Pollution source investigation, ecological environment protection measures, Honghu Lake
1, preface
Honghu Lake and Changhu Lake are the two largest natural lakes in the four lakes region, with the maximum lake capacity of 65.438+200 million m3 and 600 million m3 respectively, which play a very important role in flood control and drought relief, industrial and agricultural production, people's life, environmental protection and tourism in this region. Therefore, strengthening the unified management of Honghu Lake and Changhu Lake and realizing the sustainable development and utilization of water resources are of great significance to maintaining the sustainable development of regional economy. Seriously investigate and study the current situation of pollution sources and water environment quality in the basin, analyze its pollution load, and then put forward pollution control countermeasures and ecological environment protection measures to provide technical support for the development and management of the two lakes.
2. Characteristics of water resources
2. 1 water system distribution
Honghu Lake and Changhu Lake are located in the south-central part of Hubei Province and belong to the four-lake basin. The river network in the four lakes region is interlaced and the water system is developed. The tributaries of Changhu Lake are Taihu Port, Longhuiqiao River, Shiqiao River, Guangping River and Dagang River. Honghu Lake and Changhu Lake are connected by four main canals, and the main canals are connected with Honghu Lake through four gates: the new estuary, the liukou, the sluice and the tanzikou. In addition, Beiyuan, Xiaxin River, Huangsinan, Xiaogang and other culverts control the drainage river and Neijing River into Honghu Lake respectively.
2.2 Water resources
Generally speaking, because of its special geographical location, the two lakes basin is rich in water resources. The average annual precipitation in Honghu Lake is 1.289 mm, and the average annual runoff is 2.21.600 million cubic meters. The annual average precipitation of Changhu Lake is 1007mm, and the annual average runoff is 724 million m3. As a water supply source, the water resources of the two lakes can meet the needs of various water intake functions on the whole, but there is also water shortage in particularly dry years (seasons).
3. Water environment assessment and analysis.
3. 1 water quality assessment
The water quality of Honghu Lake and Changhu Lake was evaluated by Environmental Quality Standard for Surface Water (GB3838—2002). Pollution projects take Class III standards as control standards, and projects exceeding Class III standards are over-standard projects. Honghu Lake was rated as Class IV water body, and the items exceeding the standard were permanganate index, total phosphorus, five-day biochemical oxygen demand and ammonia nitrogen. Among them, the permanganate index is a project that generally exceeds the standard in the whole Honghu Lake, and the total phosphorus in some waters exceeds the standard. Changhu Lake is rated as Class III water body, and the main items exceeding the standard are total phosphorus and ammonia nitrogen.
3.2 Eutrophication evaluation
The eutrophication status of two lakes was evaluated by scoring method. Formula: M= 1/n∑Mi, where m is the evaluation value of lake nutritional status; Mi is the fractional value of the first parameter; N is the number of evaluation parameters. The nutritional status scores of Honghu Lake and Changhu Lake are 54.9 and 49.9, respectively, and the nutritional status is moderately eutrophic.
4. Pollution source investigation
4. 1 Investigation of classified pollution sources
4. 1. 1 industrial pollution sources
Taking 200 1 as the year, there were 128 industrial enterprises in the two lake basins, discharging 38.43 million tons of industrial wastewater, of which 2 18 1 10,000 tons reached the standard. The main pollutants in industrial wastewater are: 266 13 tons of organic oxygen-consuming substances, 9 149 tons of suspended solids, 34.4 tons of petroleum, 27.8 tons of sulfide and 6.7 tons of volatile phenol/kloc-0.
4. 1.2 Agricultural pollution sources
The two lakes basin is the main grain, cotton and oil producing area in Jianghan Plain, and the agricultural pollution sources are mainly pesticides and fertilizers. In 2006, a total of 247,300 tons of chemical fertilizers were applied in the two lake basins, including 6,543,800 tons of chemical fertilizers, 55,000 tons of compound fertilizers and 22,400 tons of compound fertilizers. * * * Application of pesticides 12545 tons, organophosphorus pesticides (such as methamidophos, methyl 1605, etc. ) is mainly used.
In addition to pesticide and fertilizer pollution, agricultural aquaculture pollution is another pollution source that can not be ignored. Large-scale farming produces a lot of feces, urine and aquaculture sewage. Although 80%~85% of them have been used and most of them have been returned to the fields, there are still a lot of losses during transportation and use, and the bacteria and nutrients such as nitrogen and phosphorus contained in them will cause water pollution. Through investigation and calculation, the number of livestock and poultry in the two lakes basin is about 3 million, and there are nearly 50 million poultry. The output of feces and sewage is 6.5438+0.4 million tons and 5.65438+0.9 million tons respectively.
4. 1.3 Urban domestic pollution
The investigation of urban domestic pollution sources is mainly based on the urban population survey, and then the domestic sewage discharge and pollutant discharge are calculated according to the domestic sewage discharge coefficient (160 ~ 200kg/ person/day) and the pollutant discharge coefficient (90g/ person/day). According to the investigation, the urban population of the two lakes basin is about 6.5438+200,000, and its domestic sewage discharge is 79.73 million tons/year. The main pollutant is organic pollution, * * * 395.465.438+0 tons (calculated by CODcr).
