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Permeable grass-covered surfaces can reduce the quantity of storm water runoff and filter out potentially harmful chemicals. The objective of this study was to develop permeable structural soils that sustained healthy turf growth and filtered heavy metals from contaminated pavement runoff. The basic soil medium was a 50:50 mixture (v/v) of expanded shale (ExSh) and quartz sand (QS). The ExSh component consisted of (i) large-diameter particles (3-6 mm), (ii) small-diameter particles (1-3 mm), or (iii) a 50:50 mixture (v/v) of the two. The basic blends were mixed with 0, 10, and 20% sphagnum peat moss (v/v) and 0, 10, and 20% natural zeolites (v/v) and placed in 15-cm-diameter pots in a greenhouse. Bermudagrass plugs were planted in each pot. The addition of sphagnum peat moss to the basic ExSh/QS blend increased bermudagrass growth and improved plant response to added fertilizer. Zeolites had no significant effect on plant growth in the absence of sphagnum peat moss. Growing mediums that contained 10 to 20% sphagnum peat moss and 10 to 20% zeolites consistently produced more bermudagrass biomass than the unamended ExSh/QS mixture. Changing the ratio of small- to large-diameter ExSh in the basic medium did not affect bermudagrass yield. Very low amounts of Cd, Cu, Pb, and Zn were recovered in leachate after the addition of 10 mg metal per pot, suggesting that most heavy metals (>99%) were retained in the growing mediums. Zeolites reduced the amount of Cd and Pb in leachate water, but not Cu or Zn.

Biosolids applications can significantly increase Hg concentrations in cultivated soils. The objective of this study was to quantify levels of mercury in soils and runoff from a biosolids-amended watershed. The study site was a terraced, cultivated watershed that received cumulative biosolids loadings of 0, 87, or 224 Mg ha(-1) between 1974 and 1993. Snowmelt runoff samples were collected from the three treatment areas in the spring of 1995. Soils were collected along transects from the 0 and 224 Mg ha(-1) biosolids treatment areas at depths of 0 to 15 and 15 to 30 cm. Mercury analysis of stored, freeze-dried biosolids samples showed that Hg concentrations during the 20-year study ranged from 12.4 mg kg(-1) initially to 2.4 mg kg(-1) near the end. Soil Hg concentrations were elevated in the surface (0-15 cm) and subsurface (15-30 cm) of the 224 Mg ha(-1) biosolids-treated terrace relative to the control. Mercury concentrations in the 0- to 15-cm soil depth ranged from 30 to 50 microg kg(-1) for the control terrace and 180 to 390 microg kg(-1) for the 224 Mg ha(-1) biosolids-treated terrace. Concentrations were lower in the 15- to 30-cm depth. Total Hg concentrations in snowmelt from the control terrace ranged from 9.2 to 27.9 ng L(-1) and 19.8 to 44.8 ng L(-1) for the biosolids-treated terraces. Most Hg was associated with particulates > 0.45 microm. Mercury concentrations were elevated in grass tissue growing near the watershed's runoff lagoon.