| Urbanized river is an important part of urban ecosystem worldwide.Along with the construction and development of cities,rivers provide stable water and fertile soil for human survival.Rivers began to serve as a conduit for material transportation as human society,cities,and transportation continued to develop.In the stage of modern urban industrialization,urban rivers play a more important role in the city becoming the water source,power source,traffic channel,pollution purification site,etc.Due to the influence of human activities,the ecology and natural landscape of rivers have been degraded seriously during the rapid urbanization.In recent years,citizens’concept of construction of eco-city has changed from"building parks in cities"to"building cities in parks".The protection and sustainable development of urban rivers and wetlands are of irreplaceable significance for Chengdu City to accelerate the construction of urban demonstration area of beautiful livable park.From the perspective of landscape ecological health,this paper studies and analyzes the current situation of water pollution of urban rivers in Chengdu.In this study,the Funan River,Jinma River and Pi River in Chengdu were taken as examples to objectively evaluate the status of river habitats,differentiate the current status of river ecosystems and analyze the ecological quality of the habitats and the spatial distribution of human disturbance.The main influencing factors of river water pollution were found by combining river water composition and river sediment composition.The spatial-temporal differences and causes of main pollution factors among three urban rivers in different Chengdu were further compared and explored.To explore the correlation between aquatic organisms and water pollution factors,heavy metal elements,aquatic biodiversity and richness in urban rivers,discover the internal driving mechanism of each environmental impact factor.In order to provide technical support for the establishment of ecological health evaluation system of urban river wetland in China,and provide theoretical basis for the restoration and improvement of urban river in Chengdu.Through one-year monitoring and analysis,the following conclusions were drawn.1)The landscape pattern and land use types of the three rivers have significant spatial differences.The construction and industrial land of Funan river and Pi River are concentrated in the middle and lower reaches.According to RHS habitat evaluation criteria,the habitat status of the three rivers under different spatial and temporal conditions was obtained.The habitat of Funan river is unstable and affected by many aspects,such as river flow velocity,riparian vegetation,land use and human activity intensity around the riparian,and bank protection type of the river.The habitat of Jinma river is relatively stable.The habitat of Pi river has a strong correlation with riparian vegetation and hydrological regime..2)WQI and WPI analysis showed that the water quality of the three rivers had significant spatial and temporal heterogeneity.The water quality of the three rivers is better in normal season than in wet season and dry season,and February is the worst month of water quality in the three rivers,which is severely polluted.The overall water quality of Funan River was the worst,which was inferiorⅴin most of the year.The Pi River was slightly polluted.The water quality of Jinma River is better than the other two rivers.The eutrophication status of the Funan river and Pi River showed a significant spatial change,with an obvious increasing trend from upstream to downstream.The eutrophication status of the Funan River and Pi River was lean or moderate,while that of Pi River was moderate.Jinma River generally presents mild eutrophication with no obvious spatial change.3)Based on the shannon-Wiener diversity index(H’)and Margalef(d _M)richness index of benthic species,the dominant benthic species were found to be different in the three rivers.The dominant benthic species in Funan river and Pi River showed significant spatial differences.The upper reaches of Funan river were mainly composed of mayoptera and other clean species live in good water quality.The middle reaches were mostly pollution-resistant species,which were heavily polluted.Downstream was light pollution.The dominant species in Jinma river were tricoptera and mayoptera,indicating that the water quality was promising.In the upper reaches of the Pi river,there were mainly tricoptera and amphipoda species that like to clean water,while in the middle reaches,oligochaeta and bdelloid species appear.In winter and spring,dirt-tolerant species appeared in the lower reaches of the Pi river,indicating serious pollution in the lower reaches in winter and spring.4)The landscape habitat status of the three rivers was significantly correlated with water quality.The Funan River was vulnerable to human activities.In Jinma River,human engineering activities and riparian vegetation attributes have an impact on water quality,indicating that its habitat was in good condition and water quality was less affected by external influences.A single habitat index affected several water quality parameters in the Pi River which indicated that some habitat indexes should be improved urgently.The analysis of eutrophication status and driving mechanism showed that the eutrophication status of the Funan river and Pi River was serious but there was no water bloom in the two rivers.According to the analysis,the imbalance of nutrient elements in the Funan River may lead to the inability of algae to proliferate,but there is still a potential risk of cyanobacteria outbreak.Although the N/P ratio suitable for algae growth in Pi river reached the nutrient condition of bloom,due to the change of hydrodynamic conditions,a large amount of water and rainwater runoff from upstream washed algae and inhibited the formation of bloom.After analysis,heavy metals in the river produced toxic effects on the reproduction of benthos and algae,caused water pollution,changed the dominant species of benthos,seriously affected the community structure of algae and photosynthesis of algae cells and reduced the synthesis of algae chlorophyll. |
