Center for Ecological Research and Forestry Applications (CREAF), Universitat Autònoma de Barcelona, Bellaterra, Spain.
Sci Total Environ. 2012 Sep 15;434:18-27. doi: 10.1016/j.scitotenv.2011.11.062. Epub 2011 Dec 24.
Surface water chemistry has changed in response to reduced atmospheric deposition of sulphur and acidity in many regions of Europe and North America. Most of these studies come from acidic or low-alkalinity surface waters under high acidic deposition. Mediterranean climates offer a different biogeochemical context, characterised by streamwaters of higher alkalinity and low acid inputs. In this paper, we use surveys of streamwater chemistry conducted in 1981-1984 and again in 2007 in the Montseny natural park (NE Spain) to test whether streamwaters of these well-buffered catchments respond to changes in atmospheric deposition, which has declined for S during the last decades in NE Spain while remaining about stable for nitrogen. The 23 sampled streams drained heathland, beech forests and evergreen oak forests in relatively undisturbed small catchments underlain by silicate bedrock. Bulk deposition of sulphate at Montseny decreased by 54% while nitrate bulk deposition increased (non-significantly) by 30% in this period. Total N deposition is estimated in the range 15-30 kg N ha(-1) y(-1) for NE Spain. This is well above threshold values (e.g. 10 kg N ha(-1) y(-1)) reported as starting nitrogen saturation symptoms in forest ecosystems in Europe. Baseflow sulphate concentrations decreased on average by 47 μeq L(-1) or 29% of early 1980s concentrations. Baseflow mean nitrate concentrations increased significantly but only from 5.5 to 8.9 μeq L(-1). Thus, despite decades of high N deposition, these ecosystems appear to be still far from N saturation. Baseflow alkalinity and base cation concentrations increased substantially, probably a combined result of decreased S deposition, enhanced silicate weathering under current higher temperatures, reduced plant cation uptake as vegetation matures, and slightly drier conditions in the survey of 2007. Overall, these well-buffered catchments have shown sizable changes in baseflow chemistry in response to changed atmospheric deposition and other environmental changes.
地表水化学性质已发生变化，这是欧洲和北美的许多地区大气中硫和酸性物质沉降减少所致。这些研究大多来自酸性或低碱性地表水，且这些地表水的酸性物质沉降较高。地中海气候提供了一个不同的生物地球化学背景，其特点是溪流的碱性较高，酸性物质输入较低。在本文中，我们利用 1981-1984 年和 2007 年在西班牙东北部蒙塞尼自然公园进行的溪流化学调查，来检验这些缓冲良好的集水区的溪流是否会对大气沉降的变化做出响应，因为过去几十年西班牙东北部的大气硫沉降已经减少，而氮的沉降则保持相对稳定。这 23 条被采样的溪流分别流经石南植被、山毛榉林和常绿栎树林，这些溪流所在的小流域相对未受干扰，基岩为硅酸盐。在此期间，蒙塞尼的硫酸盐总沉降量减少了 54%，而硝酸盐总沉降量（非显著地）增加了 30%。西班牙东北部的总氮沉降量估计在 15-30 千克 N ha(-1) y(-1)之间。这远远高于欧洲森林生态系统报道的氮饱和起始值（例如 10 千克 N ha(-1) y(-1)）。早在上世纪 80 年代初期，这些集水区的基流硫酸盐浓度就平均下降了 47 μeq L(-1)或 29%。基流硝酸盐浓度显著增加，但仅从 5.5 增加到 8.9 μeq L(-1)。因此，尽管数十年来氮的沉降量很高，但这些生态系统似乎仍远未达到氮饱和。基流的碱度和基流阳离子浓度显著增加，这可能是由于硫沉降减少、当前较高温度下增强的硅酸盐风化、植被成熟后植物对阳离子吸收减少以及 2007 年调查中略干燥的条件综合作用的结果。总体而言，这些缓冲良好的集水区的基流化学已经发生了相当大的变化，这是对大气沉降和其他环境变化的响应。
