Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901 83, Umeå, Sweden.
Environ Monit Assess. 2010 Dec;171(1-4):59-69. doi: 10.1007/s10661-010-1526-0. Epub 2010 Jun 11.
Despite decades of research about episodic acidification in many regions of the world, the understanding of what controls the transient changes in stream water chemistry occurring during rain and snow melt events is still limited. Here, we use 20 years of hydrological and stream chemical data from the paired watershed study at Bear Brook Watershed in Maine (BBWM), USA to improve the understanding of the effects of acid deposition on the causes, drivers, and evolution of episodic acidification. The long-term experimental study at BBWM includes 18 years of chemical treatment of the West Bear Brook (WB) watershed with (NH(4))(2)SO(4). East Bear Brook (EB) serves as reference. The treatment started in 1989 following a 2-year pretreatment period. We analyzed 212 hydrological episodes using an episode model that can separate and quantify individual drivers of the transient change in acid-neutralizing capacity (ANC) during hydrological events. The results suggest that 18 years of N and S addition have not affected the natural drivers of episodic acidification of base-cation dilution, marine sea salt episodes, or organic acidity during rain and snow melt events. The contribution of SO4(2-) to the ANC decline in WB has been increasing linearly since the beginning of watershed treatment, while the role of NO3- has remained relatively constant after an initial increase. This is contradictory to many previous shorter-term studies and illustrates the need for a more mechanistic understanding of the causes and drivers of episodic acidification during rain- and snow melt-driven hydrological events.
尽管在世界许多地区已经进行了几十年的关于间歇性酸化的研究，但对于控制雨、雪融化期间溪流水质化学变化的瞬态变化的因素，人们的理解仍然有限。在这里，我们利用美国缅因州 Bear Brook 流域（BBWM）的配对流域研究 20 年来的水文和溪流化学数据，以增进对酸沉降对间歇性酸化成因、驱动因素和演化的理解。BBWM 的长期实验研究包括对西 Bear Brook（WB）流域进行了 18 年的（NH4）2SO4化学处理，东 Bear Brook（EB）作为对照。处理始于 1989 年，紧随 2 年的预处理期之后。我们使用一个可以分离和量化水文事件中酸中和能力（ANC）瞬态变化的单个驱动因素的事件模型，分析了 212 个水文事件。结果表明，18 年来 N 和 S 的添加并没有影响到基阳离子稀释、海洋海盐事件或雨、雪融化期间的有机酸度等自然因素对间歇性酸化的驱动作用。自流域处理开始以来，WB 中 SO42-对 ANC 下降的贡献一直在线性增加，而 NO3-的作用在初始增加后一直保持相对稳定。这与许多以前的短期研究结果相反，说明了需要对雨、雪融化驱动的水文事件中间歇性酸化的成因和驱动因素有更深入的了解。
