The Yellow River is the most important surface river in the Yellow River Delta. The Yellow River enters Dongying City and reaches the estuary about 188km, with an average annual runoff of 31700,000 m3, which is extremely uneven during the year. During the flood season (July-June), the runoff accounts for 63% of the whole year, reaching199 million m3. Runoff in non-flood season is only 1, 654,38+0.8 billion m3. Water cuts often occur in dry season, and the time of water cuts is increasing year by year, which has a certain impact on industrial and agricultural water use and people's lives in this area. Besides the Yellow River, there are more than 20 rivers flowing into the sea, of which 15 is the main one. There are coastal rivers such as Shenxiangou, Tiao River, Caoqiao River and Chaohe River to the north of the Yellow River. Most of them flow into Bohai Bay from south to north, and the rivers are straight without major tributaries. South of the Yellow River are Guangli River, Guangpu River, Hongyi River, Xiaomai River, Xiaoqing River and Hezi River. Most of these rivers flow into Laizhou Bay from west to east. Most of these rivers are artificially excavated for alkali drainage and sewage discharge.
Figure 5- 1 Distribution Map of Oil Pollution Sources
The shallow groundwater in the Yellow River Delta is mainly replenished by atmospheric precipitation. On the one hand, it is influenced by the lateral infiltration of the Yellow River, on the other hand, it is restricted by the inundation of tidal jacking, and it is influenced by saline soil and seawater to form the main characteristics of high salinity groundwater in the modern Yellow River Delta. Therefore, most areas in this area (north of Xiaoqing River) are salty and fresh water overlapping areas and all-salt water areas, which are basically not suitable for drinking. The hydrochemical types are complex, including chloride bicarbonate-sodium magnesium type, chloride bicarbonate-sodium calcium magnesium type, chloride sulfate-sodium magnesium type, chloride-sodium calcium magnesium type and chloride-sodium water type. The salinity is more than 2g/L, most of them are more than 5g/L, and there are more than 50g/L brine in coastal areas. The main fresh water area in the area is located in front of Xiaoqing River in Nanshan, with an area of 420km2, accounting for about 5% of Dongying City. The hydrochemical type is mainly bicarbonate, with salinity of 0.5 ~ 1.5g/L and pH value of 7.0 ~ 8.5, which is a good water source for domestic and agricultural use. For more detailed information about groundwater in this area, please refer to hydrogeological conditions in the previous chapter.
In order to solve the problem of water use in Dongying area and adjust the shortage of water resources in the dry season of the Yellow River, more than 0/0 reservoirs of various types have been built. Among them, there is a large reservoir with a storage capacity of1.1.400 million m3; There are 6 medium-sized reservoirs with a storage capacity of 654.38+0.6 billion m3; There are more than one small reservoir 1 1, with a total storage capacity of 302 million m3, which basically meets the current water demand of Dongying city.
According to the basic pattern of surface water distribution in the Yellow River Delta, the industrial wastewater discharged by the overall situation (Shengli Petroleum Administration Bureau) is mainly divided into four paths, and finally discharged into the Bohai Sea. The wastewater in the isolated island area is discharged into Bohai Bay through Shenxian ditch; The wastewater in the estuary area is discharged into Bohai Bay through rivers; The wastewater from Dongying area is discharged into Laizhou Bay through Guangli River. Gudao Oil Production Plant and Zhuangxi Oil Production Plant belong to coastal beach oil fields, and industrial wastewater is mainly discharged into Laizhou Bay and Bohai Bay through lift pumps in various drainage stations. Therefore, the rivers receiving oilfield sewage mainly include Tiaojie River, Shenxiangou River, Zhimai River, Guangli River and Hongyi River, and there are also two relatively small sections of Wujiadagou River and Guangpu River.
The following is an overview of the river basin receiving sewage (see Table 5-2).
1. Overview of Tiaohe River Basin
Tiaohe River is mainly located in Hekou District, Dongying City, and flows into Bohai Bay from Xindiaokou from south to north, with a total length of 32.6km and a drainage area of 504km2. 1974 for excavation to form a river channel with drainage, flood control and sewage discharge as its main functions. Sewage flowing into Tiaohe River mainly includes oil production wastewater from Hekou Oil Production Plant, domestic sewage, wastewater from local industrial enterprises and domestic sewage.
