Arsenic Retention in Foliage and Soil after Monosodium Methyl Arsenate (MSMA) Application to Turfgrass

Abstract

Monosodium methyl arsenate (MSMA) is a commonly used herbicide for weed control in turfgrass systems. There is concern that arsenic from applied MSMA could leach to groundwater or run off into surface water, thereby threatening human and ecosystem health. The USEPA has proposed a phase-out of the herbicide but is seeking additional research about the toxicity and environmental impacts of MSMA before establishing a final ruling. Little research has systematically investigated MSMA in field-based settings; instead, risks have been inferred from isolated field measurements or model-system studies. Accordingly, the overall goal of this study was to quantify the fate of arsenic after MSMA application to a managed turfgrass system. After MSMA application to turfgrass-covered and bareground lysimeters, the majority of arsenic was retained in turfgrass foliage and soils throughout year-long experiments, with 50 to 101% of the applied arsenic recovered in turfgrass systems and 55 to 66% recovered in bareground systems. Dissolved arsenic concentrations from 76.2-cm-depth pore water in the MSMA-treated soils were consistently <2 μg L, indistinguishable from background concentrations. As measured by adsorption isotherm experiments, MSMA retention by the sandy soil from our field site was markedly less than retention by a washed sand and a clay loam. Collectively, these results suggest that under aerobic conditions, minimal arsenic leaching to groundwater would occur after a typical application of MSMA to turfgrass. However, repeated MSMA application may pose environmental risks. Additional work is needed to examine arsenic cycling near the soil surface and to define arsenic speciation changes under different soil conditions.

A C⋅As lyase for degradation of environmental organoarsenical herbicides and animal husbandry growth promoters

“…Arsenicals, both inorganic and organic, have been used in agriculture in the United States for more than a century (7). Historically, the use of inorganic arsenical pesticides/herbicides has been largely replaced by methylated arsenicals such as monosodium methylarsonic acid (MSMA), which is still in use as an herbicide for turf maintenance on golf courses, sod farms, and highway rights of way, and for weed control on cotton fields (7).…”

Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

“…This approach was used to evaluate arsenic (As) downward leaching, absorption, and translocation into plants for bermudagrass (Cynodon dactylon) systems following application of the organic arsenical herbicide monosodium methyl arsenate (MSMA) 9 . Since the 1960s, MSMA has been used in noncropland, turfgrass, and cotton production, but there is growing concern that applied As may leach downward through soils and contaminate groundwater 11,12 .…”

“…The field area contained roughly no slope, and ~1.5 cm of the lysimeter was left above ground to help prevent cross-plot contamination issues, while also allowing for proper bermudagrass management. The field area was chosen due to its low organic matter and high sand content (88% sand, 7% silt, 5% clay), representing a "worst-case" leaching scenario with respect to soil texture and As retention potential 9 . Porewater samplers were selected so that they would fit within the lysimeters, and several weeks were allowed for system equilibration prior to chemical application.…”

The organoarsenical biocycle and the primordial antibiotic methylarsenite

“…52 For example, MSMA (MAs(V)), was used for decades for weed control and is still in use today as an herbicide for turf maintenance on golf courses, sod farms, highway rights of way and weed control in cotton fields. 52 DMAs(V) (Agent Blue) was one of the rainbow herbicides used during the war in Vietnam. 53 The pentavalent aromatic arsenicals roxarsone (4-hydroxy-3-nitrobenzenearsonic or Rox(V)), nitarsone (4-nitrobenzenearsonic acid or Nit(V)) and atoxyl ( p -aminophenylarsonic acid or pASA) have been used since the 1940s as antimicrobial growth promoters for chickens, turkeys and pigs to control Coccidioides infections, improve weight gain, feed efficiency and meat pigmentation.…”