Characterization of Compost Produced at a Golf Course: Impact of Historic Mercury Accumulations In Putting Green Soil

Abstract

This paper reports on the physical and chemical properties of feedstock and compost materials used at the Clear Lake Golf Course located in southwestern Manitoba. The compost was found to have a very low organic matter content (range = 9.1 to 13.2%) and a low moisture content (27.8 to 32.8%). To improve the compost quality, two recommendations were made: (1) a composting pad should be installed to prevent soil contamination and (2) the moisture content should be monitored, particularly during the curing stage. The compost contained Hg concentrations ranging from 3.16 to 6.1 mg kg−1. The grass clippings, the primary feedstock material, had Hg concentrations ranging from 8.53 to 20.2 mg kg−1. The putting green soil Hg concentration ranged from 60.7 to 90.8 mg kg−1. Elevated Hg levels may have been due to previous mercurial fungicide use and all the values were well above the Canadian compost and soil guideline values of 0.8 and 6.6 mg kg−1, respectively. It was estimated that 104.4 kg of Hg has accumulated in the top 8 cm of the putting green soil, which cover an area of 9,290 m2. Based on a Hg flow analysis conducted on the solid materials entering and leaving the putting green soil, a passive remediation approach was recommended that involved: (1) removal of the aeration cores, (2) restrictions on the compost use, (3) construction of a composting pad, and (4) the periodic monitoring of the soil and compost Hg concentrations. Calculations suggested the soil would reach the soil quality guideline value in approximately one hundred years. This is a long period of time, and, as the data suggests a degree of bioavailability, the impact of the long-term exposure to golf course staff must be determined. As there are thousands of golf courses in North America that may have been treated with mercurial fungicide, a health risk assessment should be done on the Hg exposure levels during the handling and processing of the aeration cores and grass clippings.