Estuaries have been suggested to have an important role in reducing the nitrogen load transported to the sea. We measured denitrification rates in six estuaries of the northern Baltic Sea. Four of them were river mouths in the Bothnian Bay (northern Gulf of Bothnia), and two were estuary bays, one in the Archipelago Sea (southern Gulf of Bothnia) and the other in the Gulf of Finland. Denitrification rates in the four river mouths varied between 330 and 905 mu mol N m~(-2) d~(-1). The estuary bays at the Archipelago Sea and the Gulf of Bothnia had denitrification rates from 90 mu mol N m~(-2) d~(-1) to 910 mu mol N m~(-2) d~(-1) and from 230 mu mol N m~(-2) d~(-1) to 320 mu mol N m~(-2) d~(-1), respectively. Denitrification removed 3.6-9.0 percent of the total nitrogen loading in the river mouths and in the estuary bay in the Gulf of Finland, where the residence times were short. In the estuary bay with a long residence time, in the Archipelago Sea, up to 4.5 percent of nitrate loading and 19 percent of nitrogen loading were removed before entering the sea. According to our results, the sediments of the fast-flowing rivers and the estuary areas with short residence times have a limited capacity to reduce the nitrogen load to the Baltic Sea.
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机译:有人提出,河口在减少输送到海中的氮负荷方面具有重要作用。我们测量了北波罗的海的六个河口的反硝化率。其中四个是博特尼亚湾(博特尼亚湾北部)的河口,两个是河口湾,一个在群岛海(博特尼亚湾南部),另一个在芬兰湾。四个河口的反硝化率在330〜905μmolNm〜(-2)d〜(-1)之间变化。群岛海和博特尼亚湾的河口湾反硝化率从90μmol N m〜(-2)d〜(-1)至910μmol N m〜(-2)d〜(-1)和从230μmolN m〜(-2)d〜(-1)到320μmolN m〜(-2)d〜(-1)。反硝化作用去除了停留时间短的芬兰湾河口和河口湾总氮含量的3.6-9.0%。在群岛海中停留时间长的河口湾,入海之前,要去除高达4.5%的硝酸盐和19%的氮。根据我们的结果,流动时间短的河流和河口地区的沉积物,停留时间短,减少波罗的海氮负荷的能力有限。
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