect the speciality of element geochemical cycle under this geological environmental background. So the study on the trophic elements (carbon, nitrogen, phosphorus) is helpful to the understanding in the geochemical cycle model and eco-environmental evolution characters. This paper studied the biogeochemical characters of carbon, nitrogen and phosphorus in Yangzong Lake sediments and the influence of early diagenesis on its deposit profiles. Based on the compare of three lakes, which are Yangzong Lake, Erhai Lake and Hongfeng Lake, this paper analyzes the differences of biogeochemical characters of trophic elements in sediments which is affected by early diagenetic process, and some representations of special geological background of Yunnan-Guizhou Plateau on element geochemical cycle. Based on the study of the items, the main, conclusions we have obtained are as follows: The vertical distribution of Total C and organic C in Yangzong Lake sediment profiles changes simultaneously. The average of total C is 3.15%, and organic C is 1.33～1.46%. Two stage of "decomposition - accumulation" can be observed in the organic C profile of Yangzong Lake sediment, and the visible "deposition" stage can't be found. The drastic reduction of sulfate occurred in the profile of Yangzong Lake sediments, that SCV" is the main oxidant in the process of degradation of organic matters. Some parameters of organic C in each degradation stage which is calculated by simulation based on the changes of vertical profile are: the average depositing flux is 41.2 g/cm2 a, accumulating flux is 5.98 g/cm2 a, ratio of degradation is 0.0172 a-1, and settling time is 40.2a. 3. Like the profile of organic C in Yangzong Lake sediments, the profile of organic N could be distinguished as two stages of "decomposition - accumulation". The average depositing flux of lake sediments is 4.01 g / cm2 a, accumulating flux is 0.68g / cm2 a, ratio of degradation is 0.0168 a""1 and settling time is 41.3a; In the Yangzong Lake sediments, the proportions of organic N of different forms in total N change unconspicuously. This means that each form of organic N affects the influence of diagenesis simultaneously and they don't represent the obvious difference of degradation. The three stages character of "deposition - decomposition - accumulation" is distinguished in Yangzong Lake sediment organic phosphorus. For the influence of early diagenesis, the flux of deposition of organic P is 75% of accumulation flux. Compare with organic C and organic N, the resistance of organic P is higher than other two, so more organic P saves in the sediments. 6.The content of forms of phosphorus in Yangzong Lake sediments according to the sequence from high to .low: organic P, detrital P, Fe-bound P, authigenic P and loosely adsorbed P. Organic P, detrital P, authigenic P and total P change with the same step. The content of Fe-bound phosphorus is too low to discern the obvious rule. Each organic matter profile represents degradation stage on the top of sedimental profiles and accumulation stage at the foot of the profiles. But the profile of organic phosphorus differs with profiles of organic C and organic N. Three stages are discerned in profile of organic phosphorus. Organic P is more difficult to decompose and easier to save in Yangzong Lake sediments comparing with organic C and organic N. Through the study on the relationship of Corg : N : Porg in Yangzong Lake sediments, organic matter of Yangzong Lake sediments is proved to the part of representation of influence on environment of Yunnan - Guizhou exerted by Himalayan movement: organic matters in Yangzong Lake surface sediments reflects that Yangzong Lake contains the characters of both land lake(Corg:N value is higher than Redfield value means that its organic matters come from land) and ocean(Corg:N value changes in narrow extent). |
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