Arsenic Distribution and Speciation in a Managed Turfgrass System Following Monosodium Methylarsenate Application

ABSTRACT Monosodium methylarsenate (MSMA) is an organic arsenical herbicide commonly used in certain warm‐season turfgrasses. Recently, concerns about MSMA use have arisen because of the release of As into the environment, although the fate of applied As is not well quantified for realistic management scenarios. Greenhouse lysimeter experiments were conducted to determine As distribution and speciation over time following an MSMA application to established bermudagrass [Cynodon dactylon (L.) Pers.]. At 1 wk after treatment (WAT), up to 65% of As from MSMA was detected in bermudagrass clippings and the remaining aboveground vegetation. Elevated soil and porewater As concentrations were detected to 5 cm depth but increases were not observed below this depth. Mass balance calculations revealed that As partitioned into the soil over time, with 91% of the applied As residing in the upper 5 cm of soil solids by 8 WAT. Arsenate was the dominant As species by 2 WAT and thereafter in porewater and soil. Results indicate that turfgrass management plans could be altered to minimize potential off‐target contamination from MSMA by returning clippings following mowing events and using MSMA in a herbicide rotation.