Fig. 1.

Location of study area and mean Maryland P fertility index values (equivalent to Mehlich-3 P values) by county. UMES, University of Maryland Eastern Shore.


Fig. 2.

The flue gas desulfurization gypsum ditch filter was installed on a major collection ditch draining 17 ha. The average Mehlich-3 soil test value is approximately 450 mg kg-1. The “gypsum curtain” is a second-generation design.


Fig. 3.

Clockwise from upper left: 110 Mg of flue gas desulfurization (FGD) gypsum was used in construction; a weir impedes ditch flow and measures overflow (white arrows show direction of flow); six 10-cm tile lines (30 m long) attach to the manifold in front of the weir; tile lines embedded in sand are sandwiched in FGD gypsum above and below; and filtered effluent is routed underground around the weir and through flow and concentration monitoring instruments before release downstream.