4.2 Sewage outlet investigation
The sewage outlet along the lake is the main channel for all kinds of pollutants to enter the lake in the basin. There are three large sewage outlets around Honghu Lake, namely the main canal of Hu Si Lake, Xiaxinhe sluice and Zibeiyuan sluice. At present, the annual water output of Sanhekou is 1.375 million cubic meters, 1.654, 38+0.265 cubic meters and 1.4025 million cubic meters respectively, and the annual pollutant load is 1.2726 tons of oxygen-consuming organic matter and/kloc-respectively.
There are 7 sewage outlets around Changhu Lake, including 2 industrial sewage outlets (Shiqiao Yuya Paper Mill and Hougang Glass Factory), 2 mixed sewage pumping stations (Hougang Pumping Station and Jiaowei Pumping Station) and 3 tributaries entering the lake. At present, the annual inflow of lake water is 1 18320 cubic meters, including 5.42 million cubic meters of industrial and mixed sewage. The annual load of imported pollutants is 958 tons of oxygen-consuming organic matter, suspended matter 143 tons, 67 tons of ammonia nitrogen and 8 tons of total phosphorus.
5, pollution control countermeasures and ecological environment protection measures
5. 1 management measure 1: strengthen the remediation of key industrial pollution sources and control the amount of sewage entering the lake.
The factories and enterprises along the lake discharge wastewater into the lake area, which seriously pollutes the lake water body. Relevant departments should strengthen the rectification of key industrial pollution sources and strictly control the amount of sewage entering the lake. Especially in Shayang County, Hubei Province, some township enterprises have seriously discharged pollutants into the lake area.
5.2 Management Measure 2: Strengthen the management of lake aquaculture, greatly reduce the area of cage culture in lakes, and gradually restore the self-purification function of lake water.
At least 70% of the existing water surfaces of Honghu Lake and Changhu Lake are enclosed by cages, and the remaining water surfaces are covered with "ecstasy". By-products of cage culture will lead to water pollution, such as spoilage of residual bait, feces of fish and shrimp, death of fish and shrimp, etc., which will lead to organic pollution, poor water color and unpleasant smell. At the same time, dense cages hinder the natural flow of water, seriously affecting the normal dilution and self-purification function of water. This is the main reason why the water quality of Honghu Lake and Changhu Lake is getting worse year by year during the wet season (July-September).
5.3 Management Measure 3: Set a closed fishing season, restrict fishing (hunting), and protect the sustainable development of ecological resources of lakes and wetlands.
Honghu Lake has been established as a provincial wetland nature reserve, where there are more than 1000 kinds of wetland creatures. However, for a long time, some residents along the lake have been blindly fishing (hunting) in the lake in line with the idea of "relying on mountains to eat mountains and relying on water to eat water", resulting in a large reduction of biological resources in the reserve and even extinction of a few species. * * On the basis of scientific investigation and proper placement of fishermen along the lake, the department should establish a closed fishing (hunting) period and corresponding management measures to protect the biodiversity of lakes and wetlands and the sustainable utilization and development of biological resources.
5.4 Project Measure 1: Establish an urban sewage treatment system to centrally treat urban mixed sewage.
In view of the situation that the domestic and industrial mixed sewage in Hougang, Jiaowei Town and Qujiawan Town of Shayang County is discharged into the lake through the pump (sluice), a centralized urban sewage treatment system is established to treat the mixed sewage in front of the pump (sluice) to meet the discharge standard.
5.5 Engineering measures will separate Erhong Lake (main canal) and introduce it into Jiang Ji Lake.
Repair the south dike of Honghu Lake, the main canal of Hu Si Lake, and separate it from Honghu Lake. In this way, an average of more than one billion cubic meters of upstream water is directly discharged into the Yangtze River through Xianeijing, and at the same time, the sewage discharged into Honghu Lake through Zibeiyuan Gate and Xiaxinhe Gate is cut off, basically cutting off the pollution sources flowing into Honghu Lake. In addition, in order to ensure that Honghu Lake has a certain water level and water surface area and meet its water demand for wetland ecology and tourism functions, the Yangtze River water source is used to fill Honghu Lake. The investment cost of this project is high, and it is also the most effective way to improve the water quality of Honghu Lake.
5.6 Ecological measures: Use the waters along the lake to establish an "oxidation pond" for aquatic plants.
Generally, the water depth in the coastal waters of lakes is about 0.2m~0.8m, so it is not suitable for other purposes. However, some aquatic vascular plants with decontamination function can be planted in shallow water, such as water onion, reed and lotus. The planting area can be determined according to the sewage intake, extending from the shore to the center of the lake to100m-200m-200m, forming a banded plant buffer zone. When the sewage slowly flows through this area, the pollutants in it are absorbed by aquatic plants, thus achieving the purpose of biological treatment and purification of sewage. If emergent plants are planted, vegetation can also play the role of wave prevention and dike protection.