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Increasing dissolved silica trends in the Rhine River: an effect of recovery from high P loads?

机译：莱茵河中溶解二氧化硅的趋势在增加：从高磷负荷中恢复的影响？

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摘要

The development of river dams and further human activities (causing increased nitrogen (N) and phosphorus (P) nutrient loads), are responsible for a decline in dissolved silica concentrations (DSi) in many river systems. Here, the impact of the reduction of N- and P-concentrations on DSi is examined for the Rhine River. During the last decade of the twentieth century, annual average DSi concentrations increased by ~70% in the Rhine at Bimmen/Lobith, whereas nitrate (NO3) and phosphate (PO4) concentrations decreased by approximately one third. Accordingly, decadal changes in nutrient elemental ratios shifted the river system from DSi-limitation to P-limitation. Specifically, a seasonal DSi-concentration increase is observed from May to December for the Rhine River (with exception of June). Observed increases in DSi concentration are probably due to improvements in water-basin and land-use management, specifically a reduction in point-source P discharge, leading to P-limiting conditions for diatom growth. Data of the warm season suggest that as the system is moving through the transition from P-excess to P-limitation conditions, P-limitation according to the elemental ratio DSi/total phosphorus (TP) is occurring later than for the ratio DSi/PO4-P. Latter ratio will be buffered around ~16:1 during growing season. Reduction of N fertilization is less relevant, as N-limitation with respect to DSi is not achieved, even at the end of the analyzed period, but N-limitation may be reached in the future. Analysis of discharge–DSi relationship supports the hypothesis that DSi increase is affected by increasing P-limitation during the warm period and not only due to hydrological reasons. Results suggest, however, that the influence of hydrological parameters needs to be addressed in research for DSi concentration changes due to changed nutrient loads. Despite an overall increase in water temperature of 3°C over a 50-year period, no correlation with temperature was found for the last two decades of the twentieth century, for which DSi-data were available. In conclusion, in case of eutrophied river systems with excess of P, P-reduction may lead to an increase of DSi concentrations under certain conditions. This in turn is expected to impact not only DSi-sensitive coastal-zone ecosystems impacted by eutrophication but the carbon cycle as well.
机译：河流水坝的发展和人类的进一步活动（导致氮（N）和磷（P）养分含量的增加）是导致许多河流系统中溶解二氧化硅浓度（DSi）下降的原因。在此，研究了莱茵河中N和P浓度降低对DSi的影响。在二十世纪的最后十年中，莱茵河在比门/洛比斯的年平均DSi浓度增加了约70％，而硝酸盐（NO3 ）和磷酸盐（PO4 ）的浓度下降了约三分之一。 。因此，营养元素比例的年代际变化使河流系统从DSi限制转变为P限制。具体而言，莱茵河从5月到12月（除6月）观察到季节性DSi浓度增加。观察到的DSi浓度增加可能是由于流域和土地利用管理的改善，特别是点源磷排放量的减少，从而导致了硅藻生长的磷限制条件。温暖季节的数据表明，随着系统经历从P过剩状态向P限制状态的转变，根据元素比DSi /总磷（TP）的P限制发生的时间要晚于DSi / PO4的比率。 -P。在生长季节，后期比率将被缓冲在约16：1左右。减少氮肥施用的相关性较小，因为即使在分析期结束时也无法实现相对于DSi的N限制，但将来可能会达到N限制。流量与DSi关系的分析支持以下假设：DSi的增加受暖期P限制的增加的影响，而不仅仅是由于水文原因。但是，结果表明，在研究因营养物负荷变化而引起的DSi浓度变化时，需要解决水文参数的影响。尽管在过去的50年中水温总体升高了3°C，但是在20世纪的最后二十年中，没有DSi数据与温度相关。总之，如果富营养化的河流系统中含有过量的P，则在某些条件下P的减少可能导致DSi浓度增加。反过来，预计这不仅会影响富营养化影响的对DSi敏感的沿海地区生态系统，还会影响碳循环。

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  • 来源
    《Limnology》 |2011年第1期|p.63-73|共11页
  • 作者

    Jens Hartmann; Jason Levy; Stephan Kempe;

  • 作者单位

    Institute for Biogeochemistry and Marine Chemistry, KlimaCampus, Universität Hamburg, Bundesstrasse 55, 20146, Hamburg, Germany;

    Homeland Security and Emergency Preparedness, L. Douglas Wilder School of Government and Public Affairs, Virginia Commonwealth University, Richmond, VA, USA;

    Institute for Applied Geosciences, Darmstadt University of Technology, Schnittspahnstrasse 9, 64287, Darmstadt, Germany;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Silica; Trend; Rhine; Nutrient limitation;

    机译：二氧化硅;趋势;莱茵;营养限制;

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