Colazzo, M. und Niell, S. und Pareja, L. und Cesio, V. und Heinzen, H.
(2017)
The influence of different soil types in the pesticide residue analysis method performance.
In: Jahrestagung der DBG 2017: Horizonte des Bodens, 02.-07.09.2017, Göttingen.
Kurzfassung
Pesticide residues in soils cause increasing environmental problems. The underlying biological activity of herbicides from one cropping season to another could affect the productivity of the new crops. Agricultural practices also influence the herbicide level and their accumulation in soil. They interact with soil particles through absorption or adsorption by ionic interactions and other forces ruled by physicochemical properties such as Kow, Henry´s law constant, and Koc, as concentration dependent phenomena but soil texture and composition play a decisive role in their environmental behavior. To understand the general effect, the residues concentrations have to be precisely known. Although traditional pesticides such as organophosphates, pyerthorids and carbamates can be straightforward analysed in soils through general multirresidue methods, the determination of multiherbicide residues is a difficult task because soil is a complex and variable analytical matrix as different analyte/matrix interactions present. Herbicides are seldom applied alone but there are few methods reported capable of analysing high number of compounds. We studied the influence of 4 characteristics soils from Uruguay in 4 different methods for the residue analysis of 18 herbicides. Loam soils are the most common soils in Uruguay followed by clay ones and combinations of the two, with variable amounts of organic matter. The key step in this type of analysis is the extraction step. Seeking for a method usefull to analyze most of the soils types in Uruguay, we faced a systematic study using four different extraction procedures ( Methanol, Mixtures MeOH-Ethyl Acetate and Methanol-basic water). Nevertheless, in a first approach, we were not able to find a single method with aceptable performance for every soil under study. According to the type of soil, the best extraction solvent varied. The amount of organic matter played a role but also the texture of the soils was determinant for the method success. Finally, a two step extraction method gave the best results. The soil is firstly extracted with MeOH followed by a water extraction. The extracts are combined and analyzeed using LC-MS/MS. Herbicides could be determined at 0,1-1µg/Kg level. The method was succesfully applied to the herbicide residue analysis of more than 80 soil samples during three cropping seasons, where many pesticides were detected (Clomazone, Quinclorac, Benzosulfuron, Propanyl, Atrazine,Ametryn, among others ).
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