Abstract
In this paper, the characteristics of water pollution in Yitong River were analyzed by the comprehensive pollution index method. Combined with the pore water concentration gradient method and Fick’s first law, the release characteristics of nutrients at the sediment–water interface of Yitong River (Jilin Province, China) were studied. The results showed that the distribution trend of nitrogen and phosphorus content in the overlying and interstitial water of the Yitong River was the same, and the highest values appeared at the S3 and S5 points in the urban section. The water quality was mainly affected by nitrogen pollutants in domestic sewage. The evaluation results of the water quality comprehensive pollution index showed that the pollution degree of interstitial water in urban areas was much higher than that of the overlying water, and the endogenous nitrogen and phosphorus pollutants had the risk of diffusion to the overlying water. The exchange flux analysis of ammonia nitrogen (NH4+-N), total dissolved nitrogen (TDN), and total dissolved phosphorus (TDP) in water showed that the diffusion flux of NH4+-N ranged from 0.03 to 6.52 mg·(m2·d)−1, and the sediment was the “source” of ammonia nitrogen pollutants. The range of TDN diffusion flux was −1.57 to 11.6 mg·(m2·d) −1, and the difference between points was large. The sediment was both the “source” and “sink” of nitrogen pollutants. The range of TDP diffusion flux was −0.05 to 0.22 mg·(m2·d) −1. Except for point S8, the TDP diffused from sediment into the water body. Among all the sampling points, the diffusion fluxes of NH4+-N, TDN, and TDP at the S3 point were the largest, the release rate of endogenous pollutants was the most rapid, and the pollution to the water quality was the most serious. The results are of great significance to the exchange flux of nutrients at the sediment–water interface of rivers and the prevention and control of water eutrophication. It also provides a reference for the study of nutrient exchange flux at the sediment–water interface of rivers and other surface water bodies worldwide.
Highlights
In recent years, with the rapid development of the economy and the continuous improvement of living standards, the problem of river eutrophication in China has become increasingly prominent, which seriously threatens the water environment quality and water safety [1]
This showed that the high concentration of ammonia nitrogen produced by the decomposition of organic pollutants in domestic sewage by denitrifying bacteria was the primary source of ammonia nitrogen in the overlying water body of the river in summer
It was found that the water flow speed at this point was fast, the sediment was washed away by the water body, and the surface sediments mainly were sand and gravel, which led to the low concentration of nitrogen and phosphorus nutrients in the interstitial water [42]
Summary
With the rapid development of the economy and the continuous improvement of living standards, the problem of river eutrophication in China has become increasingly prominent, which seriously threatens the water environment quality and water safety [1]. When the water environment is disturbed, the nutrient substances with high content in sediment are released to the overlying water by diffusion, convection, and resuspension [7,8,9] This phenomenon mainly results in the content of nitrogen and phosphorus exceeding the standard limits. It is of great significance to study the distribution characteristics of nutrients and the interfacial exchange flux of sediment, interstitial water, and overlying water, and to analyze the present situation and the source of nitrogen and phosphorus pollution in water bodies [15,16]. The results can provide reference for the precise remediation of nitrogen and phosphorus pollution in the Yitong River and provide data accumulation for the distribution characteristics of nutrients in the water and sediment and the nutrient exchange flux at the sediment–water interface of North China rivers. The study provides a scientific basis for the source analysis and eutrophication treatment of rivers and other surface water worldwide, with significant theoretical and application value
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