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81.
The methods behind the predefined impulse response function in continuous time (PIRFICT) time series model are extended to cover more complex situations where multiple stresses influence ground water head fluctuations simultaneously. In comparison to autoregressive moving average (ARMA) time series models, the PIRFICT model is optimized for use on hydrologic problems. The objective of the paper is twofold. First, an approach is presented for handling multiple stresses in the model. Each stress has a specific parametric impulse response function. Appropriate impulse response functions for other stresses than precipitation are derived from analytical solutions of elementary hydrogeological problems. Furthermore, different stresses do not need to be connected in parallel in the model, as is the standard procedure in ARMA models. Second, general procedures are presented for modeling and interpretation of the results. The multiple-input PIRFICT model is applied to two real cases. In the first one, it is shown that this model can effectively decompose series of ground water head fluctuations into partial series, each representing the influence of an individual stress. The second application handles multiple observation wells. It is shown that elementary physical knowledge and the spatial coherence in the results of multiple wells in an area may be used to interpret and check the plausibility of the results. The methods presented can be used regardless of the hydrogeological setting. They are implemented in a computer package named Menyanthes (www.menyanthes.nl). 相似文献
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腾格里沙漠面积广阔 ,区内分布着数十个盐湖 ,盐湖面积大的为十余平方千米 ,小的仅为 0 .0 18km2 。盐湖卤水主要为湖表卤水 ,其矿化度较高 ,大部分盐湖卤水含盐量已达饱和 ,因而进入了自析盐阶段。盐湖卤水化学成分以 Na+ 、K+ 、Cl-、SO4 2 -、HCO3 -、CO3 2 -为主 ,占卤水总含盐量的 99% ,卤水中还有 B2 O3 、L i、I、Br等微量元素。盐湖盐类沉积有碳酸盐类、硫酸盐类和氯化物型盐类、主要盐类矿物为芒硝、钾芒硝、天然碱、泡碱、碳钾钠矾、石盐等。盐湖粘土矿物组合以蒙脱石的普遍存在为特征 ,含有少量的伊利石和水云母。 相似文献
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Removal of ammonia toxicity in marine sediment TIEs: a comparison of Ulva lactuca,zeolite and aeration methods 总被引：5，自引：0，他引：5
Burgess RM Pelletier MC Ho KT Serbst JR Ryba SA Kuhn A Perron MM Raczelowski P Cantwell MG 《Marine pollution bulletin》2003,46(5):607-618
Toxicity Identification Evaluations (TIEs) can be used to determine the specific toxicant(s), including ammonia, causing toxicity observed in marine sediments. Two primary TIE manipulations are available for characterizing and identifying ammonia in marine sediments: Ulva lactuca addition and zeolite addition. In this study, we compared the efficacy of these methods to (1) remove NH(x) and NH(3) from overlying and interstitial waters and (2) reduce toxicity to the amphipod Ampelisca abdita and mysid Americamysis bahia using both spiked and environmentally contaminated sediments. The utility of aeration for removing NH(x) and NH(3) during a marine sediment TIE was also evaluated preliminarily. In general, the U. lactuca and zeolite addition methods performed similarly well at removing spiked NH(x) and NH(3) from overlying and interstitial waters compared to an unmanipulated sediment. Toxicity to the amphipod was reduced approximately the same by both methods. However, toxicity to the mysid was most effectively reduced by the U. lactuca addition indicating this method functions best with epibenthic species exposed to ammonia in the water column. Aeration removed NH(x) and NH(3) from seawater when the pH was adjusted to 10; however, very little ammonia was removed at ambient pHs ( approximately 8.0). This comparison demonstrates both U. lactuca and zeolite addition methods are effective TIE tools for reducing the concentrations and toxicity of ammonia in whole sediment toxicity tests. 相似文献