2. Overview of Shenxian Valley
Shenxiangou is located in Gudao Oil District, Hekou District, Dongying City. At first, it was responsible for the diversion of the Yellow River. After the Yellow River was cleared into the sea from 1979, Shenxian ditch no longer assumed the responsibility of diverting water from the Yellow River into the sea, and its downstream function completely became a sewage drain. The whole river is 54 kilometers long and the drainage area is 250 square kilometers. The main wastewater pollution sources in the basin are oil production wastewater, domestic wastewater, local industrial wastewater and domestic wastewater from Gudao and Zhuangxi oil production plants.
3. Overview of Zhimai River Basin
The tributary originates from gaoqing county, Shandong Province, with a drainage area of 1338km2 and a total length of112.5km. It flows through the junction of Dongying District and Guangrao County and enters Laizhou Bay, and its function is mainly used for drainage. Receive industrial wastewater and domestic sewage from petrochemical development company, Chunliang first station, Wangjiagang United station and Shengli Power Plant.
4. Overview of Guangli River Basin
Guangli River originates from Wang Ying, Shengtuo Township, Kenli County, with a total length of 47.8km and a drainage area of 844km2. The maximum drainage capacity is148m3/s. The main sewage input into Guangli River Basin is domestic sewage from Xicheng District, industrial wastewater from Dongxin Oil Production Plant, Xianhe Oil Production Plant, Power Machinery Plant and Shengli Oil Production Plant, and wastewater from local industrial enterprises.
5. Overview of Hongyi River Basin
Hongyi originated in Cuijia Zhuangzi, Kenli County, with a total length of 47.9km, a drainage area of 265438±0.30 km2, and a maximum drainage capacity of 65,438 0.65438 m3/s. The main sewage discharged into the basin is the production and domestic wastewater from Shengli Oil Production Plant, Dongxin Oil Production Plant and Drilling Group Company, as well as the domestic wastewater from local industrial enterprises.
Table 5-2 Main Pollution-receiving Rivers and Pollutant-discharging Enterprises of Shengli Petroleum Administration Bureau
5. 1.2 Main pollution departments and sewage discharge types
From the introduction of regional economy, we can see that the main body of regional economy is oil economy, and the impact on water body is mainly industrial wastewater discharge from oil enterprises.
The specific situation of industrial wastewater discharge of enterprises is as follows:
1. Major industrial pollution industries
In the process of oil exploitation, oil production produces the most wastewater. Oil production and refining are the main pollution sectors. The pollution load rate of oil production department is 74.85%, which is the largest industrial wastewater pollution industry. The refining and chemical department is second only to the oil production department, and the pollution load ratio of equal standard is 17.36%, making it the second largest industrial wastewater pollution industry. The cumulative percentage of pollution load of the two standards is 92.2 1%. During the operation of oil and water wells, wastewater will also be produced. Because it generally enters the trunk line and runs without pollution, only a small amount of wastewater is discharged into the soil pool of the well site. 1993, the pollution load rate of the global operation department is only 0.24%, which is the department with the least industrial wastewater pollution (Figure 5-2, Figure 5-3 and Table 5-3).
Figure 5-2 Major Industrial Pollution Departments
Figure 5-3 All kinds of wastewater discharge compliance rate
Table 5-3 Evaluation Table of Major Industrial Pollution Departments
2. Major polluting enterprises in the petroleum industry
There are five major polluting enterprises of industrial wastewater, four of which are oil production plants. Xianhe Oil Production Plant is the first industrial wastewater pollution enterprise with pollution load ratio of 4 1.59%. Others are: Petrochemical Development Company, Dongxin Oil Production Plant, Gudao Oil Production Plant and Gudong Oil Production Plant in turn, and their equal standard pollution load rates are 17.36%, 12.89%, 10.24% and 6.63% respectively. The cumulative pollution load ratio of the above five units is 88.7 1%, which is the main industrial wastewater pollution enterprise.
3. Types of main pollutants discharged
Table 5-4 lists the iso standard pollution load of 1 1 pollutant. As can be seen from the table, the iso standard pollution load rate of volatile phenol is the highest, which is 5 1.63%, and it is the first pollutant. The load rate of petroleum pollution is 32.78%, which is the second kind of pollutants, and the load rate of chemical oxygen demand pollution is 12.99%, which is the third kind of pollutants. The cumulative load rate of pollution load of the three standards reaches 97.40%, which is the main pollutant. Eight pollutants, such as suspended solids, sulfide, cyanide, copper, lead, mercury, zinc and hexavalent chromium, are relatively light, and the total pollution load ratio of equal standard is only 2.6%. See Figure 5-4 for the proportion of main pollutants in wastewater.
