Management effects on glyphosate and AMPA concentrations in the PM10 emitted by soils of the central semiarid region of Argentina

Particulate material less than 10 microns (PM10) is important because it is related to negative effects on human health. The soil is one of the most important sources of PM10 which can be emitted by wind erosion, tillage and traffic on unpaved roads. In agricultural soils different fertilizers and agrochemicals are used to produce food. Glyphosate is the main herbicide used in Argentina and in the world, being the dose and the number of applications per year variable in different management system. The objective of this study was to analyze the concentration of glyphosate and its main metabolite, AMPA, in PM10 emitted by soils with different management and uses of the herbicide. For this, the first 5 cm of the following soils were sampled: 9 soils with harvest crop (HC) mostly resistant to glyphosate, under direct sowing and with at least 3 applications of glyphosate per year; 5 soils with forage crops (FC) mostly non-glyphosate resistant, under conventional tillage and one application of glyphosate per year; and 2soils with permanent pasture (PP) that did not receive glyphosate and tillage during the last 30 years. From the soil samples were extracted and collected the PM10 using the easy dust generator coupled to an electrostatic precipitator. The glyphosate and AMPA content were determined in the soils and PM10. The results showed that the percentage of glyphosate detection in PM10 was 100% in HC and FC, and 83% in PP; whereas that AMPA detection was 100% in all management systems. In the soil the detection of glyphosate was 100% in HC, 80% in FC and 0% PP.  For AMPA the percentage of detection was 100% in HC and FC, and 66% in PP. Contents of glyphosate and AMPA in the soil were higher in HC (87.1 ug kg-1 and 1015.5 ug kg-1) than in FC (4.4 ug kg-1 and 140.3 ug kg-1) and PP (0 ug kg -1 and 8.5 ug kg-1) (p <0.05). The same results were found in PM10, where glyphosate and AMPA contents in HC (279.5 ug kg-1 and 4690.5 ug kg-1) were higher than in FC (21.1 ug kg-1 and 503.4 ug kg-1 ) and PP (33.5 ug kg-1 and 128.4 ug kg-1) (p <0.05). Content of AMPA was higher than that of glyphosate in the soil and PM10 of the three managements studied.  Glyphosate and AMPA contents in the PM10 were higher than in the soil. This study shows that the most frequent use of glyphosate increases its content and that of AMPA in the soil and PM10. It is confirmed that the contents of glyphosate and AMPA in PM10 are greater than in the soil under different management systems. Our results suggest that is highly probably the existence of glyphosate and AMPA in the PM10 emitted from agricultural soils and that, in this way, glyphosate and AMPA be transported to not target areas. All those results should by confirmed under field condition.