Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 33, 1180 Vienna, Austria; WasserCluster Lunz, Dr. Kupelwieser-Promenade 5, 3293 Lunz am See, Austria.
Leibniz Institute of Freshwater Ecology and Inland Fisheries Berlin, Justus-von-Liebig-Straße 7, 12489 Berlin, Germany.
Sci Total Environ. 2022 Oct 15;843:156879. doi: 10.1016/j.scitotenv.2022.156879. Epub 2022 Jun 23.
Floodplains remove nitrate from rivers through denitrification and thus improve water quality. The Danube River Basin (DRB) has been affected by elevated nitrate concentrations and a massive loss of intact floodplains and the ecosystem services they provide. Restoration measures intend to secure and improve these valuable ecosystem services, including nitrate removal. Our study provides the first large-scale estimate of the function of large active floodplains in the DRB to remove riverine nitrate and assesses the contribution of reconnection measures. We applied a nutrient emission model in 6 river systems and coupled it with denitrification and flooding models which we adapted to floodplains. The floodplains have the capacity to eliminate about 33,200 t nitrate-N annually, which corresponds to 6.5 % of the total nitrogen emissions in the DRB. More nitrate is removed in-stream at regular flow conditions than in floodplain soils during floods. However, increasing frequently inundated floodplain areas reveals greater potential for improvement than increasing the channel network. In total, we estimate that 14.5 % more nitrate can be removed in reconnected floodplains. The largest share of nitrogen emissions is retained in the Yantra and Tisza floodplains, where reconnections are expected to have the greatest impact on water quality. In absolute numbers, the floodplains of the lower Danube convert the greatest quantities of nitrate, driven by the high input loads. These estimates are subject to uncertainties due to the heterogeneity of the available input data. Still, our results are within the range of similar studies. Reconnections of large floodplains in the DRB can, thus, make a distinct contribution to improving water quality. A better representation of the spatial configuration of water quality functions and the effect of floodplain reconnections may support the strategic planning of such to achieve multiple benefits and environmental targets.
泛滥平原通过反硝化作用从河流中去除硝酸盐，从而改善水质。多瑙河流域（DRB）受到硝酸盐浓度升高和大面积完整泛滥平原以及它们提供的生态系统服务大量丧失的影响。恢复措施旨在确保和改善这些有价值的生态系统服务，包括去除硝酸盐。我们的研究首次大规模估计了 DRB 大型活跃泛滥平原去除河流硝酸盐的功能，并评估了重新连接措施的贡献。我们在 6 个河流系统中应用了养分排放模型，并将其与我们适应泛滥平原的反硝化和洪水模型相结合。泛滥平原每年有能力去除约 33200 吨硝酸盐-N，这相当于 DRB 总氮排放量的 6.5%。在常规流量条件下，洪水期间在河流中去除的硝酸盐比在洪泛区土壤中去除的硝酸盐更多。然而，增加经常淹没的泛滥平原面积比增加河道网络显示出更大的改进潜力。总的来说，我们估计在重新连接的泛滥平原中可以多去除 14.5%的硝酸盐。Yantra 和Tisza 泛滥平原保留了最大份额的氮排放量，预计重新连接对水质的影响最大。就绝对值而言，由于输入负荷高，多瑙河下游的泛滥平原转化了最大数量的硝酸盐。这些估计由于可用输入数据的异质性而存在不确定性。尽管如此，我们的结果仍在类似研究的范围内。因此，DRB 大型泛滥平原的重新连接可以为改善水质做出显著贡献。更好地表示水质功能的空间配置和泛滥平原重新连接的效果可能支持此类规划的战略规划，以实现多重效益和环境目标。