Table 5-4 Evaluation Table of Major Pollutants in Industrial Wastewater of Petroleum Enterprises
① Six pollutants: copper, lead, mercury, CN-, zinc and Cr6+.
Figure 5-4 Types of Main Pollutants in Wastewater
5. 1.3 Surface water pollution status
In this area, 1 1 rivers of seven major river systems, such as Tiaohe, Shenxiangou, Zhimai, Guangli, Hongyi, Xiaoqing and Bohai Bay, are the main sewage receiving systems (Figure 5-5), and * * * receives 10753600 t from/kloc-0. 4456.23t pollutants were admitted, accounting for 53.59% of the total industrial wastewater pollutants in the world. Chemical oxygen demand is 3065.09 tons, petroleum is 545.84 tons, suspended matter is 820.95 tons, volatile phenol is 17.45 tons, and sulfide is 2. 17 tons, accounting for 67. 16%, 94.80%, respectively, of the total amount of similar pollutants in the global industrial wastewater.
Among the above seven main receiving sewage systems, Zhimai River, Guangli River, Xiaoqing River System and Bohai Bay are the most important receiving sewage bodies. 193 received19 94 14700 t of industrial wastewater from the main sewage outlet, accounting for 87.55% of the total industrial wastewater received by the polluted body. Accepted pollutants are 3662t, accounting for 82. 18% of the total pollutants of industrial wastewater. The tributary water system receives the largest amount of industrial wastewater, 5.499 million t, and pollutants 1.769.66 t, including chemical oxygen demand 1.238.22 t, petroleum 1.53.89 t, suspended solids 366.78t and volatile phenol1. See Table 5-2 for the acceptance of industrial wastewater pollutants by various sewage bodies.
5. 1.4 regional water environment quality assessment
1. Surface river
(1) Yellow River
The Yellow River, the most important surface river in this area, has good water quality. According to the monitoring results of Dongying Environmental Protection Monitoring Station for many years, except for the high content of suspended solids peculiar to the Yellow River, most chemical elements are within the scope of Class III water in the National Environmental Quality Standard for Surface Water (GB3838-88), and the contents of COD and petroleum exceed the Class V water quality standard. It shows that the water quality of the Yellow River entering the sea is good and can meet the requirements of drinking water sources, but it has been slightly polluted by organic substances such as oil.
The comprehensive pollution index of the Yellow River is 2.97 (see Table 5-5).
Table 5-5 Evaluation Table of Comprehensive Pollution Index of Yellow River
Conclusion: The water quality of the Yellow River is still good, which can meet the needs of drinking water sources, but it has been slightly polluted by organic substances such as oil, which should be paid great attention to in the future.
(2) Guangli River
The chemical aerobic organic indexes of all monitoring sections of Guangli River exceeded the standard in dry season, normal season and high season, and the maximum exceeding multiple was 4.096 times. In dry season, ammonia nitrogen in all monitoring sections exceeded the standard, and the maximum exceeding multiple was 2.67 times. BOD5 and total phosphorus only exceed the standard in some sections in dry season, and the exceeding standard multiples are 0.8 14 and 0.48 times respectively. Except that there is no over-standard phenomenon in each section of oil in the wet season, there are over-standard phenomena in some sections in the other two water seasons, and the maximum over-standard multiple is 8.2 1 times.
Figure 5-5 Schematic Diagram of Pollution Degree of Surface Water System
1999 the latest data of water quality monitoring results of guangli river show that CODcr and volatile phenol in xiaozhaojia section of guangli river exceed the standard, and the over-standard rates are 100% and 33.3% respectively. Six indexes in Shaying section of Guangli River, such as CODcr, CODmn, DO, BOD5, volatile phenol and petroleum, exceeded the standard, and the over-standard rates were 100%, 83.3%, 66.7%, 100%, 66.7% and 83.3% respectively. Seven indexes, such as CODcr, CODmn, BOD5, volatile phenol, oil, chloride and pH value, exceeded the standard, and the over-standard rates were 100%, 100%, 66.7%, 83.3% and 100% respectively. It can be seen from the over-standard conditions of the three sections that there are fewer over-standard projects in Xiaozhaojia section in the upstream, and more over-standard projects in Sha Ying and Guangligang sections in the middle and lower reaches, which are mainly caused by the discharge of industrial wastewater and domestic wastewater in Xicheng. The water quality of three sections of Guangli River is worse than that of Grade V water. The comprehensive pollution indexes of Sha Ying and Guangli Port in Xiao Zhao are 7.52, 27.07 and 15.78 respectively.
