Hruska J, Köhler S, Bishop K
Department of Forest Ecology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
Environ Pollut. 1999 Jul;106(1):55-65. doi: 10.1016/s0269-7491(99)00061-5.
The role of organic acids on surface water acidity as well as their buffering during anthropogenic acidification and subsequent recovery was studied in a field experiment on a total organic carbon (TOC)-rich stream draining the Svartberget catchment in northern Sweden. H(2)SO(4) was added to the stream to increase SO(4)(2-) concentration by 90 microeq l(-1) for 30 h. About 60% of the added H(+) was buffered by protonation of organic acids, another 20% was buffered by base cations released from the surface of the stream channel and only ca. 20% of the added acid remained unbuffered. TOC concentrations (27 mg l(-1)), and site density of carboxylic groups--8.6 microeq (mg TOC)(-1)--remained stable during the experiment. Two models of organic acid dissociation (a triprotic model and a monoprotic pH-dependent pKa model) were fitted to the experimental results. These models explained the observed variations in organic anions, but the model parameters were quite different from those reported by studies in Northern America and Central Europe. This experiment had substantially more buffering effect of TOC between pH 4.4 and 5.3, which is an environmentally important pH range.
在瑞典北部斯瓦特贝里集水区一条富含总有机碳（TOC）的溪流进行的野外实验中，研究了有机酸在地表水酸度方面的作用，以及它们在人为酸化及随后恢复过程中的缓冲作用。向溪流中添加硫酸，使硫酸根离子（SO₄²⁻）浓度在30小时内增加90微当量/升。添加的氢离子（H⁺）中约60%通过有机酸的质子化作用得到缓冲，另外20%通过从溪流渠道表面释放的碱金属阳离子缓冲，只有约20%的添加酸未被缓冲。实验期间，TOC浓度（27毫克/升）和羧基位点密度——8.6微当量/（毫克TOC）——保持稳定。将两种有机酸解离模型（三元酸模型和单质子pH依赖pKa模型）与实验结果进行拟合。这些模型解释了观察到的有机阴离子变化，但模型参数与北美和中欧研究报告的参数有很大不同。在pH值4.4至5.3之间，本实验中TOC的缓冲作用要大得多，这是一个对环境很重要的pH范围。
