摘要
本文评价了稳定氮同位素(δ^(15)N)用于阐述污水氮对沿海生态系统的影响,重点描述波罗的海希默兰湾个案的情况,该海湾接纳主要以溶解的无机氮(DIN)形式排泄的富含^(15)N的三级处理过的污水。巨藻(Fucus vesiculosus)和表层沉积物的δ^(15)N梯度变化曲线示踪到距排泄口24km污水衍生氮的情况。但是高δ^(15)N值(>7‰)说明污水在10km的范围内影响最大。强化的三级处理前后巨藻δ^(15)N值的比较研究表明,从距排泄口约24km到12km范围内污水氮的空间影响是减弱的,而且对于最近生长的组织中的较高的海洋δ^(15)N值来说也是下降的。沉积物中δ^(15)N的记载表明,在污水氮含量最大的年份里随着沉积物中δ^(15)N的急剧增加污水对该湾有机物的生产已造成重大的影响。当污水氮将明显的同位素特征引入系统时以及当它对有机物质的生产已产生主导影响时,生物群和沉积物中的δ^(15)N值可用来跟踪污水氮在水生生态系统中的时空影响。
This paper reviews the use of stable nitrogen isotopes (δ^(15)N) to delineate the influence of sewage nitrogen (N) in coastal ecosystems,drawing extensively on the case of Himmerfjrden, a Baltic Sea bay that receives _(15)N-enriched tertiary treated sewage that is discharged mainly as dissolved inorganic N (DIN).Gradients of δ^(15)N in macroalgae (Fucus vesiculosus) and surface sediments traced sewage-derived N to 24 km from the outfall but elevated δ^(15)N values (>7‰) indicated that the sewage influence was most pronounced within 10 km.Comparison of macroalgal δ^(15)N values before and after enhanced tertiary treatment showed a decrease in the spatial impact of sewage N from about 24 km to 12 km from the outfall and a decrease to more marine δ^(15)N values in more recent growth tissues.Sedimentary δ^(15)N records showed that sewage has had a dominant influence on organic.matter production in the bay with dramatic increases in sedimentary δ^(15)N during the years of maximum sewage N loads.In cases where sewage N introduces a distinct isotopic signature into a system and where it has had a dominant influence on organic matter production,δ^(15) N values in biota and sediments can be used to trace the spatial and temporal influence of sewage N in aquatic ecosystems.