Conclusion: The organic pollution of water quality in Guangli River is quite serious, which will be aggravated if it is not treated in time. The main sources of organic pollution in Guangli River are a large number of domestic sewage in Xicheng District, oil production wastewater from Dongxin Oil Production Plant and wastewater from coastal local enterprises.
(3) tributaries
All monitoring sections of water quality CODcr in Zhimai River exceeded the standard in dry season, normal season and high season, and the maximum exceeding multiple was 3.36 times. In normal time, there are two sections of BOD5 exceeding the standard, and the exceeding multiples are 2.835 times and 1.438 times respectively. In the dry season, there is a section in the south of Guangli shrimp farm that exceeds the standard, and the multiple of exceeding the standard is 1.5 1.
The latest data of 1999 Wang Ying section: the indicators exceeding the standard are CODcr, CODmn, DO, BOD5, volatile phenol and oil, and the exceeding standard rates are 100%, 75%, 50%, 50%, 25% and 75% respectively. The comprehensive pollution index is 12. 1. Has reached serious pollution.
Conclusion: Zhimai River has been seriously polluted, and the pollution items have increased. The pollution is mainly caused by the industrial and domestic sewage from Gaoqing and Boxing counties in the upstream, the industrial wastewater discharged from the first station of Wangjiagang United Station and various kinds of wastewater discharged by local enterprises.
(4) Xiaoqing River
According to the monitoring results of 1999 Xiaoqing River in Shi Cun and Sancha sections, it can be known that there are seven indicators exceeding the standard in Xiaoqing River in Shi Cun section, among which four indicators such as CODcr, CODmn, BOD5 and volatile phenol exceed the standard rate of 100%, while the other three indicators exceed the standard rate of DO83.3%, Hg 83.3% and petroleum/kloc-0. There are six indexes exceeding the standard in the Sanqi section of Xiaoqing River, among which the exceeding standard rate of Cl-, CODcr and CODmn is 100%, and the exceeding standard rates of the other three indexes are BOD583.3%, volatile phenol 33.3% and petroleum 16.7% respectively. The pollution indexes of Shi Cun and Sancha sections are 36.2 and 35.9 respectively.
Conclusion: The water quality of Xiaoqing River is worse than that of Class V water, and it has lost its water function.
(5) Guangpu River
Before 1999, the over-standard factors of Guangpu River water quality were chemical oxygen demand, ammonia nitrogen and arsenic.
1999, the over-standard indexes of Wang Lu section in the east of Guangpu River are CODcr, CODmn, DO, BOD5 and YOU, and the over-standard rates are 100%, 75%, 75% and 50% respectively. The comprehensive pollution index is 24.3.
Conclusion: Guangpu River has been seriously polluted. The main causes of pollution are industrial wastewater discharged by petrochemical companies, general machinery plants and Shengli power plants, and industrial wastewater and domestic sewage in Liuhu Town.
(6) Zi River
He Zi originates in Linzi District of Zibo City, flows through Guangrao County and joins Xiaoqing River in the upper reaches of Sanchahekou. 1999 The test results of Xishui and Xiaoying sections in He Zi show that seven indexes of Xishui section in He Zi, such as CODcr, CODmn, BOD5, volatile phenol, lead, oil and DO, exceed the standard, and the over-standard rates are 100%, 100% and 100% respectively. DO, CODcr, CODmn, BOD5, volatile phenol, oil and other six indicators exceeded the standard, and the over-standard rates were 25%, 65, 438+000%, 65, 438+000%, 50%, 25% and 25% respectively.
Conclusion: The water quality is worse than Grade V. The comprehensive pollution indexes of Xishui and Xiaoying sections in He Zi are 143. 1 and 16. 1 respectively, which have reached extremely serious pollution level and lost the function of water body. It mainly accepts industrial and domestic wastewater from Linzi District.
(7) Overflow River
The chemical oxygen demand of all monitoring sections of Hongyi River exceeded the standard in dry season, normal season and high season, and the maximum exceeding multiple was 5.438+05 times. Ammonia nitrogen exceeded the standard in some sections in dry season and wet season. In wet season, dissolved oxygen in some sections exceeded the standard, and the multiple of exceeding the standard was 1.26 times. For petroleum, only a few sections exceed the standard in rainy season, and the multiple of exceeding the standard is 0.79 times.
