Neal C
Institute of Hydrology, Wallingford, Oxon, UK.
Sci Total Environ. 2001 Jan 29;265(1-3):99-113. doi: 10.1016/s0048-9697(00)00652-5.
A discussion on the measurement of alkalinity in bicarbonate bearing and acidic waters is presented as a move towards developing a standardised approach within the aquatic sciences. The discussion is based on theoretical and practical considerations. Practical illustrations are provided from measurements of calcium bicarbonate bearing waters (River Thames) and acidic to near neutral waters from acidic soil systems with calcium bearing groundwater sources (the mid-Wales region and the Scottish Dee basin). A comparison of single endpoint and Gran procedures is made and the various error terms assessed. It is concluded that single endpoint and Gran methodologies are applicable in the standard pH titration used in aquatic research (pH 4.5-4.0). However, analytical errors increase, particularly for the single endpoint titration, the lower the endpoint/endpoint-range in pH. For the Thames, the value of a single endpoint over a Gran procedure is illustrated. The Thames results show that some buffering components may still be titrated out within the Gran titration range used: this leads to an underestimate in the alkalinity. Indeed, by making a comparison between single endpoint and Gran alkalinity measurements, the Thames results indicated the presence of unexpected buffering components: the interrogative nature of this type of analysis is highlighted. A standardised approach is outlined.
本文对含碳酸氢盐和酸性水体中碱度的测量进行了讨论，旨在推动水生科学领域形成标准化方法。该讨论基于理论和实际考量。文中给出了含碳酸氢钙水体（泰晤士河）以及来自含钙质地下水源的酸性至近中性酸性土壤系统水体（威尔士中部地区和苏格兰迪伊盆地）测量的实际示例。对单终点法和格兰氏法进行了比较，并评估了各种误差项。得出的结论是，单终点法和格兰氏法适用于水生研究中使用的标准pH滴定（pH 4.5 - 4.0）。然而，终点pH值/终点pH范围越低，分析误差越大，尤其是单终点滴定。对于泰晤士河，说明了单终点法相对于格兰氏法的价值。泰晤士河的结果表明，在所用的格兰氏滴定范围内，一些缓冲成分可能仍会被滴定出来：这导致碱度被低估。实际上，通过比较单终点法和格兰氏法测量的碱度，泰晤士河的结果表明存在意外的缓冲成分：突出了这类分析的探究性质。文中概述了一种标准化方法。
