富营养化湖泊沉积物有机质矿化过程中碳、氮、磷的迁移特征

摘要

采用室内培养的方法,以富营养化湖泊太湖为例,研究了沉积物有机质矿化过程中碳、氮、磷的迁移特征.结果表明,在沉积物中的有机质矿化过程中,碳以溶解性无机碳释放至水中,同时以CH4和CO2形式释放至大气中,培养结束时,CH4和CO2累积排放含量分别为1492.21和498.96mg/g(dw),其中CH4占气态碳的89.16％(以C质量计);此外,大量的氮、磷营养盐释放至上覆水体,水中总氮、总磷和铵态氮的最高浓度分别是初始浓度的62.16、28.16和139.45倍,而硝态氮浓度在整个培养过程中逐渐下降,培养末期浓度是初期的0.21倍;厌氧条件下,沉积物有机质的矿化,不仅可以生成大量的CH4、CO2气体,还能够促使沉积物中铵态氮和磷的释放;而沉积物有机质矿化释放的碳、氮、磷营养元素又能加剧湖泊富营养化程度,促进湖泊水体的初级生产力,从而增加湖泊沉积物有机质输入.这样的循环方式可能是湖泊富营养化自维持的重要机制之一.%The migration characteristics of carbon,nitrogen and phosphorus during organic matter mineralization were studied through laboratory incubation experiments,to simulate Lake Taihu,a large eutrophic lake in China.Results showed that sedimentary organic matter was mineralized and released dissolve inorganic carbon.At the end of incubation,the cumulative contents of CH4 and CO2 was 1492.21 mg/g(dw) and 498.96 mg/g(dw),respectively,with CH4 occupied 89.16％ of gaseous carbon (in C mass).In addition,a large amount of nutrients,such as nitrogen and phosphorus,were released into overlying water.The highest concentrations of total nitogen,total phosphorus and ammonium nitrogen were 62.16,28.16 and 139.45 times of the initial concentration,respectively.While nitrate nitrogen concentration declined throughout the incubation time,and its final concentration was 0.21 times of the initial concentration.Under anaerobic conditions,organic matter mineralization not only produced a large amount of CH4,CO2 but also promoted the release of ammonium nitrogen and phosphorus from sediments.These soluble inorganic nutrients further aggravate the lake eutrophication and promote the primary production,with subsequent increasing input of organic matter into lake sediment.This may be one of the important reasons for self-maintenance of lake eutrophication.