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Cadmium Solubility and Sorption in a Long‐Term Sludge‐Amended Arable Soil
Author(s) -
Bergkvist Petra,
Berggren Dan,
Jarvis Nicholas
Publication year - 2005
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/jeq2004.0385
Subject(s) - sorption , chemistry , environmental chemistry , loam , cadmium , soil water , sewage sludge , solubility , environmental engineering , sewage , soil science , environmental science , adsorption , organic chemistry
Cadmium solubility and sorption in an arable clay loam soil that had received sewage sludge for 41 years were compared to an unsludged control in batch studies. Soil pH dominated Cd sorption, explaining >92% of the variation in K d values in both treatments. At any pH, Cd sorption was apparently slightly but significantly ( p < 0.05) smaller in the sludge‐amended soil compared to the control, even though the organic carbon content was 70% larger and the ammonium oxalate–extractable iron content was roughly doubled. Correction for dissolved organic carbon (DOC) complexation with the speciation model WHAM reduced the difference in sorption between treatments, but the sludged soil still had significantly smaller K d values ( p < 0.01). Batch equilibrations without addition of Cd showed that there was no significant difference in the solubility of “native” cadmium (defined as EDTA‐extractable Cd) in sludged and control soils. The reason for the lack of increase in Cd sorption in the sludge‐amended soil has not been established, but it may be due to competition for sorption sites on humic compounds with sludge‐derived Fe and trace metals such as zinc. The fact that the pyrophosphate‐extractable (i.e., organically associated) iron content was seven times larger in the sludged soil provides some supporting evidence for this hypothesis.