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首页> 外文期刊>Estuarine Coastal and Shelf Science >Controlling factors of seasonal variation in the nitrogen isotope ratio of nitrate in a eutrophic coastal environment
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Controlling factors of seasonal variation in the nitrogen isotope ratio of nitrate in a eutrophic coastal environment

机译:富营养化沿海环境中硝酸盐氮同位素比率季节性变化的控制因素

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Seasonal changes in the nitrogen stable isotope ratio of NO_3~- (δ~(15)N_(NO_3)) were investigated in a temperate eutrophic coastal embayment in Japan. Wide variation of δ~(15)N_(NO_3) from -10.4 to 93‰ was found along with changes in temperature, dissolved oxygen concentrations, and the composition of the dissolved inorganic nitrogen (DIN) pool. Throughout the year, δ~(15)N_(NO_3) showed positive exponential and linear relationships with NO_3~- concentrations and fractions, respectively. The minima of δ~(15)N_(NO_3) were observed in spring and autumn when the NO_3~ fraction in DIN was small, while the maximum was in summer when the NO_3~~- fraction was large. These results indicate that nitrification was the dominant process that determined δ~(15)N_(NO_3) variation. The δ~(15)N_(NO_3) minima in spring and autumn suggested that hydrographic properties, such as low water temperature and short residence time of the water, suppressed the nitrifying bacterial activity in these seasons. An apparent nitrogen isotope discrimination (ε_(nit)) by nitrification was estimated as -15 to -25‰, which is similar to or slightly higher than previous laboratory estimates of marine nitrifiers. Furthermore, isotope results at the bay center over a year suggest that most of the NO_3~- was regenerated by in situ nitrification in the water-column. This implies that large amounts of regenerated nitrogen would lead the eutrophication in Ise Bay.
机译:在日本的温带富营养化沿海海域调查了NO_3〜-(δ〜(15)N_(NO_3))的氮稳定同位素比率的季节性变化。 δ〜(15)N_(NO_3)随温度,溶解氧浓度和溶解无机氮(DIN)库组成的变化,从-10.4到93‰有很大变化。全年,δ〜(15)N_(NO_3)分别与NO_3〜-浓度和分数呈正指数关系和线性关系。 DIN中的NO_3〜较小时,在春季和秋季观察到δ〜(15)N_(NO_3)的最小值,而当NO_3 ~~-较大时,在夏季观察到最大值。这些结果表明,硝化作用是决定δ〜(15)N_(NO_3)变化的主要过程。春季和秋季的δ〜(15)N_(NO_3)极小值表明,在这些季节中,诸如低水温和短水停留时间等水文特性抑制了硝化细菌的活性。通过硝化作用的明显的氮同位素歧视(ε_(nit))估计为-15至-25‰,与先前实验室对海洋硝化器的估计相似或略高。此外,海湾中心一年多的同位素结果表明,大多数NO_3-是通过水柱中的原位硝化作用再生的。这意味着大量的再生氮将导致伊势湾的富营养化。

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