(1) Traffic location
Dongying City was established in June 1983 65438+ 10 1, and it is a new oil industrial city. Oil exploration industry is the leading industry in this region, which has promoted the rapid development of service industries such as mechanical processing and catering. Agriculture is still dominated by traditional planting, and aquaculture is developing rapidly. Now, it has developed into a diversified industrial system focusing on petroleum exploitation and processing, such as crude salt and salinization processing, electromechanical, textile, building materials and electronics. Planning and construction of important energy, chemical, agriculture, animal husbandry and fishery bases and modern oil port cities. Zhang (Dian) to Dong (Ying) railway is a direct line, which is connected with beijing-shanghai railway, and the planned Huang (Hua) to Dong (Ying) railway is about to start construction. Dongying expressway runs through the north and south, with provincial highways and county and township highways extending in all directions; Dongying Port has built 5,000-ton berths 1 berth and 5 3,000-ton berths, and opened ro-ro passenger ships from Dongying to Dalian. Dongying Airport is open at 200 1, with flights to Beijing, Shanghai, Shenzhen, Xi and Harbin. Dongying city has the advantage of being near the river and facing the sea, and has initially formed a three-dimensional spatial pattern of land, sea and air, which has ushered in a rare opportunity and entered a period of great development.
The study area is located between the Yellow River and Xiaoqing River in the middle of Dongying City, with geographical coordinates of11815' ~1915' and 37 07' ~ 37 46' north latitude. The administrative scope includes Dongying District, Dongying City.
(2) topography
This area is located in the south-central part of the Yellow River Delta, bordering the Yellow River in the north, Xiaoqing River in the south and Laizhou Bay in the Bohai Sea in the east. It is located at the intersection of the alluvial plain of the Yellow River and the alluvial plain in front of Luzhong Mountain. The overall terrain is high in the northwest and low in the southeast, slightly fan-shaped and inclined to the Bohai Sea, and the terrain is low and flat. The ground elevation in the offshore area is less than 2m, and the ground slope is generally around1:10000.
According to the genetic types of landforms, it can be divided into piedmont alluvial-diluvial plain and Yellow River Delta plain.
1. piedmont alluvial plain
It is distributed in the south of Huaguan and Xiaoqing River in Guangrao County, with an area of 125km2, accounting for 3.3% of the study area. He Zi, which originated in the middle mountain area of Shandong Province, carries a large amount of material accumulation, forming a slightly inclined plain with alluvial fans as the main secondary geomorphic unit, which runs northeast with an altitude of 25 ~ 10m and a ground slope of11000 ~1/2000. The east-west direction is limited by the distribution of the main stream zone of Hezi River, and the ground is slightly inclined.
2. Yellow River Delta Plain
Influenced by both rivers and oceans, the binary phase structure of river alluvial deposits covering marine strata is formed. Under the combined action of flood of the Yellow River, alluvial and diluvial deposits in front of Lushan Mountain and marine sediments, a landform with alternating high, slope and depression was formed. According to its geomorphological characteristics, it can be divided into four types of micro-geomorphology: highland, sloping land, low-lying land and intertidal zone.
(3) Meteorology and Hydrology
This area is located in the warm temperate monsoon climate zone, and its main climate features are obvious changes in four seasons, rapid warming in spring, less precipitation, high wind speed and dry climate. High temperature, high humidity and concentrated precipitation in summer; In autumn, the temperature plummeted, the rainfall plummeted, and the autumn was crisp; Winter is cold and dry, with little rain and snow. The climatic characteristics of spring drought, summer waterlogging and late autumn drought are formed in a year. Annual average temperature 12.3℃, extreme maximum temperature 410.9℃, extreme minimum temperature -23.3℃, multi-year average frost-free period 203.6d, soil freezing period 80d, and maximum frozen soil depth 60cm. The average annual precipitation in the area is 543.2mm, and the average annual evaporation is1135 mm.
Natural disasters caused by meteorological factors mainly include wind disaster, hail disaster, flood disaster, drought and storm surge.
Wind disasters are mainly strong winds, dry-hot winds and tornadoes. Strong wind is one of the main disasters, which is easy to cause crops lodging and building damage. Strong winds in the northeast of coastal areas often cause seawater backflow, resulting in storm surge disasters. In terms of geographical distribution, it is more in the north and gradually decreases from north to south. In winter and spring, there are more strong winds along the coast than inland; In summer, there are more thunderstorms and strong winds in inland areas than in coastal areas. The dry-hot wind is mostly southwest wind, which occurs in mid-May and June, and mainly harms wheat filling. There is a small tornado in the territory.
