Glossary of Terms
This section contains a glossary of terms, all of which are used in the text. It is not intended to be exhaustive, but to explain briefly those terms which often cause difficulties or may be confusing to the inexperienced reader.
Absorbance A measurement of the absorption of light; absorbance = log I 0 /I , where I 0 is the intensity of the incident radiation and I is the intensity of the transmitted radiation. The operational scale is 0-1.2, but the normal working range is towards the lower half of the scale. Absorption The process of incorporation of a gas or liquid into the bulk of a body, or the attenuation of light passing through a liquid. Accuracy Closeness of a result to the true value. Acid rain Rain with a pH of less than 5.6 (unpolluted value). The chemistry of its formation is complex but often originates from combustion processes producing SO 2 /SO 3 (SO x ) and NO/NO 2 (NO x ). Activity Concentration of ions in water after correction for their thermodynamic non-ideal behaviour. At low concentration, activity โผ concentration, while at infinite dilution, activity = concentration. Adsorption The process where molecules of a gas or liquid adhere to the surface of a body. Aerobic Presence of oxygen, normally referring to microbial activity. Anaerobic Absence of oxygen, normally referring to microbial activity. Analyte The specific compound or ion within a sample which is being analysed. Anion A negatively charged ion. Anthropogenic Man-made. Atmosphere The gases surrounding a body. The most obvious example is the atmosphere surrounding the earth but the term can be applied elsewhere, e.g.