蠡湖表层沉积物氮矿化过程及其赋存形态变化

蠡湖控源截污10年后,水体中总氮仍处于一个较高水平.为探讨沉积物氮的释放对上覆水体的影响,利用淹水培养法研究沉积物矿化过程中不同形态氮的变化特征,并探讨了矿化过程中有机氮和无机氮的转化过程.结果表明,矿化作用前后沉积物中游离态氮(FN)均值由94.26 mg·kg~(-1)增加到230.71 mg·kg~(-1),以氨氮(NH+4-N)和溶解性有机氮(SON)为主;可交换态氮(EN)均值由82.50 mg·kg~(-1)增加到165.32 mg·kg~(-1),以氨氮(NH+4-N)占绝对优势;而酸解态氮(HN)均值由1 044.70mg·kg~(-1)减少到815.93 mg·kg~(-1),以氨基酸态氮(AAN)为主,残渣态氮(RN)基本保持不变.淹水培养过程中酸解态总氮的比例由67.18%下降到52.50%,减少量主要由AAN和铵态氮(AN)的矿化分解引起,且AAN是沉积物矿化后无机氮最有效来源之一.对比河口和湖区表明,沉积物氮总量越大,可矿化无机氮越大.

Variation of Nitrogen Forms in Sediments of Lihu Lake During Mineralization

After 10 years of controlling point source sewage in Lihu Lake, the total nitrogen in water is still at a higher level. To explore the effects of sediment nitrogen release on overlying water, the method of submerged water cultivation was used to study changing characteristics of different nitrogen species in the process of sediment mineralization and the exchange between organic nitrogen and inorganic nitrogen of the mineralization process transformation process was discussed. The results showed that, the mean value of free nitrogen(FN) increased from 94.26 mg·kg^-1 to 230.71 mg·kg^-1 after nitrogen mineralization in the sediment, when ammonium and solved organic nitrogen (SON) were dominant; the mean value of exchangeable nitrogen (EN) increased from 82.50 mg·kg^-1 to 165.32 mg·kg^-1 with ammonium being the main species; the mean value of acid solution nitrogen (HN), which gave priority to amino acid nitrogen (AAN), decreased from 1044.70 mg·kg^-1 to 815.93 mg·kg^-1, and residual nitrogen (RN) basically remained unchanged. In the submerged cultivation process, acid solution state of total nitrogen fell from 67.18% to 52.50%, the reduction was mainly caused by mineralization and decomposition of AAN and ammonium nitrogen (AN), moreover, AAN was one of the most effective sources of inorganic nitrogen after sediment mineralization. Comparison of the results of estuaries and lakes showed that, the larger the amount of sediment was, the more the mineralized inorganic nitrogen was.