Conclusion: The water quality of Hongyi River is also seriously polluted by organic matter, and its main sources are industrial wastewater and domestic wastewater from Shengli Oil Production Plant, Dongxin Oil Production Plant and Kenli Refinery.
(8) Choose a river
The chemical oxygen demand of Tiaohe River exceeded the standard in all monitoring sections in dry season, normal season and high season, and the multiple of exceeding the standard was 3.904 times. Some sections of other organic pollution indicators such as ammonia nitrogen, dissolved oxygen and biochemical oxygen demand exceed the standard in dry season and normal season, and the multiple of exceeding the standard is 1.28 times, 3.96 times and 0.272 times respectively.
Conclusion: Tiaohe River has been polluted by organic matter. The main causes of water pollution in Tiaohe River are oil production, domestic wastewater and wastewater from local enterprises in Hekou Oil Production Plant.
(9) Shenxiangou
The chemical oxygen demand (COD) of all sections in Shenxian gully in dry season, normal season and high season exceeded the standard, and the maximum exceeding multiple was 13.72 times. Other organic pollution indicators: all sections of ammonia nitrogen in dry season exceed the standard, and the maximum exceeding multiple is 0.56 times; In the dry season, the total phosphorus in one section exceeded the standard, and the exceeding multiple was 1.75 times. Dissolved oxygen and biochemical oxygen demand basically exceeded the standard in dry season, and the maximum exceeding multiples were 9.0 and 7.3 times respectively. The pollution index of petroleum basically exceeds the standard in dry season, normal season and high season, and the maximum exceeding multiple is 1.68 times.
Conclusion: The water pollution in Shenxiangou is quite serious. The water pollution in Shenxiangou mainly comes from the industrial and domestic sewage of Ma Jun paper mill, Zhuangxi oil production plant and Gudao oil production plant.
(10) Wujiadagou
The organic pollution index chemical oxygen demand in Wujiadagou exceeded the standard in three water periods, with the maximum exceeding multiple of 1.93 times, biochemical oxygen demand and dissolved oxygen exceeding the standard in 1 water period, with exceeding multiples of 0.027 and 1.305 times respectively.
Conclusion: The water pollution in Wujiadagou is lighter than that in other rivers, which belongs to the type of organic pollution. The main causes of pollution are the oil production wastewater discharged from Wangjiagang Station of Xianhe Oil Production Plant and the wastewater discharged from nearby local enterprises.
2. Shallow seawater in the oilfield
Shengli Oilfield is one of the key development zones, with rich shallow and beach underground reservoirs. This area is also a traditional fishing ground in China, a good place for economic fish, shrimp and shellfish to lay eggs, hatch and fatten, and an aquaculture base. In the process of oil exploitation, oil and other pollutants will have a certain impact on the nearby seawater. In addition, the untreated river sewage is directly discharged into the sea, which also has a great impact on the water quality in the coastal waters.
In order to fully understand the water quality of shallow seawater in the oilfield, Shengli Oilfield organized the project "Environmental Impact Assessment and Research on Development and Construction of Shengli Oilfield and Oil Exploration and Development in Shallow Seas" on 1989, and conducted a comprehensive investigation and evaluation on the water quality in shallow seas and the pollution status of sediments in shallow seas. At that time, the sea area under investigation started from Majia estuary in the north and reached Weihe estuary in the south. The latitude and longitude of the sea area ranged from 1 17 58.3' to1930.1'e, 3711. The sea area under investigation includes 0 ~15m isobath, 12 sections and 49 large observation stations. Among the 49 large-scale observation stations, there are 3 continuous observation stations, which measure relevant water quality parameters every two hours and monitor them continuously for 24 hours. The investigation time of shallow water is one voyage in dry season (May) and one voyage in wet season (August). In shallow water quality survey, only the surface layer is taken when the water depth is less than 10m, and the surface layer and bottom layer are taken when the water depth is 10 ~ 15m. The evaluation method is recommended by the Research Report on the Evaluation Method of Offshore Water Quality in China 1990 published by the Institute of Marine Environmental Protection of the State Oceanic Administration in March, and the evaluation standard is the first class seawater standard in the Seawater Quality Standard GB 3097-82. The seawater quality is divided into four grades: A, B, C and D. The grades A, B and C are roughly equivalent to Class I, Class II and Class III seawater, and those inferior to Class III seawater belong to Class D. Except for sewage outlets, Class D seawater is not allowed in any sea area (Figure 5-6).
