Study Of Water Quality Evaluation And Pollutant Spatio-temporal Distribution For Complicated River System

The river system is a kind of environmental systems with plenty of non-determinacy and complex changes.In order to comprehensively assess water quality and study spatial-temporal characters to the complicated river systems,the multiple emerging techniques can be employed under the framework of system theory,such as the large-scale data analysis,computer technology and information technology.The above method enables to evaluate the water quality quantitatively and visually,and study the distribution characteristics of its key indexes,which is meaningful for the scientific environmental projects and comprehensive countermeasures.This dissertation firstly investigated the natural,social,economic,and river situations of Linyi national development zone.Then,this complicated river system which includes interconnected rivers with different scales and functions was chosen as the research object.By conducting the comprehensively assessment for water quality and pollution spatial-temporal distribution characteristics,the study intends to provide scientific basis of water environmental projects and countermeasures for river systems nearby and those in the other regions in China.The major research contributions are as follows:?1?Study and application of comprehensive water quality assessment based on Canadian Water Quality Index?CWQI?modelThe CWQI model is efficient in comprehensive analysis to long series and large-scale data,which has huge advantages than any other methods in the water quality assessment of complex river systems.According to the pollution features in China,the factor analysis method was applied to optimize the participating factors of CWQI.Therefore,adaptive governances can be generated based on CWQI in the research area.The inland river system of Linyi national development zone was chosen as the study area,and the CWQI method was applied to evaluate water quality and pollution distribution.The results show that:?a?The water quality of all monitored sections is worse than Grade 5,and the water quality is heavily polluted.The NH₃-N and TP are the dominant factors and the minor factors are COD_Cr,BOD₅,and potassium permanganate index.?b?The overall inland water quality determined by CWQI models is poor and cannot meet the value corresponding to Grade 4 in guideline.?c?The single factor evaluation method can figure out the major pollution factors while the CWQI method can reflect the comprehensive water quality of local river system on the whole.The combination of the above two methods can make the water evaluation more scientific,comprehensive and accurate.?d?The overall changing trend of inland water quality determined by Spearman rank correlation coefficient is not obvious.The changing trend of proportion of monitored sections classified as Grade 4 doesn't reach the significant level and the variation of water quality remains stable.The proportion of monitored sections classified as Grade 5 shows a significant increasing trend.The proportion of monitored sections classified as worse than Grade 5 shows a significant decreasing trend.The CWQI values of inland river system are moderate.Though some measures have been taken,the water quality keeps nearly unchanged.?e?By analyzing the exceedance rate and average times of exceedance,it is concluded that S6^S11 are heavily polluted,mainly in Xiebai River,Pengbai River,Xiaodungou,Huangbai drain and the downstream of Yubai River.?2?The development and application of comprehensive evaluation system for black and odorous water based on complicated river systemFrom the perspective of system theory,this dissertation has combined the organoleptic evaluation with the comprehensive water quality identification index to develop an assessing system to evaluate the black and odorous water for complicated river system.By applying this evaluation system to the study area,the critical threshold of inland river system of Linyi development zone is determined as 6.7.The black and odorous water was found in Ligong River,Xiaobudong Trunk,Yubai River,Xiebai River,Pengbai River and Xiaodungou from June 2016 to May 2017.Through data analysis and field investigation,this dissertation has researched the main reason that leads to the appearance of black and odorous water and proposed feasible solutions.?3?Development of large-scale water quality inversion model based on Remote Sensing?RS?technologyBased on the theory of water quality remote sensing monitoring,this dissertation has developed RS-based models for CWQI,ammonia nitrogen?NH₃-N?and Total Phosphorus?TP?by taking Yi River and Shu River as examples of large-scale river system.According to the Pearson correlation analyses between spectroscopic and measured data,sensitive bands and their combinations were revealed.In order to calculate quantitative relation between satellite reflectivity and water quality data,RS data processing software ENVI was deployed to process and validate linear regression models.The results show that:?a?The correlation coefficients?r?for CWQI,NH₃-N and TP using red band are the highest in both Yi River and Shu River,and the absolute value of r ranges from 0.7264 to 0.9118.Therefore,the red band reflectance was chosen to establish remote sensing models of CWQI,NH₃-N and TP for both Yi River and Shu River.?b?Remote sensing models of CWQI,NH₃-N and TP for Yi River and Shu River were established by linear fitting,respectively.For Yi River and Shu River,the fitting coefficient R² ranges from 0.498 to 0.822 and the correlation coefficient r for validation is between 0.740 and 0.937.Even though the models of NH₃-N and TP have lower fitting coefficient,the validating correlation coefficients are satisfactory and the error values are relatively small.Then it can be concluded that it is feasible to establish models using red band and ground-measured data,and the corresponding models can be used for monitoring CWQI,NH₃-N and TP for Yi River and Shu River,and furthermore,future studies.?4?Study on spatial-temporal distribution and environmental governances of Yi River and Shu River using Remote Sensing TechnologyThe distribution characteristics for CWQI,NH₃-N and TP were acquired using the water quality remote sensing models for Yi River and Shu River,and the Geographic Information System?GIS?technology was employed for its spatial and temporal distribution characteristic analysis.The results show that:?a?From 2014 to 2017,the overall water quality of Yi River and Shu River has improved gradually.NH₃-N and TP concentrations can meet the requirement of Grade 3,and are seasonally changed.The water quality is relatively poor in dry season.?b?The utilization of land on the banks and the industrial structure difference both have influence on the water quality of Yi River.The water quality of Yi River is much better that that of Shu River.Yi River is closed to the city,and the sewage network and treatment facilities are relatively complete.As a result,sewage and industrial wastewater have no obvious effect on the water quality of Yi River.NH₃-N and TP concentrations tend to increase from upstream to downstream in Shu River.Based on the utilization of land on the banks of Shu River,the main pollution sources are villages,farmlands and chemical enterprises.The reason that leads to the better water quality of Yi River is that it is near to urban area where sewage treatment facility is perfect,while Shu River is heavily affected by the above-mentioned pollution sources.NH₃-N and TP concentrations are increased in some regions.