March 28, 2013
The objective of this project was to study the uptake of metals by edible mushrooms in forests treated with biosolids at the University of Washington Pack Experimental Forest near Eatonville, Washington. Sampling occurred from 2010 to 2011 within five sites; three treated with biosolids and two non-treated controls. We collected and analyzed metals concentrations from a total of 113 samples representing 11 species of edible mushrooms, as well as organic and mineral soil substrates. Silver, arsenic, cadmium, chromium, and lead remained significantly elevated in mineral and organic horizons in soils that had been treated with biosolids in 1982 or earlier. Overall, mushrooms from biosolids-treated sites had significantly elevated silver and cadmium. Metals uptake showed a strong species-specific relationship, with some mushrooms’ metals concentrations much lower than the substrate in which they were growing, while other species showed strong patterns of active uptake. In particular, Clavulina spp. (coral fungi) and Gomphidius subroseus accumulated silver at levels from twenty- to eighty-fold above substrate levels, and Boletus spp. and Gomphidius subroseus accumulated lead at levels two- to four-fold above substrate levels. Based on the EPA oral reference dose, an average person consuming 50 g per year of some of these species would be exposed to as much as 7% of their annual reference dose for As, and up to 6% for Pb, therefore consumption of larger amounts of Laccaria amethysto-occidentalis, Clavulina cristata, Gomphidius subroseus, Lactarius luculentus, and Clavulina aff. cinerea is not advised.