稻田水体碳氮稳定同位素组成与时空变化研究

Temporal and Spatial Variation in Stable Carbon and Nitrogen Isotope in Paddy Field Water

利用稳定同位素技术研究了稻田沟渠、池塘、湿地等水体的碳、氮稳定同位素组成特征与时空变化。结果表明,水中颗粒性有机物(Particulate organic matter,POM)δ13C值(稳定性碳同位素比值)在-31.5‰^-24.3‰之间变化,平均值为-27.7‰,可能主要来自于浮游植物和浮游动物的贡献。POM稳定性碳同位素比值存在明显的季节变化,呈现出春、夏季高于秋、冬季的趋势。浮游动物与POM稳定性碳同位素比值之间的时空变化存在一定的相关性,说明研究区内浮游动物对内源有机碳的利用可能主要来自POM。颗粒性有机物δ15N存在秋、冬季高于春、夏季的趋势,但空间差异不显著,其中湿地的变化幅度相对较大(3.2‰~6.3‰),δ15NPOM平均值为4.1‰,说明研究区固氮作用较小,外源物的污染程度较低。

Since the stable isotope composition was widely used as tracers in the process of pollutant migration and transformation, stable isotope analyses of carbon and nitrogen in paddy field sampled from Nanjing irrigation area were studied. The results showed that delta C-13 values of particulate organic matter （POM） were between - 31.5%～ - 24.3%0, with an average value of - 27.7% The stable carbon and nitrogen characters of particulate organic matter （POM） varied greatly in different sites. The isotopic signatures of both POM and zooplankton remained sufficiently distinct from each other throughout the period of study. Delta C-13 values of particulate organic matter and zooplankton showed some seasonal variation, reflecting higher values during spring and summer than autumn and winter. But delta N-15 values were more constant except the last sampling. The spatial and temporal variations of delta C-13 values were similar between zooplankton and POM, which meaned that POM may be the main resource of zooplankton. The minimum delta N-15 value of POM was 3. 1% and nitrogen fixation could be ignored in the study area. This study was the first to quantify such a seasonal switch in zooplankton and particulate organic matter in paddy field.