Hail disaster occurred in April ~165438+10, especially in May ~ July. Light hail disasters occur almost every year, and heavy hail disasters occur once every seven years on average. Hail mostly occurs in the north and northeast, and gradually decreases from north to south.
Drought and flood disasters often occur in this area. During the period of 1800 ~ 1995, the drought lasted for 96 years, with an average of 2.05 times. In 1984, floods occurred once every 2.33 years on average, and droughts and floods often occurred alternately in a year.
This area is the hardest hit by storm surge. Storm surges mostly occur in April and May and August and September, and are formed by the coupling of astronomical tide and meteorological tides under specific local geographical conditions. In the past hundred years, there have been seven storm surges close to or higher than 3.5m (Yellow Sea base), among which1April 5, 964 was the most serious. At that time, the submerged area was generally 22 ~ 27 kilometers away from the coastline, and the average sea level of the Yellow Sea was above 2.5 ~ 3.5 meters. ..
The water systems in this area are mainly the Yellow River and Huaihe River. The Huaihe River system includes Yongfeng River, Guangli River, Zhimai River and Xiaoqing River. The Yellow River Diversion Reservoir can be seen everywhere, including a large reservoir, 17 medium-sized reservoir and several small reservoirs. Yellow River Diversion Irrigation Area includes Shengli Irrigation Area, Caodian Irrigation Area, Mawan Irrigation Area and Shallow Water Irrigation Area.
(4) Vegetation
1. Natural vegetation
Dongying is a deciduous broad-leaved forest area in warm temperate zone. There are no zonal vegetation types in the area, and the distribution of vegetation is mainly restricted by water, soil salinity, groundwater level, salinity, landform types and human activities. Natural vegetation is mainly herbaceous plants, with less woody vegetation, mainly meadow landscape. There are more than 40 families of plants, 1 10 genus and 160 species, among which Gramineae and Compositae are the most. Among herbs, perennial herbs are dominant, especially all kinds of halophytes. Natural vegetation has a great relationship with the years of soil formation and soil salt content in this area. According to soil salt content, different plant communities are distributed. Among the natural vegetation, coastal halophytes are dominant, accounting for 56.5% of the natural vegetation, swamp vegetation and aquatic vegetation account for 265,438+0% of the natural vegetation, shrub tamarisk accounts for 265,438+0% of the natural vegetation, and broad-leaved forest accounts for only about 65,438+0.5% of the natural vegetation.
2. Farmland vegetation
It is mainly distributed in lightly and moderately salinized areas in fluvo-aquic soil and salinized fluvo-aquic soil. The main cultivated crops are winter wheat, corn, soybean, sorghum and millet. The cash crops are cotton and peanuts. And the forage grass is mainly alfalfa and so on.
Among the cultivated tree species are Robinia pseudoacacia, Sophora japonica, Salix matsudana, Salix weeping willow, Populus tomentosa, Ulmus pumila and Mulberry. Shrubs include Amorpha fruticosa, willow and tamarisk. Economic tree species mainly include jujube, peach, apple and so on. Ornamental trees include holly, boxwood, orange, bauhinia, rose, rose and jasmine. Weeds in farmland include green bristlegrass, barnyard grass, crabgrass, thrush, cattail, purslane, reed, thatched grass, bitter herb, apocynum venetum, dandelion, plantain and sweet clover.
(5) Soil salinization
1. Classification of saline-alkali land
According to the different chemical composition, saline-alkali soil can be divided into three categories: saline soil, alkaline soil and saline-alkali soil.
Saline soil refers to soil containing soluble salts harmful to the normal growth of crops. Soluble salts are mainly composed of cations Na+, Ca2+, Mg2+ and anions Cl-, so42- and HCO-3.
Alkaline soil: refers to the soil in which crops are affected by exchangeable sodium. This kind of soil contains high concentration of HCO-3 (including CO2-3), which combines with Na+ in the soil to form sodium bicarbonate, which makes the pH value of the soil higher. It is a kind of soil that is more harmful to crops than saline soil.
Saline-alkali soil refers to the soil that contains both excessive soluble salt and excessive exchangeable sodium. Saline-alkali soil has both salt and alkali hazards, so it can also be called saline-alkali soil.
According to the soluble salt composition and content of the soil in this area, the soil is mainly saline soil, accounting for 84%, alkaline soil accounts for 10%, and saline-alkali soil with both salt damage and alkali damage accounts for 6%. The classification standard of soil salinization (comprehensive investigation report of hydraulic environment geology in the Yellow River Delta) is as follows:
Total salt content of non-saline soil
Total salt content of light saline-alkali soil = 0.2 ~ 0.4g/ 100g soil;
Total salt content of moderately saline-alkali soil = 0.4 ~ 0.6g/ 100g soil;
Total salt content of severe saline-alkali soil >: 0.6g/ 100g soil.
