I. Overview of the study area
(I) Physical geography and socio-economic profile
The study area is located in Qiqihar City in the western part of the Songnen Plain, on the east side of the Nenjiang River, bordering Fuyu County in the north, and Lindian and Durburt Mongol Autonomous County in the east, and Tailai County in the south. The geographic coordinates of the study area are 123°53′-124°15′E, 47°10 ′-47°24′N, 27.39 km east-west and 26.32 km north-south, with a total area of 720.9 km2, and the altitude generally ranges from 200 to 500 m. The topography is mainly plain. The terrain is predominantly plain, with a horseshoe shape, high in the southeast and low in the center, gradually decreasing from north to south. Qiqihar has a cold-temperate continental monsoon climate, with a warm arid agro-climatic zone in the south, a mild semi-arid agro-climatic zone in the center, and a cool semi-humid agro-climatic zone in the north. The average annual temperature ranges from 0.7 to 4.2℃, with a difference of about 3.5℃ between the north and the south. The annual precipitation is between 400 and 550 mm, and the average annual frost-free period is 122 to 151 d. The soils in Qiqihar are mainly dark brown soil, black soil, black calcium soil, meadow soil, swamp soil, meadow alkaline soil and sandy soil. Most of the soils in Qiqihar are characterized by high heat, good permeability and light texture.
Qiqihar is one of the old industrial bases in northeast China with heavy machinery and metallurgy industry as the main body, and it is the second largest city in Heilongjiang Province, with a complete industrial system including chemical industry, light industry, textile, building materials, food, electronics, medicine and other categories, and it is the political, economic, scientific and technological, cultural and educational, commercial and trade center and an important transportation hub in the western part of Heilongjiang Province, with the city governing 7 districts, 1 city and 8 counties. city and 8 counties, with a population of 561.1×104 (143.9×104 in urban areas).
(2) hydrogeological profile
Qiqihar is located in the Nenjiang River low plain, geomorphologically across the alluvial tilted plains, alluvial-valley plains, alluvial-lakeland low plains of three geomorphological units. The hydrogeological conditions are relatively complex, and the stratigraphy consists of thick Cretaceous and Neoproterozoic terrestrial clastic sediments and loose accumulations dominated by Quaternary sands and gravels.
The Quaternary loose accumulations in the study area are relatively thick, generally 160-190 m. A layer of weakly permeable sub-clay or sub-sand layer, generally less than 7 m thick, is common at 40-60 m, which separates the aquifers in the area into the upper submerged water and the lower pressurized water, which are obviously different in hydraulic characteristics. The thickness of the upper submerged aquifer is 24.3-43.0 m, and the water-bearing medium is mainly sand and gravel, followed by medium-coarse sand and medium-fine sand, with several layers of sub-clay and sub-sand lenses, and the depth of the water table is 2-5 m. The water is abundant, and the water influx of a single well is more than 2,000 m3/d. The thickness of the lower pressurized water aquifer is thicker, and the thickness of the middle Renovation Unity aquifer is generally 70-85 m, and the water-bearing medium is gravel-bearing medium-coarse sand and sandy gravel, and the thickness of the lower Renovation Unity aquifer is generally 20-20 m, and the thickness of the middle Renovation Unity aquifer is generally 20-20 m. The thickness of the middle Pleistocene aquifer is generally 70-85 m, and the water-bearing medium is gravelly medium-coarse sand and gravel, while the thickness of the lower Pleistocene aquifer is generally 20-50 m. The water-bearing medium is gravelly medium-coarse sand and medium-fine sand. The depth of water level is 3~5 m, and the water quantity is rich, and the water quantity of a single well in the north is more than 2,000 m3/d, and the water quantity of a single well in the south and southeast is 1,200~2,000 m3/d.
