Long-term increase in dissolved organic carbon in streamwaters in Norway is response to reduced acid deposition
Long-term increase in dissolved organic carbon in streamwaters in Norway is response to reduced acid deposition
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DOI：
10.1021/es070557f
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发表时间：
2007-11-15
影响因子：
11.4
通讯作者：
Hole, Lars
中科院分区：
文献类型：
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作者：
De Wit, Heleen A.;Mulder, Jan;Hole, Lars
在欧洲和北美，淡水中溶解有机碳（DOC）的浓度显著增加，但其驱动机制尚不清楚。在这里，我们测试了1985年至2003年间挪威三个酸敏感集水区TOC（总有机碳，90-95% DOC）的显著增加（14%至36%）是否与气候、水文和/或酸沉积有关。流域TOC出口增加了10% - 53%，仅在一个站点上显著增加。TOC的季节变化主要受气候控制，而SO4和no3的沉积与TOC呈负相关，解释了TOC的长期增加。我们提出腐殖质电荷增加和离子强度降低——两者都增加了有机物的溶解度——作为减少酸沉积和增加TOC之间的统计关系的机制解释。从1985年到2003年，所有位点的离子强度都显著下降，而TOC的电荷密度在其中两个位点从1-2 meq g(-1) C增加到约5 meq g(-1) C，而在第三个位点的5 meq g(-1) C保持不变。根据ph依赖的羧基去质子化和离子强度依赖的有机分子排斥力来讨论有机物的溶解度。
Concentrations of dissolved organic carbon (DOC) in freshwaters have increased significantly in Europe and North America, but the driving mechanisms are poorly understood. Here, we test if the significant increase in TOC (total organic carbon, 90-95% DOC) in three acid-sensitive catchments in Norway of 14 to 36% between 1985 and 2003 is related to climate, hydrology, and/or acid deposition. Catchment TOC export increased between 10 and 53%, which was significant at one site only. The seasonal variation in TOC was primarily climatically controlled, while the deposition of SO4 and NO3-negatively related to TOC-explained the long-term increase in TOC. We propose increased humic charge and reduced ionic strength-both of which increase organic matter solubility-as mechanistic explanations for the statistical relation between reduced acid deposition and increased TOC. Between 1985 and 2003, ionic strength decreased significantly at all sites, while the charge density of TOC increased at two of the sites from 1-2 meq g(-1) C to about 5 meq g(-1) C and remained constant at the third site at 5 meq g(-1) C. The solubility of organic matter is discussed in terms of the pH-dependent deprotonation of carboxylic groups and the ionic strength-dependent repulsion of organic molecules.