| The study of river self-purification ability has important guiding significance for the control of water pollution and the restoration of water ecology.Biological action is the most critical part of the river's ability to self-purify.At the same time,the difference in biological structure will directly affect the self-purifying ability.The role of microorganisms and the degradation ability of aquatic animals and plants to pollution are different.The paper studies the role of different biological structures in river self-purification,and establishes the relationship between self-purification ability and biological structure.In order to explorer the role of biological effects in river self-purification,in-situ static microbial degradation coefficients were measured at a total of 9 points in the urban mainstream,rural tributary,and rural mainstream sections of the Qing-Yi River from July to September 2017.Water quality indicators include COD,ammonia nitrogen,total nitrogen and total phosphorus,and high-throughput detection of microorganisms was performed on characteristic river sections.In 2017 and July-September 2019,watershed biological aquatic surveys were conducted.Collection and analysis of aquatic plants,benthic and fish samples,and determination of water environmental factors were carried out.The coefficient was calculated,and the species composition and community structure of the aquatic organisms in the watershed were analyzed.The effect of large-scale aquatic organisms on macroscopic self-purification was studied.The results show:(1)Main groups of microorganisms in the characteristic river sections are Pyrus,Thermomonas,Flower buds,Pseudomonas,etc.Most of them are common obligate aerobic bacteria.The degradation principles of COD,NH3-N,TN and TP in water bodies are different,leading to the dominant aerobic microbial community in the river,which determines that the biological self-purification of the river is mainly reflected in the stronger purification of oxygen-consuming pollutants.After killing the microorganisms,the degradation ability of the concentration of oxygen-consuming pollutants is significantly reduced,but the stable microbial degradation has played a role in the degradation of COD by about 76% and a role of ammonia nitrogen by48%.(2)The dominant species of the main biological community in the main stream of the Qing-Yi River are: aquatic organisms: Yarrow,Reeds,Cotoneaster,and Goldfish algae;Benthic organisms: Silkworm,Chigger larvae;Fish: wheat ear fish,Catfish and Chinese sturgeon.According to the analysis of biodiversity,the Shannon-Winner averages of aquatic plants,benthic organisms,and fish in the Qing-Yi River are 1.165,0.743,and 1.538,respectively;the average values of Marglef species richness are0.926,0.532,and 0.352;The average values of Pielou were 0.776,0.550,and 0.869,respectively.Among them,the benthic was most affected by environmental factors.After cluster analysis,the Shannon-Winner diversity index of aquatic organisms,benthic and fish can represent the structural characteristics of aquatic organisms.RDA analysis of dominant degradation species,biodiversity and COD,ammonia nitrogen,total phosphorus along the course of the degradation coefficient and DO along the way attenuation coefficient,showed that aquatic plants have a greater impact on the degradation coefficient of COD and ammonia nitrogen.The degradation of total phosphorus by benthic soil has a greater relationship with the attenuation of DO.(3)After comparing the water quality,biodiversity,and degradation coefficient before and after ecological restoration in the Qing-Yi River Basin.It was found that they showed a positive relationship as a whole.Combining the previous studies of microorganisms and aquatic plants,it is shown that during the river self-purification process,different organisms have different degradation capabilities for different pollutants,which is the root cause of the river's self-purification ability. |
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