稻田沟渠-湿地系统的碳氮稳定同位素组成特征

Stable carbon and nitrogen isotope characters in rice paddy ditch and wetland system

由于稳定同位素在特定污染源中具有特定的组成,在污染物质迁移转化过程中作为示踪剂而广泛应用。针对目前农业面源污染较为严重的现状,该文利用碳氮稳定同位素研究了灌区内外源物输入对稻田沟渠-湿地系统的贡献。结果表明,水中颗粒性有机物(particulate organic matter,POM)由于受到光照、营养物质不同导致POM在各采样点组成不同,δ13C变化范围较大,均值为-27.8‰,与大型水生植物和浮游植物接近,此类植物可能是POM的主要来源。水中δ13CDIC(dissolved inorganic carbon,DIC)与浮游植物呈线性相关,浮游动物δ13C与浮游植物存在一定相关性,而浮游植物与POM之间不存在显著性差异,说明研究区内浮游动物对內源有机碳的利用主要是取食浮游植物低持斜聿愠粱?δ13C值变化范围在-27.2‰～-21.8‰之间,明显高于水体POM含量,说明表层沉积物存在比颗粒有机物更富集碳的藻类与陆源碎屑等物质。各采样点颗粒有机物δ15N值的范围3.1‰～4.2‰,平均值为3.6‰,其中湿地δ15N高于其他采样点。沉积物δ15N平均值为-0.6‰,与大气中N2较为接近。

According to the situation of severe non-point source pollution in agriculture,taking Nanjing Gaochun irrigation area as study area,the contributions of endogenesis and exogenous inputs to the system were invetigated using stable carbon and nitrogen isotope characteristics analysis.The results showed that the stable carbon and nitrogen characters of the particulate organic matter （POM） varied greatly,the average value was-27.82‰,closed to the aquatic plants and phytoplankton,which may be the main sources of POM.The main factor of phytoplankton was δ13C of DIC （dissolved inorganic carbon） in the water,the linear correlation between δ13C of DIC and δ13C of phytoplankton proved DIC concentration of the δ13C of phytoplankton.In this experiment,each sampling point between phytoplankton and POM was no significant difference,meanwhile the δ13C of zooplankton and phytoplankton were correlated,indicated that zooplankton concentrated organic carbon from phytoplankton as food.The δ13C value changed in sediment range between-27.2‰ to-21.8‰,more carbon than POM,which indicated that sediment composition accumulated more organic carbon than the water particles.The average of δ15N in this experiment was-0.6 ‰,closed to N2 in atmosphere.