Assessing Bioavailability of Metals in Biosolids-Treated Soils

Plant-availability of metals in biosolids-treated soils may be mathematically described by M t = C x [1 - e - (k x t)] where M t (mg kg -1 ) is the cumulative metal removal from the biosolids-treated soils by growing and harvesting plants for t years, C is the total phytoavailable metal pool of the soil (mg kg -1 ) at t = 0, and k is the metal absorption rate coefficient (yr -1 ). The total available metal pool, C, is defined as metals extractable by organic acids in the rhizosphere of growing plants and k is related to the kinetics of metal release by organic acids. Half-life of the available metals in biosolids-amended soils may be derived from k. Experiments were conducted to characterize the concentration and composition of the organic acids. A successive extraction method was used to extract metals from biosolids-treated soils for determinging C and k. In this manner, the plant available metals of the bioslids-treated soils are defined by the total avialble metals, half-life, and duration of plant growing. Examples showed that the total available metals of the biosolids-amended were 18 to 39, 0.12 to 2.0, 7.4 to 13, 24 to 46, 1.2 to 2.1 , and 43 to 53 per cent of the total Cd, Cr, Cu, Ni. Pb, and Zn in the soils. This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below