| In recent years, most of the lakes and reservoirs in China have been seriously polluted, and then, eutrophication is one of the most serious pollution of type in water, which is formed by the factors such as physical, chemical and biological factors. The sediment is a very important role in the carrier of the pollutant, and has a collection of nitrogen and phosphorus in the water body. Nutrients in the sediment will be released into the overlying water, causing the second pollution of the lake reservoir when some conditions of the water body change. Because the sediment of lake and reservoir has good continuity, large information, and good stability and so on, the distribution law can reflect the living environment and climate characteristics of the surrounding residents to a certain extent. We decided to study on the vertical profile in Beidagang Reservoir Sediment and collected 10 the sediment profile samples which are about 30cm. First of all, the collected samples were treated by dehydration, and the vertical variation of the water content of the sediment was calculated; Then, by comparing and analyzing the contents of organic matter (OM) in Beidagang Reservoir Sediment, find its source and pollution degree, and then further research the vertical space distribution characteristics of organic matter in sediments. Next, the object is to understanding eutrophication status (mainly including surface contents of TN and TP) in Beidagang Reservoir Sediment, study the vertical distribution characteristics of the TN and TP, and then sum up the changing trend of nutrition. Ultimately, it is one of the most important messages for studying features about Beidagang Reservoir Sediment that on the basis of arrangement for experimental data, analysis whether there is a relationship between TOC, TN and TP in Beidagang Reservoir Sediment Core profiles,and calculate columnar sediment C/N, C/P and N/P ratio of columnar sediment, to find the main source of TOC, TN and TP in the region. In addition, an conjoint analysis method that are C/N with δ13C、δ15N was used to estimate the main source of organic in this article, and provide a theoretical basis for improving the ecological environment in the lakes or reservoir. The mainly research results are as follows:(1) Vertical distribution characteristics of the water content in Beidagang Reservoir Sediment.The result of experiment about moisture content is that its overall trend is decrease with the increase of depth and this change is very obvious, moisture content were 53.04,44.4438.10,32.48,29.39,28.08,29.43,27.78,26.65,25.61,24.32,22.38, 2.168,22.65 from 0 cm to 28cm deep and in 0-10cm depth, the changes are significantly, however below the depth of 10 cm, the decrease trend are slowly. In the hand of appearance characteristic, surface sediment presents grey flow plastic outward and high water content. With the increase of the depth, sediments gradually become firm and moisture content decreased, the color is also gradually from deep to shallow.(2)Distribution of TOC(Total organic carbon) in Beidagang Reservoir SedimentThe average content of TOC in the surface sediments of Beidagang Reservoir was 3.678%, and the organic pollution index value was 0.76 by calculation of organic pollution index formula. It was a negative result that the pollution level belong to four grade (because the number 0.76≥0.50). There was obvious characteristic about TOC in vertical direction. The overall change trend was decreasing with depth. In addition, the decrease of the content of the 0-10cm in the range of 10cm depth was significantly greater than the following.(3)Distribution characteristics of nutrient salts (TN and TP) in Beidagang Reservoir SedimentThe average contents of TP and TN in surface sediment of Beidagang Reservoir Sediment were 0.296% and 0.545%, respectively, and the content of organic nitrogen was significantly higher than that of 0.133, According to the classification of organic nitrogen evaluation and classification standard, the content of organic nitrogen (TN) is grade IV organic nitrogen pollution. Through the analysis of content TN and TN in the Beidagang Reservoir, the results showed that the water quality has been eutrophic, compared with our other lakes and reservoirs in nutrient levels, was still in good condition relatively. Similar to the vertical change trend of TOC, the change of the content of nutrient salt in the Beidagang reservoir sediment was decreased with the increase of depth. The change trend of TN was obvious, and the decrease trend in the range of 0-10cm depth was faster than that of 10 cm below. For TP, even though the trend of change was large, it still showed that the change direction was similar to TN and TOC.(4) Assessement of pollution levels about organic matter and nutritive salt in sediments of Beidagang reservoirExperimental results show that organic index is higher than 0.50, and belong to IV level pollution. The content of organic matter in the Beidagang reservoir sediment has exceeded. Besides, the nitrogen content is 0.296%, greater than 0.133%, and is IV level pollution drown by grading standards of organic nitrogen contamination evaluation in sediments. Compared with organic and nitrogen, content of phosphorus element is in a moderate level of pollution. Overall view, Beidagang reservoir has been polluted at a certain degree.(5)Analysis on the relationship between organic matter and nutrient in the column sediments of Beidagang reservoirIn the vertical distribution, the total organic carbon (TOC) and total nitrogen (TN) showed a significant relationship. Through the SPSS data analysis method, the results showed that the correlation equation isy= 13.44x - 0.199, and the correlation coefficient is 0.977. In other words, TOC and TN have significant correlation. However, there was no significant correlation between the total organic carbon and total phosphorus, which indicates that the phosphorus in the sediments of the Beidagang reservoir is mainly from resource of pollution, but the release of organic matter only accounts for a small proportion, at the same time, Total nitrogen and total phosphorus results (no correlation) showed that there were different sources of nitrogen and phosphorus. The reason may be that the organic matter and total nitrogen content is homologous, and then nitrogen is mainly generated by the release of organic matter. Yet the source is more complex for phosphorus. The contents of various nutritional elements in the sediments of different sampling points in the Beidagang reservoir were little changed. Details are as follows. C/N ratio was in the range of 11.000-13.432, average value 12.388. according to the size of the C/N ratio can be the main source of nutrients in determination of Beidagang Reservoir is algae; C/P ratio and N/P value range of variation were 4.935-24.182,0.401-1.892, the average value respectively 9.528,0.775, the C/P value changes greatly, even though the evaluation of the results of the ratio C/P and N/P haven’t unified standard, it also reflects the regional sources of pollution and the absorption characteristics of the transformation from another aspect in Beidagang Reservoir.(6) Distribution characteristics of δ13C and δ15 in Beidagang Reservoir SedimentThe method of use of C/N and δ13C、 δ15N can be more accurate to determine the source of organic matter in sediment. And by this experiment test, the figures marked that variation range of δ13C value is between-15.5‰ and-24.8‰, and the average value is (-21.1±2.2)‰. At the same time, the variation tend of δ15N is similar to δ13C, and the δ13N value is between-1.9‰ and 3.1‰, and the average value is(1.5±1.1)‰. According to the numerical characteristics, preliminary judgment is that the source of δ13C and δ15N in organic matter are stable. The source of organic is mixed type. On the one hand, the organic matter is from terrestrial soil organic matter, on the other hand, from hydroplankton in Reservoir.(7)Significance of organic carbon, nitrogen and phosphorus in sediment on the environmentThe rapid increase of population and the rapid development of industry and agriculture in modern times is mainly reason for eutrophication. The rapid aggravate of these aspects release a large number of pollutants to the different environmental media, in-depth understanding of the environmental behavior of pollutants is imminent. In a way, studying the vertical distribution of sediment organic carbon and nutrients and their relationship not only can provide a theoretical basis for human prevention and control of water pollution, can also help us to deeply understand the earth between different medium water environmental behavior. In addition, eutrophication is need to experience a long time evolution process, and the vertical distribution of the sediment can be used as a means of environmental records to provide strong evidence for the accumulation of nutrients in the water body. |
PDF Full Text Request