丹江口水库表层沉积物不同形态氮的赋存特征及其生物有效性

为了揭示丹江口水库沉积物氮空间分布特征及其生物有效性,采用连续分级提取法研究了表层沉积物中可交换态氮(Exchangeable nitrogen,EN)、酸解态氮(Acid hydrolysable nitrogen,HN)及残渣态氮(Residue nitrogen,RN)的赋存特征,同时结合生物可利用态氮的含量,探讨了各形态氮对生物可利用态氮的贡献。结果表明,丹江口水库沉积物中总氮(Total nitrogen,TN)在425~5796 mg/kg之间,平均为1 319.32 mg/kg,其中EN、HN和RN的平均值相对比例为2.15∶1.95∶1,且各形态氮含量的空间分布呈入库河流大于库区开阔区域的特征,尤其在丹江、老灌河以及犟河-堵河入库口的含量较大。潜在矿化氮(Potential mineralized nitrogen,PMN)含量在40.20~1 468.95 mg/kg之间,平均为275.06 mg/kg,其中EN对丹江口水库沉积物PMN的贡献较大,比例在19.85%~90.80%之间,平均为63.47%。各形态氮在不同的水环境条件下发生迁移转化,保持着水-沉积物界面氮的动态平衡。

OCCURRENCE CHARACTERISTICS AND BIO-AVAILABILITY OF NITROGEN FRACTIONS IN SEDIMENTS OF DANJIANGKOU RESERVOIR

In order to reveal the spatial distribution and bio-availability of nitrogen speciation in sediments of Danjiangkou Reservoir, the exchangeable nitrogen (EN), the acid hydrolysable nitrogen (HN) and the residue nitrogen (RN) in the surface sediment were analyzed by sequential extraction method. The results show that TN in the Danjiangkou Reservoir was 425-5796 mg/kg, with the mean value of 1319.32 mg/kg, the average value of EN, HN and RN relative proportions is 2.15: 1.95: 1, and the spatial distribution of various forms of nitrogen content in warehousing river is higher than the reservoir, especially in Danjiang, Laoguan river and the mouth of Jiang river - Du river. Nitrogen mineralization potential was 40.20-1468.95mg/kg, with the mean value of 275.06 mg/kg; the exchangeable nitrogen's contribution to the danjiangkou reservoir sediment PMN is bigger, ratio between 19.85%-90.80%, with the average of 63.47%. Migration and transformation of different forms of nitrogen happened in different water environment conditions, keeping dynamic balance between water and sediment.