| The net air-water exchange flux of polybrominated diphenyl ethers (PBDEs) in the Great Lakes and the atmospheric presence of glyphosate and aminomethylphosphonic acid (AMPA) in the farm fields are reported here for the first time. Paired air and surface water samples were collected during May and July from Lake Michigan in 2005 and Lake Superior in 2006. Average atmospheric PBDE concentrations and deposition were higher over Lake Michigan than Lake Superior and higher at nearshore urban than open-lake sites. Additionally, annual mass budgets of PBDEs for the Great Lakes are presented by estimating atmospheric deposition, wastewater treatment plant discharge, burial of lake sediments, and lake water outflow. The results indicated that annual mass budget of sum6PBDE (BDE-47, 66, 100, 99, 154, and 153) for Lake Michigan was a net increase with 270 kg yr-1. In contrast, the budget for Lake Superior approached equilibrium with a net increase of 14 kg yr-1. Wet deposition was the major contributor (71-75%) of the total sum6PBDE inputs to both lakes. Glyphosate and AMPA were detected only in the particle phase of air samples in Mississippi and Iowa in 2007-2008. The frequency of glyphosate detection ranged from 61 to 100% (in air) and 63 to 92% (in rain). The highest concentrations of glyphosate and AMPA in both air and rain were found during the periods of intense glyphosate applications. Glyphosate and AMPA were removed efficiently from the air by particle scavenging in rainfall events. Based on annual mass budgets of glyphosate in Mississippi and Iowa study sites, less than 0.1% of the applied glyphosate moved into the atmosphere due to application spray drift (0.01%-0.05%), and wind erosion (<0.01%-0.02%). |
