First of all, highway construction has improved the environment.
Highway construction has played an extremely important role in promoting economic development along the route and improving the production and life of factories, mines and residents. Oases in arid areas are distributed in the desert in sheets or spots, and the distance between oasis and desert is generally long, so the traffic is inconvenient and the overall quality of traffic environment is poor. Highway construction in desert areas can improve the regional environment.
(1) Highway construction is conducive to improving the environmental quality of oases.
Oasis in desert area is the only place for human survival and reproduction. Highway is the main channel connecting oasis. Before 1949, there were only a few main simple highways in Xinjiang, and the traffic was inconvenient. Oasis is mainly a natural oasis, and the environment is mostly in a natural state. Since the founding of New China, especially since the implementation of the western development, the highway construction in Xinjiang has been very fast. The mileage of highway construction has increased rapidly, and expressways from Tufan to Urumqi to Da (Huangshan) and Urumqi to Kuitun have been built one after another, which has accelerated the flow of people, logistics and information, improved the productivity of desert areas and reduced natural oases and artificial oases. Reservoirs are built on the edge of fan-shaped areas and river valleys. Building fertile land in the desert; It also caused the environmental evolution from grassland to cultivated land and saline-alkali land to cultivated land and sandy land to cultivated land and saline-alkali land.
Highway construction has improved the road environment in desert areas.
With the development of environmental protection and disaster prevention in highway construction in desert areas, the environment in some highway areas has been improved. For example: ① Planting Hu Yangshu with a width of 3 ~ 4m on both sides of 3 15 National Road and in the east of Hotan City, so that the sandy Gobi is covered with green clothes, the desert becomes an oasis and the environment becomes better; ② In the section of Laofengkou Highway in Tacheng, in order to prevent the wind and snow from blocking the smooth road traffic, a large forest was planted on the east side of the highway, which turned the grassland into woodland and greatly improved the environment; ③ The Taklimakan Desert Highway crosses the Taklimakan Desert. In order to prevent sand dunes from climbing onto the highway and blocking traffic and transportation, artificial willows were planted on both sides of the highway to prevent wind and sand, which turned the former desert into an oasis and the desert highway into a green corridor, and the environment changed significantly due to highway construction.
Highway construction can promote the development of tourism in desert areas.
The desert area is rich in tourism resources, including Ya Dan, desert, Karez, Gobi, oasis and other unique tourism resources. Tianchi Lake in Tianshan Mountain, Bayinbuluke Grassland in Xinjiang, Hanas Lake in Altai Mountain and Rainbow Beach in Brzin are famous at home and abroad, which have great attraction for domestic and foreign tourists. Before 1980s, there were few roads and inconvenient transportation in Xinjiang, and few tourists traveled to desert areas. After 1990s, with the construction of National Highway 2 17 and National Highway 2 16, the number of tourists entering Xinjiang has increased year by year, and tourism has become one of the main industries in Xinjiang's economy. The artificial scenic spots in Tianchi and Hanas Lake have increased, and the environment has become more beautiful.
(d) Highway construction is conducive to the development of mineral resources and the improvement of mining environment.
The desert area is rich in mineral resources. With the proven mineral reserves in Xinjiang and the needs of regional economic development, highways will be built to develop mineral resources. For example, the Cocotohai mining area in Altay was a desert before the development of precious stones and asbestos mines. With the development of mineral resources and the construction of the highway from Fuyun to Keketuohai mining area, Keketuohai Town has been formed. After the construction of artificial towns and the improvement of the environment, an oasis with beautiful environment has been formed.
(e) Highway construction promotes urbanization and improves land economic benefits.
Highway engineering will improve the regional traffic situation in general, especially the socio-economic environment of nodes or intersections will be greatly improved. With the acceleration of urbanization in Xinjiang, highway nodes have become the main gathering places of population and funds in the region, and the tertiary industry represented by real estate will be given priority. With the rapid increase of urban construction land, the number and average area of urban land patches have also increased significantly, showing the characteristics of urban land distribution along the highway and the formation of highway node towns showing spatial concentration; Secondly, at the intersection of expressway network and expressway and other traffic trunk lines, due to the acceleration of urbanization, the population will concentrate on the location of these nodes, increasing the demand for non-staple foods such as vegetables, fruits, fish and meat. Under the action of the laws of market economy, the income gap per unit land area will obviously increase, which will lead to the transformation of land use in the surrounding areas where the node is located to high-yield and more intensive land use methods, such as farmland to orchard and aquaculture, and woodland to farmland and orchard. Farmland patches will show a trend of continuous fragmentation, while woodland and orchard as a whole will show the characteristics of spatial concentration, and agricultural land will change from low-efficiency to high-efficiency
The second is the environmental deterioration caused by highway construction.