The main sources of submerged water recharge are the atmospheric precipitation seepage recharge, the river seepage recharge, the lateral runoff recharge, and the irrigation water seepage recharge, and the main discharging methods are the artificial mining, evaporation, and the over-flow recharge to the pressurized water. The main sources of pressurized water recharge are the overflow recharge from the upper dive, lateral runoff recharge, and the main discharge methods are artificial mining and lateral runoff discharge.
The diving and pressurized water of the fourth system in the area are neutral low-mineralization bicarbonate fresh water. pH value is generally between 6.6 and 8.36; TDS is 230-800 mg/L in diving and 140-380 mg/L in pressurized water; total hardness is 120-500 mg/L in diving and 90-170 mg/L in pressurized water; the hydrochemistry type is basically the same for both of them, which is HCO3-Ca, H HCO3-Ca, HCO3-Ca-Na, HCO3-Na-Ca types are dominant, followed by HCO3-Ca-Mg type water. Since the dive has been relatively heavily polluted, the water chemistry type has become more complex, and a polluted water chemistry type characterized by the presence of large amounts of nitrates and chlorides has been formed in the central city-Damintun-Yushutun area. In addition, influenced by the primary environment, the aquifer is commonly interbedded with silty subclay, and the decomposition of organic matter in its silt, forming a reducing environment, reduces the high-valent iron and manganese in the medium to low-valent iron and manganese; therefore, the iron and manganese content in the groundwater is generally high, but the content does not change much from year to year.
(C) Groundwater quality monitoring data
The water quality monitoring data of this study mainly comes from the water quality analysis results of the groundwater dynamic Changguan wells set up by Qiqihar Geological and Environmental Monitoring Station in the dry period from 1998 to 2002, and the water quality monitoring points***31, of which there are 14 submersibles and 17 pressurized waters (Tables 13-14 Table 13-15). The monitored items are mainly pH, total hardness, ammonia nitrogen, nitrate, nitrite, arsenic, mercury, chromium, lead, fluorine, cadmium, iron, manganese, sulfate, fluoride, copper, zinc, iodide and so on. Qiqihar City, groundwater quality evaluation and pollution early warning system, the realization of these monitoring data, such as adding, modifying, deleting, querying and other basic management functions, see Figure 13-7.
Table 13-14 Qiqihar City, groundwater diving water quality monitoring data statistics
Table 13 -15 Statistical table for monitoring the quality of pressurized groundwater in Qiqihar City
(4) Spatial information of the study area
The spatial information includes the geographic base map of the study area, the lithology distribution map, the zoning map of the early warning parameter of groundwater quality, the map of the distribution of the water source and the source of contamination, and the map of the current state of land use (see Figs. 13-8 to 13-10). Figure 13-10).
Figure 13-7 Groundwater quality monitoring data management in Qiqihar
Figure 13-8 Spatial information interface of the study area
Figure 13-9 Schematic topography of the study area
Original scale: 1:50,000
The study area is located in the middle of Qiqihar. >Figure 13-10 Schematic distribution of lithology in the air-packed zone of the study area
Original scale 1:50000
II. Evaluation of groundwater quality in Qiqihar City
Three methods, namely, national standard, fuzzy comprehensive judgment and BP neural network, are used to evaluate the diving and pressurized water every year. The evaluation results have both data tables and contour lines and contour surface maps. For example, Figure 13-11 is a table of evaluation results obtained by using BP neural network evaluation method for diving in 2002, and Figure 13-12 is a contour plot obtained by using national standard comprehensive evaluation for diving in 1998.
Figure 13-11 Evaluation results of BP neural network for diving in 2002
Figure 13-12 Schematic diagram of contour lines obtained by comprehensive evaluation of national standards for diving in 1998
The evaluation results show that the quality of groundwater in Qiqihar City has the following characteristics:
(1) The exceeding components in the zone are: ammonia nitrogen, nitrate, nitrite, arsenic, total hardness, chloride, sulfate, iron and manganese.
