Chapter 15
Potential Leaching of Herbicides Applied to Golf Course Greens A. E. Smith and W. R. Tillotson
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Agronomy Department, University of Georgia, Griffin, GA 30223-1797
A critical issue facing the turfgrass industry is the environmental fate and safety of pesticides used in the management of recreational facilities. The purpose of our research program was to develop a data base for the determination of the potential movement of pesticides from golf course greens into potable aquifers. Lysimeters were developed, in the greenhouse, for the measurement of herbicide leachingfromsimulated greens. Data were obtainedfromlysimeters containing 'Tifdwarf' bermudagrass maintained as simulated greens and receiving treatments of the dimethylamine salt of 2,4-D as a split application at rates of 0.56+0.56 kg ae ha on a two week interval. Only minute quantities of 2,4-D were detected in the effluent from the lysimeters containing two mixtures of rooting media. These data were compared to the estimated values obtained from the GLEAMS mathematical model simulations using parameters independently determined to describe the lysimeter system. The GLEAMS model overestimated the actual data-values receivedfromthe lysimeter experiments on the potential for 2,4-D to leach through both rooting-media profiles. -1
Although agriculture represents the largest use of pesticides in North America, use on turfgrass is a routine part of modem living. The use of pesticides has tremendous impact on productivity and quality of turfgrass. Color, uniformity, and density may be affected adversely by incursions of weeds, disease, and insects. The public demand for high quality and uniform turf often requires the use of intensive management to maximize pest control and nutrient availability (18). Pesticides promote sustained turf quality, reduced labor costs, and reduced energy expenses. Accurate estimates of the quantity of pesticides used on turfgrass are difficult to develop, since most of the pesticides produced for this market are available through a wide variety of outlets and may be applied by the owner, by a pest control operator, or by municipal or other government agencies. Probably, on an area
0097-6156/93/0522-0168$06.00/0 © 1993 American Chemical Society
In Pesticides in Urban Environments; Racke, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
15.
SMITH & TILLOTSON
Leaching of Herbicides on Golf Course Greens
basis, golf course greens receive more pesticides than most other turfgrass uses. Despite the obvious cultural and economic benefits, conflicts have developed over pesticide use in relation to environmental quality issues.
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TURFGRASS PESTICIDES Turfgrass is typically the most intensively managed biotic system in urban landscapes. The increasing interest by the general public for the environmental impact and human safety of certain management practices used at recreational facilities is a major concern for the research and regulatory institutions responsible for turfgrass management practices. A critical issue facing the turfgrass industry is the environmental fate and safety of pesticides used in the management of recreational facilities. The enhanced interest in nutrient and pesticide use is, in general, a response to their increased use since the 1960s and the advancements in technology allowing scientists to detect their presence at very low concentrations. Many compounds which, because of their constituents (many contain halogens or nitrogen), can be detected in sub-parts per billion. Once the part per million was the visible limit, now we commonly measure things in parts per trillion. We will achieve recognition of concentrations of a part per quadrillion in the next decade. One day, we may recognize that there is something of everything in everything else, and that a glass of water probably contains a molecule of every compound on earth. "Yesterday's zero is no longer zero, and today's zero will not be zero tomorrow" (11). Concerns for the wide-spread use of pesticides began to develop during the 1950s and 1960s. The public alarm raised about pesticides in the 1960s has been translated into legislative controls. The results have been more rigid testing of pesticides prior to their registration and attempts to restrict pesticide application to competent people. Concerns about human and environmental welfare have been an important concept behind this legislation and the growing concern will, ultimately, result in more legislated controls on the use of pesticides. Since many of the controls placed on pesticide use increases the visibility of a use (i.e. mandatory posting of the area prior to treatment), public inquiries are also increased. A common problem in the scientific community is the concern that we may not have all of the answers for these inquiries and there must be a concerted effort to develop research programs ofriskassessment for pesticide uses. A major concern for the impact of pesticides on the environment is their potential entrance into drinking water sources which is facilitated by movement in surface water and groundwater from the treated site. Although the preponderance of the drinking water for rural areas comes from groundwater, much of the drinking water in urban areas is derived from surface water containments such as reservoirs. It is estimated that as much as 95% of the drinking water for some major metropolitan areas comes from reservoirs. Nutrients and pesticides are transported to surface water containments in runoff water and eroded sediment. Erosion and surface runoff processes in relation to water quality and environmental impacts have been examined by Anderson et al. (1), Leonard (12), and Stewart et al. (22). Although conclusive evidence of health effectsfromlong-term exposure to pesticides has yet to be established, there is intense public perception of risk concerning pesticides in drinking water (19). The EPA is currently working to establish drinking water standards of reference doses for surface and groundwater (10). Standards will be based on the same toxicological research used to establish reference doses (formerly called Acceptable Daily Intake, or ADI) for food. These standards will be the
