Contamination Characteristics Of Nitrogen And Phosphorus In Sediments And Simulation Of Its Profile Concentration In Pore Water From Shiwuli River In Chaohu Lake

Based on the analyzed date, the chemical forms, pollution characteristics andbio-availability of nitrogen and phosphorus in the sediments from Shiwuli River inChaohu Lake were investigted and its profile concentrations in pore water in theplanted alternanthera philoxeroides fields was modeled in this paper.The main contents and results of this study can be summed up as follows:（1） The bio-available nitrogen and phosphorus in the surface sediments（0¹0cm） collected from15sampling points in Shiwuli River were analyzed andspatial characteristics of them were explored by way of chemical sequentialextraction method. Study results showed that there was significant variability of thecontent levels of various bio-available nitrogen and phosphorus forms. Generally,the four bio-available nitrogen forms comprised53.4%to67.9%of the totalnitrogen（TN） and the content levels of them follows the sequence: w（SOEF-N）＞w（IEF-N）＞w（SAEF-N）＞w（WAEF-N）, of which the w（SOEF-N） was411.35⁹65.47mg/kg with a proportion of33.4%⁴3.7%. The four bio-availablephosphorus forms comprised47.3%to89.4%of the total phosphorus（TP） and thecontent levels of them follows the sequence: w（SAEF-P）＞w（SOEF-P）＞w（WAEF-P）＞w（IEF-P）, of which, the w（SAEF-P） was311.74⁹60.33mg/kg witha proportion of33.0%⁷8.0%. Generally, there was weak correlation between thefour bio-available nitrogen forms, while notable correlation could be found for thebio-available phosphorus forms. But there were no significant correlations betweenthe bio-available nitrogen and phosphorus forms.（2） Chemical forms and spatial distribution characteristics of nitrogen andphosphorus in the sediments （0⁶0cm）, collected from seven sampling points inShiwuli River, were investigated and their correlations were analyzed. The studyresults showed that total nitrogen （TN） was dominantly comprised of organicnitrogen. And the contents of calcium-phosphorus and iron-phosphorus were thehighest among the different phosphorus forms. There were significant differencesin the distribution characteristic of content levels of different phosphorus forms inthe longitudinal direction, while little change can be found for nitrogen had. In thevertical direction, all nitrogen forms （i.e. TN, ON and NO₃^--N）presented obviousvariability, and active phosphorus （i.e. Ex-P, Al-P and Fe-P）showed surface enrichment while the contents of inactive phosphorus （Oc-P, Ca-P, De-P and Or-P）had no significant changes with the depth increase.（3） The effects of alternanthera philoxeroide on the nitrogen and phosphoruscharacteristics of sediments and pore water were explored according to three classicrepresentative sampling points in the planted alternanthera philoxeroides fields and onereference site in the seldom vegetation. Study results indicated that the contents ofbulk density and organic matters increased obviously while the nitrate nitrogendeclined as a result of the existence of alternanthera philoxeroides. On the interfaceof sediments and overlying water, there were obvious concentration gradients bothfor ammonia nitrogen and nitrate nitrogen. And the former presented a possiblediffusion trend from the overlying water to the sediments, but the latter showed areverse trend. As for phosphate, howener, there had no notable regularity.（4） The profile concentrations of nutrients in pore water in the plantedalternanthera philoxeroides fields were modeled by means of the Origin software. Itwas shown that ammonia nitrogen and nitrate nitrogen fit the exponential function（c_x=exp（c₀+c1x）or c_x=exp（c₀+cx+c₂x²ï¼‰ï¼‰ well. But the fitting effect of phosphatewas not good owing to the complex changing progress.