(2) "three nitrogen" pollution is serious, 14 dive monitoring points in the ammonia nitrogen exceeded 10, the highest content of 2.35 mg / L (No. 100 point in 2000), exceeding the water quality standards 8 times; nitrate exceeded 7, the highest content of 444.12 mg / L (228 point in 2002), exceeding the water quality standards of 7 (2002), 4 times more than the water quality standards; nitrite exceeded 12, the highest content of 1.680 mg / L (point 2 2002), 24.6 times more than the water quality standards.
(3) local total hardness exceeded the standard (15, 27, 228 points), the highest content of 1043.67 mg / L (228 points 2002); local arsenic exceeded the standard (2, 27, 183 points), the highest content of 0.079 mg / L (27 points 2001).
(4) The iron and manganese content in the groundwater in the area is generally higher, which is mainly controlled by the primary environment, the aquifer in the area is mostly silty sub-clay interlayer, its silt in the decomposition of organic matter, the formation of the reducing environment, so that the medium of high iron and manganese into low iron and manganese substances, therefore, the iron and manganese content of the groundwater is generally higher, but there is not much change in the past years.
Third, the prediction of groundwater quality in Qiqihar City
Using the two prediction models provided by the system, the gray model GM (1,1) and the time series analysis, the prediction can be made on the water quality of all wells at the same time, and the prediction of the water quality of specific wells can also be made according to the conditions of the year, the number of the point, the period of the water, and the water layer. The gray model GM(1,1) is suitable for short- and medium-term prediction of water quality, see Figure 13-13. time series analysis is suitable for medium- and long-term prediction of water quality, and before using time series analysis for prediction, in addition to selecting the predicted point number, water period, and aquifer, it is also necessary to set the corresponding weights for the prediction. Theoretically, the range of weights is 0 to 1, but in the application of the weights should be set according to the objective circumstances. If the data difference between adjacent years is relatively large, set a larger weight; conversely, set a smaller weight. In general, the size of the weights should not exceed 0.3, see Fig. 13-14.
Four, groundwater pollution risk evaluation in Qiqihar region
(I) Evaluation of intrinsic vulnerability of aquifers
The data of seven evaluation factors of intrinsic vulnerability evaluation of aquifers will be processed, and plotted into seven pieces of diagrams.
Figure 13-13 Gray prediction results
Figure 13-14 Prediction results of time series analysis
(1) Aquifer depth D
The aquifer depth information mainly comes from the borehole data, and the spatial distribution map of aquifer depth is obtained by using the Kriging interpolation, and then it is reclassified according to the evaluation criteria Table 13-2. Table 13-2 of the evaluation standard is reclassified. The depth of submersible aquifer in Qiqihar area is generally 2~5 m, and the grading of aquifer depth is shown in Fig. 13-15.
(2) Net recharge R
Net recharge = precipitation infiltration coefficient×yearly average effective rainfall in mm, and the yearly average effective rainfall in Qiqihar area is 419.9 mm, and the infiltration coefficient is divided into five zones from west to east, and the infiltration coefficient is divided into five zones from west to east. The infiltration coefficient is divided into five zones, from west to east is 0.30, 0.05, 0.23, 0.18, 0.07. After reclassifying the calculation results according to the evaluation standard, the net recharge grading diagram is shown in Fig. 13-16.
Figure 13-15 Aquifer depth grading diagram
Figure 13-16 Net recharge grading diagram Figure 13-16 Schematic diagram of net recharge grading
(3) Aquifer medium type A
The lithology of aquifer in Qiqihar area mainly consists of sand and gravel, fine sand with gravel, fine sand, gravel-bearing medium-coarse sand, gravel-bearing medium-fine sand, gravel-bearing coarse sand, medium sand, fine sand and gravel-bearing medium-sand soil, and the corresponding characteristic values are shown in Table 13-16. 16. The grading of aquifer medium type is shown in Figure 13-17.