2. Distribution of saline-alkali land
The distribution of saline-alkali land in this area is closely related to topography. From the coastline to the inland, the degree of salinization tends to be lighter.
(1) heavily salinized soil
The main coastal zones are distributed in coastal lowlands, Sha Ying East-Guang Bei Farm and coastal zone within 9 ~ 15 km. Area 1 100km2, accounting for 29%.
(2) Moderately salinized soil
It is mainly distributed in the periphery of the distribution area of low-lying and severe saline-alkali soil, within the range of 10km to the north of Dongcheng, and in some areas such as the south of Western Song Dynasty, Kenan and Dongji-Jiahao. The area is 800km2, accounting for 2 1%.
(3) Slightly salinized soil
Mainly distributed in the lowlands, gentle slopes and low-lying areas in the central and western parts of the study area. The area is 875km2, accounting for 23%.
(4) Non-salinized soil
It is distributed in the highland of the Yellow River influence zone, the front highland of the southern alluvial-diluvial plain and the gentle slope of the central and western regions. Area 1025km2, accounting for 27%.
3. Causes of soil salinization
The formation of saline-alkali soil is mainly influenced by many factors, such as hydrology, meteorology, geology, landform, soil particle composition and hydrogeological conditions, and is the result of the interaction of many factors. This area belongs to the arid and semi-arid climate zone of warm temperate zone. The evaporation capacity is several times that of rainfall, and a large amount of water evaporates, so that the salt in the water remains in the surface soil, which is prone to soil salinization in the process of salt accumulation for a long time. In addition, due to the influence of natural and human factors, the surface and underground runoff is not smooth, and the groundwater level is rising, which is another important reason for soil salt accumulation. Because it is located in the coastal zone, direct seawater immersion and storm surge flooding are the main factors of soil salinization in the coastal zone.
Second, the geological background conditions
Dongying area is based on Archean, Paleozoic and Mesozoic, and there are huge Cenozoic strata on it, with the maximum thickness of about 7000 meters. The sedimentary layers are mainly Paleogene and Neogene.
The strata exposed on the surface are all Quaternary (Qp):
Lower Pleistocene (Qp 1): The bottom is buried 252 ~ 420 m, with alluvial, marine and lacustrine deposits. Mainly silty clay, silty soil and 1 ~ 6 layers of fine sand or silty fine sand. The thickness of single sand layer is 1.5 ~ 10m, and the colors are mostly brownish yellow, brownish red, grayish green and taupe. It contains calcareous sediments and calcium nuclei, with gray-green spots, reticulation and rust spots. The structure is compact and the fracture surface is developed.
Middle Pleistocene (Qp2): The buried depth at the bottom of the layer is 157 ~ 200m, which is alluvial marine deposit. Grayish yellow and brownish yellow silty clay mixed with silty soil, silty sand and silty fine sand. The sand layer gradually increases from west to east, with 1 ~ 4 layers, reaching 8 layers in Kenli County, with a thickness of 1 ~ 10m and a maximum thickness of 22m. Calcium-containing nuclei, iron-manganese nodules, gray-green spots and reticular, gray-white calcium deposits and fractures can be seen locally.
Upper Pleistocene (Qp3): The buried depth at the bottom of the layer is 79 ~ 10 1m, which is mainly alluvial and marine deposits. The lithology is mainly grayish yellow, khaki silty soil and silty clay mixed with sand, and the eastern part is mostly silty soil. The sand layer is fine sand, silty sand, grayish green mesh, calcareous core and loose structure.
Holocene (Qh): The thickness is generally about 26m, mainly marine strata and Yellow River Delta deposits formed after the third transgression (Holocene transgression), and the bottom is only about 2m with continental river and lake deposits before transgression; Its sedimentary sequence is continental layer, tidal flat deposit, shallow sea deposit and delta deposit from bottom to top. Holocene can be divided into the following three groups:
Kenli Formation: It is a river and lake sediment in the early Holocene, and consists of fine sand, extremely fine sand, silty sand and clayey silty sand.
Pile Group 5: marine deposit in a broad sense, mainly composed of silty sand and clayey silty sand. The first part is coastal salt marshes and intertidal sediments. The former is carbon silty sand, while the latter is interbedded with silty sand and clayey silty sand, with lenticular bedding and vein bedding. Bottom 14C age 8835 ~ 8870. The second stage is from shallow sea deposits to delta deposits formed before transgression in the early Holocene, which are silty sand and clayey silty sand. The third section is the underwater delta and tidal flat deposits formed since 1855, which are composed of silt and clayey silt.
