Epsilon Archive for Student Projects

Abstract

In 2001 the Lake Vänern Society for Water Conservation¹ started a project about xenobiotics in lake Vänern. The present study is a part of that project and the aim was to collect information from investigations of pesticide residues in surface- and groundwater in the catchment area of lake Vänern. With the results in mind, possible effects on nature and on human beings are discussed.

In the catchment area of lake Vänern five streams (Fåglabäcken, Lidan, Nossan, Tidan and Uveredsbäcken) have been investigated regarding pesticide residues during several years. Several other streams have also been investigated but only at few occasions. Pesticides have
been detected at 55% of the total amount of analyses. In Fåglabäcken, Lidan, Nossan, Tidan and Uveredsbäcken the indicated concentration of one or several substances have exceeded the NC-value at several occasions. When the NC-value is exceeded the substance together with other substances may cause injuries to aquatic organisms (Crommentuijn et al., 1997). In some of the streams the MPC-value also was exceeded. When MPC is exceeded the substance alone may cause injuries to aquatic organisms (Crommentuijn et al., 1997). In total, 20 substances have been found in the investigated watercourses during the period of 1986-2000. The most common pesticide residues were bentazone, MCPA, mecoprop and dichlorprop. The concentrations of pesticide residues in the watercourses were probably not high enough to cause acute toxic effects to aquatic organisms. But they may give rise to sublethal effects in the environment, like reduced fertility.

Information about investigations has been collected from 24 water purification plants that use groundwater as incoming water and from ten plants that use water from lakes or streams. Pesticide residues were found in about 40% of the investigations of incoming water. Most of
the plants where pesticide residues have been found have taken measures to reduce the concentrations. The most common substances found at water purification plants were bentazone and MCPA. In 52% of the 13 investigated private wells pesticide residues were found. The pesticide residues found in drinking water do probably not give rise to any significant health risks. However, in order to avoid reason for concern, drinking water should preferrably be prepared from water free of contaminants