三峡库区典型消落带草本植物氮磷养分浸泡释放实验

三峡库区消落带植被淹水后腐烂分解,可能成为影响库区水环境安全的重要营养源.以三峡库区6种消落带优势草本植物茎叶为材料,利用室内浸泡模拟实验,测定上覆水中氮磷浓度的变化,结合初始基质碳、氮、磷含量分析,力图查明消落带草本植物淹水后氮磷养分释放特征.结果表明:①消落带植物初始基质碳、氮含量差异显著,而磷含量彼此相近.②消落带植物淹水分解造成上覆水pH升高,氧化还原电位(Eh)降低,氮磷养分快速释放和上覆水氮磷浓度增加,总氮(TN)和总磷(TP)释放量分别为(3.85±2.53)、(1.33±0.73)mg.g-1.消落带植物淹水TN和氨氮(NH4+-N)的释放过程呈抛物线状,TP呈对数曲线状.TN、TP的释放峰值时间平均15 d,NH4+-N平均33 d.养分释放量和释放速率均呈TN>TP>NH4+-N的特点,消落带植被经过3个月的浸泡,TN、NH4+-N和TP的释放负荷分别为:22.4、8.9、4.5 kg.hm-2.③植物初始基质的C含量越低,N、P含量越高,植物淹水后氮磷养分的释放量和释放速率就越大.

Nitrogen and Phosphorus Release from Herbaceous Vegetation Under Simulated Inundation Experiment of Water-Level Fluctuation Zone in the Three Gorges Reservior Area

Nitrogen and phosphorus release from herbaceous vegetation of water-level fluctuation zone in the Three Gorges Reservior (TGR) area could become a crucial source which may deteriorate water quality of TGR. Stems and leaves of the dominant herbaceous plants from water-level fluctuation zone were collected and inundated in the laboratory for measuring nitrogen and phosphorus release along with decay process. Results show that: 1 The differences of initial carbon and nitrogen content among herbaceous plants of water-level fluctuation zone are remarkable, except intial phosphorus content. 2 The decomposition of vegetation under inundation causes the increase of pH, the decrease of Eh of the overlying water and the release of nitrogen and phosphorus. The release amount of total nitrogen (TN) and total phosphorus (TP) are (3.85±2.53),(1.33±0.73)mg·g^-1 respectively.The release process of TN and ammonia nitrogen (NH₄⁺-N) shows a parabolic curve, whereas TP releases fits in a logarithmic curve. The average peak time of TN and TP concentration is in the 15^th day of inundation, while NH₄⁺-N is in the 33^th day. The release amount and rate of nutrients follow the sequence in TN>TP>NH₄⁺-N. The average loads of TN, TP and NH₄⁺-N release from vegetation decay in three months' inundation are 22.4, 8.9 and 4.5 kg·hm^-2 respectively. 3 The lower initial C and higher initial N and P content of plant, make an advantage for nitrogen and phosphorus release when plants are inundated in flooding period of TGR.