Diaokou Formation: It is deposited in the upper delta plain, and its thickness varies with altitude, and it is composed of yellow silt and brown clayey silt.
Three. General situation of regional hydrogeology
Groundwater resources in the Yellow River Delta mainly exist in Quaternary and Tertiary porous aquifers, and the formation and distribution of each aquifer are controlled by geological structure, paleogeography and paleoclimate. In different stages of geological and historical development, the rise and fall of the crust affected the evolution and migration of paleogeography and paleoclimate conditions, which led to the spatial overlap and alternation of strata with different geological ages, different genetic types and different material sources in the area, and the distribution of aquifers became more complicated. Generally speaking, with the advance of geological history and the continuous decline of the crust, the proluvial and its aquifer in this area gradually retreated from south to north until it was pointed out. Alluvial fans (groups) from early Pleistocene to late Pleistocene extended to Shikou-Liu Hu-Guangrao Salt Field, while late Pleistocene-Holocene was limited to the south of Xiaoqing River. Therefore, in the vertical direction, the particles in the aquifer become thinner from top to bottom, and in the horizontal direction, from south to north, the thickness becomes thinner. Alluvial stratum is the main occurrence form of fresh water in the Yellow River Delta. With the decrease of alluvium from south to north, the underground fresh water body decreases and the salty water body increases. From the all-fresh water area south of Shi Cun-Xu Yan-Daozhuang line in the south of Guangrao County to the two-story structural area with salty upper and light lower, and the all-salt water area north of Lijin-Dongying-Liuhu line.
According to the hydraulic properties and buried depth of groundwater, the aquifers in the area can be divided into three aquifer groups: shallow groundwater-micro confined water, middle confined water (60-200 m) and deep confined water (>: 200m). This time, we mainly study shallow groundwater.
1. Occurrence conditions of shallow groundwater
Shallow phreatic water-micro confined water refers to groundwater buried within 60m depth, which can be divided into fresh water, brackish water, brackish water, salt water, salt water and brine according to its salinity (Figure 13- 1).
Shallow fresh water is mainly buried in the present Yellow River Hanoi beach area. The lithology of aquifer is mainly silty sand, with fine sand locally. The buried depth of roof is 5 ~ 10m, the buried depth of fresh water bottom interface is 15 ~ 30m, the thickness of sand layer is 5 ~ 10m, and the water inflow of single well is 200 ~ 500m3/d. ..
Shallow brackish water is mainly distributed within 3 ~ 3.5km of the Yellow River influence zone west of Kendong, west of Dongji-Niuzhuang, south of Chenguanzhuang and south of Dingzhuang. The lithology of the aquifer is mainly silty sand, the buried depth of the top plate is 0 ~ 10m, the buried depth of the bottom interface of fresh water is 10 ~ 20m, the thickness of sand layer is 5 ~ 10m, and the water inflow of a single well is less than 200m3/d, which is closely related to shallow fresh water and shallow salt water.
Shallow salt water and salt water are widely distributed in the east of brackish water area, the west of Yong 'an-Shengli Town-Guang Bei Farm in the middle of the investigation area, the east coast of Xiadong Town and along the Yellow River. Its formation is caused by delta facies and marine sediments. The lithology of aquifer is mainly silty sand, and locally silty fine sand. The thickness of aquifer is 5 ~ 20m, the buried depth of roof is 5 ~ 10m, and the water inflow of single well is 240 ~ 720m3/d ... There is a close hydraulic connection between the boundary area and shallow salt water.
Shallow brine is distributed in the eastern coastal area south of Erlian-Xiazhen-Yongfeng Estuary in Ma Jun and east of Guang Bei Farm-Shengli Town-Yong 'an. The brine layer is marine strata, silt and silt, with a brine layer thickness of 10~20m ~ 20m and a single well water inflow of 50 ~ 240m3/d. There is a certain aquifuge between the shallow brine and the upper and lower brine layers, and the hydraulic connection is weak.
2. Shallow groundwater recharge and discharge conditions
Precipitation infiltration recharge is the main recharge source of shallow groundwater. Because the precipitation changes greatly in different seasons and years, the time distribution of infiltration recharge varies greatly and lags behind. Generally speaking, precipitation infiltration recharge is often received from July to 10, and there is little or no infiltration recharge in other months. Precipitation infiltration recharge is affected by many factors, which are related to precipitation intensity, precipitation time distribution, soil water content before rainfall, micro-topography, lithologic structure of vadose zone, buried depth of groundwater level and vegetation coverage. Among them, precipitation characteristics, lithology of vadose zone and groundwater depth are the main influencing factors.
