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Effect of Chloride in Soil Solution on the Plant Availability of Biosolid‐Borne Cadmium
Author(s) -
Weggler Karin,
McLaughlin Michael J.,
Graham Robin D.
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.4960
Subject(s) - biosolids , cadmium , chemistry , shoot , fertilizer , chloride , soil water , environmental chemistry , cadmium chloride , agronomy , environmental engineering , soil science , environmental science , biology , organic chemistry
Increasing chloride (Cl) concentration in soil solution has been shown to increase cadmium (Cd) concentration in soil solution and Cd uptake by plants, when grown in phosphate fertilizer– or biosolid‐amended soils. However, previous experiments did not distinguish between the effect of Cl on biosolid‐borne Cd compared with soil‐borne Cd inherited from previous fertilizer history. A factorial pot experiment was conducted with biosolid application rates of 0, 20, 40, and 80 g biosolids kg −1 and Cl concentration in soil solution ranging from 1 to 160 m M Cl. The Cd uptake of wheat ( Triticum aestivum L. cv. Halberd) was measured and major cations and anions in soil solution were determined. Cadmium speciation in soil solution was calculated using GEOCHEM‐PC. The Cd concentration in plant shoots and soil solution increased with biosolid application rates up to 40 g kg −1 , but decreased slightly in the 80 g kg −1 biosolid treatment. Across biosolid application rates, the Cd concentration in soil solution and plant shoots was positively correlated with the Cl concentration in soil solution. This suggests that biosolid‐borne Cd is also mobilized by chloride ligands in soil solution. The soil solution CdCl + activity correlated best with the Cd uptake of plants, although little of the variation in plant Cd concentrations was explained by activity of CdCl + in higher sludge treatments. It was concluded that chloro‐complexation of Cd increased the phytoavailability of biosolid‐borne Cd to a similar degree as soil (fertilizer) Cd. There was a nonlinear increase in plant uptake and solubility of Cd in biosolid‐amended soils, with highest plant Cd found at the 40 g kg −1 rate of biosolid application, and higher rates (80 g kg −1 ) producing lower plant Cd uptake and lower Cd solubility in soil. This is postulated to be a result of Cd retention by CaCO 3 formed as a result of the high alkalinity induced by biosolid application.