Management considerations to minimize environmental impacts of arsenic following monosodium methylarsenate (MSMA) applications to turfgrass

Abstract

Monosodium methylarsenate (MSMA) is an organic arsenical herbicide currently utilized in turfgrass and cotton systems. In recent years, concerns over adverse impacts of arsenic (As) from MSMA applications have emerged; however, little research has been conducted in controlled field experiments using typical management practices. To address this knowledge gap, a field lysimeter experiment was conducted during 2012-2013 to determine the fate of As following MSMA applications to a bareground and an established turfgrass system. Arsenic concentrations in soil, porewater, and aboveground vegetation, were measured through one yr after treatment. Aboveground vegetation As concentration was increased compared to nontreated through 120 d after initial treatment (DAIT). In both systems, increased soil As concentrations were observed at 0-4 cm at 30 and 120 DAIT and 0-8 cm at 60 and 365 DAIT, suggesting that As was bound in shallow soil depths. Porewater As concentrations in MSMA-treated lysimeters from a 30-cm depth (22.0-83.8 μg L(-1)) were greater than those at 76-cm depth (0.4-5.1 μg L(-1)). These results were combined with previous research to devise management considerations in systems where MSMA is utilized. MSMA should not be applied if rainfall is forecasted within 7 DAIT and/or in areas with shallow water tables. Further, disposing of MSMA-treated turfgrass aboveground vegetation in a confined area - a common management practice for turfgrass clippings - may be of concern due to As release to surface water or groundwater as the vegetation decomposes. Finally, long-term MSMA use may cause soil As accumulation and thus downward migration of As over time; therefore, MSMA should be used in rotation with other herbicides.

Risk Assessment for Children Exposed to Arsenic on Baseball Fields with Contaminated Fill Material

“…Lower infield soil concentrations suggest that the arsenic compound was added to grassier areas for lawn treatment. Although, the organic arsenic compounds, such as MSMA, are considered less toxic than the inorganic forms, these methylated organic acids are considered carcinogenic and management practices for their use are heavily emphasized today [ 11 , 34 ]. In addition studies have shown that the organic MSMA compound may degrade to inorganic forms over time [ 13 ].…”

“…Effective January 2004, CCA-treated wood was no longer manufactured in the U.S. for residential uses, but its use to treat industrial wood products continues today. Arsenic has also been used historically as a pesticide for the control of insects (insecticides), as crop desiccants, and to control weeds (herbicides) [ 10 , 11 , 12 ]. Arsenic-containing insecticides include inorganic forms of lead arsenate, calcium arsenate, and copper acetoarsenite.…”

“…Arsenic compounds used as herbicides include both the inorganic arsenicals and the organic arsenicals. Inorganic arsenical herbicides were used in the U.S. through 1993 and include the use of sodium arsenite to remove vegetation from rights-of-way and drainage ditch banks [ 11 ]. Until its phase out in 2009, organic arsenical herbicides, including monosodium methyl arsenate (MSMA), were used on lawns and turf—in particular golf courses [ 13 ].…”

MSMA: Knowledge Gaps to Aid Appropriate Regulation of an Efficacious Herbicide

“…To minimize As loading to the environment, MSMA should be used as part of comprehensive management plans that utilize integrated pest management strategies such as lower application rates at optimal timings. Water management strategies that control irrigation and drainage and restrict application of MSMA in areas with a shallow water table or when heavy rains are forecasted can help reduce As runoff, leaching potential, and species conversion (Mahoney et al, 2015a). Additionally, food crops that accumulate As, such as rice and apples, should not be grown in areas where MSMA use was extensive (Abedin et al, 2002), and nonagronomic land uses for which human-soil contact probabilities are high, such as housing subdivisions, schools and playgrounds, should only be developed after monitoring and remediation have taken place.…”

“…In laboratory studies, many of which have used excessive MSMA loading rates and low soil‐solution ratios, rapid species transformation and redistribution of As from solid to aqueous phases have been observed (Shimizu et al, 2011a,b), whereas field research using recommended MSMA application rates has suggested tight cycling of As within the soil‐plant‐water system (Matteson et al, 2014; Mahoney et al, 2015b). Column and field studies evaluating As leaching potential following MSMA application have shown elevated porewater As concentrations to 40 cm depth but not to 76 cm in established turfgrass systems (Feng et al, 2005; Matteson et al, 2014; Mahoney et al, 2015a), although the extent of downward migration of As to groundwater depends on edaphic and management conditions. In Florida, the one state where MSMA use is now banned in turfgrass systems, elevated groundwater As (up to 815 μg/L) near golf courses and As accumulation in golf course lake systems have been reported (Wiegand 1999; Pichler et al, 2008).…”