In Pesticides in Urban Environments; Racke, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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170
PESTICIDES IN URBAN ENVIRONMENTS
maximum contaminant levels (MCLs) allowed for pesticide concentrations in potable water. The MCLs for only a few pesticides used on turfgrass have been recommended. The recommended MCL for 2,4-D is 70 ppb. In addition to federal efforts to alleviate environmental quality concerns, state governments are in the process of developing water quality regulations (5,14). State governments recognize the need to protect valuable surface and groundwater resources through both education and enforcement. Some states, such as California, New York, Nebraska, and Wisconsin have selected a regulatory approach to water quality issues (14). Others, including Iowa, are legislating a combined approach of education, research, and demonstration (9). The initial distribution of the chemical applied to turfgrass ultimately determines the amount of pesticide reaching the intended target and the amount of pesticide that will be lost from the turf ecosystem before reaching the intended target There are many obstacles that a molecule must maneuver following application before reaching a point of concern in the environment A pesticide that is primarily distributed in the turf canopy may undergo significant volatilization and/or photo-oxidation. These initial losses of applied chemical will result in insufficient pesticide concentrations to affect the intended target pest A pesticide that is initially distributed in the thatch layer may be strongly adsorbed. Sequestering of a pesticide in the thatch may reduce its efficacy and possibly delay degradation. The pesticides may form complexes with water soluble organic compounds which are susceptible to leaching losses. The initial distribution of a pesticide in the turf system is a function of the type and rate of pesticide applied, the method used to apply the pesticide, and the rate and timing of subsequent watering or irrigation. Available information on the mobility and potential for contaminating ground water of pesticides used on turf is limited. Cohen et al. (4) sampled and analyzed waterfrom16 monitoring wells on golf courses and found chlorpyrifos, 2,4-D, dicamba, isofenophos, and trichloropyridinol in one of the wells, chlorothalonil in 2 wells, DCPA in 3 wells, heptachlor epoxide in 4 wells, chlordane in 7 wells and DCB A in 9 wells. Eighty percent of the compounds were found in concentrations less than 5.0 ppb. In a comprehensive review of turf pesticides, Walker et al. (25) concluded that "Quantitative data on national or regional pesticide use for pest and disease management on golf courses is currently not available". Currently, there are over 14,000 golf courses in the United States. Assuming an average size of 120 acres per course (2) there are over 1.68 million acres of turfgrass in the golf course industry. Assuming that 2% of these acres are managed for putting greens there are 31.2 thousand acres of greens in the United States. The National Golf Foundation estimates that a golf course will need to be opened every day, during the 1990's to keep pace with the projected increase in the number of golfers (15). Many golf course greens are constructed for maximum infiltration and percolation of water through the rooting media. Root zone mixture composition generally includes at least 85% by volume (97% by mass) sand allowing for rapid water percolation and an extremely low cation exchange capacity. Additionally, soil sterilization is recommended during construction for weed and disease management (24). The sterilization ultimately influences the soil microbial decomposition of applied pesticides. These characteristics of the root zone mixture could allow for the rapid movement of pesticides through the rooting mixture allowing for a potential source of contamination of the effluent water from the greens into surface water drainage channels. However, the tight thatch overlying the rooting media is very important in the retention and degradation of most pesticides. y
In Pesticides in Urban Environments; Racke, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
15.
SMITH & TILLOTSON
Leaching of Herbicides on Golf Course Greens
Downloaded by MONASH UNIV on November 27, 2015 | http://pubs.acs.org Publication Date: February 18, 1993 | doi: 10.1021/bk-1993-0522.ch015
Studies by several investigators (3, 6,16,20,21) showed that the chlorinated hydrocarbon insecticide chlordane and several organophosphorus pesticides were retained in large amounts (>90%) by bluegrass thatch and that only small amounts (
