Variation Characteristics Of Water Environment In The Estuary Of Tangxihe River (Chaohu Lake) And Its Simulation And Assessment

In order to investigate the temporal and spatial characteristics of the estuarywater environment in Chaohu Lake,9sampling points were established in theTangxi River estuary from September2012to July2013to collect waterre gularlyand sediments samples in different seasons. Based on the physicochemical analysisof water and sediment samples, we analyzed the nitrogen and phosphorusspace-time variation in the study water; Statistical analysis techniques carried outto analyze correlation and difference between the indexs. Simulation andassessment of the eutrophication status of water body was conducted on the basis ofthe combined and crossed characteristics of eutrophication evaluation system. Themain results were as follows:(1)The average concentration of TN, NH4+and TP exceeded V class standards of"surface water environment quality standard "(GB3838-2002). The TN/TP ratioshowed that nitrogen was a predominant limiting nutrient in the study estuary. Inthe running and stagnant water, the variation of TN and NH4+concentrations wasrelatively similar, but the concentrations of NO3-existed substantial differences andgreat temporal-spatial fluctuation appeared in the concentrations of NO3-and NO2-.Approximately the same change trend occurred in the concentrations of TP and SRPin the running and stagnant water, except in October2012and the following year inApril and June, the concentrations of TP and SRP in the running water is lower thanthat in the stagnant water.(2) Correlation analysis results showed that nutrient metrics between nitrogenand phosphorus were significantly correlated except between NO2-and TN, NO2-and TP, NO2-and SRP. According to the results of variance analysis, there weresignificant differences among NO3-, TN, SRP, TP and EC in the running andstagnant water.(3) According to the environmental quality standard of TN proposed by U.S.Environmental Protection Agency, TN in the estuary sediments was mainly in theclean level. In nitrogen metrics, the contents of NH4+and NO3-in spring andsummer is higher; in autumn and winter, nitrogen mainly exists in the form oforganic nitrogen, the contents of NH4+and NO3-decreased significantly. Thecontents of TP in the sediments ranged from55.75to1775.98mg·kg-1, higher inwinter and lower in summer; Ex-P only accounts for0.05%~7.41%of TP, higherin autumn and lower in summer. The contents of Fe/Al-P fluctuated significantly in space-time, higher in spring and lower in summer. The content of OM in thesediments ranged from1401.50to83029.05mg·kg-1, and had the same varyingpattern with TP.(4) Correlation analysis was conducted between pollution factors in thesediments. Results showed that OM was significantly correlated to nitrogen andphosphorus in different forms except NO3-; TN was found to be significantlyrelated to nitrogen and phosphorus in different forms except NH4+and Ex-P; TP didnot show any significant correlation to NO3-, NH4+and Ex-P.(5) Under the combined and crossed characteristics of randomness, fuzziness,grey and uncertainty in lake and reservoir water environment system,extended-blind number theory and comprehensive nutrition state index methodwere integrated to build eutrophication assessment and state identification modelsapplied in eutrophication assessment for estuary of Tangxi River. Study resultsshowed that the estuarine waters of Tangxi River were seriously eutrophic, with thedegree of credibility higher than51%. And under the fuzzy-cut set level of0.8,the expection value of comprehensive nutrition state index reached79.13,presenting the level of serious eutrophication.