Evaluating Off-Site Migration of Arsenic from Msma into Sod Farm Pond Systems.

Monosodium methanearsonate (MSMA) is a common organic arsenical herbicide used to control weeds on sod farms. Under certain environmental conditions, MSMA can be converted to highly toxic inorganic forms of arsenic (As). This research aims to examine and quantify arsenic accumulation in sod farm pond systems following MSMA use. Soil cores from sod fields, pond sediment cores, sediment pore water, and pond surface water samples were collected over time and evaluated for their arsenic concentrations. Samples from areas of MSMA use were compared to those from background areas where MSMA had not been sprayed. Sod field cores had elevated levels of As, especially right after spraying, at the surface but gradually decreased with depth. All surface water samples had As concentrations well below the drinking water As standard, but many pond pore water samples adjacent to sprayed fields had elevated levels of As. Some pond sediment cores showed elevated As concentrations, as compared to background cores, at the surface, whereas others showed normal As concentrations throughout their profiles. These results suggest that there has been no--to-minimal off-target As movement following MSMA use within the studied systems. Future work will evaluate As speciation, retention and concentration gradients.