The evaluation results of seawater quality are as follows:
(1) Single seawater quality grade
COD: There are 1 station exceeding the standard, which is located at the mouth of Shenxian ditch, and the exceeding standard rate is 1.7%. Only the intertidal zone of Shenxiangou is of Class D water quality, which affects the nearby shallow waters, making its water quality of Class C to Class B, and the COD water quality of other evaluated waters is of Class A..
Petroleum: 7 stations exceeded the standard, including 6 in intertidal zone, near Xiaoqing River 1 station, and the exceeding standard rate was 12%. The local pollution caused by oil in the sea area is obvious, especially in two places, one is the intertidal zone at the mouth of Shenxian River and the other is the intertidal zone between Wanghekou and Xiaoqing River. The worst water quality grade of petroleum appears in the mouth of Shenxian ditch, which is class D. The intertidal zones in Gudong and Xiaoqing estuaries are both Grade B. ..
Volatile phenol: The stations exceeding the standard for volatile phenol are mainly located in the intertidal zone between Gudong and Shenxian Goukou, with 3 stations exceeding the standard, and the exceeding standard rate is 1 1.5%. The water quality from Tiaohekou, Shenxiangoukou, Huanghekou, Xiaoqing River, Wanghekou to Laizhou Bay bottom belongs to the first class. ..
Figure 5-6 Zoning Map of Shallow Water Quality in Oilfield
(2) Comprehensive quality grade of seawater
The average results of two water periods are evaluated by comprehensive water quality grade. The worst water quality is in the intertidal zone at the mouth of Shenxian gully. The main pollutants are petroleum and COD, especially the petroleum exceeds the standard. Class B water quality is near the intertidal zone and within a small range of the intertidal zone of Guangli estuary, and the subtidal zone is basically Class A water quality. The water quality of most areas in the survey area belongs to Class A, which is the first class seawater quality.
Because sediments can well reflect the pollution status and history of water environment, this survey not only evaluated the seawater quality, but also evaluated the pollution status of sediments in shallow beaches.
(3) the status of shallow sea and tidal flat sediments
Through the geological investigation of shallow sea and tidal flat, it is found that the quality of tidal flat and shallow seabed in other areas is not beyond the standard except the intertidal sediments in Gudong Oilfield. The width of gray-black mud in Gudong Oilfield is about 100m ... It is extremely serious in terms of pollution degree. Oil pollution exceeds the standard by 40 times, sulfide pollution exceeds the standard by 2.5 times, and the contents of phenol and organic matter are also the highest in the whole region. Judging from the development speed of pollution, when Shengli Oilfield conducted the environmental impact assessment of Gudong Oilfield in June 1986+00, the quality of sediments in this sea area was still good, with no over-standard items and no obvious oil pollution. The current situation is obviously caused by the rapid accumulation of oil in the sewage discharged from the oilfield at the bottom of the beach after 1986.
In addition, through the analysis of the pollution index of sediments in the whole region, it can be found that the pollution index of tidal flat is the smallest, and the pollution index of coastal sediments in shallow sea is greater than that of tidal flat, but less than that of shallow sea far offshore. It shows the zonal zoning phenomenon of sediment pollution index increasing from tidal flat to deep water (contrary to the zonal zoning of shallow water quality), on the one hand, it reflects the trend that oil and other pollutants are mainly transported to the sea area with weak hydrodynamic force after entering the sea; On the other hand, it is also due to shallow water near the beach, sufficient water exchange, high oxidation potential and difficult formation of pollutants.
In a word, through the comprehensive investigation of the water quality and sediments in the Yellow River Delta coastal zone, it can be seen that the seawater pollution in 1989 sea area mainly occurs in the offshore of Gudong Oilfield. Because the oil field is close to the sea, the drainage station directly discharges the sea, which has a great impact on the seawater, but the pollution is limited to the intertidal zone, especially the water quality in Shenxian ditch and Guangli estuary is poor, and the water quality in most areas is basically the general first-class seawater quality.
After 10 years, the water quality monitoring data in coastal waters collected in 1999 were evaluated according to GB 3097- 1997 standard. In addition, according to the different functional zones of sea areas, Class III and Class II standards are adopted for evaluation, among which Dongying Port and Chengdao Oil Development Zone in Bohai Sea are evaluated according to Class III standards, and the rest are evaluated according to Class II standards. See Table 5-6 for the results of water quality evaluation in coastal waters.