Table 13-16 Characteristic values of aquifer medium type
(4) Soil medium type S
The soil medium type in Qiqihar area mainly consists of sand, sub-sand, sub-clay, loess sub-clay, and miscellaneous fill. The corresponding characteristic values are shown in Table 13-17. The grading of aquifer media types is shown in Figure 13-18.
Table 13-17 Soil Media Types Grading Criteria
Figure 13-17 Schematic Diagram of Aquifer Media Types Grading
The soil media types in Qiqihar are mainly sand, sub-clay, loess-like sub-clay, and miscellaneous fill. p>
Figure 13-18 Schematic diagram of soil medium type grading
(5) Terrain slope T
Terrain slope is calculated from the elevation of the elevation point elevation through the surface analysis in the spatial analysis of the slope map, Qiqihar region slope grading is shown in Figure 13-19.
(6) Baogas Belt medium type J
The main types of air-packed belt medium in Qiqihar area are sand, sub-sand, loess-like sub-clay, and sub-clay. The corresponding eigenvalues are shown in Table 13-18, and the classification of air pocket media types is shown in Figure 13-20.
Table 13-18 Eigenvalues of air pocket media types
Figure 13-19 Schematic diagram of terrain slope classification
Figure 13-20 Eigenvalues of air pocket media types in Qiqihar area
This figure shows the classification of air pocket media types in Qiqihar area. p>Figure 13-20 Schematic diagram of the grading of medium type in the air inclusion zone
(7) Aquifer permeability coefficient C
Aquifer permeability coefficient is divided into four zones, and its grading standard refers to Table 13-2, and the correspondence between the level and vulnerability conclusions is shown in Table 13-19. The grading is shown in Figure 13-21.
Table 13-19 Correspondence between levels and vulnerability conclusions
The classification diagrams obtained for each evaluation index are weighted and superimposed according to the following formula, resulting in the divisional map of the inherent vulnerability of the aquifer in Qiqihar area, which is shown in Figure 13-22.
Figure 13-21 Schematic diagram of aquifer permeability coefficient classification
Figure 13-22 Schematic diagram of aquifer intrinsic vulnerability zoning in Qiqihar region
(II) Evaluation of pollution source loading risk
The evaluation of pollution source loading risk in Qiqihar city was conducted with the year 2000 The total amount of pollutants discharged in the city in 2000 was 33,044.39 t, including 21,149.77 t of chemical oxygen demand, 11,576.81 t of suspended solids, 223.31 t of petroleums, 59.46 t of volatile phenols, 103.39 t of cyanide, 2.04 t of hexavalent chromium, 7.30 t of arsenic, and 15.05 t of sulphide. The main sewage discharge area is Longsha District.
Use of fertilizers and pesticides in urban areas (1999), the amount of fertilizers applied 13,750 t, of which 7,563 t of nitrogen fertilizer, potash 2,275 t, 953 t of phosphorus fertilizers, compound fertilizers 2,959 t, the amount of pesticide use of 295 t.
Industrial solid wastes and municipal garbage: solid wastes are mainly concentrated in the Tiefeng District and Longsha District. "Ninth Five-Year Plan" industrial solid waste ****15 kinds, 1335.58×104t, including fly ash, slag, smelting slag, hazardous waste, tailings, 950.41×104t, accounting for 71.31% of the total amount of solid waste. 2000 various solid waste as follows: hazardous waste 3.3206×104t, smelting slag, tailings, 950.41×104t, accounting for 71.31% of the total amount of solid waste. 104t, smelting slag 9.30×104t, fly ash 125.04×104t, slag 54.01×104t, gangue 0.01×104t, other 68.63×104t, totaling 260.31×104t.
Solid waste utilization in 2000: hazardous waste 2.68×104t, smelting waste 7.58×104t, coal gangue 0.01×104t, other 68.63×104t, total 260.31×104t. ×104t, fly ash 74.83×104t, slag 53.85×104t, other 64.46×104t, total 203.41×104t.
