Soil is an important part of the environment. Due to the unreasonable factors in human industrial and agricultural production, it has led to the rapid accumulation of toxic and harmful substances in soil, which has reduced the yield and quality of plant production and seriously threatened human life and health. This study mainly studies soil pollution and groundwater pollution in Langfang urban planning area. The pollution of soil environment is mainly Hg, Cd and Pb, and the pollution of groundwater is mainly salinity, total hardness, F, CI, Mn, NO3-N and Fe.
1. Soil environmental pollution
1. Pollution status
The single point pollution of p>Hg is mainly distributed in Fengsheng Community, Hebei Geophysical Exploration Institute and Nanjianta Village. Cd elements are mainly distributed near the triangle; Pb element is mainly distributed in Yinhe Building, Pipeline Bureau Hospital and other places, and the pollution degree ranges from initial pollution to significant pollution (as shown in Figure 2-7, Figure 2-8 and Figure 2-9).
2. Harm of pollution elements
The pollution of soil environment will eventually accumulate in human body through trophic level or food chain.
Organic Hg accumulates in the brain, invades the central nervous system and destroys the cerebral vascular tissue, which can cause a series of central nervous system poisoning symptoms and congenital dementia. When Pb is poisoned, advanced neurological dysfunction and infant mental retardation occur. The symptoms of Cd poisoning are atherosclerotic renal atrophy, bone softening and deformation, carcinogenesis, teratogenesis, hypertension, diabetes and emphysema.
3. Types, scope and causes of pollutants
There are hundreds of factories and mines besides many government agencies, universities, institutions, shops, hotels, restaurants, entertainment and other industries in Langfang city, including 27 metal products and metal components companies, 39 general machinery companies, 27 chemical raw materials companies, 51 paper printing and packaging companies, and 21 electronic and electrical general equipment and equipment factories. They consume a lot of organic chemical fuels (hydrocarbons, oil and natural gas) and inorganic metal ores, and discharge a lot of waste water, waste gas, waste residue, smoke and dust into the environment. The standard rate of their purification treatment has not yet reached 111%, which is bound to have a certain negative impact on various environmental factors (air, water, soil, biology, etc.).
from the distribution of single element pollution, the high-value area of Hg is mainly distributed along both sides of Jingshan Railway, with the highest value of 811×11-9, which is located between Yuhua Road and Fengsheng Road. In addition, the content of Lisangyuan, Xihutun, Nanjianta and Beichang is relatively high, which is more than 111×11-9; The high value area of Cd element is located at the intersection of Yinhe Road-Xinhua Road, Aimin Road-Jiefang Road in the middle, Zhaizhezhuang in the northwest and Pengzhuang-Jujube Forest in the southeast. The high value area of Pb element is located in Zhougezhuang, Zhongsuo to Pengzhuang and Jujube Forest.
the measurement of soil in the vertical profile of 11km running through the urban area (from Beixiaoying to Nanjianta) shows that from the deep to the surface, the contents of Hg, Cd and Pb change the most, followed by As and Cu, which also shows that these elements are the main inorganic pollution elements in the area.
4. Pollution zoning
According to the weighted average method, the pollution indexes of Hg, Cd, Cu, Pb, Zn, N and other elements are selected, and the points exceeding the standard are comprehensively evaluated.
figure 2-7 current content map of soil Hg pollution in Langfang urban planning area
figure 2-8 current content map of soil Cd pollution in Langfang urban planning area
figure 2-9 current content map of soil Pb pollution in Langfang urban planning area
The formula is:
Comprehensive impact assessment of urban geological environment problems and regional sustainable development: taking Langfang urban planning area as an example
In the formula:
table 2-3 comprehensive weight table of each element factor
according to the formula, the comprehensive index is calculated, the soil environmental quality is divided into five grades, and the environmental quality zoning map of Langfang urban planning area is compiled (figure 2-11). P≤1 clean area; 1.1 < p ≤ 1.6 is still clean area; 1.6 < p ≤ 11 initial pollution area; 11 < p ≤ 25 significantly polluted areas; P > 25 heavily polluted areas.
