Authors:
Uttam Saha, Lena Ma, Timothy Townsend, Edmund Azah, Abioye Fayiga
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Abstract:
There are concerns that the composting of yard waste triggered by waste reduction at landfills
could damage crops due to possible contaminant transfer from waste to compost. Yard waste
compost and mulch samples were collected from 6 districts in Florida and analyzed for
metals/metalloids and herbicide content. Zinc (Zn) had the highest concentration (4.01 to 270
mg/kg) while cadmium (Cd) had the lowest (0.28 to 3.44 mg/kg). The concentrations of heavy
metals, Zn, copper (Cu), chromium (Cr) and lead (Pb) were higher than other metal/metalloids;
arsenic (As), nickel (Ni), selenium (Se), molybdenum (Mo) and Cd. However, the concentrations
of all nine metals/metalloids were below USEPA maximum allowable limits. Out of the 14
herbicides tested in compost samples; four herbicides, dalapon, dichlorprop, 2, 4-D and
chloramben were not detected in any of the districts. The remaining 10 herbicides had very low
concentrations ranging from 0.006 to 12.7 mg/kg. This may be due to degradation of herbicides
during composting. The persistent herbicide, picloram was detected in one of the districts at a
concentration of 0.007 mg/kg while dicamba was detected in two districts at concentrations
ranging from 0.11 to 0.34 mg/kg. Although, the concentrations of the herbicides were far below
the soil clean up target levels, some of them might be toxic to plants at low concentrations. Yard
waste compost appears to be relatively safe with respect to its metal concentrations while
detection of persistent herbicides makes it potentially dangerous to crop growth.
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