The desert region is ecologically fragile, and highway construction is easy to cause environmental degradation, mainly in the following aspects.
(a) Highway construction has reduced the vegetation coverage in the road area.
According to the requirements of highway planning and design, such as straight line and bend, the highway will cross the oasis and the trees will inevitably be cut down. For example, to rebuild the highway from Altay to Brzin, it is necessary to cut down 6,672 trees of all kinds, mainly artificial forests in the 0-4 km section of Altay Pass. Cutting down trees will reduce vegetation coverage and regional environmental quality, especially cutting down farmland shelterbelts, which will have adverse effects on crop growth and landscape. Moreover, highway construction cuts down trees and occupies grasslands, resulting in the loss of regional plants, thus causing the loss of plant photosynthesis and reducing the release of oxygen into the atmosphere. With the decrease of regional vegetation coverage, ecological benefits will be lost. Generally speaking, the ecological benefits of green plants are 3 ~ 5 times of their economic benefits. The decrease of plants will also dry the climate in desert areas and aggravate desertification.
The desert area consists of sand, sand piles and sand dunes. In addition to mobile sand dunes, desert plants such as Haloxylon ammodendron, Salix psammophila, Alhagi, Artemisia selengensis, etc. generally grow in desert areas, and there is desert crust on the surface of Gurbantonggut Desert in Junggar Basin. Both desert plants and crusts have the function of sand fixation, which will destroy plants and crusts in the road area in the process of highway construction, thus strengthening sandstorm activities in the road area, intensifying land desertification, and causing quicksand to hinder the smooth road transportation.
The groundwater level in the wetland area is very high. When the highway passes through the wetland area, if the water supply source of the wetland is blocked, some wetland plants will die because of lack of water. For example, in the section from Altay, Brzin to K76-78 of National Highway 2 17, due to the high gravel soil subgrade and no water culvert, the water supply to the wetland on the west side of the highway was cut off, which led to the decline of groundwater level and the death of a large number of plants planted with reeds, resulting in the vegetation coverage rate on the west side of the road being only 1%, while that on the east side reaching 85%, resulting in the death of swamp wetland plants due to highway construction.
In the process of highway subgrade construction in desert area, it is necessary to use the earth and stone near the subgrade. When bulldozers push the soil, they also uproot plants, which leads to the decrease of vegetation coverage in highway construction in plain desert grassland areas. Moreover, due to the drought and lack of rain in this area, it is very difficult to restore plant ecology, and the bare soil makes desertification more serious.
(2) Highway construction provides favorable terrain conditions for the occurrence of road diseases.
When the highway design line crosses the platform and hilly area, the subgrade will be dug straight, forming cutting and steep slope, thus forming artificial landform, breaking the natural landform and providing favorable landform conditions for the intensification of soil erosion and the occurrence of road diseases. The results show that: ① the waste slag from highway construction in mountainous areas provides a material source for debris flow. For example, in the process of subgrade excavation of Du ()-Che Expressway on National Highway 2 17, due to improper spoil, a large amount of gravel and sediment accumulated in the valley, which provided materials for the occurrence of rainstorm and debris flow. In summer, soil erosion in mountainous areas is intensified, and mountain torrents and mudslides occur, which is harmful to highway traffic and river valley oasis. ②2 17 National Highway Duku Section, Urumqi-Bashan (Luntai)-Hejing Highway, and Fukang-Tianchi Highway cross Tianshan Mountain. Due to subgrade excavation, landslides and collapse surfaces appear, which collapse under the action of gravity, or slip surfaces are formed by flowing water, and landslides occur under the action of gravity. According to the preliminary investigation, there were four landslides and collapses from Fukang to Tianchi (Table 9-2).
Table 9-2 Distribution of Geomorphological Disasters of Fukang-Tianchi Highway in Sangong River Basin of Tianshan Mountain
In the southern and northern foothills of Tianshan Mountain, some gullies which were occupied by torrential flood erosion were filled in during the highway construction, and engineering measures were taken to block and drain them. Therefore, the road construction in the plain area of the piedmont slope changed the surface runoff path. However, due to the lack of precipitation in arid areas, heavy rains occur from time to time with great intensity. For example, in the summer of 1996, mountain torrents were formed on the Fukang-Qitai highway due to heavy rain at the foot of the mountain, and the floods carried a lot of sediment and gravel to block the drainage culvert of the highway and destroy the highway.