As can be seen from the figure, the soil pollution in the urban planning area of Langfang City includes initial pollution area, clean area and clean area.
II. Groundwater pollution
1. Current situation of sewage discharge
According to the report of Environmental Status Assessment and Countermeasures of Water Engineering in Langfang City in 2198, there are 61 sewage outlets in this area, including 43 underground pipes and 17 open channels; There are 33 industrial places, 21 living places and 6 mixed industrial life places; There are 53 annual discharges and 7 intermittent discharges. The actual annual discharge of waste sewage into the river in the whole region is 42,158,111 cubic meters, accounting for 54.9% of the total discharge of waste sewage into the river in Langfang (including counties and cities). Industry is the main pollutant in this region, followed by life. See Table 2-4 for the annual discharge of major pollutants into the river.
Table 2-4 Annual Discharge of Major Pollutants into the River
Figure 2-11 Regional Map of Soil Environmental Quality in Urban Planning Area of Langfang City
2. Ways and Ways of Pollution
At present, no large-scale pollution has been found in deep groundwater in this area because of its strong anti-pollution ability. Only a few wells have not established a first-class health protection zone, but individual indicators of bacteria exceed the standard. The anti-pollution ability of shallow groundwater is weak, and pollution is more common. Its pollution modes include direct pollution and secondary pollutant. Direct pollution generally occurs in areas where industry and population are concentrated and pollution prevention ability is weak, and surface water directly seeps into the ground, forming a large area of shallow groundwater with high pollution; Secondary pollutant mode generally appears in the suburbs and the irrigation areas on both sides of the sewage drainage canal, and generally forms annular or zonal pollution. After long-term transportation, the concentration of pollutants is greatly reduced, so the pollution degree is low.
the pollution route of shallow groundwater in this area is generally vertical infiltration pollution type, that is, surface pollutants penetrate vertically into groundwater through vadose zone to pollute groundwater. In addition, surface water pollutants pass through a few wells or underground sewage pipes, forming a lateral infiltration pollution type, which is generally smaller than the vertical pollution area.
3. Groundwater pollution degree
(1) Detection status of groundwater pollution: ① Shallow groundwater. The detection rate of various pollutants is 111%, and the main pollutants are total hardness, NO3-N, Cl, and F. In 2111, the over-standard rate of NO3-N was 111%, and the over-standard rate of total hardness was 88.9%. The main over-standard substances were total hardness, dissolved total solids, Fe, Mn and F, and the average over-standard rates of Mn and total hardness were 87.3% and 84.9% respectively.
② deep groundwater. The detection rate of various pollutants is 1.111%, and the main substances exceeding the standard are F and Fe, with annual average exceeding standard rates of 66.4% and 24.2% respectively. In some years, Mn, NO3-N and Zn also exceeded the standard.
(2) Pollution zoning. The groundwater pollution index method is used to partition the pollution degree, and the calculation formula of comprehensive pollution index is:
comprehensive impact assessment of urban geological and environmental problems and regional sustainable development: taking Langfang urban planning area as an example
where: Pw is groundwater pollution index
Ci is the detection content of a pollutant
Coi is the initial value of a pollutant
n is the number of pollutants participating in the evaluation
According to the comprehensive pollution index.
Table 2-5 Classification Table of Groundwater Pollution Degree in Urban Planning Area
The shallow groundwater pollution degree in this area is divided into three grades. The area of unpolluted area (area I) accounts for 64.5% of the total area; Followed by light pollution area (area II), accounting for 33.1%; Moderately polluted area (Zone III) only accounts for 2.4% (as shown in Figure 2-11). Moderately polluted areas are distributed in built-up areas; The light pollution area is distributed in the periphery of the built-up area, mainly in the south and west of the built-up area, and a small piece appears in the eastern jujube forest village; The remaining areas are unpolluted areas.
fig. 2-11 zoning map of pollution degree of shallow groundwater in Langfang city
4. Groundwater quality evaluation
According to the Monitoring Report of Geological Environment in Langfang City, Hebei Province, the shallow and deep groundwater in this area were evaluated by using the national Groundwater Quality Standard (GB/T14848-93).
