Department of Aquatic Sciences and Assessment, SLU, Uppsala, P.O. Box 7050, Sweden.
Ambio. 2011 Dec;40(8):891-905. doi: 10.1007/s13280-011-0208-7.
Long-term (1860-2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated base cation (BC) release rates (weathering) varied in a relatively narrow range of 47-62 or 42-47 meq m(-2) year(-1), depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted changes in acid neutralizing capacity (ΔANC ca. 10-41 μeq l(-1)) and pH (ca. ΔpH = 0.1-0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants, temporal changes in soil element pools, and fluxes of Al between compartments.
长期（1860-2010 年）集水区质量平衡计算依赖于模型和假设，这些都是酸化评估中的不确定性来源。在本文中，我们报告了 MAGIC 在四个瑞典 IM 森林集水区酸化模型中的应用，这些集水区受到了不同程度的酸化胁迫。模型质量平衡中的不确定性主要与沉积情景以及关于硫酸盐吸附和土壤质量的假设有关。估计的基础阳离子（BC）释放速率（风化）在相对较窄的范围内变化，为 47-62 或 42-47 meq m(-2) year(-1)，具体取决于关于土壤阳离子交换能力和基础饱和度的假设。通过改变铝的溶解度或引入允许在更酸性 pH 值下增加 BC 释放的动态风化反馈，在所有站点都观察到对预测的酸中和能力变化（ΔANC ca. 10-41 μeq l(-1)) 和 pH (ca. ΔpH = 0.1-0.6) 的系统影响。减少 BC 释放率、植物对 BC 的自然酸化吸收的时间和程度、土壤元素库的时间变化以及 Al 在不同隔室之间的通量等方面的不确定性，对于预测未来 pH 和 ANC 的变化更为可靠。
