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181.
Anders Grimvall Claudia von Brömssen Göran Lindström 《Environmental monitoring and assessment》2014,186(8):5135-5152
Advances in process-based modelling of loads of nitrogen and phosphorus carried by rivers have created new possibilities to interpret time series of water quality data. We examined how model runs with constant anthropogenic forcing can be used to estimate and filter out weather-driven variation in observational data and, thereby, draw attention to other features of such data. An assessment of measured and modelled nutrient concentrations at the outlets of 45 Swedish rivers provided promising results for total nitrogen. In particular, joint analyses of observational data and outputs from the catchment model S-HYPE strengthened the evidence that downward trends in nitrogen were due to mitigation measures in agriculture. Evaluation of modelled and observed total phosphorus concentrations revealed considerable bias in the collection or chemical analysis of water samples and also identified weaknesses in the model outputs. Together, our results highlight the need for more efficient two-way communication between environmental modelling and monitoring. 相似文献
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Christian Huber Manuela Baumgarten Axel Göttlein Verena Rotter 《Water, Air, & Soil Pollution: Focus》2004,4(2-3):391-414
More than 85% of the mountainous spruce forest of the Bavarian Forest National Park died after bark beetle attack during the last decade. The elemental budget of intact stands and of different stages after the dieback was investigated. N-fluxes in throughfall of intact stands were lower (12–16 kg ha-1 a-1) than in an earlier study in an intact mountainous spruce stand in the Bavarian Forest National Park and were reduced in the first years after the dieback (3–5 kg N ha-1 a-1). Nitrate-N fluxes by seepage water of intact stands at 40 cm depth, which is below the main rooting zone, were moderate (5–9 kg ha-1 a-1). After the dieback of the stands, NH4 + concentrations were increased in humus efflux as were NO3 - concentrations in mineral soil. Due to the relatively high precipitation, dilution of the elemental concentrations in seepage was considerable.Therefore, NO3 - concentrations were usually below the level of drinking water (806 μmol NO3 - L-1), with lowest concentrations after the snowmelt and highest in autumn. Nitrate concentrations were elevated from the first year until the 7th year after the dieback. Total NO3 --N losses by seepage until the 7th year after the dieback equalled 543 kg N ha-1. Aluminium fluxesafter the dieback were enhanced in the mineral soil from 55 to 503 mmolc m-2 a-1 (average of 8 yr), K+ fluxes from 8 to 37 mmolc m-2 a-1, and Mg2+ fluxes from 13 to 35 mmolc m-2 a-1. The consequences for the nutritional status of the ecosystem, the hydrosphere, and forest management are discussed in the paper. 相似文献
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