Pesticide Levels in Groundwater: Value and Limitations of Monitoring
This chapter discusses some examples of the information available on pesticide occurrence in groundwater. Even if the environmental risk from pesticides was recognized relatively early, the occurrence of pesticides in groundwater was detected much later. Herbicides represent the main class of pesticides responsible for groundwater contamination. In particular, as groundwater could be used as a drinking water supply without any treatment, it must comply with the quality standards set up for human consumption. Extremely high concentrations or high frequency of detection could be the consequence of a very specific and particularly oriented monitoring plan. Herbicides are often applied directly on soil, whereas other pesticides, with the exception of nematicides and of insecticides used in soil disinfection, are generally spread on plants. Thus, leaching into groundwater is very likely, favored by high solubility and low soil sorption capability, especially if there is rain or the fields are irrigated.