Chemistry and Transport of Metals from Entrenched Biosolids at a Reclaimed Mineral Sands Mining Site

Abstract

Deep row incorporation of biosolids is an alternative land treatment method whose typically high rates may result in elevated pollutant transport. The objectives of this research were to compare the effects of entrenched biosolids stabilization type and rate on heavy metal chemistry and mobility. Two rates each of Alexandria (Virginia) Sanitation Authority anaerobically digested (213 and 426 dry Mg ha(-1)) and Blue Plains (Washington, DC) lime-stabilized (329 and 657 dry Mg ha(-1)) biosolids were placed in trenches at a mineral sands mine reclamation site in Dinwiddie County, Virginia, in summer 2006. Vertical and lateral transport of heavy metals from the biosolids seams were determined by analyzing leachate collected in zero tension lysimeters below the trenches and suction lysimeters adjacent to the trenches. Silver, Cd, Pb, and Sn did not move vertically or laterally to any significant extent. During the 15-mo period following entrenching, lime-stabilized biosolids produced higher cumulative metal mass transport for Cu (967 g ha(-1)), Ni (171 g ha(-1)), and Zn (1027 g ha(-1)) than did the anaerobically digested biosolids and control. Barium mass loss was similar for both biosolids. All metals moved primarily with particulates. MINTEQA) predicted that > 70% of Cu was bound to fulvic acids, whereas > 80% of Ba was found as Ba2+. As pH decreased with time, free ions of Zn decreased and the metal's association with fulvic acids increased. Largely insignificant transport of metals into the lysimeters demonstrated that biosolids-borne heavy metals posed little risk to groundwater even when entrenched in very coarse-textured soil.

Bioavailability of Barium to Plants and Invertebrates in Soils Contaminated by Barite

“…Speciation of Ba is well-known to influence solubility. , Chloride, acetate, perchlorate, and nitrate salts of Ba are readily soluble in water, but barite (BaSO 4 ) is a highly insoluble mineral. , Barite is insoluble in water, acids, and bases and on its own is unlikely to cause a risk to humans or the environment. Barite is orally administered to patients deliberately as a radiological tool to visualize the gastrointestinal tract.…”

Environmental Impact of Exceptional Quality Biosolids Use in Urban Agriculture

“…to a depth of 40 cm in every plot for installation of the lysimeters. Kynar tubing was used to transport leachate from the lysimeter reservoir to the surface with aid of an electric pump (Lasley et al, 2010). One end of the Kyanar tubing was covered with a fine screen and placed at the bottom of the lysimeter.…”

Transformations of Nitrogen and Carbon in Entrenched Biosolids at a Reclaimed Mineral Sands Mining Site

“…Installation of the zero tension lysimeters was conducted in June and July 2006 just before biosolids entrenchment. The overall biosolids seam instrumentation and dimensions are schematically shown in Lasley et al (2010) The lysimeters were evacuated via Kynar tubing (Kynar, Philadelphia, PA) by pumping leachate with an electric pump to the surface.…”