Degradation and sorption of the fungicide tebuconazole in soils from golf greens☆
Graphical abstract
Introduction
The sport of golf is growing in popularity worldwide. Environmental concerns about course construction and management have been raised with regard to the impact of golf courses on nearby water resources (Baris et al., 2010, Cohen et al., 1999, Magri and Haith, 2009). These constructed landscape elements are composed of different playing zones, including roughs, tees, fairways and greens. One of the design challenges, especially with greens, is to ensure efficient drainage to protect the turf grass cover from becoming moist or flooded due to heavy rain events or intensive irrigation, for example, which may encourage fungal diseases (Baris et al., 2010). This is achieved by a construction using mostly permeable materials, facilitating efficient removal of excess water from golf courses. The most common way of constructing golf greens worldwide follows the US Golf Association (USGA) guidelines (Larsbo et al., 2008). USGA greens are characterized by the excavation of the original top soil and the addition of a sandy layer (called a “root zone mixture”) followed by a drainage layer consisting of coarse gravel (USGA, 2004) (Fig. 1A). Another popular construction is what is known as the “push-up” green, which in contrast to USGA greens uses the native soil material (Fig. 1B) and therefore generally has a relatively high organic matter content (Oppold, 1997). Most push-up greens have lower porosity and hydraulic conductivity than USGA greens and therefore drain to a lesser extent (Oppold, 1997).
Due to the dense structure of and stress (mowing nearly every day to 3–5 mm length) applied to turf grass on golf greens, fungicides are used extensively to prevent fungal growth. The frequency of pesticide application may be higher in these areas compared to agricultural land, for example (Magri and Haith, 2009), and combined with the intensive irrigation on golf greens presents possibilities for the leaching of fungicides from golf greens to drainage and groundwater. Water quality data with pesticide concentrations exceeding drinking water threshold limits have recently been reported in Europe and across the United States in connection with golf courses (Baris et al., 2010, Cohen et al., 1999, Magri and Haith, 2009, Wu et al., 2002). The degradation and sorption processes occurring within and below the green thatch layer (Fig. 1) are major parameters that determine leaching potential once the fungicides leave the foliage cover (Magri and Haith, 2009). Generally, however, the extent and rate of these processes and the soil parameters controlling them are unknown for many of the fungicides used on golf greens.
Tebuconazole ((RS)-1-p-chlorophenyl-4,4-dimethyl-3-1(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol) (TBZ) is a broad-spectrum benzotriazole fungicide used in the management of greens to repress fungal growth which negatively affects the turf grass cover and thereby the quality of the golf course. TBZ is also used in the agricultural production of different cereal crops, for example, and is reported to be moderate to highly persistent in different soils, with the time taken for 50% dissipation ranging from 49 to 610 days, and no or very limited mineralization of either the chlorophenyl or triazole rings (a maximum of 0.4% of the added 14C-labeled TBZ mineralized after 112 days of incubation) (Bending et al., 2007, Conclusion on the Peer Review, 2014, Strickland et al., 2004). The sorption of TBZ in these soils is primarily controlled by the organic matter and mineral contents (Conclusion on the Peer Review, 2014, Cadkova et al., 2012) and TBZ as part of a commercial product has generally been observed to have a higher soil sorption compared to analytical grade TBZ alone (Cadkova et al., 2013a). In parallel to the fungicides, surfactant products are also used on greens to reduce hydrophobicity in the turf and underlying sandy root zone, and thereby provide better drainage from the surface and improved water access for grass roots (Larsbo et al., 2008, Aamlid et al., 2009).
The objectives of this study were therefore to estimate the degradation and sorption of the fungicide TBZ in soils below two types of greens (USGA and push-up) in 12-cm vertical profiles covered by three different types of turf grass. The effect of additives in a commercial fungicide formulation and the addition of a commonly used surfactant product on the sorption and degradation of TBZ were elucidated and an attempt made to correlate this to simple soil parameters.
Section snippets
Chemicals
Analytical grade tebuconazole (TBZ; (RS)-1-p-chlorophenyl-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol; CAS RN 107,534-96-3, > 99.3% purity) was purchased from Sigma Aldrich and [phenyl ring-U-14C]-TBZ (5.225 MBq mg−1, purity > 98%) from IZOTOP (Budapest, Hungary). The commercial TBZ product, Orius 200 EW® (Orius; 200 g TBZ L−1), was purchased from ADAMA Northern Europe B.V. (formerly Makhteshim-Agan). The surfactant Revolution® was purchased from Aquatrols Corporation, (NJ, USA)
Sample characteristics
Samples were obtained from six different golf courses covering the two green types: USGA and push-up (Table 1). All greens except one had been treated with different fungicide products since 2010. Five of the greens had received TBZ in the form of the commercial product Folicur®, and different surfactant products had been used frequently on five of the six courses (Table 1). All soil samples can be characterized as sandy, with different proportions of fine, medium and coarse sand (Table 2). The
Discussion
Detection of pesticides in fresh water resources, such as surface and groundwater, are often linked to intensive agricultural production. In some areas, however, pesticide contamination may primarily be related to use in private gardens, but recreational activities too, such as golf, have been linked to the detection of pesticides (e.g. Cohen et al., 1999). Golf courses are man-made landscape elements that are intensively managed, which often involves the use of different kinds of pesticides to
Acknowledgments
This study was funded by the Danish Environmental Protection Agency (MST-667-00185) and the science fund of the Pesticide Leaching Assessment Programme, PLAP. We would like to thank the many people who have contributed to this project, especially the six green keepers at the golf courses for facilitating soil sampling on the greens, Aquatrols for providing Revolution®, Spire M. Kiersgaard, Pernille Stockmarr and Christina R. Lynge for their help in the laboratory, and Claire Tarring for
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This paper has been recommended for acceptance by Klaus Kummerer.