Kunlun Mountain has strong mountain uplift and river undercutting, and steep valley slope. Most rural roads built in mountainous areas lack slope protection projects, and there are many collapses, landslides and mudslides. The sandstorm in the foothills is serious, and the sandstorm in the Luopu-Qira highway is serious. Sand dunes climb the highway to block traffic (photo 57). In June of 20 10, there were 14 sand buried highways within the distance of1km (Table 9-3).
Table 9-3 Distribution of Main Road Geomorphological Disasters in Qira River Basin on the Northern Slope of Kunlun Mountain
(c) The deterioration of physical and chemical properties of water and soil caused by highway construction
When the highway crosses rivers and ditches, the dust generated by excavation, filling and pavement construction will pollute the water quality and even block the riverbed and ditches; Oil leakage from construction machinery and sewage generated by washing machinery flow into rivers and channels to pollute the water quality, which makes the water quality of rivers and channels worse.
Soil (Lufan)-Wu (Lumuqi)-Da (Huangshan) high-grade highway makes the soil along the highway loose, the vegetation coverage decreases, the wind erosion intensifies, the soil thickens, and the contents of P, K and salt decrease. There is slight lead pollution in the soil along Wuqi Highway (Qian, 200 1).
Saline-alkali land is widely distributed in desert areas. Saline-alkali soil is generally sticky and the groundwater level is high. When highway construction passes through saline-alkali land, if the flow path of groundwater in saline-alkali land is blocked, the groundwater level on one side of the highway will rise, and the secondary salinization will increase or swamp will occur, which will aggravate the soil salinization in some areas. This phenomenon can be seen on the highway crossing the alluvial fan of Dila River on the southern slope of Tianshan Mountain and the Kaidu River Delta in Yanqi Basin.
(d) Road traffic noise endangers people's health in oasis areas.
Once the expressway is completed, with the increase of automobile traffic, road traffic noise will increase, which will adversely affect the health of people along the road such as schools, office buildings and residential buildings. For example, the daytime road traffic noise in front of the teaching building of Qieke Township Middle School in Kiriko, Altay City exceeds the regional standard value1in the Standard for Urban Regional Environmental Noise (GB3096-93); According to the four standards of traffic trunk lines, the recent nighttime noise in Xiaheleke Village exceeded the standard by 3.8dB, and the mid-term nighttime noise exceeded the standard by 5.0dB.
(5) Highway construction pollutes the atmospheric environment in the highway area.
The dust produced by highway construction leads to excessive dust concentration in the surrounding air. As shown in the figure, during the construction of the highway from Urumqi to Da (Huangshan), the TSP over-standard rate was 72.5%, the maximum monitoring value was 4.78mg/m2, and the dust over-standard rate was 52.5%, with the maximum value of 247t/ km2 per month. With the continuous increase of traffic volume after running, the exhaust gas, vibration and noise emitted by vehicles have become public hazards, which will have a negative impact on people's production and living environment along the highway.
Automobile exhaust, road dust, road drainage, road maintenance, dust from transporting goods, accidents of transporting dangerous goods, etc. The waste gas produced in the process of highway transportation will pollute the road environment.
(6) Highway construction worsens the living environment of wild animals in desert areas.
There are few animals in desert areas, mainly rodents and reptiles. Because the activities of construction machinery and personnel interfered with the normal activities of nearby wild animals, some animals fled the road far away. In addition, highway construction will directly cause the death of soil animals, amphibians and reptiles, mammals and birds entering the construction area.
In the area where the highway passes, the highway construction destroys the natural vegetation in the road area, resulting in a decrease in coverage and a decrease in food for animals; The crossing of the highway makes the habitats of some wild animals artificially divided, which affects or restricts the activities, reproduction and migration of wild animals to a certain extent. Chemical pollutants, such as heavy metals, salts, organic substances, etc. The artificial light produced in the process of highway operation can cause visual interference, and it has adverse effects on the predation, growth, reproduction, migration and distribution of wild animals to varying degrees. Highway traffic noise directly affects the communication, living habits and mating of birds, and it is easy for wild animals to cause physiological stress and physiological disorder in a noisy environment for a long time. Roads provide convenient transportation for poachers and pose a threat to the survival of animals; Vehicles driving on the highway are harmful to the safety of animals crossing the highway. For example, on August 15, August 17, September 1 day and September 8, 2007, on the section of Xinjiang 2 16 National Road that runs through Xinjiang Karamaili ungulates nature reserve, four incidents occurred continuously. According to incomplete statistics, since 2005, 20 goose-throated antelope have been killed, and dead birds can still be seen on the road.
In addition, after the expressway runs, the harmful substances produced by automobiles will gradually worsen the living environment of organisms, such as air, water, soil, etc., leading to stunting of organisms, decreased reproductive function, increased diseases and decreased disease resistance, leading to a decrease in the number, and may even affect the entire biological community.