ABSTRACT
The intensive use of water in its different functions exposes this resource to human impacts of various kinds. Industrial use leads to the discharge of industrial pollutants, mostly from point sources of high intensity: typical examples are solvents, intermediates, and other process chemicals. In contrast to this, the household use of water leads to widespread contamination at low concentrations. The probably most important group of compounds in this context is that of personal care and cosmetic products (PCCPs), which are practically in ubiquitous use, and enter water bodies despite having passed through communal waste water treatment plants (WWTPs). Agriculture has a further important impact on water quality: (inorganic) fertilizers and organic pesticides (mostly herbicides, insecticides, and fungicides) are used in large quantities in intensive farming, and antibiotics in cattle breeding. Transportation is the third major source releasing organic (various hydrocarbons) and organometallic compounds into the hydrosphere. When discussing these impacts and the analytical methods for the determination of analytes with such widely varying properties, it must be borne in mind that water bodies act not only as large reservoirs but also as reactors: The euphotic (well-illuminated) zone, typically representing the top few meters (depending on the content of particulate matter and sunlight intensity) of the water column, is the zone where photochemical reactions take place. Throughout the water column, organic and organometallic compounds may be transformed as a result of biological activity, photolysis, or hydrolysis, and in the anoxic zones of the sediments, reductive reactions may take place (Figure 13.2). All these processes lead to an increase in the complexity of water samples: these contain not only parent compounds, but also their metabolites, formed in the different types of reaction taking place in different zones of the water column.
