Aquatic Plant Roots Organic Acid Drive Sediment Nitrogen And Phosphorus Transformation Mechanism

In this paper,six kinds of typical aquatic plants in TaiHu lake(Vallisneria natans,Potamogeton malaianus,Phragmites australis,Acorus calamus,Nymphoides peltatum,Water chestnut)as the research object,and the little molecular organic acids in six kinds of aquatic plant roots were collected in different temperature(15?,25? and 30 ?)and under the different nitrogen and phosphorus levels.Root secretion collected after lyophilization enrichment was determinated the species of little molecule organic acid by high performance liquid chromatography(HPLC).Oxalic acid and formic acid is the prevalence of two kinds of organic acid in six kinds of aquatic plants,including formic acid content is the highest,followed by lactic acid and oxalic acid in addition and lactic acid is also widespread.This three kinds of organic acids is total organic acid content of 33%to 95%.The content of organic acid secreted by Acorus calamus slump sharply in 30?,and oxalic acid,formic acid and lactic acid than the highest period production fell by 54.97%,57.35%and 98.03%respectively.However,the little molecule of organic acid content secreted by the roots of Nymphoides peltatum is the highest in 30?.Little molecule of organic acid content secreted by the roots of Vallisneria natans decline with increasing temperature,and the Potamogeton malaianus,Phragmites australis and Water chestnut secret the biggest organic acid at 25 ?.Phosphorus deficiency induced acetic acid and malic acid secret largely,the Vallisneria natans,Acorus calamus,Nymphoides peltatum and water chestnut didn't detect the acetic acid under the condition of abundant phosphorus,but acetic acid production in the phosphorus deficiency were 26.38 mg/L,15.78 mg/L,39.36 mg/L and 33.38 mg/L,as well as water caltrop secrete malic acid content increased by 46.8%.High nitrogen stress significantly reduced the kinds and content of the aquatic plant roots secretion little molecule weight of organic acid.High nitrogen stress inhibits production of lactic acid in aquatic plant roots compared with the normal nitrogen level,and also reduce the content of oxalic acid and formic acid,which has significant inhibitory effect for water chestnut root secretion of malic acid and succinic acid.We collected three kinds of sediments(including Dong Tai Hu,Jin Hu Xin and Gong Hu Wan)in TaiHu lake where we plant Vallisneria natans,Acorus calamus and Nymphoides peltatum respectively,for 90 days.We collected aquatic plant rhizosphere and non rhizosphere sediment that were determinated the ion of phosphorus after lyophilization every once in a while.The results showed that the aquatic plant roots prompt the content of exchangeable phosphorus to lower in the sediment,and the exchangeable phosphorus has the most obvious reduce in sediments of Jin Hu Xin under the action of Vallisneria natans roots(78.3%).Al-P,Ca-P and Fe-P content increases under the activation of roots,among them,the content of Al-P increase by 265.6%under the influence of Vallisneria natans roots in Dong Tai Hu sediments,the content of Fe-P increase by 1134.33%under the influence of Acorus calamus roots in Gong Hu Wan sediments,the content of Ca-P increase by 251.28%under the influence of Acorus calamus roots in Da Pu sediments,and the content of ammonia nitrogen reduce by 59.24%under the influence of Vallisneria natans roots in sediments.We configure oxalic acid,formic acid,lactic acid standard solution,as well as three kinds of organic acid mixture,then We will mix acid with freeze-dried sediment samples mixed in certain proportion,and set up the pure water controlled trials.In the next moment,we take supernatant to determine the content of dissolve phosphorus and ammonia nitrogen after using Bed temperature incubator to mix fully for 72 hours.Results show the content of dissolve phosphorus and ammonia nitrogen increase faster than in pure water in supernatants.It found the mixed acid extraction rate is higher than single organic acid that pure water,oxalic acid,formic acid,lactic acid and mixed acid solution respectively extracte three kinds of insoluble phosphate,but also found the extraction ratio of Al-P is highest,followed by Fe-P,finally is Ca-P.