Glyphosate, N-phosphonomethyl glycine, is a non-selective herbicide with a wide spectrum of action. The major metabolite that occurs during the microbial degradation of glyphosate is aminomethylphosphonic acid (AMPA), which is also formed during the decomposition of other phosphate compounds, including detergents. In Slovenia, 12.5 tons of glyphosate were sold in 2014. Glyphosate has a small Henry constant of 2.10 x 10-7 Pa m3 mol-1, which means that glyphosate is non-volatile. The degradation of glyphosate in the soil is predominantly biological. The half-life depends on various environmental factors, such as temperature and humidity, and the properties of the soil. The glyphosate half-life is between 1 and 40 days, and the AMPA is from 25 to 75 days. Glyphosate and AMPA are strongly adsorptively bound to the soil particles, so their leaching potential is low. Studies have shown that glyphosate residues are more commonly found in surface water than in groundwater. The problem of glyphosate residues and AMPA is mainly in surface waters used as a source of drinking water. The European standard for drinking water for individual pesticides is 0.1 μgL-1, and in some studies the standard for drinking water has been exceeded. Glyphosate residues in surface waters can also pose a threat to non-target species of plants and animals. In a all-European study analysing the glyphosate content in 317 surface soil samples, the higest frequency of glyphosate was found in Portugal (in 53% of soil samples) and the lowest in Poland (in 7% of soil samples).
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