| In the paper the status of eutrophication and countermeasures in Songhua Lake, which is an important lake in Jilin Province, were studied. The conception of eutrophication and several contented theories were introduced, as well as the eutrophication status in lakes in and abroad and the harmfulness of eutrophication. Otherwise, the development in eutrophication researches was particularly introduced. Nowadays, the main control methods of eutrophication abroad were nutrients countermeasures, lake sediments countermeasures, aquatic organism countermeasures and some other ones. The nutrients countermeasures included chemical coagulation sedimentation, dilution and bath, and selective drainage. The lake sediments countermeasures included digging, lake sediments treatment and bottom layers aeration. While the aquatic organism countermeasures including organism removal countermeasures whole lake aeration. Lots of researches and investigations have showed that the status of eutrophication had been worse and worse in China. At the mean time, the effects were not contented. The main causes were complicated, including wide nutrients sources, the difference of nutrients controlled standard between rivers and lakes and the complicated water treatment techniques as well.In this paper the importance and ways to study on the Songhua Lake were discussed. Firstly, the status of eutrophication in Songhua Lake was studied. According to the inspected data from Jilin province environment inspect center from 2000 to 2003 and regulate of eutrophication techniques, we selected the typical monitoring spots and data. The selected five monitoring spots are Dafengman, Shashihu, Huifahekou, Huashulinzi and Xiaohuangdi. Secondly, the analysis and assessment of eutrophication were carried on. In the study, according to the regulate of eutrophication techniques, six indexes were selected as the assessment parameters, which were SD (secchi disc), DO (dissolved oxygen), permanganate index, TN(total nitrogen), TP(total phosphorus) and chlorophyll. We have carried out four contrastive analyzes which were the contrastive analyzes of certain months in each monitoring spots, each monitoring spots in each year, certain months of five monitoring spots. Then calculating with the corrected Casson index method, we gained the TLI lists of certain months of each monitoring spots from 2001-2003 and the average annual TLI of 2002 and 2003. 51.4454 in 2002,and 47.6776 in 2003. Then, according to the classification method and standard of nation environment center, we assessed the lake eutrophication of each year with the result that it was mesotrophication in 2001, light eutrophication in 2002, and mesotrophication in 2003. Above all, we gained the dynamic change by and large.Based on the dynamic change of eutrophication from 2001 to 2003, the causes of eutrophication in the Songhua Lake were analyzed. The results indicated that the main reason to the eutrophication in Songhua Lake was due to the nutrient materials input resulted from human activities. The analyze showed that the sources of nutrient were the fertilizer losing from farmland, dejecta discharge of livestock in breeding industry, urban and rural sewerage from daily living and industry, the release of N and P from sediment and the impact of aquiculture. All of the sources above, the leakage of fertilizer that contains phosphorus was an important factor, so much as the most important. In another hand, the main limiting factors of eutrophication were the climate situation and the fluidity of the Songhua Lake. However, the limiting factors of nutrient were not clearly revealed.With the reference of the previous information, we found the conclusion that the Songhua Lake had experienced the periods from oligotrophic, mesotrophication to light eutrophication. Before 2002, the manage departments paid little attention to the eutrophication control, for there was no eutrophication phenomena in the Songhua lake. However, it was at the edge of eutrophication that the Songhua Lake was. And... |