"Ninth Five-Year Plan" at the end of the period, the amount of hazardous wastes from the initial 8.878×104t to 3.3206×104t, comprehensive utilization amount 2.3206×104t. 104t, the amount of comprehensive utilization 2.68×104t, the utilization rate is 80.71%, the amount of disposal 0.6403×104t, the disposal rate is 99.99%, and the emission is 0.000226×104t, which only accounts for 0.0068% of the total amount. The generation of hazardous waste is mainly distributed in the mechanical, electrical and electronic equipment manufacturing industry and other industries in Furalki, Longsha and Mills Hill districts. The regional distribution is highly concentrated, with Furalki District accounting for 99.86% of the total hazardous waste.
In 2000, the amount of domestic waste generated was 71×104t, of which 21.7×104t was disposed of in landfills, 14.2×104t was disposed of in general, and 35.1×104t was disposed of in a simple way.
The wastewater discharge in Qiqihar City is shown in Table 13-20.
Table 13-20 Qiqihar wastewater emissions (unit: 104t)
Qiqihar North three districts (Tiefeng District, Longsha District, Jianhua District) *** there are three red star, Liming, Xiangyang living garbage treatment plant, Nanshan garbage dumping site. Among them, the Liming waste treatment plant and the Nanshan dumpsite cover an area of more than 30,000 m2, and the Red Star waste treatment plant covers an area of 40,000 m2 (3 pools). Xiangyang garbage treatment plant covers an area of 20 000 m2. sanitary landfill areas of the three harmless waste treatment plants of Red Star, Liming and Xiangyang *** count 6, with a total construction area of 121 900 m2 and a volume of 1 463 000 m3. From May 12, 2000 onwards, the three harmless waste treatment plants of Red Star, Liming and Xiangyang have been completed and put into operation one after another, with a daily treatment capacity of 800 t of domestic garbage, and up to now *** treatment of the central city of nearly 100 × 104t of domestic garbage, suction and discharge of garbage leachate 12.5 × 104t, 150,000 m3 of construction waste. 1 October 2003, the centralized disposal of medical waste project formally started construction, completed and put into use, the central city of medical waste will be carried out in a harmless centralized disposal.
Qiqihar city oxidation pond was built in 1970, is located in the city center area 17.5 km southwest of the old set of rivers, oxidation pond on the west side of the left bank of the Nenjiang River, the tail and the Nenjiang River connection. All projects by the nullah, oxidation - storage ponds, gates, pumping stations and other structures, nullah length of 6 km, the combination of the canal and the head of the pond with a pumping station, the head of the pond to the end of the pond discharge gate length of 9.3 km.
Oxidation of the pond north of the yellow sand beach from the new Litun, south of the Ngongxi district of the big five Fuma, accounting for the area of the old river channel of 8 km2, with an average of about 5.6 km2 of water surface, nearly 5.6 km2 during the period of abundant water, the water surface is about 5.6 km2, and the water surface is about 5.6 km2 during the period of abundant water. km2, the average water surface of about 5.6 km2, nearly 7 km2 in the period of abundant water. it bears the urban area of 60×104 population of urban mixed sewage self-care purification. Qiqihar oxidation ponds built at the beginning of the daily acceptance of sewage 10 × 104m3, after the reconstruction in 1986, the daily acceptance of sewage up to 25 × 104m3. 1998 by the Nenjiang River flood damage, 1999 repair desilting, the daily acceptance of sewage capacity up to 46 × 104m3. Therefore, the main source of pollution in Qiqihar is the red star, Liming, Xiangyang domestic waste treatment plant, workers Tun industrial solid waste dumps and the workers Tun. solid waste dumps, as well as oxidation ponds and outfalls. The loading risk of pollution sources in Qiqihar area obtained after the system operation is shown in Figure 13-23.
(C) Pollution Hazard Evaluation
According to the map of land use status quo in Qiqihar, the groundwater in the residential area is regarded as drinking water, the groundwater in the area of vegetable land, water field and farmland is regarded as non-potable, and the rest of the area is not used. The pollution hazard of Qiqihar area obtained by the system is shown in Figure 13-24.