① shallow groundwater. There is no distribution area of Class I, II and III water in the shallow groundwater in Langfang urban planning area, but mainly Class IV water distribution area. The main substances that cause poor water quality in this area are: total hardness, total dissolved solids, nitrate, iron, manganese and chloride. Judging from the overall water quality distribution, the groundwater quality in the northwest is slightly better than that in the southeast.
② deep groundwater. There is no distribution area of Class I and III water in the deep groundwater in Langfang urban planning area, mainly Class II water and Class IV water. Class II water is mainly distributed in the southeast of the urban planning area of Langfang City, and the rest of the vast areas are mainly Class IV water distribution areas, as shown in Table 2-6, and only a few points are Class V water (old state grain depot west of the urban planning area). The components with high single element are F, Fe and Mn, which belong to primary pollution.
table 2-6 water quality distribution table
5. harm of pollutant f to human body
a proper amount of f (1.5 ~ 1.5 mg/d) is an essential element for human beings and animals, which can promote the calcification of teeth and bones and form a protective layer on the outside of teeth. Without it, dental caries and bone deformation are prone to occur.
excessive F(≥4mg/d), whether it enters human body from drinking water, food or air, will affect endocrine functions such as thyroid gland, inhibit enzyme system, affect central nervous system and destroy conditioned reflex. The most serious fluorosis is skeletal fluorosis: bone lesions, destruction, accumulation, softening, adventitial bone hyperplasia, ligament calcification, osteoporosis, followed by muscle atrophy and limb deformation.
after a large amount of f enters the body, it can form caf 2, which is mixed with cartilage tissue in bone, destroying phosphorus and calcium metabolism and affecting the normal development and growth of bone. CaF2 also leads to incomplete calcification of teeth and damage of tooth enamel.
6. endemic fluorosis, skeletal fluorosis distribution and prevention and treatment
the high fluorine content in groundwater in urban planning area has caused endemic fluorosis. According to the statistics in 2111, the population of endemic areas in this area was 174,611, accounting for 37.96% of the population in urban planning area. The main symptom of fluorosis is dental fluorosis, followed by skeletal fluorosis. The main cause of fluorosis in this area is drinking groundwater with high fluoride for a long time. Since the 1981s, the municipal party committee and municipal government have attached great importance to the treatment of endemic fluorosis, invested a lot of manpower and material resources, improved water to reduce fluoride, and treated fluorosis from the source of the disease, which has achieved good results in the past 21 years. By the end of 2111, there were 58,111 people who benefited from improving water and reducing fluoride, accounting for 91.55% of the population in the ward.
to sum up, the soil pollution in this area is mainly point pollution, and the trend of soil heavy metal pollution is distributed along both sides of Jingshan Railway and the old city, and the pollution degree is initial pollution. Shallow groundwater pollution is divided into three grades, of which unpolluted areas account for the majority, unpolluted areas account for 64.5% of the total area, lightly polluted areas account for 33.1%, and moderately polluted areas only account for 2.4%. The most polluted area is located in the built-up area, followed by the periphery of the built-up area, the suburbs, Wanzhuang, Jiuzhou, Yangzhou and other central and southern urban planning areas, which are the production bases of non-staple food and vegetables in this area. From 1996 to 2111, the pollution assessment results in the past five years showed that the pollution showed a decreasing trend, the area of unpolluted areas gradually increased, and the heavily polluted and severely polluted areas disappeared, which indicated that Langfang City had achieved remarkable results in controlling urban pollution in recent years. However, the distribution of heavily polluted areas at present is related to the sewage discharged by starch factories and wineries in the north-west of the urban built-up area, which is the south-west side of the upstream of urban water sources, which is unfavorable to the protection of water sources.
The deep groundwater in this area is mainly Class IV water, and Class II water is mainly distributed in the southeast of urban built-up areas.
The endemic fluorosis and skeletal fluorosis caused by high groundwater F in this area have been controlled from the source with the attention and strong investment of party committees and governments at all levels, with a control rate of 91.55%.