摘要
河流入海口被认为对减少输送到海洋里的氮负荷有很重要的作用。我们监测了北波罗的海的6个海湾河口的脱氮速度。其中4个是波的尼亚湾(波的尼亚湾的北部海湾)的河口,两个是河口海湾,一个在群岛海(波的尼亚湾南部海湾),另一个在芬兰湾。4个河口脱氮作用的速度介于330～905μmolN/m^2·d之间。群岛海和波的尼亚湾的河口海湾脱氮作用的速度分别为90～910μmolN/m^2·d,230～320μmol N/m^2·d。脱氮作用能够去除掉河口处和芬兰湾的河口海湾处的总氮负荷量的3.6%～9.0%,在这些地方停留的时间是短暂的。而停留时间很长,在河口海湾群岛海入海之前4.5%的硝酸盐负荷和19%的氮负荷能被去除掉。根据我们的监测结果,快速流动的河流以及河口地区的沉积物停留短暂,去除流向波罗的海的氮负荷的能力有限。
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 μmol N m^(-2) d^(-1).The estuary bays at the Archipelago Sea and the Gulf of Bothnia had denitrification rates from 90 μmol N mm(-2) d^(-1) to 910 μmol N m^(-2) d^(-1) and from 230 μmol N m^(-2) d^(-1) to 320 μmol N m^(-2) d^(-1), respectively.Denitrification removed 3.6-9.0% 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% of nitrate loading and 19% 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.
