Spatio-Temporal Distribution Characteristics And Response Analysis Of Non-Point Source Pollution In The Jianjiang River Basin

Jianjiang,the largest river along the western coast of Guangdong Province,is the mother river that nurtures tens of millions of people in the western region of Guangdong.In recent years,due to the rapid development of society,environmental issues have posed severe challenges to non-point source pollution,nitrogen and phosphorus,as the main nutrients in water bodies,are the main representatives of non-point source pollution research.Based on this,this article takes the control area of Huazhou Station in the Jianjiang River Basin as the research object.by analyzing the land use matrix and local development planning,three different land use scenarios are set up,and the distributed hydrological model SWAT is used to study the spatiotemporal distribution characteristics of non-point source pollution nitrogen and phosphorus in the basin under different land use scenarios,simultaneously using SPSS19.0 and Canoco4.5 to analyze the response between non-point source pollution nitrogen,phosphorus,natural hydrology,and socio-economic factors in the watershed,to provide theoretical support for the protection and improvement of the water environment and water quality in the watershed.The main achievements are as follows:（1）Aiming at the applicability of the SWAT model in this area,according to the DEM,land use,soil type and meteorological and hydrological data of the study area,the SWAT model of the control area of Huazhou Station in the Jianjiang River Basin was constructed,select relevant types of sensitivity parameters to calibrate and verify monthly runoff,monthly total nitrogen,and monthly total phosphorus at Huazhou Station.The results show that:all the indicators of the constructed SWAT model meet the requirements of model operation,and can simulate the runoff,total nitrogen and total phosphorus processes in the study area well,it can be used for follow-up research in this area.（2）Regarding the direction of future land use change in the research area,through a comprehensive analysis of the land use change matrix of the research area from 2005to 2018 and the"Overall Urban Planning of Maoming City（2011-2035）",it can be concluded that:,The future land use types in the controlled area of Huazhou Station in the Jianjiang River Basin are changing and developing towards an increase in construction land.（3）In order to reveal the spatio-temporal distribution characteristics of non-point source pollution under different land use scenarios,the SWAT model was used to simulate the nitrogen and phosphorus load intensities in watersheds under three different land use scenarios,the results show that:From the perspective of annual load intensity,farmland contributes the most to nitrogen and phosphorus production in the study area,and forest land contributes the least.From the perspective of yearly distribution,the load intensity of nitrogen and phosphorus is closely related to rainfall,and the rainy season is a critical period for the control of pollutants in the study area.From a spatial perspective,agricultural land is a key area for controlling watershed pollution.（4）To explore the response relationship between non point source pollution,natural hydrology,and socio-economic factors,the water quality data of the watershed was analyzed using SPSS19.0 and Canoco4.5,The results indicate that TP has significant variability,mainly positively correlated with the number of people in the primary industry.NH₃-N is mainly negatively correlated with rainfall,runoff,water temperature in natural hydrological factors,as well as the total value of the primary,secondary,and tertiary industries in the social economy,and per capita GDP.NO₃-N is mainly negatively correlated with natural hydrological factors such as runoff and p H,and significantly positively correlated with the number of people in the secondary and tertiary industries,as well as the total value of the primary,secondary,and tertiary industries in the social economy.（5）Based on the analysis and research on the temporal and spatial distribution characteristics of non-point source pollution and its response in this paper,in order to reduce the output of nitrogen and phosphorus from non-point source pollution in the watershed,it is necessary to strengthen management and control measures in various aspects such as land use,natural hydrological factors,and socio-economic factors;joint efforts between the government,enterprises,and the public are required to form an atmosphere in which the whole society jointly protects water resources,so as to realize the sustainable development of water quality in the basin.This study can provide research ideas for the control of pollutants,and provide theoretical support for protecting and improving the water environment and water quality in the basin.