|Lerch, Robert - Bob|
Submitted to: International Association of Environmental and Analytical Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/13/2000
Publication Date: 3/31/2001
Citation: Lerch, R.N., Li, Y.X. 2001. Analysis of hydroxylated atrazine degradation products in soils. International Association of Environmental and Analytical Chemistry. 79(3):167-183. Interpretive Summary: Atrazine is the major herbicide used for weed control in corn. In soils, atrazine degrades to several different compounds, including hydroxyatrazine (HA), deethylhydroxyatrazine (DEHA), and deisopropylhydroxyatrazine (DIHA) which are collectively referred to as hydroxylated atrazine degradation products (HADPs). Although many laboratory studies show that the HADPs are eoften the major degradation products of atrazine in soils, no generally accepted method for their analysis in soils has been developed. In addition, few researchers have measured the amounts of HADPs in soils under field conditions, and no confirmed reports of DEHA and DIHA levels in soils exist. This study was conducted to develop a routine method for the extraction and analysis of HADPs in soils. The developed method has three major steps: 1) HADP extraction from soil; 2) clean-up of unwanted organic compounds and concentration of HADPs in the extract; and 3) determination of HADP concentrations. Using this new method in combination with existing methods for atrazine and its other degradation products we can, for the first time, present a more accurate picture of all the atrazine residues (i.e., atrazine and its stable degradation products) in soils 1-2 years after atrazine application. HADPs comprised an average of 91% of the total atrazine residues in three agricultural surface soils with lengthy atrazine use histories. The impact of this work is to definitively show that repeated atrazine use results in HADPs as the predominant atrazine residues in surface soils. This work will primarily benefit scientists studying the fate of atrazine in the environment, but growers will indirectly benefit because possible regulations governing atrazine usage will be based on a more complete understanding of atrazine fate in the environment.
Technical Abstract: Hydroxylated atrazine degradation products (HADPs) are a major class of atrazine metabolites that are persistent in soils and contaminate surface waters throughout the Midwestern United States. The developed method employs a mixed-mode extractant [3:1 0.5M KH2PO4, pH 7.5:CH3CN (v/v)] designed to disrupt the two primary mechanisms of HADP sorption to soils: cation exchange and hydrophobic interactions. Strong anion exchange solid-phase extraction (SPE) is used for sample clean-up followed by isolation and concentration using strong cation exchange SPE. HADPs were quantitated by LC/MS/MS and LC/UV. Method recoveries were determined by spiking 14C-HADPs into three soils with lengthy atrazine use histories. Recoveries ranged from 74-81% for 14C-hydroxyatrazine (HA), 79-88% for 14C- deethylhydroxyatrazine (DEHA), and 64-77% for 14C-deisopropylhydroxy- atrazine (DIHA). HADP soil concentrations ranged from 66.9-178 ug kg**-1 for HA, 8.99-40.9 ug kg**-1 for DEHA, and 5.27-16.2 ug kg**-1 for DIHA. Utilization of the mixed-mode procedure, in conjunction with existing methodologies for analysis of atrazine and its chlorinated metabolites, enables a more complete and accurate quantitation of all the major stable atrazine residues in soils. HADPs comprised an average of 91% of the total atrazine residues in three agricultural surface soils, with HA the major constituent present in all soils. These data indicate that repeated atrazine use results in HADPs as the predominant atrazine residues in surface soils.