(IV) Pollution Risk Evaluation
After evaluating the inherent vulnerability of the aquifer, the loading risk of the pollution source, and the pollution hazard, the three will be superimposed with the comprehensive consideration to obtain the pollution risk map of Qiqihar area, and the specific evaluation method is shown in Table 13 The specific evaluation method is shown in Table 13-10, and the evaluation results are shown in Fig. 13-25 through computer operation, where "0" indicates low risk, "1" indicates medium risk, " 2" indicates high pollution risk.
Figure 13-23 Schematic diagram of loading risk of pollution sources in Qiqihar region
Figure 13-24 Schematic diagram of pollution hazards in Qiqihar region
V. Early warning of groundwater pollution in Qiqihar
Early warning of groundwater pollution comprehensively takes into account the current status of groundwater quality, trends in water quality changes, and trends of groundwater pollution. Water quality trends, groundwater pollution risk of three factors, *** there are 45 possible states, through the computer analysis and calculation can determine the different states. The result of early warning is expressed by the degree of alert, "0" means "no alert"; "1" to "4" are in the order of "Light warning", "Medium warning", "Heavy warning" and "Huge warning". the threat level of groundwater contamination is getting more and more serious.
(I) Single-factor early warning
Through the groundwater quality evaluation, it is found that the phenomenon of exceeding the standard of ammonia nitrogen, nitrate, nitrite, arsenic, total hardness, iron and manganese in groundwater in Qiqihar is relatively serious, in which iron and manganese are mainly controlled by the primary environment, and there is not much change in the past years. Therefore, for water quality single factor early warning can be ammonia nitrogen, nitrate, arsenic early warning.
Taking arsenic as an example, firstly, the concentration value of the evaluation factor is extracted from the database, and secondly, the water quality status quo evaluation of the factor in the observation wells is carried out according to the national standard (GB/T14848-93), and the spatial distribution map of the factor in the study area is obtained through spatial interpolation as a result of the status quo of the water quality, see Figure 13-26. Then Daniel's Spearman's rank correlation coefficient method was used to analyze the multi-year trend of the concentration of the factor in the observation wells, and the spatial interpolation was used to obtain the trend distribution map, see Figure 13-27; finally, the distribution map, trend map, and the pollution risk map of the status quo were analyzed and calculated by the computer system to obtain the early warning result map, see Figure 13-28.
Figure 13-25 Schematic diagram of pollution risk in Qiqihar region
Figure 13-26 Schematic diagram of current distribution of arsenic in Qiqihar region
Figure 13-27 Schematic diagram of arsenic change trends in Qiqihar region Schematic diagram
Figure 13-28 Schematic diagram of early warning results of arsenic contamination in Qiqihar region
Most of the study area does not exceed the arsenic concentration, but there are three observation wells in the southwest of the arsenic concentration reaches the standard of Class V water, and years of monitoring results show that there is a tendency to further deterioration, so the region is a giant warning area, the pollution is very serious. In addition the arsenic concentration near the urban area meets the standard of Class III water, and there is no obvious trend over the years, but the risk of pollution is high, so the region is a heavy alarm area, which needs to be focused on.
Ammonia, nitrate pollution warning results are shown in Figure 13-29, ammonia pollution area is small, nitrate pollution is very serious, part of the total hardness of the region belongs to the heavy warning.