Table 5-6 Assessment Results of Water Quality in Coastal Waters
Through the evaluation and comparison of seawater quality between 1989 and 1999, although the evaluation standards are different, the projects exceeding the standard cannot be effectively compared, but the shallow sea seawater in most areas of 1989 belongs to the general first-class seawater quality, and the intertidal zone of Gudong Oilfield, the main polluted area, is mostly the second-class seawater quality, while 1999 investigated.
Conclusion: Since 1986, the pollution of shallow sea water has intensified and the polluted area has a tendency to expand.
3. Groundwater
In some areas of the Yellow River Delta, the content of pollution elements in shallow groundwater exceeds the drinking water standard, and the heavily polluted areas are mainly distributed along the sewage river, towns and industrial concentration areas. In addition, Dongying has a low terrain and is seriously affected by foreign sewage. According to the monitoring, the groundwater pollution in Dongying City is mainly shallow groundwater pollution, mainly petroleum, volatile phenol and COD, and the groundwater pollution in the shallow fresh water distribution area in the south of Guangrao County is the most harmful to people. In particular, the groundwater along the Hezi River is yellow and black in some areas. In addition, pesticide residues were also detected in shallow groundwater. According to the detection results of 1992 ~ 1995, dimethoate (detection value of 0.4 ~ 12 mg/dm3) and bhc (detection value of 0 ~ 0. 18 mg/dm3) were mainly found. People gradually realized the harm of groundwater pollution and tasted the bitter fruit brought by human beings, because suspicious areas that may be related to groundwater pollution or early sewage irrigation were found, with large livers and high cancer incidence (Figure 5-7).
Figure 5-7 Schematic Diagram of Shallow Groundwater Quality Zoning
(1) Groundwater pollution along the He Zi River
Hezi River is a seriously polluted river. Due to the intensive exploitation of shallow groundwater on both sides of the river, the sewage in He Zi has a strong recharge effect on groundwater, which leads to serious groundwater pollution along the river. The groundwater in coastal areas has an odor and is yellow-gray, and the shallow groundwater above 60m is no longer drinkable.
According to the analysis data of vertically arranged groundwater sampling points in He Zi, the main pollutants are volatile phenol and oil, and arsenic and hexavalent chromium are also detected. The volatile phenol is 4.5 ~ 4.7 times higher than the drinking water standard. The pollution degree of groundwater decreases with the increase of distance from Hezi River. The polluted areas are distributed in wucun-Zaohuli-Huangqiu-Baituqiu area on the west bank of He Zi River and He Lin area in Xizhuying-Yangzhuang-Liqu-Guo Xin area on the east bank, with an area of about 32km2. The polluted area is distributed in a strip with a width of 2 ~ 3 km along the Hezi River, and the distance from the boundary of the polluted area to the Hezi River is generally 1.0 ~ 1.5 km. The oil content in shallow groundwater in this area is generally 0. 18 ~ 0.50 mg/L, which exceeds the sanitary standard for drinking water, and the COD content is generally 0.90 ~ 2.00 mg/L, with the highest value of 8.68mg/L, which exceeds the sanitary standard for drinking water. In addition, the detection rate of Cr6+ and Mo in shallow groundwater in this area is relatively high, with the detection rate of Cr6+ being about 40%, and the detection rate of Mo generally being 0.005 ~ 0.025mg/L ... and 80%, with the content generally being 0.00 1 ~ 0.005 mg/L (see Table 5-7
Table 5-7 Water Quality Analysis Results of Groundwater Pollution Monitoring Section along He Zi River
The unpolluted area is located in the areas of Lamb-Zhangda-Jin Wang and Dazhangdan-Xiying, which are far away from Hezi River, with an area of about 109km2. The area is far from Hezi River, and the shallow groundwater is only slightly polluted. The content of COD in shallow groundwater in this area is generally 0.87 ~ 1. 17 mg/L, the content of Cr6+ is generally 0.008 mg/L, and the content of molybdenum is generally 0.00 1 ~ 0.002 mg/L, which are all lower than the sanitary standard for drinking water. Shallow groundwater in this area basically meets the requirements of water supply quality for people and livestock (Figure 5-8).
Figure 5-8 Schematic diagram of groundwater pollution assessment zoning along the He Zi River.