Irrigation infiltration is an important recharge project of shallow groundwater resources in the irrigation area of Yellow River Diversion in the central and western regions. Irrigation infiltration is related to irrigation mode, irrigation quota and irrigation times. Different irrigation methods and irrigation quotas have different irrigation infiltration intensities. Flood irrigation is the main irrigation method in this area, and the flood irrigation quota is generally 60 ~ 100 m3/ mu.
The lateral seepage recharge of rivers mainly occurs along the Yellow River. The main and branch canals of Yellow River Diversion belong to seasonal drinking water, and other rivers belong to rain-source flood discharge canals, which have short running time and little groundwater recharge. In the area along the Yellow River, the lateral infiltration recharge of the Yellow River is second only to the precipitation infiltration recharge. According to the relevant research results (investigation and evaluation report on main geological environment problems in the middle and lower reaches of the Yellow River (Shandong section), 65438+February 2002), the groundwater recharge width along the Yellow River Delta is 3km.
Groundwater runoff is mainly controlled by topography and surface hydrology, and the direction of groundwater runoff moves from west to east and from the Yellow River to southeast (within the influence zone of the Yellow River). The hydraulic gradient is 0.5/1000 ~ 0.5/1000.
The buried depth of groundwater level is generally
The main discharge mode of shallow groundwater in this area is phreatic evaporation. Except for the southwest and western border areas, as well as the shallow groundwater fresh water and brackish water in the upper reaches of the Yellow River in Ninghai as supplementary water sources for rural domestic water, they have basically not been developed and utilized.
Figure 13- 1 Background of Shallow Groundwater Environment
Four. Distribution and development of oil and gas resources
Dongying is an important oil-bearing area in Shengli Oilfield, where oil and natural gas resources are widely distributed, with 80% of petroleum geological reserves and 85% of oil production concentrated. Up to now, the proven oil-bearing area is 1 148.6438+0 km2, and the petroleum geological reserves are several billion tons. The exploration of oil and gas resources in this area began at 1955, 196 1 The source rock was first discovered in Shahejie Formation of Tertiary in Huaba 7 Well, 1 The industrial oil flow with a daily output of 8. 1t was obtained in Dongying Formation of Tertiary in Huaba 7 Well, which opened the prelude to oil and gas exploration in North China. On September 23rd, 1962, Ying 2 well drilled on Dongying structure produced 555 tons of oil per day, which was the highest oil well in China at that time. Since the large-scale petroleum exploration campaign started in 1964, Shengli Oilfield has built the second largest petroleum industrial base in China. Up to now, 42 oil fields have been developed in the Yellow River Delta, mainly involving 12 oil fields of three oil production plants in this area, with a total of 4,727 oil wells with an annual output of 10.45 million t (table 13- 1).
Table 13- 1 Summary of Oil Exploitation Status
The exploitation of oil and gas resources often leads to oil pollution of water and soil. Pollution sources are mainly point source pollution sources such as crude oil pollution, cuttings and mud pollution during oil drilling, oil crude oil scattered near oil wells, oil storage tanks for collecting crude oil, oil pipeline leakage, and river pollution caused by wastewater discharge from petrochemical enterprises (photo 13- 1 to 13-8). Waste drilling mud and sludge precipitated from drilling sewage treatment contain a lot of petroleum crude oil, and the petroleum content is between 244 and 57540 mg/kg (dry mud), with an average of 8807.2mg/kg (dry mud); In addition, the waste sludge contains a lot of heavy metal chromium, and the total chromium content ranges from 8.28 ~ 1 187.0mg/kg (dry sludge), with an average of 267.54mg/kg (dry sludge). Most of the solid wastes produced by drilling are concentrated in the mud pit. After drilling, the well site was leveled and the mud pit was buried, which seriously polluted the nearby soil. The oil content of waste mud varies from 915 to 37960 mg/kg (dry weight), with an average of 5855mg/kg (dry weight); The total chromium content ranges from1.11~ 485.0 mg/kg (dry weight), with an average value of 145.86mg/kg (dry weight). The oil in the waste mud mainly comes from the inside of the oil well.
The bottom mud of oil tanks, settling tanks, sewage tanks and grease traps in oil field transfer stations and joint stations, as well as the oil sands and sludge removed by refineries, range from161500 to 900800 mg/kg (dry weight), with an average of 360 162mg/kg (dry weight). See table 13-2 for the main polluting enterprises and pollutant emissions in the region.
Table 13-2 Major oil pollutant discharge units and pollutant discharge units: t