Figure 13-29 Schematic diagram of early warning results of ammonia nitrogen and nitrate pollution in Qiqihar region
(II) Comprehensive early warning
Figure 13-30 is a map of the current status of groundwater quality in Qiqihar region, from which it can be seen that the quality of shallow groundwater in the eastern part of the study area is Category III, and that in the western part of the study area, the quality of shallow groundwater in the western part of the study area is Category IV. The shallow groundwater quality in the western part of the study area is class IV water, which is no longer drinkable. By analyzing the trend of water quality pollution composite index of each monitoring well, the water quality of monitoring well No. 27 near Gudian station has improved, the water quality of monitoring well No. 41 located in Chahanuo village has deteriorated, and the water quality of the remaining monitoring wells has no obvious change, see Figure 13-31. Figure 13-32 shows the groundwater pollution in Qiqihar area. Early warning map, because the shallow groundwater in the region has generally suffered from pollution, the concentration of tri-nitrogen in the groundwater has reached the standard of class IV or class V water, so the calculation results are greatly affected by the current status of the groundwater, in the urban area and the vicinity of the city to the heavy, huge warning is dominated by. In the eastern part of the city warning is dominated by mild and moderate.
Figure 13-30 Schematic diagram of the current status of groundwater quality in Qiqihar
Figure 13-31 Schematic diagram of the distribution of the trend of changes in groundwater quality in Qiqihar
Figure 13-32 Schematic diagram of the results of the early warning of groundwater contamination in Qiqihar
Figure 13-32 Schematic diagram of the results of the early warning of groundwater contamination in Qiqihar< /p>
In fact, the early warning system for groundwater pollution should be used in areas where groundwater is not polluted to prevent pollution. In the areas of Qiqihar where the groundwater generally suffers from different degrees of pollution, the role and significance of using the pollution early warning system is limited and does not play the role of early warning.
(C) Qiqihar groundwater pollution causes and preventive measures
1. Groundwater pollution causes
Qiqihar area of the fourth system dive by the more serious pollution, the main reasons for the pollution are the following:
(1) Groundwater pollution early warning of the giant police, heavy police area most of the oxidation ponds near the Nenjiang River and the labor lake, groundwater dynamic monitoring data Confirmation of the Nenjiang River and Labor Lake perennial recharge of groundwater, contaminated ponds, rivers and lakes directly infiltration pollution of the fourth system of diving.
(2) The depth of the aquifer in the area is generally less than 4.5 m, and the lithology of the air-packed zone is mostly sub-clay, sub-sand and fine sand, and industrial seepage pits, wells and domestic sewage wells are all over the area, and every year there are 11,720 t of industrial wastewater and domestic sewage seeping into the ground through the seepage pits and seepage wells, which has caused the pollution of groundwater.
(3) the suburbs of vegetable fields and agricultural areas for a long time a large number of pesticides, fertilizers, fertilizers, pesticides, according to statistics, the annual use of fertilizers amounted to 17,531 t 178 t, these fertilizers, pesticides, irrigation water or rainwater seepage pollution of groundwater.
(4) industrial slag, domestic garbage and other solid waste piles and landfills is an important point of groundwater pollution sources, according to statistics, the annual discharge of industrial slag in the area of 186 × 104t, 63 t of domestic garbage. these slag and garbage are not harmless, most of the seepage control measures, in the atmospheric precipitation under the effect of filtration, can produce a large number of pollutants containing a variety of leachate, which is downward through the airbag, and then the leachate is released into the groundwater, and then the groundwater is polluted. The leachate can directly seep into the aquifer through the air pocket, which is an important way to cause the pollution of the fourth system of diving.
2. Groundwater Pollution Prevention Measures
(1) Strictly prohibit excessive discharge of industrial wastewater, and improve the seepage control standards of oxidation ponds and pollution discharge channels to prevent sewage from seeping into the ground.
(2) Accelerate the construction of urban drainage facilities, improve the drainage system, gradually cancel the urban domestic sewage seepage wells and simple toilets, and strictly prohibit the use of seepage pits (wells) in the form of industrial wastewater discharge.
(3) Accelerate the construction of urban waste treatment plants, promote scientific farming, rational fertilization (can increase the number of fertilizer application, reduce the amount of fertilizer each time), the appropriate amount of irrigation.
(4) Improve urban greening, not only can beautify the environment and regulate the climate, but also can absorb ammonia and nitrogen in the soil and reduce the pollution of groundwater.