长江口海域悬浮颗粒有机物的稳定氮同位素季节分布与关键生物地球化学过程

摘要

对2010年2、5、8、11月份长江口海域水体中的悬浮颗粒物进行稳定氮同位素分析。根据不同季节、不同区域内悬浮颗粒有机物的稳定氮同位素组成（δ15 Np）值的变化研究水体中氮的迁移、转化等生物地球化学过程，揭示其环境行为，从而对该海域的氮循环机制进行探索。研究发现：长江口海域悬浮颗粒物的稳定氮同位素组成具有较宽的分布范围，δ15 Np值分布范围为-1.1‰～8.6‰，具有明显的时空分布特点，反映了不同程度的陆源输入和氮的生物地球化学过程的影响。其中，2月份生物反应较弱，δ15 Np分布体现了陆源和海源的混合特征；5月和11月份上层水体δ15 Np随叶绿素a升高而降低，指示了生物的同化吸收作用；8月和11月δ15 Np和总溶解无机氮呈现极显著正相关关系，说明该海域发生了氮的矿化再生。%The isotopic composition of suspended particulate matters (δ15 Np) in surface water was studied during February ,May ,August and November of 2010 in the Changjiang River estuary .Based on the variations of δ15 Np in different seasons and regions ,the biogeochemical processing of nitrogen transformation was studied and its envi-ronmental implications were also revealed . The results showed that δ15 Np of SPM was in a wide range of-1.1‰ -8.6‰ ,varying with seasons and geographic regions ,which reflected influences of riverine input and bi-ogeochemical processes .In February ,the variation of δ15 Np reflected the mixing between riverine and marine ni-trogen;in May and November ,δ15 Np decreased with increased Chl a in the surface waters ,which indicated assimi-lation ;in August and November ,significant positive relationships were found between δ15 Np and DIN ,which indi-cated remineralizaion and nitrification .