The middle and deep groundwater in the area is basically unpolluted and the water quality is good. Only a few villages have cascade pollution due to the exploitation of middle and deep groundwater, and the pollution is punctate and the pollution range is small. These pollution spots are mainly distributed in Yangzhuang, Zhaozhuang and Zhuang Ming along the Zihe River in the south, and Wangchangwuzi and Changxuzhuang in the north. The distance between the deep wells with cascade pollution in the south and Hezi River is less than 200m, all of which were dug in the early 1980s, and the depth is less than160m. The main pollutants are petroleum and Cr6+, and the content of petroleum is generally 0.44 ~ 1.06 mg/L, which exceeds the sanitary standard for drinking water. The content of Cr6+ is generally 0.0 1 ~ 0.02 mg/L. The groundwater pollution in the middle and deep layers in the north is also caused by the cascade pollution of the upper brine.
(2) Groundwater pollution along Xiaoqing River.
Xiaoqing River is a seriously polluted river. Due to the influence of Xiaoqing River water, the shallow groundwater on both sides of the river has been seriously polluted. 58 kinds of organic substances have been detected in groundwater, of which 365,438+0 kinds are directly from industrial wastewater and Xiaoqing River water. The concentrations of benzo (a) pyrene and CCL4 _ 4 in individual sampling points are several times or even hundreds times higher than the national drinking water standard, respectively, and the pollution degree is serious. The essence of shallow groundwater pollution is organic pollution. The existing research results show that in 1 year, the longitudinal dispersion of phreatic aquifer is 0.42m, and the diffusion speed of Xiaoqing River pollutants to phreatic water is about 2.8m m. At present, the pollution range of shallow groundwater has reached about 500m m. Xiaoqing River discharges groundwater on both banks in dry season and normal season, and only replenishes shallow groundwater for a short time in wet season. Therefore, Xiaoqing River mainly pollutes groundwater through the diffusion of pollutants. Another way of pollution is Xiaoqing River sewage irrigation. According to the investigation, there are still sewage irrigation areas on both sides of Xiaoqing River, which has aggravated the pollution of groundwater, soil and food crops.
(3) The present situation of groundwater pollution in the Yellow River Delta Plain.
The Yellow River Delta plain area north of Xiaoqing River is the main oil development area of Shengli Oilfield, and the main industrial enterprises in Dongying City are also in this area, and the groundwater is also polluted to varying degrees. According to the data of sampling points, the groundwater pollution zone is mainly distributed near the surface pollution source, and the groundwater pollution degree is light in the area far from the pollution source. The main pollutants are petroleum, volatile phenol and heavy metals such as cadmium, lead and hexavalent chromium, as shown in Table 5-8.
Conclusion: the shallow groundwater in this area is mainly polluted, and the main pollutants are coliform bacteria, total bacteria, petroleum, COD and ammonia nitrogen, among which coliform bacteria, petroleum and total phosphorus are the most serious. The heavily polluted areas are mainly distributed along the sewage river, towns and industrial concentrated areas, while other areas are lightly polluted. In contrast, the pollution of deep groundwater is less, and the projects exceeding the standard are mainly petroleum and volatile phenol. However, in this area, due to the less development and utilization of groundwater, the pollution of groundwater has not attracted enough attention, and now less monitoring work has been done.
4. Reservoir
The water quality of reservoirs in this area is generally good and has not been negatively affected by oil development. The water quality of Xin 'an Reservoir, Guangnan Reservoir, Gudong Reservoir, Guang Bei Reservoir, Gubei Reservoir, Geng Jing Reservoir and Minfeng Reservoir was tested. The pH value is between 7.69 and 8.42, and the highest value is close to the standard of 8.5, but it does not exceed the standard, which basically belongs to moderate alkaline water quality. Although the water source of each reservoir comes from the Yellow River, due to the influence of long storage time and high surface salt content, the water quality pH value of each reservoir, especially Geng Jing Reservoir, has increased. Organic pollutants were detected in all reservoirs, and the detection rate of volatile phenol and cyanide was not less than 80%, but they were all lower than the national standard of surface water/kloc-0. The problem of microbial pollution in reservoir water quality deserves attention. According to the national Class III water quality standard, the total coliform group is 6.5438+0.0000 /L, and the coliform group in Guang Bei Reservoir is as high as 30,000/L. This phenomenon clearly shows that human activities are seriously affected, and residents' life and grazing are the main causes of microbial pollution, which can only be used as drinking water after purification and disinfection.
Conclusion: The water quality of reservoirs in this area is generally good and has not been negatively affected by oil development. The problem of microbial pollution deserves attention.
Table 5-8 Monitoring Data of Shallow Groundwater Pollution in Yellow River Delta Plain